Past Seminars
Spring 2023
Rhine Samajdar, Princeton University
January 24, 2023
Title: Quantum dimer models in the age of Rydberg quantum simulators
Abstract: Strongly interacting arrays of Rydberg atoms provide versatile platforms for exploring exotic manybody phases and dynamics of correlated quantum systems. Motivated by recent experimental advances, we investigate the quantum phases that can be realized by such Rydberg atom simulators in two dimensions. We show that the combination of Rydberg interactions and appropriate lattice geometries naturally leads to constrained dimer models and emergent Z_{2} gauge theories endowed with matter fields. Based on this mapping, we demonstrate how Rydberg platforms can be used to realize topological spin liquid states based solely on their native van der Waals interactions. We also discuss the nature of the fractionalized excitations of two distinct classes of such Z_{2} quantum spin liquid states and illustrate their rich interplay with proximate solid phases.
January 31, 2023
Title: Maximal Entangling Rates from Holography
Abstract: We prove novel speed limits on the growth of entanglement, equal time correlators, and spacelike Wilson loops in spatially uniform timeevolving states in strongly coupled CFTs with holographic duals. These bounds can also be viewed as quantum weak energy conditions. Several of the speed limits are valid for regions of arbitrary size and with multiple connected components, and our findings imply new bounds on the effective entanglement velocity of small subregions. In 2d CFT, our results prove a conjecture by Liu and Suh for a large class of states. Key to our findings is a momentumentanglement correspondence, showing that entanglement growth is computed by the momentum crossing the HRT surface. In our setup, we prove a number of general features of boundaryanchored extremal surfaces, such as a sharp bound on the smallest radius that a surface can probe, and that the tips of extremal surfaces cannot lie in trapped regions. Our methods rely on novel global GR techniques, including a delicate interplay between Lorentzian and Riemannian Hawking masses. While our proofs assume the dominant energy condition in the bulk, we provide numerical evidence that our bounds are true under less restrictive assumptions.
February 7, 2023
Title: JT gravity with matter, generalized ETH, and Random MatricesAbstract: The Eigenstate Thermalization Hypothesis (ETH) asserts that at sufficiently late times, chaotic manybody quantum theories may be described statistically. We consider an ensemble defined by a singletrace twomatrix model, where one matrix represents the Hamiltonian and the other represents a simple operator. The matrix potential is chosen such that the disk correlators of the matrix model agree with the disk correlators of JT gravity minimally coupled to a massive free scalar field. We compute cylinder correlators in the matrix model, which correspond to wormhole amplitudes in the dual gravity theory. We also comment on how our construction could be generalized to statistical models of higherdimensional holographic CFTs. The ensemble must be constrained to respect the largeN algebra of the light operators.
February 14, 2023
Title: String Theory in Offshell Backgrounds: The Sphere Partition Function and Black Hole Entropy.Abstract: The worldsheet theory of string backgrounds is a CFT with zero central charge. This is the definition of onshell string theory. In offshell string theory, on the other hand, conformal invariance on the worldsheet is explicitly broken, and the worldsheet theory is therefore a QFT with a UV cutoff.
In the first part of the talk, I will explain Arkady Tseytlin’s prescriptions for constructing classical (treelevel) offshell effective actions and provide a general proof, using conformal perturbation theory, that it gives the correct equations of motion, to all orders in perturbation theory and α′. I will also show how the offshell prescriptions are equivalent to quotienting out by the gauge orbits of a regulated moduli space with operator insertions.
In the second part of the talk, I will explain the underlying conceptual structure of the Susskind and Uglum black hole entropy calculation. I will show how the classical (treelevel) effective action and entropy S = A/4G_{N} can be calculated from the sphere diagrams.
Time permitting, I will discuss ongoing work on a stringy derivation of the holographic entanglement entropy (the RT formula).
February 21, 2023
February 28, 2023
Title: NonInvertible Symmetries in Supergravity.
Abstract: I discuss the existence of noninvertible symmetries in 11d and 10d maximal Supergravity. These symmetries should be broken or gauged by the UV completion. We will see that the presence of Dbranes in String Theory explicitly breaks them.
March 7, 2023
Title: Recent Progress in Quantum Gravity
Abstract: The structure of the bulk Hilbert space in quantum gravity is very different from standard quantum field theory. An illustration of this assertion is the wellknown holographic principle which states that the dimension of the Hilbert space of a gravitational region scales with its boundary area instead of the volume. Mathematically, this is described by the fact that the diffeomorphism invariance enforces a dressing of any local bulk operator by a gravitational Wilson line to a place where gravity can be decoupled (in the absence of any diffeomorphism breaking background configurations). This has significant implications for the finestructure of the states in the Hilbert space in quantum gravity, for example there is no factorization of the Hilbert space of a gravitational region into subregions which is nevertheless the usual starting point to study entanglement properties of Hilbert space states in quantum field theories. Misunderstanding of this special property of quantum gravity constantly causes puzzles such as Hawking's famous black hole information paradox and the AMPS firewall paradox. The recent progress in the understanding of the brandly new emergent concept entanglement island sheds light on these questions in quantum gravity. In this talk, I'll give a quick review of Hawking's information paradox, the AMPS firewall paradox and their resolution in the KarchRandall braneworld by the emergence of entanglement island then I'll discuss the implications to these paradoxes and quantum gravity in general from the physics of the KarchRandall braneworld.
March 14, 2023
Title: Long Time Limits of Generalized Ricci FlowAbstract: We derive rigidity results for generalized Ricci flow blowdown limits on classes of nilpotent principal bundles. We accomplish this by constructing new functionals over the base manifold that are monotone along the flow. This overcomes a major hurdle in the nonabelian theory where the expected Perelmantype functionals are not monotone and do not yield results. Our functionals were inspired and built from subsolutions of the heat equation, which we discovered using the nilpotency of the structure group and the flow equations. We also use these and other new subsolutions to prove that, given initial data, the flow exists on the principal bundle for all positive time and satisfies type III decay bounds. In future work, we will apply these results to study the collapsing of generalized Ricci flow solutions and to classify type III pluriclosed flows on complex surfaces.
March 21, 2023
Title: Quenching the Black Hole Zoo
Abstract: Many properties of black holes, such as their entropy, are universal; this suggests that there is a commonality in their statistical description. In this talk, I will discuss nonuniversal aspects of nearextremal black holes in 4D N=2 SUGRA, which are encoded in deformations away from an idealized AdS_2 geometry. Such features are important to understand in order to construct a microscopic dual of (the nearhorizon region of) nearextremal black holes. I will discuss an interesting pathology that appears for certain backgrounds: the entropy as computed from the onshell action can become negative. I will argue that this pathology can be resolved within the regime of semiclassical gravity by considering quenched instead of annealed quantities.
March 21, 2023
Title: Is the extensive mutual information model a QFT?
Abstract: I will introduce the socalled extensive mutual information model (EMI), which is the unique solution to the known axioms of the ground state mutual information of a CFT, when one imposes extensivity on its arguments. Using various results concerning the mutual information of largely separated regions, I will then show that the EMI cannot describe the ground state mutual information of a CFT in dimensions greater than two. This result suggests that the set of known axioms of the mutual information might be incomplete.
March 28, 2023
Title: Entwinement and bulk reconstruction in AdS3/CFT2
Abstract: A nice setup to investigate subtle aspects of how spacetime emerges from the internal degrees of freedom in holographic theories is provided by AdS3/CFT2 holography. There, quotients of AdS3 with conical singularities possess several extremal "surfaces" (curves in D=3) anchored to a fixed boundary region. The length of those curves which are extremal but nonminimal was conjectured in the past to compute some loosely defined notion of entanglement between internal degrees of freedom in the dual CFT. This quantity was dubbed "entwinement". In this talk, I will give a more precise picture of how entwinement can be defined for the setup relevant to AdS3/CFT2 holography, in which the field theory is a symmetric product orbifold CFT. In the process, it will become clear that this notion is indeed what the lengths of extremal but nonminimal curves are computing. Time permitting, I will also put forward some more speculative questions related to the general program of bulk reconstruction that can be discussed in the setup of quotient geometries in AdS3/CFT2.
April 4, 2023
Title: Horizon Scattering, Partition Functions, and Edge ModesAbstract: Ideal gas thermal canonical partition functions for quantum fields outside (inside) a black hole (de Sitter) horizon are illdefined due to an infinite density of normal modes originating from the continuous nature of the spectrum. In this talk, I will explain how to make sense of this computation by viewing the Lorentzian field equation in a black hole background as an effective 1D scattering problem. The scattering phases encode nontrivial information about the singleparticle density of states (DOS) and can be extracted by ``renormalizing" the DOS with respect to a reference DOS. This defines a renormalized thermal free energy up to a choice of reference. Interestingly, we discover that the 1loop Euclidean path integral, as computed by the DenefHartnollSachdev (DHS) formula, fixes the reference free energy to be that on a Rindlerlike region. Time permitting, I will explain how extending the DHS argument to spinning fields allows us to unambiguously identify a bulkedge split for their Euclidean partition functions. The bulk part captures the renormalized thermal free energy described above, while the edge part is related to quasinormal modes that fail to analytically continue to a subset of Euclidean modes with enhanced falloffs near the origin.
April 11, 2023
April 18, 2023
Title: Entanglement entropies for Lifshitz fermionic fields at finite density
Abstract: The entanglement entropies of an interval for the free fermionic spinless Schroedinger field theory at finite density and zero temperature are investigated. The interval is either on the line or at the beginning of the half line, when either Neumann or Dirichlet boundary conditions are imposed at the origin. We show that the entanglement entropies are finite functions of a dimensionless parameter proportional to the area of the rectangular region in the phase space identified by the Fermi momentum and the length of the interval.
For the interval on the line, the entanglement entropy is a monotonically increasing function. Instead, for the interval on the half line, it displays an oscillatory behaviour related to the Friedel oscillations of the mean particle density at the entangling point.
By employing the properties of the prolate spheroidal wave functions or the expansions of the tau functions of the kernels occurring in the spectral problems, determined by the two point function, we find analytic expressions for the expansions of the entanglement entropies in the asymptotic regimes of small and large area of the rectangular phase space region. Extending our analysis to a class of free fermionic Lifshitz models, we find that the parity of the Lifshitz exponent determines the properties of the bipartite entanglement.
April 25, 2023
Title: Spaces of QFTs and tameness
Abstract: I will discuss the notion of a space of quantum field theories, and explain various approaches to its definition and some of its expected properties.
I will then cover joint work with Thomas Grimm and Lorenz Schlechter on tameness of quantum field theories. This is based on the mathematical concept of ominimal structures which has been very powerful for proving finiteness results. Given a QFT or a space of QFTs, we define a corresponding structure, and conjecture in many cases that it is tame (ominimal). We also show that Feynman amplitudes at any fixed loop order
are tame.
May 2, 2023
Stefano Baiguera, Ben Gurion University
May 23, 2023
Title:
The cosmological switchback effect
Abstract:
The volume behind the black hole horizon was suggested as a holographic dual for the quantum computational complexity of the boundary state in AdS/CFT. This identification is strongly motivated by the switchback effect: a characteristic delay of complexity growth in reaction to an inserted perturbation, modelled as a shockwave in the bulk. Recent proposals of de Sitter (dS) holography suggest that a dual theory could be living on a stretched horizon near the cosmological horizon.
In this talk, I will show how the spacetime volume behind the cosmological horizon in SchwarzschilddS space reacts to the insertion of shockwaves in an attempt to characterize the properties of this dual theory. I will demonstrate that a switchback effect can be observed in dS space. That is, the growth of complexity is delayed in reaction to a perturbation. This delay is longer for earlier shocks and depends on a scrambling time which is logarithmic in the strength of the shockwave and proportional to the inverse temperature of the cosmological dS horizon. This behavior is very similar to what happens for AdS black holes, albeit the geometric origin of the effect is different.
Fall 2022
August 23, 2022
Djordje Radicevic, Brandeis University
"Entanglement entropy and the latticecontinuum correspondence"
Abstract: Entanglement entropy (EE) is notoriously tricky (or impossible) to rigorously define in quantum field theory. However, EE is straightforward to define in a finitedimensional quantum system. The recent progress in understanding the correspondence between lattice and continuum theories now makes it possible to define and study EE in continuum theories via finite, latticebased quantities. I will explain how this works and how two interesting lessons emerge. One is that the divergences associated to the EE in continuum theories are not governed by the smallest UV scale (the lattice spacing) but rather by a much larger scale (the "smoothing length"). The second is that the ReehSchlieder theorem can be formulated in the context of lattice theories, with the smoothing length once again playing a key role in determining its breakdown.
August 30, 2022
Anurag Anshu, Harvard University
"NLTS Hamiltonians from good quantum codes"
Abstract: The NLTS (No LowEnergy Trivial State) conjecture of Freedman and Hastings [2014] posits that there exist families of Hamiltonians with all low energy states of nontrivial complexity (with complexity measured by the quantum circuit depth preparing the state). Our recent work https://arxiv.org/abs/2206.13228 (with Nikolas Breuckmann and Chinmay Nirkhe) proves this conjecture by showing that the recently discovered families of constantrate and lineardistance QLDPC codes correspond to NLTS local Hamiltonians. This talk will provide background on the conjecture, its relevance to quantum manybody physics and quantum complexity theory, and touch upon the proof techniques.
September 6, 2022
Phuc Nguyen, Brandeis University
"Lightray moments as endpoint contributions to modular Hamiltonians"
Abstract: We consider excited states in a CFT, obtained by applying a weak unitary perturbation to the vacuum. The perturbation is generated by the integral of a local operator J of modular weight n over a spacelike surface. We show that the modular Hamiltonian with respect to the excited state and the Rindler subregion has a contribution associated with the entangling surface, which has the form of a sum of lightray moments of the perturbing operator J and its descendants. This endpoint contribution is sensitive to the details of the perturbation near the entangling surface, including the shape of the spacelike surface. For perturbations on null planes only moments of J itself appear in the endpoint contribution.
September 13, 2022
Jonathan Sorce, Massachusetts Institute of Technology
"The connected wedge theorem and its consequences"
Abstract: I will discuss new work with Alex May and Beni Yoshida that elaborates the connection between bulk causal structure and boundary entanglement in AdS/CFT. The key result is a new theorem showing that certain complicated bulk causal structures must be supported by an associated pattern of largeN bipartite boundary entanglement. I will also explain how this gravityoriented program has taught us new things about quantum information theory that have implications for nongravitational physics.
September 20, 2022
Gong Cheng, University of Maryland
"Large N Matrix Quantum Mechanics as a Quantum Memory"
Abstract: We explore the possibility of building a quantum memory that is robust to thermal noise using large N matrix quantum mechanics models. First, we investigate the gauged SU(N) matrix harmonic oscillator and different ways to encode quantum information in it. By calculating the mutual information between the system and a reference which purifies the encoded information, we identify a transition temperature, Tc, below which the encoded quantum information is protected from thermal noise for a memory time scaling as N^2. Conversely, for temperatures higher than Tc, the information is quickly destroyed by thermal noise. Second, we relax the requirement of gauge invariance and study a matrix harmonic oscillator model with only global symmetry. Finally, we further relax even the symmetry requirement and propose a model that consists of a large number N^2 of qubits, with interactions derived from an approximate SU(N) symmetry. In both ungauged models, we find that the effects of gauging can be mimiced using an energy penalty to give a similar result for the memory time. The final qubit model also has the potential to be realized in the laboratory.
October 4, 2022
Åsmund Folkestad, Massachusetts Institute of Technology
"The Penrose Inequality as a Constraint on Low Energy Quantum Gravity"
Abstract: In this talk, I argue that the Penrose inequality (PI) can be used to constrain low energy theories compatible with AdS/CFT. It is shown that the PI can be violated for minimally coupled scalar fields, and I produce exclusion plots on couplings that respect the PI. I also present numerical evidence that topdown scalar theories and supersymmetric theories respect the PI. In the case where the dominant energy condition holds, a proof of the PI for spherical, planar or hyperbolic symmetry is given. Finally, similar to the BreitenlohnerFreedman bound, I give a necessary condition for the stability AdS that constrains coupling constants (beyond the scalar mass).
October 11, 2022
Dan Carney, Lawrence Berkeley National Laboratory
"Comments on hunting the graviton"
Abstract: Detecting “a graviton” is an obviously interesting goal, if it is possible. Dyson has given some compelling arguments that this might be impossible. I’ll review his arguments and suggest two possible alternatives. One is that it may be possible to detect entanglement generated between mesoscopic objects through their gravitational interactions; I’ll review some proposals for this and discuss to what extent this is related to the existence of gravitons. The other is a more direct counter example to Dyson’s argument, using certain axion detector architectures repurposed as graviton detectors.
October 25, 2022
Eugene Tang, Massachusetts Institute of Technology
"Recent developments in asymptotically good quantum lowdensity parity check codes"
Abstract: Lowdensity parity check (LDPC) codes are errorcorrecting codes which encode information in an extremely succinct manner. Classically, LDPC codes are a gold standard for errorcorrection, used today for everything from WiFi to solidstate memories. A long standing open problem in quantum errorcorrection is the existence of asymptotically good families of quantum LDPC codes, i.e., codes defined by lowweight stabilizers that encode a maximum amount information and correct a maximum amount of errors. In this talk, I will survey the recent developments on LDPC codes, culminating in the explicit construction of good quantum LDPC codes in 2021. Time permitting, we will talk about their role as efficient quantum memories and other consequences for physics and computer science.
November 1, 2022
ShuHeng Shao, Stony Brook University
"Fractons on Graphs"
Abstract: What lattice models can be defined on a general graph, which only has vertices and edges? Ising model is the simplest such example. We present some new lattice models that can be defined on a general graph, based on the discrete Laplacian operator. Some of them are fracton/lineon models, and their ground state degeneracies are related to the complexity of the graph.
November 8, 2022
Zhencheng Wang, University of California, Santa Barbara
"Null states and time evolution in a toy model of black holes"
Abstract: Recent work has shown that by taking into account nonperturbative contributions to the gravitational path integral, the actual number of degrees of freedom becomes much smaller than the number of degrees of freedom predicted by semiclassical EFT. In particular, in the context of black hole evaporation, this guarantees that entropy of the radiation is bounded by the BekensteinHawking entropy, thus produces the Page curve. This establishes a map between a larger ``naive" Hilbert space and a smaller ``physical" Hilbert space, where a large number of null states are quotiented out. In this talk, I will discuss two questions about the dynamics of quantum gravity in the presence of null states: 1) Can we transfer null states into a gravitational system by coupling it to a nongravitational quantum system? 2) How do we compare time evolutions in the naive and physical Hilbert spaces? I will show explicit results that address these two questions using the MarolfMaxfield topological gravity model as a toy model. This talk is based on work in progress with Xi Dong, Maciej Kolanowski, Xiaoyi Liu and Donald Marolf.
November 15, 2022
Martin Sasieta, Brandeis University
"Wormholes from heavy operator statistics in AdS/CFT"
Abstract: We construct simple higher dimensional euclidean wormhole solutions that reproduce the statistical description of the correlation functions of an ensemble of heavy CFT operators. Effectively, the operators backreact on the geometry in the form of a thin shell of dust particles. Assuming dynamical chaos in the form of the ETH ansatz for the operator, we demonstrate how these wormholes arise from the statistical description of its matrix elements in the spectrum of the CFT. The solutions correspond to saddle points dominated different microcanonical bands in the CFT. We show that these wormholes encode the intrinsic noise amplitude of the black hole in the twopoint correlation function of the heavy operator at late times. Finally, we elaborate on the role of these wormholes in the context global symmetry violating effects in quantum gravity.
November 29, 2022
Sergio Hernandez Cuenca, Massachusetts Institute of Technology
"Replica wormholes and the spectrum of nearextremal black holes"
Abstract: Since most of us are probably still feeling a heavy stomach after Thanksgiving, I will give a blackboard talk that is hopefully easy to digest. I will begin by explaining a general lowtemperature pathology that thermal entropies suffer from when the spectral density of a system lacks a discrete ground state. The appearance of this pathology in all computed examples for nearextremal black holes, and its absence for those which preserve some supersymmetry at extremality, will provide a consistent picture of why a correct inclusion of wormhole contributions to the gravitational path integral should suffice for fixing these issues. In particular, I will argue that a nonperturbative completion of the topological expansion in gravity is not needed, but that replica wormholes are essential for restoring lowtemperature thermodynamics, studying spectral statistics near extremality, and extending microstate counting beyond BPS black holes.
Spring 2022
January 25, 2022
Gregory Bentsen, Brandeis University
"Protecting quantum information with sparse nonlocal interactions"
Abstract: Entanglement is a valuable resource, but it tends to be very fragile. Recent work driven by Clifford circuit simulations, however, has demonstrated that strong scrambling can generate volumelaw entanglement that persists despite the presence of ongoing continuous measurement. In this talk I describe how fast scrambling dynamics generated by longrange and sparse nonlocal interactions can be used to improve a system’s robustness to measurement, allowing for manybody entanglement to survive at substantially higher rates of measurement compared to circuits featuring only local interactions. Further, I will show that these longrange interactions also improve the code properties (code rate, code distance) of the dynamicallygenerated errorcorrecting codes which underpin the volumelaw phase. Nonlocal interactions of this type can be implemented in nearterm quantum simulators using cavities with a multifrequency drive or in Rydberg chains with tweezerassisted shuffling.
February 1, 2022
Eric Sharpe, Virginia Tech
"An introduction to decomposition"
Abstract: In this talk I will review recent work on `decomposition,' a property of 2d theories with 1form symmetries and, more generally, ddim'l theories with (d1)form symmetries. Decomposition is the observation that such quantum field theories are equivalent to ('decompose into’) disjoint unions of other QFTs, known in this context as "universes." Examples include twodimensional gauge theories and orbifolds with matter invariant under a subgroup of the gauge group. Decomposition explains and relates several physical properties of these theories  for example, restrictions on allowed instantons arise as a "multiverse interference effect" between contributions from constituent universes. First worked out in 2006 as part of efforts to understand string propagation on stacks, decomposition has been the driver of a number of developments since. In the first half of this talk, I will review decomposition; in the second half, I will focus on the recent application to anomaly resolution of WangWenWitten in twodimensional orbifolds.
February 8, 2022
Phuc Nguyen, Lehman College, CUNY
"Scrambling and the black hole atmosphere"
Abstract: We argue that the scrambling time is the same, up to a numerical factor in three or more spacetime dimensions, as the time for the atmosphere to fall across the horizon or escape, to be replaced by new atmosphere. We propose that these times agree because the physical scrambling process is part and parcel of the atmosphere refreshment process. We provide some support for this relation also in two dimensions, but the atmosphere is not as localized, so the argument is less justified.
February 15, 2022
Albion Lawrence, Brandeis University
"Ocean turbulence from space"
Abstract: In this talk I will first outline some basic regimes of ocean dynamics, organized by spatial and temporal scales. I will then describe the use of satellite altimetry to observe ocean dynamics for ``balanced" motions in which the Coriolis and gravitational forces dominate the NavierStokes equations. Finally, I will discuss a current theory of the energization of the submesoscale, at which vertical motion becomes important, and give evidence from altimetry that this picture is correct. This talk is based on work with Jörn Callies at Caltech; a preprint can be found at https://arxiv.org/abs/2201.09136.
March 1, 2022
Sumit Das, University of Kentucky
"AdSKasner and Path Integral Complexity"
Abstract: Over many years, AdSKasner backgrounds have been used to probe signatures of spacelike singularities in the field theory dual. In this talk I will first briefly review aspects of earlier work in this direction. I will then describe some recent work on the behavior of path integral complexity and its universality in these backgrounds.
March 8, 2022
Dan Roberts, Massachusetts Institute of Technology
"The Principles of Deep Learning Theory"
Abstract: Deep learning is an exciting approach to modern artificial intelligence based on artificial neural networks. The goal of this talk is to provide a blueprint — using tools from physics — for theoretically analyzing deep neural networks of practical relevance. This task will encompass both understanding the statistics of initialized deep networks and determining the training dynamics of such an ensemble when learning from data. Borrowing from the "effective theory" framework of physics and developing a perturbative 1/n expansion around the limit of infinite hiddenlayer width, we will find a principle of sparsity that will let us describe effectivelydeep networks of practical largebutfinitewidth networks. This talk is based on a book, "The Principles of Deep Learning Theory," coauthored with Sho Yaida and based on research also in collaboration with Boris Hanin. It will be published this summer by Cambridge University Press.
March 15, 2022
Charles Cao, University of Maryland
"Fun with Quantum Lego"
Abstract: The quantum gravity community has benefited immensely from quantum information theoretic concepts in the past decade. In this talk, we take the reverse direction and look at how progress in AdS/CFT can return the favour. Inspired by the holographic codes, I introduce a flexible and graphically intuitive framework that constructs complex quantum error correction codes from simple codes or states, generalizing code concatenation. More specifically, we represent the complex code constructions as tensor networks built from the tensors of simple codes or states in a modular fashion. Using a set of local moves known as operator pushing, one can derive properties of the more complex codes, such as transversal nonClifford gates, by tracing the flow of operators in the network. To highlight the framework's range of capabilities and to provide a tutorial, I lay out some examples where we construct and customize nontrivial codes using simple quantum lego blocks. Surprisingly, we also find that the surface code is equivalent to the 2d BaconShor code after ``dualizing'' its tensor network encoding map.
March 29, 2022
Ning Bao, Northeastern University
"The Holographic Fault Tolerance Threshold is the HawkingPage Phase Transition"
Abstract: We study the error threshold properties of holographic quantum errorcorrecting codes. We demonstrate that holographic CFTs admit an algebraic threshold, which is related to the confinementdeconfinement phase transition. We then apply geometric intuition from holography and the HawkingPage phase transition to motivate the CFT result, and comment on potential extensions to other confining theories.
April 12, 2022
Lukas Homeier, LMU Munich
"Quantum Simulation of Z2 lattice gauge theories with dynamical matter in (2+1)D"
Abstract: Gauge fields coupled to dynamical matter are a universal framework in many disciplines of physics, ranging from particle to condensed matter physics, but remain poorly understood at strong couplings. In the past years a new perspective has emerged through analog quantum simulation platforms which have become a powerful tool to study interacting quantum manybody systems in a highly controllable fashion. Here we propose a scheme, in which a Z2 gauge structure emerges from local two and onebody interactions in two spatial dimensions. The scheme is suitable for Rydberg atom arrays and enables to experimentally study both (2+1)D Z2 lattice gauge theories coupled to dynamical matter (Z2 mLGT) and quantum dimer models on the honeycomb lattice, for which we derive effective Hamiltonians. We discuss ground state phase diagrams of the effective Z2 mLGT for U(1) and quantum Z2 matter featuring deconfined phases. Further, we present experimental perspectives and show signatures of disorderorder free localization as well as the Schwinger effect in (2+1)D using smallscale exact diagonalization studies. Our proposed scheme allows to experimentally study not only longstanding goals of theoretical physics, such as Fradkin and Shenker's conjectured phase diagram, but also go beyond currently accessible numerical regimes.
April 26, 2022
Natalia PinzaniFokeeva, Massachusetts Institute of Technology
"Enstrophy and black hole supertranslations"
Abstract: Enstrophy is an approximately conserved charge in 2+1 dimensional nonrelativistic fluids that implies an inverse energy cascade in turbulent flows. In this talk, I will present an algorithm on how to construct an enstrophy current for generic fluid flows (relativistic and non). In addition, I will show how a subset of certain horizon symmetries of 3+1 dimensional AdS black holes also leads to enstrophy conservation in the dual holographic fluid theory.
June 7, 2022
Romain Vasseur, University of Massachusetts, Amherst
"Measurementinduced criticality and chargesharpening transitions"
Abstract: Monitored quantum circuits (MRCs) exhibit a measurementinduced phase transition between arealaw and volumelaw entanglement scaling as a function of the measurement rate. In this talk, I will first review our understanding of such measurementinduced phase transitions. I will argue that MRCs with a conserved charge additionally exhibit two distinct volumelaw entangled phases that cannot be characterized by equilibrium notions of symmetrybreaking or topological order, but rather by the nonequilibrium dynamics and steadystate distribution of charge fluctuations. These include a chargefuzzy phase in which charge information is rapidly scrambled leading to Luttingerliquidlike spatial fluctuations of charge in the steady state, and a chargesharp phase in which measurements collapse quantum fluctuations of charge without destroying the volumelaw entanglement of neutral degrees of freedom. I will present some statistical mechanics and effective field theory approaches to such chargesharpening transitions.
Fall 2021
September 13, 2021
Xiao Chen, Boston College
"Emergent criticality in nonunitary random dynamics"
Abstract: We present random quantum circuit models for nonunitary quantum dynamics of free fermions in one spatial dimension. Numerical simulations reveal that the dynamics tends toward steady states with logarithmic violations of the entanglement area law and power law correlation functions. Moreover, starting with a shortrange entangled manybody state, the dynamical evolution of entanglement and correlations quantitatively agrees with the predictions of twodimensional conformal field theory with a spacelike time direction. We argue that this behavior is generic in nonunitary free quantum dynamics with timedependent randomness, and we show that the emergent conformal dynamics of twopoint functions arises out of a simple “nonlinear master equation.” In addition, we construct solvable quadratic SachdevYeKitaev chains with nonunitary dynamics in the large N limit and we argue the emergent conformal field theory is due to the existence of the Goldstone modes in the enlarged replica space.
September 20, 2021
ShaoKai Jian, Brandeis University
"Phase transition in von Neumann entanglement entropy from replica symmetry breaking"
Abstract: We study the entanglement transition in monitored Brownian SYK chains in the largeN limit. Without measurement the steady state nth Renyi entropy is obtained by summing over a class of solutions, and is found to saturate to the Page value in the \(n \rightarrow 1\) limit. In the presence of measurements, the analytical continuation \(n \rightarrow 1\) is performed using the cyclic symmetric solution. The result shows that as the monitoring rate increases, a continuous von Neumann entanglement entropy transition from volumelaw to arealaw occurs at the point of replica symmetry unbreaking.
October 4, 2021
Vladimir Narovlansky, Princeton University
"Negativity in random tensor networks and holography"
Abstract: We will discuss mixed state entanglement in random tensor networks, using the notion of negativity. Tensor networks are useful in manybody physics, as well as in holography, particularly in fixedarea states. We find the negativity spectrum, which is the analog of entanglement spectrum, in a general random tensor network with large bond dimensions, using a related flow network problem. We also study mixed states of a system coupled to gravity, such as a black hole with its Hawking radiation. We find island contributions in such systems, and show the Euclidean wormhole origin of these contributions in a JackiwTeitelboim gravity model.
October 11, 2021
Djordje Radicevic, Brandeis University
"Confinement and Flux Attachment"
Abstract: Fluxattached gauge theories are a novel class of lattice gauge theories whose gauge constraints involve both electric and magnetic operators. Like ordinary gauge theories, they possess confining phases. Unlike ordinary gauge theories, their confinement does not imply a trivial gapped vacuum. Instead, the confining phases subtly straddle a boundary between topological and trivial phases. I will describe some salient properties of these phases for different choices of flux attachment. In particular, I will demonstrate a simple example of a gapped, local theory whose topological entanglement entropy is positive (i.e. whose total quantum dimension is less than one).
October 19, 2021
Chanda PrescodWeinstein, University of New Hampshire, Durham
"Large Scale Structure from Microphysics"
Abstract: In this talk, I will describe my efforts to understand the nature of the mysterious dark matter. I provide an overview of the general problem and then describe my current approach to it, which is to characterize the behavior of a proposed dark matter particle, the axion. I will give some insight into how I am using a range of tools  model building, computation, and neutron stars  to get at the basic question of “what is the statistical mechanics of axion dark matter?” I will discuss work that shows that the selfinteraction should not be ignored and that the sign of the interaction makes a significant difference in the evolution of the system, both for QCD axions and fuzzy dark matter.
October 25, 2021
Lorenzo di Pietro, University of Trieste
"Analyticity and Unitarity for Cosmological Correlators"
Abstract: Based on https://arxiv.org/abs/2108.01695. I will consider quantum field theory on a rigid de Sitter space. I will first discuss how the perturbative expansion of latetime correlation functions to all orders can be equivalently generated by a nonunitary Lagrangian on a Euclidean AdS geometry. I will use this to explain the analytic structure of the spectral density that characterize a latetime fourpoint function. Then I will discuss a positivity condition that encodes the unitarity of the time evolution in the bulk de Sitter space. If time permits I will discuss some concrete examples in perturbation theory that illustrate these properties.
November 1, 2021
Jieqiang Wu, University of California, Santa Barbara
"Algebra of diffeomorphism invariant observables in JackiwTeitelboim gravity"
Abstract: Diffeomorphism symmetry is an intrinsic difficulty in gravitational theory, which appears in almost all of the questions in gravity. As is well known, the diffeomorphism symmetries in gravity should be interpreted as gauge symmetries, so only diffeomorphism invariant operators are physically interesting. However, because of the nonlinear effect of gravitational theory, the results for diffeomorphism invariant operators are very limited.
In this work, we focus on the JackiwTeitelboim gravity in classical limit, and use Peierls bracket (which is a linear response like computation of observables’ bracket) to compute the algebra of a large class of diffeomorphism invariant observables. With this algebra, we can reproduce some recent results in JackiwTeitelboim gravity including: traversable wormhole, scrambling effect, and SL(2) charges. We can also use it to clarify the question of when the creation of an excitation deep in the bulk increases or decreases the boundary energy, which is of crucial importance for the “typical state” version of the firewall paradox.
In the talk, I will first give a brief introduction of Peierls bracket, and then use the Peierls bracket to study the brackets between diffeomorphism invariant observables in JackiwTeitelboim gravity. I will then give two applications of this algebra: reproducing the scrambling effect, and studying the energy change after creating an excitation in the bulk. Reference: 2108.04841
November 8, 2021
Grant Remmen, University of California, Santa Barbara
"Amplitudes and the Riemann Zeta Function"
Abstract: In this talk, I will connect physical properties of scattering amplitudes to the Riemann zeta function. Specifically, I will construct a closedform amplitude, describing the treelevel exchange of a tower with masses \(m^2_n = \mu^2_n\), where \(\zeta(\frac{1}{2}\pm i \mu_n) = 0\). Requiring real masses corresponds to the Riemann hypothesis, locality of the amplitude to meromorphicity of the zeta function, and universal coupling between massive and massless states to simplicity of the zeros of \(\zeta\). Unitarity bounds from dispersion relations for the forward amplitude translate to positivity of the odd moments of the sequence of \(1/\mu^2_n\).
November 15, 2021
Paul Fendley, University of Oxford
"Free fermions and parafermions"
Abstract: Free fermions are ubiquitous in theoretical physics. Typically such models are found by expressing the Hamiltonian and/or action as a sum or integral over bilinears of local fermionic operators or fields, sometimes requiring a JordanWigner transformation. I describe models that become free fermionic only after under a much subtler transformation that is both nonlocal and nonlinear in the original interacting fermions. Including also the usual fermion bilinears breaks the solvability but allows a simple lattice analog of an interacting conformal field theory, very useful for numerical analysis. I will also give a brief overview of how freeparafermion chains can be solved in a similar fashion.
November 22, 2021
Jordan Cotler, Harvard University
"Black hole microstate statistics from Euclidean wormholes"
Abstract: Over the last several years, it has been shown that black hole microstate level statistics in various models of 2D gravity are encoded in wormhole amplitudes. These statistics quantitatively agree with predictions of random matrix theory for chaotic quantum systems; this behavior is realized since the 2D theories in question are dual to matrix models. But what about black hole microstate statistics for Einstein gravity in 3D and higher spacetime dimensions, and ultimately in nonperturbative string theory? We will discuss progress in these directions. In 3D, we compute a wormhole amplitude that encodes the energy level statistics of BTZ black holes. In 4D and higher, we find analogous wormholes which appear to encode the level statistics of black holes. Finally, we study analogous Euclidean wormholes in the lowenergy limit of type IIB string theory; we provide evidence that they encode the level statistics of black holes in AdS5 x S5. Remarkably, these wormholes appear to be stable in appropriate regimes, and dominate over braneantibrane nucleation processes in the computation of black hole microstate statistics.
November 29, 2021
Jonathan Harper, Brandeis University
"An introduction to hyperthreads"
Abstract: Bit threads, a dual description of the RyuTakayanagi formula for holographic entanglement entropy (EE), can be interpreted as a distillation of the quantum information to a collection of bell pair between different boundary regions. In this talk I will discuss a generalization to hyperthreads which can connect more than two boundary regions leading to a rich and diverse class of convex programs. By modeling the contributions of different species of hyperthreads to the EE’s of simple multipartite states (namely GHZ and perfect tensors) I will argue that this framework may be useful for helping us to begin to probe the multipartite entanglement of holographic systems. Furthermore, I will demonstrate how this technology can potentially be used to understand or possibly prove entropy cone inequalities and may provide an avenue to address issues of locking.
December 2, 2021
Chris Akers, Massachusetts Institute of Technology
"Quantum minimal surfaces from quantum error correction"
Abstract: In 2016 Harlow taught us that we can understand the RyuTakayanagi formula as a feature of quantum error correction. This explained how we should think about both the entanglement wedge and the area term in the formula. However, his analysis only applied in the special case of small code subspaces, in which the entanglement wedge is the same for all states. I'm going to tell you about my recent work with Geoff Penington, in which we generalize this story to arbitrarily large code subspaces. Moreover, we derive that the entanglement wedge should minimize the area plus entropy of bulk fields. This involves defining the entanglement wedge via a new kind of quantum error correcting code, reducing to Harlow's in the appropriate special case. This also naturally leads to a precise quantum information theoretic definition of the area of bulk surfaces. Based on https://arxiv.org/abs/2109.14618.
Spring 2021
February 15, 2021
Brian Swingle, Brandeis University
"Towards Transport and Operator Growth at Low Temperature"
Abstract: We now have a variety of tools and solvable models to address energy/charge transport and operator growth at high temperature in quantum lattice models. However, we have much less control over the low temperature regime, where we expect a field theory description. I'll talk about some progress in this direction reported in two recent papers, one on transport with Cris Zanoci (2012.11601) and one on operator growth with Subhayan Sahu (2005.10814). I'll emphasize open questions and opportunities for collaboration.
February 22, 2021
Djordje Radicevic, Brandeis University
"Lessons from the latticecontinuum correspondence"
Abstract: A year ago, I described plans for a comprehensive study of the latticecontinuum correspondence, an effort to quantitatively understand how continuum QFTs can emerge from large but finite quantum systems. The fundamentals of this correspondence are now established for Abelian QFTs with scalars, fermions, and gauge fields in all dimensions. This has lead to many new insights into old questions, not least of which is a new way to rigorously define many continuum QFTs using their lattice counterparts. I will give a basic overview of this research program and will then describe some of its consequences: a definition of operator product expansions directly on the lattice, new insights into phase structures of compact scalars and Abelian gauge theories, and a generalization of Noether's theorem to discrete symmetries.
March 1, 2021
Gregory Bentsen, Brandeis University
"MeasurementInduced Phase Transitions at Large N"
Abstract: Measurementinduced phase transitions (MIPT) are a novel class of dynamical quantum manybody phase transitions driven by a competition between unitary scrambling dynamics, which generate manybody entanglement, and local projective measurements, which tend to destroy this entanglement. While these phase transitions are clearly visible in numerical experiments with Clifford circuits, analytical approaches are limited and the nature of the critical point remains unclear. Here we approach this problem using a Brownian circuit model, and obtain a pathintegral expression for the order parameter featuring a largeN limit that can be analyzed exactly using steepestdescent methods. For the simplest Brownian circuit model, we find that the transition is described by a $Z_2$ symmetrybreaking transition, reminiscent of the classical Ising model with the measurement rate $p$ playing the role of temperature. In future work we hope to apply this technology to the study of MIPT dynamics in more general models, with a view toward understanding the various universality classes represented by MIPT dynamics.
March 8, 2021
Steve Naculich, Bowdoin College
"A Tale of Two Exponentiations in N=8 Supergravity"
Abstract: Fourpoint gravitational scattering amplitudes can exhibit two types of exponentiation. In momentum space, oneloop infrared divergences exponentiate to give higherloop amplitudes modulo an IRfinite remainder function. On the other hand, at high energies and small angles, the fourpoint amplitude can be expressed in impact parameter space as the exponential of an eikonal phase. We explore the interplay of these two types of exponentiation in N=8 supergravity, and show how each can inform us about the structure of the other.
March 22, 2021
Irene Valenzuela, Harvard University
"ChernWeil Global Symmetries and How Quantum Gravity Avoids Them"
Abstract: The Swampland program aims to determine the constraints that an EFT must satisfy to be consistent with a UV completion in quantum gravity. One of the most important proposed constraints is the absence of global symmetries, meaning that any global symmetry must be gauged or broken. In this talk, I will discuss a class of generalized global symmetries, which we call “ChernWeil global symmetries,” that arise ubiquitously in gauge theories. The Noether currents of these ChernWeil global symmetries are given by wedge products of gauge field strengths and their conservation follows from Bianchi identities, so they are not easy to break. However, exact global symmetries should not be allowed in a consistent theory of quantum gravity, and how quantum gravity avoids them can teach us many things about the physics of UV consistent EFTs. In particular, I will explain how these symmetries are typically gauged or broken in string theory. Interestingly, many familiar phenomena in string theory, such as axions, ChernSimons terms, worldvolume degrees of freedom on extended objects, and branes ending on or dissolving in other branes, can be interpreted as consequences of the absence of ChernWeil symmetries in quantum gravity, suggesting that they might be general features of quantum gravity.
March 31, 2021
Sarah Shandera, Pennsylvania State University
"Subsystem statistics for outofequilibrium qubits"
Abstract: Motivated by questions asked in cosmology to understand the origin of structure in the universe, I will introduce a family of qubit systems initialized and evolved according to rules designed to mimic the thermodynamics of the early universe. I will present results on the correlation properties and statistics of all sizes of subsystem, which give preliminary data toward answering the question: What are the minimum ingredients required in order for the variance of the free energy in small subsystems to increase in time?
April 5, 2021
Philipp Kunkel, Stanford University
"Programmable interactions in an array of atomic ensembles"
Abstract: I will present our recent experimental advances in generating highly tunable interactions between neutral atoms which offers new prospects for quantum computation as well as quantum simulation. Our system consists of a 1D array of atomic ensembles coupled to an optical cavity which induces spinmixing between the atoms. Controlling the spectrum of the drive field enables us to tune the sign as well as the range of these interactions. I will show how we use this technique to implement dynamics in various effective geometries such as frustrated 2D lattices and treelike geometries where the latter are connected to holographic models of quantum gravity. In the realm of quantum information, these new capabilities pave the way to engineer quantum states with specific spatial entanglement structures for quantum sensing and quantum computation.
April 12, 2021
David Poland, Yale University
"Charting the Landscape of 3d CFTs"
Abstract: I will summarize progress at using the conformal bootstrap to solve 3d CFTs. These include the critical 3d Ising model, the O(N) vector models, and the minimal 3d SCFT. Recent results for the O(2) modelresolve a longstanding discrepancy between experiment and and Monte Carlo simulations, while results for the O(3) model prove the instability of Heisenberg magnets to cubic anisotropy.
April 19, 2021
Arthur Hebecker, University of Heidelberg
"From Swampland and Weak Gravity to Global Symmetries and Wormholes"
Abstract: After a brief reminder of the Swampland idea in general and the Weak Gravity Conjecture in particular, I will focus on global symmetries. Given that exact global symmetries are forbidden by quantum gravity, it is natural to expect that bounds on the quality of approximate global symmetries exist. So far, holographic arguments have only been provided for the exact case. I will discuss a classification of approximate global symmetries and describe a simple argument, based the Weak Gravity Conjecture, for a quantitative bound on the subclass of "gaugederived" global symmetries. This has intriguing relations to wormholebased arguments, which I will also present. I will end with a brief discussion of the fundamental problems associated with euclidean wormholes and of some recent developments in this context.
April 26, 2021
Andrew Daley, University of Strathclyde
"Manybody dynamics and quantum advantage with cold atom quantum simulators"
Abstract: The exceptional control available in experiments with cold atoms in optical potentials, and with trapped ions, has opened new opportunities to explore manybody quantum dynamics with timedependent control. This goes beyond existing manybody systems as we are able to engineer unique features such as genuine longrange interactions, and microscopic control over dissipation. In analogy with the quantum optics of single atoms and photons, we can often work in scenarios where the separations of relevant energy scales allows us to write microscopic models for open quantum systems  with strong interparticle interactions. I will give an overview of the capabilities of these systems, illustrated with some of our theory group's recent work on coherent dynamics with longrange interactions and controlled dissipative dynamics. I will also address the question of whether quantum simulators already allow us quantitative access to controlled dynamics beyond the computational abilities of existing classical computers, i.e., a practical quantum advantage.
May 3, 2021
Brianna GradoWhite, Brandeis University
"Multimouth Traversable Wormholes"
Abstract: Recently, several examples of traversable wormholes supported by wellcontrolled quantum effects and respecting reasonable energy conditions have been constructed. In this talk, I will describe generalizations of such solutions involving more than two mouths in the same asymptotic region. These wormholes may be traversed between any pair of mouths, are four dimensional, and are asymptotically flat up to the presence of possible magnetic fluxes or cosmic strings that extend to infinity. From a dual field theory point of view, when AdS asymptotics are added to our construction, multiparty entanglement may play an important role in the traversability of the resulting wormhole.
May 10, 2021
Thomas Schuster, University of California, Berkeley
"Manybody quantum teleportation via operator spreading in the traversable wormhole protocol"
Abstract: By leveraging shared entanglement between a pair of qubits, one can teleport a quantum state from one particle to another. Recent advances have uncovered an intrinsically manybody generalization of quantum teleportation, with an elegant and surprising connection to gravity. In particular, the teleportation of quantum information relies on manybody dynamics, which originate from stronglyinteracting systems that are holographically dual to gravity; from the gravitational perspective, such teleportation can be understood as the transmission of information through a traversable wormhole. In this talk, I will introduce a new mechanism for manybody quantum teleportation  dubbed peakedsize teleportation. Intriguingly, peakedsize teleportation utilizes precisely the same quantum circuit as traversable wormhole teleportation, yet has a completely distinct microscopic origin: it relies upon the spreading of local operators under generic thermalizing dynamics and not gravitational physics. I will demonstrate peakedsize teleportation across a variety of physical systems, including random unitary circuits and the SachdevYeKitaev model (at high temperatures). I will conclude by outlining potential experimental realizations of manybody quantum teleportation, with applications to: (i) characterizing the size distributions of operators in stronglycorrelated systems and (ii) distinguishing between generic and intrinsically gravitational scrambling dynamics.
Fall 2020
September 14, 2020
Delilah Gates, Harvard University
"Maximum Observable Blueshift from Circular Equatorial Kerr Orbiters"
Abstract: The region of spacetime near the event horizon of a black hole can be viewed as a deep potential well at large gravitational redshift relative to distant observers. However, matter orbiting in this region travels at relativistic speeds and can impart a significant Doppler shift to its electromagnetic emission, sometimes resulting in a net observed blueshift at infinity. In this talk we investigate emission produced by isotropic monochromatic emitters on circular equatorial orbits around a Kerr black hole, and obtain simple relations describing how the maximum blueshift encodes black hole spin and inclination. We find that small values of the maximum blueshift yield an excellent probe of inclination, while larger values provide strong constraints on spin or inclination in terms of the other.
September 21, 2020
Geoff Penington, University of California, Berkeley
"Leading order corrections to the quantum extremal surface prescription"
Abstract: We show that a naïve application of the quantum extremal surface (QES) prescription can lead to paradoxical results and must be corrected at leading order. The corrections arise when there is a second QES (with strictly larger generalized entropy at leading order than the minimal QES), together with a large amount of highly incompressible bulk entropy between the two surfaces. We trace the source of the corrections to a failure of the assumptions used in the replica trick derivation of the QES prescription, and show that a more careful derivation correctly computes the corrections. Using tools from oneshot quantum Shannon theory (smooth min and maxentropies), we generalize these results to a set of refined conditions that determine whether the QES prescription holds. We find similar refinements to the conditions needed for entanglement wedge reconstruction (EWR), and show how EWR can be reinterpreted as the task of oneshot quantum state merging (using zerobits rather than classical bits), a task gravity is able to achieve optimally efficiently.
September 30, 2020
Pratik Rath, University of California, Berkeley
"The Page Curve for Reflected Entropy"
Abstract: Reflected Entropy is a bipartite correlation measure with a simple geometric holographic dual, the minimal entanglement wedge cross section. This duality further motivates the idea that spacetime emerges from entanglement. Further, it illustrates the richness of the multipartite entanglement structure of holographic systems. A particularly interesting feature that we focus on in this talk is the phase transition between a connected and disconnected entanglement wedge where the reflected entropy jumps discontinuously. We explain how this phase transition is resolved in random tensor networks which serve as toy models for holography. This argument based on the replica trick motivates a general ansatz for the mechanism of the phase transition in AdS/CFT.
October 5, 2020
Luca Delacretaz, University of Chicago
"Heavy Operators and Hydrodynamic Tails"
Abstract: The late time physics of interacting QFTs at finite temperature is controlled by hydrodynamics. For CFTs this implies that heavy operators  which are generically expected to create thermal states  can be studied semiclassically. We show that hydrodynamics universally fixes the OPE coefficients C_{HH'L}, on average, of all neutral light operators with two nonidentical heavy ones, as a function of the scaling dimension and spin of the operators. These methods can be straightforwardly extended to CFTs with global symmetries, and generalize recent EFT results on large charge operators away from the case of minimal dimension at fixed charge. I will also revisit certain aspects of late time thermal correlators in QFT and other diffusive systems.
October 12, 2020
Horacio Casini, Centro Atomico Bariloche
"Entropic order parameters for symmetries in QFT"
Abstract: In QFT there is an algebra of operators attached to any spacetime region. Simple degradations of the most harmonious possible relation between algebras and regions are shown to encode generalized symmetries. Nets of algebras with these symmetries allow for a non uniqueness of the algebras that can be assigned to a given region. This non uniqueness suggests a simple geometrical order parameter in terms of a relative entropy. These satisfy a ''certainty relation'' connecting the statistics of the order and disorder parameters for complementary regions. We describe how the lore about phases of theories with generalized symmetries is seen in this new picture.
October 19, 2020
Jennie Traschen, UMass Amherst
"The Schottky Anomaly of de Sitter Black Holes"
Abstract: Black holes with Λ > 0 (SdS) have fascinating properties that are distinct from the asymptotically flat or AdS cases, starting with the fact that there are two horizons in the spacetime, one black hole and one cosmological. The two horizons have different temperatures and the total gravitational entropy is the sum of the horizon areas. As a result, both the mass M and entropy S are bounded between minimum and maximum values. Intriguingly, there is an extremum in the specific heat ∂M/∂Tb as well as in the curve ∂S/∂Tb, which resemble the Schottky anomaly of a two level system in statistical mechanics. In this talk we investigate classical and quantum mechanical features of SdS thermodynamics that make it resemble the physics of a paramagnet. We start by showing that the Schottky behavior is to be expected for classical fluctuations based on the first laws for SdS black holes. Second, we present calculations of black hole and cosmological particle production in SdS and find that the quantum fluctuations share the behavior of classical ones.
November 2, 2020
Alexey Milekhin, Princeton University
"Quantum error correction and large N"
Abstract: In recent years quantum error correction(QEC) has become an important part of AdS/CFT. Unfortunately, there are no fieldtheoretic arguments about why QEC holds in known holographic systems. The purpose of this talk is to fill this gap by studying the error correcting properties of the fermionic sector of various large N theories. Specifically we examine SU(N) matrix quantum mechanics and 3rank tensor O(N)^3theories. Both of these theories contain large gauge groups. We argue that gauge singlet states indeed form a quantum error correcting code. Our considerations are based purely on large N analysis and do not appeal to a particular form of Hamiltonian or holography.
November 9, 2020
Anton Kapustin, California Institute of Technology
"WessZuminoWitten terms and the geometry and topology of lattice systems"
Abstract: WessZuminoWitten terms are topologicallynontrivial terms in the effective actions which arise from integrating out shortdistance degrees of freedom which couple of slowlyvarying scalar fields. They can be viewed as higherdimensional generalizations of the Berry connection. This viewpoint suggests that WZW terms encode the nontrivial topology of the space of massive field theories and should arise also in the context of gapped lattice systems. I will explain how to compute WZW terms for a family of gapped lattice systems in d spatial dimensions. The answer suggests an important role for coarse geometry as introduced by J. Roe.
November 23, 2020
Shiraz Minwalla, Tata Institute of Fundamental Research
"Constraints on Tree Level Gravitational Scattering"
Abstract: Motiviated by a combination of the Chaos bound and AdS/CFT, we conjecture that all classical theories that give rise to S matrices that grow faster than s^2 in the Regge limit are unphysical. We then present a complete and exhaustive classification of all kinematically allowed exchange and contact S matrices (assuming that the vertices that generate the contact diagrams are polynomial in momenta and that no more than a finite number of intermediate particles are exchanged) and demonstrate that the only classical S matrix obeying these constraints and also the conjectured bound on Regge scattering in six or lower spacetime dimensions is the Einstein S matrix.
November 30, 2020
Charles Cao, University of Maryland
"Towards Emergent Gravity in Approximate Quantum Error Correction Codes"
Abstract: It is known that the AdS/CFT correspondence is related to approximate quantum error correction codes. However, the exact manner in which gravity can arise in such codes remains largely unexplored. Here we construct an approximate quantum error correction code which can be represented as a holographic tensor network. In the "noiseless" limit, it admits a local logdepth decoding circuit and reproduces certain properties of holography, such as the RyuTakayanagi formula and subregion duality, much like other known holographic codes. However, the code becomes approximate when "coherent noise" is injected, allowing it to capture features analogous to those of gravity, such as backreaction, subspacedependence, and approximate bulk locality. I will explain how these features are manifested in the tensor network.
Spring 2020
January 21, 2020
Andrew Rolph, Brandeis University
"Replica wormholes and the black hole information paradox"
March 24, 2020
Bogdan Stoica, Harvard University
"Entanglement entropy, mutual information, and state decomposition for an arithmetic perspective"
Abstract: I will present some work in progress on understanding information theoretic quantities in holography from a padic point of view. The talk will be informal.
March 31, 2020
Djordje Radicevic, Brandeis University
"The UV structure of scalar field theories"
Abstract: I have recently proposed a rigorous procedure for establishing the correspondence between lattice and continuum theories of fermions. This procedure led to a definition of current algebras, infrared dualities, and operator product expansions in a finite, completely well defined setting. The crucial insight was that the UV behavior of fermion field theories must be defined using two different UV cutoffs, a lattice spacing and a "string scale" that controls how smoothly the fields vary in space. In this talk I will briefly review this past work, and then I will describe how the analogous procedure is carried out for bosonic quantum theories. This case  still a work in progress  is considerably subtler, and I will show that even the ordinary free scalar field theories require a hierarchy of at least five scales to endow them with a proper UV completion.
April 7, 2020
Djordje Radicevic, Brandeis University
"The UV structure of scalar field theories, part 2"
Abstract: I have recently proposed a rigorous procedure for establishing the correspondence between lattice and continuum theories of fermions. This procedure led to a definition of current algebras, infrared dualities, and operator product expansions in a finite, completely well defined setting. The crucial insight was that the UV behavior of fermion field theories must be defined using two different UV cutoffs, a lattice spacing and a "string scale" that controls how smoothly the fields vary in space. In this talk I will briefly review this past work, and then I will describe how the analogous procedure is carried out for bosonic quantum theories. This case  still a work in progress  is considerably subtler, and I will show that even the ordinary free scalar field theories require a hierarchy of at least five scales to endow them with a proper UV completion.
April 21, 2020
Juan Pedraza, University College London
"Quantum corrections to entanglement entropy after local quenches in AdS_3/CFT_2"
Abstract: We compute the leading 1/N corrections to entanglement entropy after a local quench created by a light primary operator of dimension Δ, both in the language of largec CFTs and in the gravitational dual. The bulk picture of the quench corresponds to a oneparticle excited state of a scalar field theory coupled to gravity. The state is fully timedependent: the particle is initially created at (or close to) the boundary of AdS and then falls into the deep IR, backreacting the geometry as its wavefunction evolves in time. According to the FLM prescription, the entanglement entropy at O(1) receives two contributions: one due to the change in the area in the backreacted geometry, and another one due to bulk entanglement entropy. We compute both contributions and find an exact match with the CFT calculation, providing a nontrivial check of the FLM formula in a dynamic setting. We comment on the implications of our results in the context of black holes and the information paradox.
April 28, 2020
Mark Hertzberg, Tufts University
"Dark Sectors, Naturalness, and the Higgs"
Abstract: Modern developments in quantum gravity, especially string theory, suggest that the Standard Model (SM) degrees of freedom are not unique; that a typical low energy effective theory should include a large assortment of hidden sector degrees of freedom. It is therefore puzzling that cosmological constraints from BBN and CMB reveal that the early universe was almost entirely dominated by the SM, when the inflaton could have decayed into many sectors. Furthermore, the SM taken seriously to high scales, possesses an instability that would be catastrophic during inflation, as I will quantify in detail, and yet no new physics has been seen to correct this. In this talk, I put forth an explanation for all of these puzzles: the hidden sectors are in fact entirely natural with O(1) input parameters; this means all unprotected masses are pushed up to high scales and project out of the spectrum, while only massless (or protected) degrees of freedom remain, and so the inflaton can only reheat these sectors through higher dimension operators. On the other hand, the SM possesses a special feature: it includes a light Higgs, presumably for life to exist, and hence it allows a renormalizable coupling to the inflaton, which allows rapid decay into the SM. I then show that this naturally (i) removes the instability in the Higgs potential both during and after inflation, (ii) explains why the SM is dominant in the early universe, (iii) allows dark matter to form in hidden sector/s through subsequent strong dynamics, which I describe in detail, (iv) allows for high reheating and baryogenesis, and (v) accounts for why there so far has been no direct detection of dark matter or new physics beyond the SM.
Fall 2019
September 6, 2019
Edgar Shaghoulian, Cornell University
"Quantum Gravity in a Finite Box"
September 10, 2019
Stefan Stanojevic, Brown University
"AllLoop Singularities of Scattering Amplitudes in Massless Planar Theories"
September 17, 2019
Djordje Radicevic, Brandeis University
"Gauge Theories With Nonstandard Gauge Constraints"
Abstract: Pure YangMills theory obeys a local constraint given by the Gauss law div E = 0. Alternative gauge constraints are known to exist: the most notable example is provided by ChernSimons theory. However, detailed explorations of theories with nonstandard gauge constraints in the UV (e.g. on a lattice) have not been performed until very recently, when their importance was affirmed on several different fronts. In this talk I will discuss two new classes of nonstandard gauge theories. The first class involves theories in arbitrary dimension that can be shown to dualize to theories of ordinary fermions (these are higherdimensional exact bosonization dualities). The second class involves theories of fractons, pioneered by condensed matter and quantum information communities, which are some of the most interesting examples of gapped theories not described by any kind of conventional topological order.
September 24, 2019
Xi Yin, Harvard University
"Dinstantons and the nonperturbative completion of c=1 string theory"
Abstract: I will discuss the effect of ZZ instantons in c=1 string theory, which leads to a new proposal for the nonperturbative completion of the duality between c=1 string and the matrix quantum mechanics.
October 1, 2019
ShuHeng Shao, Institute for Advanced Study, Princeton University
"Anomalies and Bounds on Charged Operators"
Abstract: We study the implications of ’t Hooft anomaly (i.e. obstruction to gauging) on conformal field theory, focusing on the case when the global symmetry is Z2. Using the modular bootstrap, universal bounds on (1+1)dimensional bosonic conformal field theories with an internal Z2 global symmetry are derived. The bootstrap bounds depend dramatically on the ’t Hooft anomaly. In particular, there is a universal upper bound on the lightest Z2 odd operator if the symmetry is anomalous, but there is no bound if the symmetry is nonanomalous. We comment on the implication to the Weak Gravity Conjecture in AdS3.
October 8, 2019
Albion Lawrence, Brandeis University
"Hamiltonian fluid dynamics and the quasilinear approximation"
October 15, 2019
Andrea Dei, ETH Zürich
"Different perspectives on AdS3/CFT2 holography"
Abstract: I will discuss AdS3/CFT2 holography from the two perspectives of integrability and worldsheet CFT and comment on their relations and recent results. In particular, I will show how to match nullvector constraints on correlation functions and explain how some structure constants can be explicitly derived and matched on the two sides of the duality. This amounts to one of the very first holographic matches of nonprotected AdS3/CFT2 correlators.
October 22, 2019
Matthew Headrick, Brandeis University
"Bit threads and holographic entropy inequalities"
Abstract: I will discuss the ongoing effort to understand holographic entropy inequalities in the language of bit threads. I will start with the proof of the MMI inequality, focusing on the proof method. I will then explain why this method does not immediately extend to higher inequalities, and I will describe the current state of our efforts to develop new methods to prove those inequalities.
November 5, 2019
Thomas Faulkner, University of Illinois
"A canonical purification for the entanglement wedge crosssection"
Abstract: I will discuss a new proposal for the CFT dual of the entanglement wedge crosssection. Our results will be compared to the original entanglement of purification conjecture.
November 19, 2019
Juan Pedraza, University College London
"Constraining higher order gravities with subregion duality"
Abstract: In higher derivative theories, gravity can travel slower or faster than light. With this feature in mind, I will revisit the construction of the causal and entanglement wedges in this type of theories, and argue that they must be constructed using the fastest mode instead of null rays. I will explain how the property of causal wedge inclusion, i.e., the fact that the causal wedge must be contained in the entanglement wedge, can be used to obtain strong constraints on the higher derivative gravity couplings. The results are similar to the bounds previously obtained by Camanho et. al. based on high energy graviton scattering. I will present a systematic analysis in GaussBonnet gravity to illustrate our findings.
December 3, 2019
Mark Hertzberg, Tufts University
"Explanation for why the early universe was dominated by the standard model and stable"
Abstract: Modern developments in quantum gravity, especially string theory, suggest that the Standard Model (SM) degrees of freedom are not unique; that a typical low energy effective theory should include a large assortment of hidden sector degrees of freedom. It is therefore puzzling that cosmological constraints from BBN and CMB reveal that the early universe was almost entirely dominated by the SM, when the inflaton could have decayed into many sectors. Furthermore, the SM taken seriously to high scales, possesses an instability that would be catastrophic during inflation, as I will quantify in detail, and yet no new physics has been seen to correct this. In this talk, I put forth an explanation for all of these puzzles: the hidden sectors are in fact entirely natural with O(1) input parameters; this means all unprotected masses are pushed up to high scales and project out of the spectrum, while only massless (or protected) degrees of freedom remain, and so the inflaton can only reheat these sectors through higher dimension operators. On the other hand, the SM possesses a special feature: it includes a light Higgs, presumably for life to exist, and hence it allows a renormalizable coupling to the inflaton, which allows rapid decay into the SM. I then show that this naturally (i) removes the instability in the Higgs potential both during and after inflation, (ii) explains why the SM is dominant in the early universe, (iii) allows dark matter to form in hidden sector/s through subsequent strong dynamics, which I describe in detail, (iv) allows for high reheating and baryogenesis, and (v) accounts for why there so far has been no direct detection of dark matter or new physics beyond the SM.
December 10, 2019
Hong Liu, Massachusetts Institute of Technology
"Void formation in operator growth, entanglement, and unitarity"
Abstract: The structure of the Heisenberg evolution of operators plays a key role in explaining diverse processes in quantum manybody systems. We discuss a new universal feature of operator evolution: an operator can develop a void during its evolution, where its nontrivial parts become separated by a region of identity operators. Such processes are present in both integrable and chaotic systems, and are required by unitarity. We show that void formation has important implications for unitarity of entanglement growth and generation of mutual information and multipartite entanglement. As an application, we argue that operators which make up the density operator of a black hole can “jump” outside the black hole after the Page time, providing the underlying physical mechanism for a recent semiclassical prescription for the resolution of a black hole information loss puzzle. We study explicitly the probability distributions of void formation in a number of unitary circuit models, and conjecture that in a quantum chaotic system the distribution is given by the one we find in random unitary circuits, which we refer to as the random void distribution. We also show that the random void distribution leads to the same pattern of entanglement growth for multiple intervals as in (1 + 1)dimensional holographic CFTs after a global quench, which implies that it leads to maximal entanglement growth, and suggests that it underlies the timeevolution of holographic systems.
Spring 2019
January 15, 2019
Brian Swingle (University of Maryland)
"Universality in the Spread of Quantum Chaos"
January 29, 2019
Jonathan Harper (Brandeis University)
"Bit Threads and Entanglement of Purification"
February 5, 2019
Andrew Rolph (Brandeis University)
"TT deformations and SYK"
February 12, 2019
Bogdan Stoica (Brandeis University)
"General relativity from padic strings and automorphic forms"
February 26, 2019
Harsha Hampapura (Brandeis University)
"Proving ANEC from GSL"
March 5, 2019
Alastair GrantStuart (Brandeis University)
"Algebraic holography"
March 12, 2019
Adolfo del Campo (UMass Boston)
"Extreme Decoherence and Quantum Chaos"
March 19, 2019
Jieqiang Wu (MIT)
"Covariant phase space with boundaries"
March 26, 2019
Pranjal Nayak (University of Kentucky)
"Eigenstate thermalization (ETH) in the SYK model and the Schwarzian theory: an Analytic Approach"
April 2, 2019
Matthew Kleban (NYU)
"Black hole area quantization and gravitational waves"
April 9, 2019
An Huang (Brandeis University)
"A mathematical motivation of padic sigma models"
April 16, 2019
Ronak Soni (Stanford University)
"BRST v/s EPR"
April 30, 2019
Mark Van Raamsdonk (University of British Columbia)
"Spacetime from bits and cosmology from black holes"
Fall 2018
September 4, 2018
Christian Jepsen (Princeton)
"pAdic Holography"
September 18, 2018
Sabrina Pasterski (Harvard)
"Superrotations and Celestial Correlators"
October 2, 2018
Onkar Parrikar (UPenn)
"Emergent classical spacetime from microstates of an incipient blackhole"
October 9, 2018
Sergei Dubovsky (New York University)
"Complementarity from Identity"
October 16, 2018
Albion Lawrence (Brandeis University)
"Effective field theory and quintessence"
October 23, 2018
Jacopo Sisti (SISSA)
"Holographic Entanglement Entropy in AdS_4/BCFT_3 and the Willmore Functional"
October 30, 2018
Matthew Reece (Harvard)
"Large Field Ranges, UV Cutoffs and Photon Masses"
November 6, 2018
Lampros Lamprou (MIT)
"Entanglement Holonomies"
November 13, 2018
Daniel Jafferis (Harvard)
"Entanglement in 2D Gravity"
November 27, 2018
Nemanja Kaloper (UC Davis)
December 11, 2018
Bogdan Stoica (Brandeis University)
"Einstein equations from padic string"
Spring 2017
March 6
Shinobu Hosono (Gakushin University)
"Birational geometry from the moduli spaces of mirror CICYs"
Host: Albion Lawrence
March 27
Harsha Hampapura (Brandeis)
"The Large N Limit of the O(N) Model"
Host: Albion Lawrence
May 1
Nishant Agrawal (UMass Lowell)
"Early Universe cosmology with largescale structure"
Host: Albion Lawrence
Fall 2016
August 29
Gregory S. Adkins (Franklin and Marshall College)
"Effective field theory based calculation of positronium energy levels"
Host: Richard Fell
September 8
Bogdan Stoica (Brandeis)
"Tensor networks, padic fields, and algebraic curves: arithmetic and the AdS_3/CFT_2 correspondence"
Host: Matthew Headrick
September 12
Gaston Giribet (Brandeis and Univ. of Buenos Aires)
"Stringy horizons"
Host: Matthew Headrick
September 19
Brian Swingle (Brandeis and Harvard)
"What kinds of states can be prepared by Euclidean path integral?"
Host: Matthew Headrick
September 26
Andrew Strominger (Harvard)
"Area, Entanglement Entropy and Supertranslations at Null Infinity"
Host: Matthew Headrick
October 10
Jennifer Lin (IAS)
"Algebraic Entanglement Entropy and Holography"
Host: Bodgan Stoica
October 25
Sam McCandlish, ’12 (Stanford)
"A Stereoscopic Look into the Bulk"
Host: Matthew Headrick
October 31
Netta Engelhardt (Princeton)
"Into the Bulk: A Covariant Approach"
Host: Matthew Headrick
November 7
Cesar Agon (Brandeis)
"Comments on Entanglement Negativity for Free Fermions in 1+1 Dimensions"
Host: Matthew Headrick
November 14
Washington Taylor (MIT)
"Where in Ftheory is the Supersymmetric Standard Model?"
Host: Matthew Headrick
November 21
Harsha Hampapura (Brandeis)
"Classification of Twodimensional Rational Conformal Field Theories"
Host: Matthew Headrick
November 28
Djordje Radicevic (Perimeter)
"The Ergodicity Landscape of Quantum Theories"
Host: Bogdan Stoica
December 1
Steven Gubser (Princeton)
Joint IGERT/HEGT Seminar
"padic AdS/CFT"
Host: Albion Lawrence
Spring 2016
January 20
Cindy Keeler (Niels Bohr Institute)
"A caveat for applied holography"
Host: Ida Zadeh
January 25
Gerald Dunne (UConn)
"Resurgence and NonPerturbative Physics: Decoding the Path Integral"
Host: Ida Zadeh
February 1
Jessie Shelton (UIUC)
"Asymmetric reheating and cold dark sectors"
February 8
Chris Herzog (Stony Brook University)
"Tales from the Edge: Boundary Terms and Entanglement Entropy"
Host: Ida Zadeh
February 22
Tarek Anous (MIT)
"Black Hole Collapse in the 1/c Expansion"
Host: Ida Zadeh
February 29
Mark Mueller (MIT)
"Entanglement Entropy and Variational Methods in Interacting Quantum Field Theories"
Host: Ida Zadeh
March 7
Brent Nelson (Northeastern University)
"A Geometrical Approach to Particle Physics"
March 14
Matthew Headrick (Brandeis)
"Bit threads and holographic entanglement, part II"
March 21
Antal Jevicki (Brown)
"BiLocal Holography"
Host: Ida Zadeh
April 4
Erik Tonni (SISSA)
"Some geometrical aspects of entanglement in CFT and Holography"
April 6
Daniel Harlow (Harvard)
"Subregion Duality and the Entanglement Wedge in AdS/CFT"
Host: Albion Lawrence
Curtis Asplund (Columbia University)
"De Sitter spaces emerging from entanglement in conformal field theories"
Host: Ida Zadeh
May 2
Albion Lawrence (Brandeis)
"Axiondriven inflation and quantum gravity"
Fall 2015
August 31
Nima Lashkari (MIT)
Host: Ida Zadeh
"Gravity dual of quantum Fisher information"
September 10
Cesar Agon (Brandeis)
"Quantum Corrections to Holographic Mutual Information"
September 21
Sasha Zhiboedov (Harvard)
Host: Ida Zadeh
September 29
Ida Zadeh (Brandeis)
"Higgsing the Stringy Higher Spin Symmetries"
October 12
Andrew Liam Fitzpatrick (BU)
Host: Albion Lawrence
October 19
Sarah Harrison (Harvard)
"LandauGinzburg orbifolds and symmetries of K3 CFTs"
Host: Albion Lawrence
October 26
Omer BenAmi (TelAviv University)
"Renormalization group flow of entanglement entropy on spheres"
November 2
Beni Yoshida (Caltech)
Host: Ida Zadeh
"Chaos in quantum channels"
November 9
Swapnamay Mondal (HarishChandra Research Institute)
"Black Hole microstate counting using pure D brane systems"
Host: Matthew Headrick
November 16
Mehrdad Mirbabayi (IAS)
"Cosmological Consistency Conditions and Their Implications for CMB and Large Scale Structure"
Host: Ida Zadeh
November 23
Simon Gentle (UCLA)
"Entanglement entropy of surface operators"
Host: Matthew Headrick
November 30
Brian Swingle (Stanford)
"Complexity Equals Action"
Host: Matthew Headrick
December 7
Howard Schnitzer (Brandeis)
"Renyi entropy for the SU(N)_1 WZW model on a torus"
Host: Ida Zadeh
Spring 2015
January 12
Robert Caldwell (Dartmouth)
"The Chiral Imprint of a Cosmic Gauge Field on Primordial Gravitational Waves"
January 26
Igor Klebanov (Princeton)
"O(N) Models and Higher Spin AdS/CFT"
February 3
Guido D'Amico (NYU)
"PhotonAxion conversion in cosmic light"
February 9 (rescheduled to April 20)
Tracy Slatyer ( MIT)
"GeV GammaRays from the Central Milky Way and the Case for Annihilating Dark Matter"
February 23
Aron Wall (IAS)
"Quantum Extremal Surfaces"
February 26 Special Seminar
Eric Bergsheoff (University of Groningen)
March 2
Sarah Harrison (Harvard)
"Moonshine and string theory"
March 9
Matthew Headrick (Brandeis)
"RyuTakayanagi without minimal surfaces"
March 16
Martin Kruczenski (Purdue University)
"Wilson loops and minimal area surfaces in hyperbolic space"
March 23
Ilarion Melnikov (Harvard)
"Moduli spaces for (0,2) QFTs"
March 30
Tom Hartman (Cornell)
"Conformal Field Theory in the Largec Limit"
April 13
Howard Schnitzer 80th Birthday Celebration.
Talks held in Abelson 333 and Rosenstiel 118.
Speakers:
Paul Townsend (Cambridge University), "The Third Way to 3D Gauge Theory," (Abelson 333)
Mark Schnitzer (Stanford University), "Reading neural codes, ~1000 cells at a time in behaving mice," (Rosenstiel 118)
Burt Ovrut (University of Pennsylvania), "The Decoupling Theorem and the Supersymmetric BL Model: from the Unification Scale to the LHC," (Abelson 333)
Marcus Spradlin (Brown University), "Scattering Amplitudes and Cluster Algebras," (Abelson 333)
April 20
Tracy Slatyer ( MIT)
"GeV GammaRays from the Central Milky Way and the Case for Annihilating Dark Matter"
April 27
Masoud Soroush (Brandeis)
"Supersymmetry in Curved Backgrounds"
Fall 2014
September 8
Christoph Keller (Rutgers)
"3d Gravity, Universality and Poincare Series"
September 15
Steven Avery (Brown)
"General Bounds on the Evolution of Entanglement Entropy"
September 22
Dan Freedman (MIT)
"Explicitly Broken Supersymmetry with Exactly Massless Moduli"
September 29
Jared Kaplan (Johns Hopkins)
"AdS Locality, Gravity, and Black Hole Physics from the CFT Bootstrap"
October 6
Ida Zadeh (Brandeis)
"Rényi entropies and pure quantum gravity partition functions"
October 13
Dam Thanh Son (U. Chicago)
"Quantum Hall effect and NewtonCartan geometry"
October 20
Robert Penna (MIT)
"Spinning Black Holes and the Membrane Paradigm"
October 27
Jie Gu (Bonn University). Rescheduled.
"Braiding knots with topological string"
November 3
Parthasarathi Majumdar (Ramakrishna Mission Vivekananda University)
"Critical Mass of Neutron Stars : A Black Hole Entropic View"
November 10
Albion Lawrence (Brandeis)
"Coarsegrained quantum dynamics"
November 17
Thomas Dumitrescu (Harvard)
"Deformations of Superconformal Field Theories"
November 24
Ben Safdi (MIT)
"Renyi entropy, stationarity, and entanglement of the conformal scalar"
December 1
Jie Gu (Bonn University)
"Braiding knots with topological string"
Spring 2014
January 14
Masoud Soroush (Brandeis)
"Knot invariants and topological strings"
January 21
Matthew Headrick (Brandeis)
"Entanglement entropy in quantum field theory: An overview"
February 4
Mukund Rangamani (Durham)
"Effective actions for anomalous hydrodynamics"
February 11
Miguel Paulos (Brown University)
"Bootstrapping with precision"
February 25
Alex Maloney (McGill)
"Supersymmetry in de Sitter Space"
March 4
Bartek Czech (Stanford)
"On UV/IR entanglement, or closed curves in AdS_3"
March 11
Al Shapere (Kentucky)
"Constraints on the spectra of 2d CFTs"
March 25
David Shih (Rutgers)
"The Status of SUSY after Run I of the LHC
Note different location: SSC  337, third floor of Shapiro Science Center
April 1
James Halverson (KITP)
"Anomaly Nucleation as New Motivation for WIMPs"
April 8
Weijia Li (Beijing Normal U. and Harvard)
"Periodically driven holographic superconductor"
April 29
Bong Lian (Brandeis)
"Recent progress on period integrals"
Fall 2013
September 3
Ida Zadeh (Brandeis)
"Operator mixing in the D1D5 CFT near the orbifold point"
September 10
Matthew Headrick (Brandeis)
"What can holographic entanglement entropy teach us about general relativity?"
September 24
Anastasia Volovich (Brown)
"Motivic amplitudes and cluster coordinates"
October 1
Lara Anderson (Virginia Tech)
"Tbranes and geometry"
October 15
Tom Faulkner (IAS)
"Some results on entanglement in holographic field theories"
October 22
Matthew von Hippel (Simons Center)
"Hexagon functions: Bootstrapping the threeloop remainder function"
October 29
Gokce Basar (Stony Brook)
"Resurgence theory, ghost instantons and analytical continuation of path integrals"
November 5
Schlomo Razamat (IAS)
"3d dualities from 4d dualities"
November 12
Julian Sonner (MIT)
"The Schwinger effect and the geometry of entanglement"
November 13
Samir Mathur (Ohio State)
"Fuzzballs vs. squids"
November 19
Albion Lawrence (Brandeis)
"Metastability and instability in holographic gauge theories"
Dec. 3
Babak Haghighat (Harvard)
"Mstrings and their orbifolds"
Spring 2013
January 15
Matthew Headrick (Brandeis)
"BoseFermi duality and entanglement entropies"
January 22
Jianyang He (Brandeis)
"Holographic entanglement entropy and strong subadditivity"
January 29
Misha Smolkin (Perimeter)
"Black hole entropy vs entanglement entropy revisited"
February 5
Daniel Harlow (Princeton)
"Quantum Computation vs. Firewalls"
February 12
Joe Minahan (Uppsala)
"N^3 behavior from 5dimensional super YangMills"
March 4
Alejandra Castro (Harvard)
"Curiosities and Coincidences in Black Hole Physics"
March 5
Silviu Pufu (MIT)
"The Ftheorem and monopole operators in 3d CFTs"
March 6
Andrew Waldron (UC Davis) Note room change: Abelson 333
"Acausality of Massive Gravity"
March 12
Daniel Friedan (Rutgers)
"Geometry of the 2d renormalization group"
March 19
Chris White (Glasgow)
"BCJ Duality, the double copy and the soft limit"
April 9
César Agón (Brandeis)
"On the Beaming of Gluonic Fields at Strong Coupling"
April 16
Albion Lawrence (Brandeis)
"Holography and Renormalization"
April 23
Emanuel Katz (Boston University)
"A New Theory of Anyons"
Fall 2012
October 15
Alessandro Tomasiello (Milan)
"A Geometric Classification of Supersymmetric Solutions in String Theory"
November 13
Shinobu Hosono (Tokyo)
"Mirror symmetry of determinantal quintics in P^{4}"
Spring 2012
January 17
Zvi Bern (UCLA)
"Gravity as a double copy of gauge theory"
January 24
Albion Lawrence (Brandeis)
"Axion monodromy"
January 31
Marco Aldi (Brandeis)
"Quantum sigmamodel and twisted Tduality"
February 7
Jacob Bourjaily (Harvard)
"Quantum Field Theory and the Analytic SMatrix, Redux"
February 14
Brian Shuve (Harvard)
"A WIMPy Baryogenesis Miracle"
February 21
No seminar. Midterm recess.
February 28
Per Berglund (UNH)
"Global Embeddings for Branes at Toric Singularities"
March 6
Matt Roberts (NYU)
"Entanglement entropy after a local quench: A holographic story"
March 13
Massimo Porrati (NYU)
"Surprises with Interacting High Spin Particles"
March 20
Matthew Headrick (Brandeis)
"Properties of entropy in holographic theories"
March 27
Jonathan Heckman (IAS)
"4D Gravity as a Twistor Matrix Model"
April 3
Shamit Kachru (Stanford)
"New Horizons in Holography"
April 17
Matt Reece (Harvard)
"Supersymmetry, Naturalness, and the LHC: Where Do We Stand"
Sam McCandlish (Brandeis)
"Bending and Breaking Time Contours: A World Line Approach to Quantum Field Theory"
Fall 2011
September 6
Jianyang He (Brandeis)
"Holographic condensed matter theory"
September 20
Brian Wecht (Harvard and Queen Mary)
"Quantum Field Theory Without Lagrangians"
September 27
Takemichi Okui (Florida State)
"Viable gravity mediation"
October 11
Horatiu Nastase (Instituto de Fisica Teorica, UNESP, Brazil)
"Advances in maximally supersymmetric scattering amplitudes"
"Lecture 1: "Perturbative N=4 SYM and N=8 supergravity amplitudes"
October 18
Ronen Plesser (Duke University)
"Geometry of perturbative heterotic vacua"
October 19
Horatiu Nastase (Instituto de Fisica Teorica, UNESP, Brazil)
"Advances in maximally supersymmetric scattering amplitudes"
"Lecture 2: "AdS/CFT and applications""
November 1
Dr. Andrew Zayakin (LMUGarching)
"Exact oneloop strong coupling results for string spectrum in AdS4 x CP3 versus the allloop Bethe Ansatz"
November 8
Dr. Ben Freivogel (MIT)
"Completely Stable Oscillations in Conformal Field Theories"
Amit Sever (Perimeter)
Spring 2011
January 25
Xingang Chen (Cambridge University)
"Strongly coupled inflation"
March 15
Dimitra Karabali (Lehman College)
"Casimir Effect: Edges and Diffraction"
Spring 2010
January 26
Xi Yin (Harvard University)
"Higher spin gauge theory and holography"
February 2
Matthew Headrick (Brandeis University)
"Holography and entanglement entropy"
February 9
Wei Song (Harvard University)
"The KerrFermi sea"
February 23
Ilya Gruzberg (University of Chicago)
"Quantum Hall transitions and conformal restriction"
March 2
Diego Hofman (Harvard University)
"Generalized LifshitzKosevich scaling at quantum criticality from the holographic correspondence"
March 9
Lance Dixon (SLAC)
"Perturbative Ultraviolet Behavior of N=8 Supergravity"
March 16
Mboyo Esole (Harvard University)
"New weak coupling limits in Ftheory and nonKodaira singular fibers"
March 23
Miranda Cheng (Harvard University)
"Deforming the Lifshitz Holography"
April 8
Eric Bergshoeff (University of Groningen)
"Massive Gravity in Three Dimensions"
April 13
Simone Giombi (Harvard University)
"Quantum AdS_5 x S^5 superstring in the AdS lightcone gauge"
April 19
Hong Liu (MIT)
"From Black Holes to Strange Metals"
April 27
Alex Maloney (McGill University)
"Where are the Microstates of the Kerr Black Hole?"
May 4
Albion Lawrence (Brandeis University)
"An effective field theory for chaotic inflation"
Henriette Elvang (University of Michigan)
"New approach to counterterms in N=8 supergravity"
Fall 2009
September 22
Gaston Giribet (University of Buenos Aires and CONICET)
"The Black Holes of New Massive Gravity"
October 13
Hajar Ebrahim (Brandeis University)
TBA
October 27
Sumit Das (University of Kentucky)
"Spin models and emergent gauge fields at Lifshitz points"
November 3
Sakura SchaferNameki (KITP/UC Santa Barbara)
"Constraining Ftheory model building"
November 10
Radu Roiban (Penn State University)
"On short strings in AdS_5 x S^{5}"
Spring 2009
January 13
Hong Liu (MIT)
"A worldsheet instantoninduced 3rd order phase transition"
January 27
Stephen Naculich (Bowdoin College)
"Iterative structures in N=4 SYM and N=8 supergravity amplitudes"
February 3
Marcus Spradlin (Brown University)
"Aspects of graviton scattering amplitudes"
February 9
Toby Wiseman (Imperial College London)
"Lattice simulation of thermal D0branes"
February 10
Andrew Neitzke (Harvard University)
"BPS wallcrossing and 3dimensional ﬁeld theory"
February 17
Michael Duff (Imperial College London)
"Black holes, qubits and octonions"
February 24
Isaac CohenAbbo (Brandeis University)
"About the nature of dark matter and dark energy"
March 3
John McGreevy (MIT)
"Gravity duals of nonrelativistic quantum critical points"
March 10
Matthew Headrick (Brandeis University)
"New approaches to numerical CalabiYau metrics"
March 17
Frederik Denef (Harvard University)
"Orientiholes"
March 24 and March 31
Albion Lawrence (Brandeis University)
"Black holes and gauge theory"
April 21
Nathaniel Reden (Brandeis University)
"Constraints on inflation"
April 28
Shiraz Minwalla (TIFR)
"Weak field black hole formation in asymptotically AdS spacetimes"
June 23
Claudio Chamon (Boston University)
"Why glasses? vs. universality in glassy dynamics"
Fall 2008
September 9 and 23
Cecilia Garraffo (University of Buenos Aires)
"Ultraviolet corrections to the EinsteinHilbert action"
September 16
Hajar Ebrahim (Brandeis University)
"Black holes and qubits"
September 29
Matthew Headrick (Brandeis University)
"Tachyon actions in string theory: a nogo theorem"
October 7
Hajar Ebrahim (Brandeis University)
"Quantum entropy function from AdS2/CFT1 correspondence"
October 14
Ian Swanson (MIT)
"An overview of the closed string tachyon"
October 16
Herman Nicolai (AEI Potsdam)
"M2 branes and maximal gauged supergravities in D=3"
October 21
Sean Hartnoll (Harvard University)
"Holographic superconductors"
October 28
Matthias Wapler (Perimeter Institute)
"Transport properties of holographic defects"
November 4
Alessandro Tomasiello (Harvard University)
"AdS4 vacua in string theory, and their CFT duals"
November 11
Cynthia Keeler (Harvard University)
"Closed string tachyon condensation in E8"
November 18
Howard Schnitzer (Brandeis University)
"Regge behavior in N=4 superYangMills theory"
November 25
Delia SchwartzPerlov (Tufts University)
"The path(s) most taken: anthropic selection in the landscape"
December 4
Gaston Giribet (U. of Buenos Aires)
"Duality between nonrational CFTs and their string theory interpretation"
December 11
Chethan Gowdigere (HRI Allahabad)
"Explicit CalabiYau metrics on resolved spaces"
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