Catherine Broderick
(781) 736-2803  

List of Events

Fall 2016

All seminars take place at 2pm on Thursdays in Volen 119, unless otherwise indicated.

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Thursday, September 15

Matthew Roberts (U. of Chicago)
3:30 pm
Abelson 229
Emergent geometry in quantum Hall states & the composite Fermi liquid
Host: Albion Lawrence

Wednesday, October 5 

Arijeet Pal (Oxford)
10:00 am

Abelson 307
Finite temperature mobility
edge in many-body localized systems
Host: Kabir Ramola

Thursday, October 13

An Huang (Brandeis)
2:oo pm
Volen 119
Graph embedding, quadratic forms, and toric geometry
Host: Albion Lawrence

Thursday, October 20

Shreyas Gokhale (MIT)
2:00 pm
Volen 119
Dissecting the glass transition through critical experiments on colloids
Host: Bulbul Chakraborty

Abstract: The human race has engineered and manipulated glasses since times immemorial and yet, the basic physics underlying glass formation continues to elude our grasp. Even the most basic question of whether glass formation is a fundamentally thermodynamic or dynamic phenomenon remains unanswered. This state of affairs is due largely to the fact that available experimental data on molecular liquids, over as many as fourteen orders of magnitude, are unable to distinguish between macroscopic predictions of competing theoretical frameworks. In this talk, I will demonstrate how information on particle dynamics from experiments on dense colloidal suspensions can be harnessed to critically compare and contrast microscopic predictions of the random first-order transition theory (RFOT) and dynamical facilitation (DF), two of the most prominent competing theories of glass formation. In particular, I will show that a detailed analysis of shapes of cooperatively rearranging clusters of particles reveals a dynamical crossover from a facilitation dominated regime to one dominated by collective hopping events postulated within RFOT. Further, I will discuss how quenched disorder in the form of an amorphous wall can potentially serve as a diagnostic tool to assess the relative importance of structural relaxation mechanisms envisioned in RFOT and DF. In a broader context, these results indicate that even over the limited dynamical range available to colloid experiments and numerical simulations, dynamical crossovers can yield valuable insights into the physical processes responsible for glass formation.

Thursday, November 3

No seminar. (President Liebowitz' inauguration)

Tuesday, November 8 (4pm in Abelson 131)

Special IGERT/Physics Department Colloquium
Jeffrey Morris, CUNY
Friction and adhesion in colloids: Yielding, thickening, jamming
Host: Bulbul Chakraborty

Abstract: In recent work, we have shown [1,2] that frictional interactions provide a rational basis for both continuous and discontinuous shear thickening in viscous suspensions.   When the repulsive forces (such as those due to electrostatic or steric colloidal stabilization) are overwhelmed by shearing forces, contact is assumed to occur, and the system transitions from a low-viscosity (lubricated) to a high-viscosity (frictional) state. Contacting particles may experience both adhesive forces as well as friction.  We will consider the influence of attractive forces at contact, in combination with the stabilizing repulsive forces.  This combination of forces would be seen in the case of particles with van der Waals attraction in combination with colloidal stabilization.  For sufficient attractive force a yield stress and shear thinning give way to the shear thickening response, a behavior observed in certain flocculated dispersions.  At sufficient yield stress, the shear thickening is completely obscured, as the dispersions shear thins after yielding directly onto the high-viscosity (frictional) plateau.  The suggestion that a material may exhibit both yielding at low stress and jamming at large stress [3] is explored. 

1. R. Seto, R. Mari, J. F. Morris & M. M. Denn 2013 Discontinuous shear thickening of frictional hard-sphere suspensions. Phys. Rev. Lett. 111 218301.
2. . R. Mari, R. Seto J. F. Morris & M. M. Denn 2015 Discontinuous shear thickening in Brownian suspensions by dynamic simulation. Proc. National Acad. Sci.
  112. 15326.
3. N. J. Wagner & J. F. Brady 2009 Shear thickening in colloidal dispersions. Phys. Today62, 27-32.

Thursday, November 17

Daniel Ruberman (Brandeis)
2:00 pm
Volen 119
Topological configurations of complex lines
Host: Albion Lawrence

Configurations of lines in the plane have been studied since antiquity. In recent years, combinatorial methods have been used to decide if a specified incidence relation between certain objects ("lines") and other objects ("points") can be realized by actual points and lines in a projective plane over a field. For the real and complex fields, one can weaken the condition to look for topologically embedded lines (circles in the real case, spheres in the complex case) that meet according to a specified incidence relation. I will explain some joint work with Laura Starkston (Stanford) giving new topological restrictions on the realization of configurations of spheres in the complex projective plane.

Thursday, December 1

Steven Gubser (Princeton)
Joint IGERT/High Energy Theory Seminar
2:00 pm
Volen 119
p-adic AdS/CFT
sponsored by DOE
Host: Albion Lawrence

Abstract:  I will explain how replacing the real numbers by the p-adic numbers and the bulk geometry of anti-de Sitter space by a discrete graph, we can arrive at a new version of the AdS/CFT correspondence with some links to the p-adic string.  Two-point, three-point, and four-point correlators can be computed starting from a classical action in the bulk.  In some cases, adelic product identities show interesting relationships with standard results in ordinary AdS/CFT.  I will describe candidate geometries for Wilson loops and comment on some ongoing work to find further probes of the correspondence.