## Past Seminars

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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 volume-law entanglement that persists despite the presence of ongoing continuous measurement. In this talk I describe how fast scrambling dynamics generated by long-range and sparse nonlocal interactions can be used to improve a system’s robustness to measurement, allowing for many-body entanglement to survive at substantially higher rates of measurement compared to circuits featuring only local interactions. Further, I will show that these long-range interactions also improve the code properties (code rate, code distance) of the dynamically-generated error-correcting codes which underpin the volume-law phase. Nonlocal interactions of this type can be implemented in near-term quantum simulators using cavities with a multifrequency drive or in Rydberg chains with tweezer-assisted 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 1-form symmetries and, more generally, d-dim'l theories with (d-1)-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 two-dimensional 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 Wang-Wen-Witten in two-dimensional 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 Navier-Stokes 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

"AdS-Kasner and Path Integral Complexity"

Abstract: Over many years, AdS-Kasner backgrounds have been used to probe signatures of space-like 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 hidden-layer width, we will find a principle of sparsity that will let us describe effectively-deep networks of practical large-but-finite-width networks. This talk is based on a book, "The Principles of Deep Learning Theory," co-authored 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 non-Clifford 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 non-trivial codes using simple quantum lego blocks. Surprisingly, we also find that the surface code is equivalent to the 2d Bacon-Shor code after ``dualizing'' its tensor network encoding map.

March 29, 2022**Ning Bao**, Northeastern University

"The Holographic Fault Tolerance Threshold is the Hawking-Page Phase Transition"

Abstract: We study the error threshold properties of holographic quantum error-correcting codes. We demonstrate that holographic CFTs admit an algebraic threshold, which is related to the confinement-deconfinement phase transition. We then apply geometric intuition from holography and the Hawking-Page 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 many-body systems in a highly controllable fashion. Here we propose a scheme, in which a Z2 gauge structure emerges from local two- and one-body 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 disorder-order free localization as well as the Schwinger effect in (2+1)D using small-scale 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 Pinzani-Fokeeva**, 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

"Measurement-induced criticality and charge-sharpening transitions"

Abstract: Monitored quantum circuits (MRCs) exhibit a measurement-induced phase transition between area-law and volume-law entanglement scaling as a function of the measurement rate. In this talk, I will first review our understanding of such measurement-induced phase transitions. I will argue that MRCs with a conserved charge additionally exhibit two distinct volume-law entangled phases that cannot be characterized by equilibrium notions of symmetry-breaking or topological order, but rather by the non-equilibrium dynamics and steady-state distribution of charge fluctuations. These include a charge-fuzzy phase in which charge information is rapidly scrambled leading to Luttinger-liquid-like spatial fluctuations of charge in the steady state, and a charge-sharp phase in which measurements collapse quantum fluctuations of charge without destroying the volume-law entanglement of neutral degrees of freedom. I will present some statistical mechanics and effective field theory approaches to such charge-sharpening transitions.

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Fall 2021

September 13, 2021**Xiao Chen**, Boston College

"Emergent criticality in non-unitary random dynamics"

Abstract: We present random quantum circuit models for non-unitary 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 short-range entangled many-body state, the dynamical evolution of entanglement and correlations quantitatively agrees with the predictions of two-dimensional conformal field theory with a spacelike time direction. We argue that this behavior is generic in non-unitary free quantum dynamics with time-dependent randomness, and we show that the emergent conformal dynamics of two-point functions arises out of a simple “nonlinear master equation.” In addition, we construct solvable quadratic Sachdev-Ye-Kitaev chains with non-unitary 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**Shao-Kai 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 large-N limit. Without measurement the steady state n-th 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 volume-law to area-law 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 many-body physics, as well as in holography, particularly in fixed-area 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 Jackiw-Teitelboim gravity model.

October 11, 2021**Djordje Radicevic**, Brandeis University

"Confinement and Flux Attachment"

Abstract: Flux-attached 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 Prescod-Weinstein**, 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 self-interaction 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 late-time correlation functions to all orders can be equivalently generated by a non-unitary Lagrangian on a Euclidean AdS geometry. I will use this to explain the analytic structure of the spectral density that characterize a late-time four-point 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**Jie-qiang Wu**, University of California, Santa Barbara

"Algebra of diffeomorphism invariant observables in Jackiw-Teitelboim 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 non-linear effect of gravitational theory, the results for diffeomorphism invariant operators are very limited.

In this work, we focus on the Jackiw-Teitelboim 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 Jackiw-Teitelboim 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 Jackiw-Teitelboim 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 closed-form amplitude, describing the tree-level 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 Jordan-Wigner transformation. I describe models that become free fermionic only after under a much subtler transformation that is both non-local and non-linear 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 free-parafermion 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 non-perturbative 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 low-energy 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 brane-anti-brane 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 Ryu-Takayanagi 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 Ryu-Takayanagi 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.

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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 lattice-continuum correspondence"

Abstract: A year ago, I described plans for a comprehensive study of the lattice-continuum 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

"Measurement-Induced Phase Transitions at Large N"

Abstract: Measurement-induced phase transitions (MIPT) are a novel class of dynamical quantum many-body phase transitions driven by a competition between unitary scrambling dynamics, which generate many-body 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 path-integral expression for the order parameter featuring a large-N limit that can be analyzed exactly using steepest-descent methods. For the simplest Brownian circuit model, we find that the transition is described by a $Z_2$ symmetry-breaking 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: Four-point gravitational scattering amplitudes can exhibit two types of exponentiation. In momentum space, one-loop infrared divergences exponentiate to give higher-loop amplitudes modulo an IR-finite remainder function. On the other hand, at high energies and small angles, the four-point 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

"Chern-Weil 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 “Chern-Weil global symmetries,” that arise ubiquitously in gauge theories. The Noether currents of these Chern-Weil 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, Chern-Simons 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 Chern-Weil symmetries in quantum gravity, suggesting that they might be general features of quantum gravity.

March 31, 2021**Sarah Shandera**, Pennsylvania State University

"Sub-system statistics for out-of-equilibrium 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 sub-system, 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 sub-systems 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 spin-mixing 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 tree-like 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 sub-class of "gauge-derived" global symmetries. This has intriguing relations to wormhole-based 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

"Many-body 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 many-body quantum dynamics with time-dependent control. This goes beyond existing many-body systems as we are able to engineer unique features such as genuine long-range 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 inter-particle 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 long-range 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 Grado-White**, Brandeis University

"Multi-mouth Traversable Wormholes"

Abstract: Recently, several examples of traversable wormholes supported by well-controlled 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

"Many-body 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 many-body generalization of quantum teleportation, with an elegant and surprising connection to gravity. In particular, the teleportation of quantum information relies on many-body dynamics, which originate from strongly-interacting 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 many-body quantum teleportation -- dubbed peaked-size teleportation. Intriguingly, peaked-size 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 peaked-size teleportation across a variety of physical systems, including random unitary circuits and the Sachdev-Ye-Kitaev model (at high temperatures). I will conclude by outlining potential experimental realizations of many-body quantum teleportation, with applications to: (i) characterizing the size distributions of operators in strongly-correlated systems and (ii) distinguishing between generic and intrinsically gravitational scrambling dynamics.

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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 one-shot quantum Shannon theory (smooth min- and max-entropies), 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 one-shot quantum state merging (using zero-bits 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 non-identical 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 field-theoretic 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 3-rank 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

"Wess-Zumino-Witten terms and the geometry and topology of lattice systems"

Abstract: Wess-Zumino-Witten terms are topologically-nontrivial terms in the effective actions which arise from integrating out short-distance degrees of freedom which couple of slowly-varying scalar fields. They can be viewed as higher-dimensional generalizations of the Berry connection. This viewpoint suggests that WZW terms encode the non-trivial 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 log-depth decoding circuit and reproduces certain properties of holography, such as the Ryu-Takayanagi 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 back-reaction, subspace-dependence, 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 p-adic 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 large-c CFTs and in the gravitational dual. The bulk picture of the quench corresponds to a one-particle excited state of a scalar field theory coupled to gravity. The state is fully time-dependent: 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 non-trivial 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

"All-Loop Singularities of Scattering Amplitudes in Massless Planar Theories"

September 17, 2019**Djordje Radicevic**, Brandeis University

"Gauge Theories With Nonstandard Gauge Constraints"

Abstract: Pure Yang-Mills 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 Chern-Simons 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 higher-dimensional 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

"D-instantons and the non-perturbative 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 non-perturbative completion of the duality between c=1 string and the matrix quantum mechanics.

October 1, 2019**Shu-Heng 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 non-anomalous. 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 null-vector 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 non-protected 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 cross-section"

Abstract: I will discuss a new proposal for the CFT dual of the entanglement wedge cross-section. 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 Gauss-Bonnet 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 many-body 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 semi-classical 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 time-evolution 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 p-adic strings and automorphic forms"

February 26, 2019**Harsha Hampapura** (Brandeis University)

"Proving ANEC from GSL"

March 5, 2019**Alastair Grant-Stuart** (Brandeis University)

"Algebraic holography"

March 12, 2019**Adolfo del Campo** (UMass Boston)

"Extreme Decoherence and Quantum Chaos"

March 19, 2019**Jie-qiang 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 p-adic 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)

"p-Adic 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 p-adic 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 large-scale 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, p-adic 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 F-theory is the Supersymmetric Standard Model?"

Host: Matthew Headrick

November 21

**Harsha Hampapura** (Brandeis)

"Classification of Two-dimensional 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

"p-adic 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 Non-Perturbative 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)

"Bi-Local 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)

"Axion-driven 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)

"Landau-Ginzburg orbifolds and symmetries of K3 CFTs"

Host: Albion Lawrence

October 26**Omer Ben-Ami** (Tel-Aviv 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** (Harish-Chandra 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 Caldwel**l (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)

"Photon-Axion conversion in cosmic light"

February 9 (rescheduled to April 20)**Tracy Slatyer** ( MIT)

"GeV Gamma-Rays 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)

"Ryu-Takayanagi 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 Large-c 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 B-L 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 Gamma-Rays 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 Newton-Cartan 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)

"Coarse-grained 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 - 3-37, 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 D1-D5 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)

"T-branes 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 three-loop 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)

"M-strings and their orbifolds"

###
Spring 2013

January 15**Matthew Headrick** (Brandeis)

"Bose-Fermi 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 5-dimensional super Yang-Mills"

March 4**Alejandra Castro** (Harvard)

"Curiosities and Coincidences in Black Hole Physics"

March 5**Silviu Pufu** (MIT)

"The F-theorem 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 2-d 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 sigma-model and twisted T-duality"

February 7**Jacob Bourjaily** (Harvard)

"Quantum Field Theory and the Analytic S-Matrix, 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** (LMU-Garching)

"Exact one-loop strong coupling results for string spectrum in AdS4 x CP3 versus the all-loop 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 Kerr-Fermi sea"

February 23**Ilya Gruzberg** (University of Chicago)

"Quantum Hall transitions and conformal restriction"

March 2**Diego Hofman** (Harvard University)

"Generalized Lifshitz-Kosevich 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 F-theory and non-Kodaira 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 light-cone 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 Schafer-Nameki** (KITP/UC Santa Barbara)

"Constraining F-theory 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 instanton-induced 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 D0-branes"

February 10**Andrew Neitzke** (Harvard University)

"BPS wall-crossing and 3-dimensional ﬁeld theory"

February 17**Michael Duff** (Imperial College London)

"Black holes, qubits and octonions"

February 24**Isaac Cohen-Abbo** (Brandeis University)

"About the nature of dark matter and dark energy"

March 3**John McGreevy** (MIT)

"Gravity duals of non-relativistic quantum critical points"

March 10**Matthew Headrick** (Brandeis University)

"New approaches to numerical Calabi-Yau 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 Einstein-Hilbert action"

September 16

**Hajar Ebrahim** (Brandeis University)

"Black holes and qubits"

September 29

**Matthew Headrick** (Brandeis University)

"Tachyon actions in string theory: a no-go 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 super-Yang-Mills theory"

November 25

**Delia Schwartz-Perlov** (Tufts University)

"The path(s) most taken: anthropic selection in the landscape"

December 4

**Gaston Giribet** (U. of Buenos Aires)

"Duality between non-rational CFTs and their string theory interpretation"

December 11

**Chethan Gowdigere** (HRI Allahabad)

"Explicit Calabi-Yau metrics on resolved spaces"