Department of

# Mathematics

Seminar Calendar
for Math-Physics Seminar events the year of Friday, April 21, 2017.

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events for the
events containing

Questions regarding events or the calendar should be directed to Tori Corkery.
      March 2017             April 2017              May 2017
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4                      1       1  2  3  4  5  6
5  6  7  8  9 10 11    2  3  4  5  6  7  8    7  8  9 10 11 12 13
12 13 14 15 16 17 18    9 10 11 12 13 14 15   14 15 16 17 18 19 20
19 20 21 22 23 24 25   16 17 18 19 20 21 22   21 22 23 24 25 26 27
26 27 28 29 30 31      23 24 25 26 27 28 29   28 29 30 31
30


Thursday, January 19, 2017

12:30 pm in 464 Loomis Laboratory,Thursday, January 19, 2017

#### One-loop Effective Potentials via Quasinormal Modes.

###### Cindy Keeler (Niels Bohr Institute)

Abstract: We present a method of calculating one-loop effective potentials for quantum fluctuations from quasinormal modes. We will demonstrate the method for a harmonic oscillator and a scalar in De Sitter space. After briefly discussing its application in Anti-de Sitter space, we will speculate on the physical meaning of this mathematical trick as well as its extension to fields with higher spin, to product spaces, and to spaces with non-Dirichlet boundary conditions.

Thursday, February 9, 2017

12:30 pm in 464 Loomis Laboratory,Thursday, February 9, 2017

#### Anomaly free SO(3), SO(5), and SO(6) gauge theories from F Theory

###### Mboyo Esole (Northeastern Math)

Abstract: Orthogonal groups in F Theory are delicate to define as they require a condition on the Mordell-Weil group of the generic elliptic fiber to distinguish them from spin groups. Moreover, the orthogonal groups discussed in the literature are SO (7+k) with k>0. In this talk, I will discuss the explicit construction of lower rank orthogonal groups in F Theory, classify their singular fibers and matter content in 4, 5, and 6 dimensional spacetimes. I will also present the details of their uplift from 5 to 6 dimensions, the cancellations of 6 dimensional anomalies and the structure of the Coulomb phases of the five dimensional theory. All this will be presented as an exercise in intersection theory using a new pushforward theorem for Chow rings of blowups.

Thursday, March 9, 2017

12:30 pm in 464 Loomis Laboratory,Thursday, March 9, 2017

#### Gauged Wess-Zumino actions, equivariant cohomology, and the electromagnetic response of symmetry-protected topological phases

###### Matthew Lapa (Illinois Physics)

Abstract: I will introduce the notion of a symmetry-protected topological (SPT) phase protected by the symmetry of a group G, and then present a calculation of the electromagnetic response of some bosonic SPT phases with G=U(1) in all dimensions. Remarkably, we find that the magnitude of the response of these bosonic SPT phases in spacetime dimensions 2m-1 or 2m differs from that of their more familiar fermionic counterparts by a numerical factor of m!, in agreement with previous results in low dimensions. The calculation uses a description of an SPT phase in terms of a nonlinear sigma model (NLSM) with theta term for the bulk and Wess-Zumino term for the boundary. The target space of the NLSM is a sphere of a particular dimension, and a crucial part of the NLSM description is an action of the group G=U(1) on the target space. I will show that the bulk response of the SPT phase can be deduced from the form of the gauged Wess-Zumino action describing the boundary coupled to the electromagnetic field. The construction of the gauged Wess-Zumino action is related to the U(1)-equivariant cohomology of the sphere, and I will explain this connection in detail. In particular, for even-dimensional spheres our result is equivalent to an equivariant extension of the volume form on the sphere with respect to the U(1) symmetry. On the other hand, for odd-dimensional spheres our result gives a physical interpretation for why such an extension fails. This talk is based on the paper arXiv:1611.03504 written together with Chao-Ming Jian, Peng Ye, and Taylor L. Hughes.

Thursday, March 16, 2017

12:30 pm in 464 Loomis Laboratory,Thursday, March 16, 2017

#### Quivers, Monopoles and q-geometric Langlands

###### Vasily Pestun (IHES)

Abstract: I will present the relationship between N=2 4d quiver gauge theories and integrable system of periodic monopoles and its quantization, and some conjectures concerning q-deformation of the geometric Langlands correspondence.

Thursday, March 30, 2017

12:30 pm in 464 Loomis Laboratory,Thursday, March 30, 2017

#### Non-local Virasoro algebras

###### Gabriele La Nave (Illinois Math)

Abstract: In recent years there have been various proposals explaining physical phenomena via the use of more or less explicitly non-local actions. This is the case of the recent work Guillou-Nunez-Schaposnik on 3-dimensional Bosonization or in the (mostly phenomenological) proposal of Hartnoll and Karch on the strange metal, where they hypothesize the presence of an anomalous dimension for the vector potential. The natural question that arises is to what extent can one construct generalization of the Virasoro algebra that accommodate for the needs of non-local operators. P. Phillips and I in recent work construct such generalizations, thus providing a mathematical foundation for the quest of such non-local CFT's.

Thursday, April 6, 2017

12:30 pm in 464 Loomis Laboratory,Thursday, April 6, 2017

#### CANCELLED

###### Anatoly Dymarski (Kentucky Physics)

Thursday, April 13, 2017

12:30 pm in 464 Loomis Laboratory,Thursday, April 13, 2017

#### Toward classification of 5d SQFTs

###### Hee-Cheol Kim (Harvard Physics)

Abstract: Non-trivial 5d SUSY theories can be engineered in string theory by using brane constructions or M-theory compactification on CY3. Such theories have interacting UV fixed points. We propose a systematic way to classify non-trivial 5d gauge theories by extending the previous attempt by Intriligator, Morrison and Seiberg. We will present the full classification of 5d gauge theories with simple gauge groups which flow to non-trivial fixed points.

Thursday, April 20, 2017

12:30 pm in 464 Loomis Laboratory,Thursday, April 20, 2017

#### Bulk locality from modular flow

###### Aitor Lewkowycz (Stanford Physics)

Thursday, April 27, 2017

12:30 pm in 464 Loomis Laboratory,Thursday, April 27, 2017

#### Entanglement branes in a two-dimensional string theory

###### Gabriel Wong (Virginia Physics)

Abstract: There is an emerging viewpoint that classical spacetime emerges from highly entangled states of more fundamental constituents. In the context of AdS/CFT, these fundamental constituents are strings, with a dual description as a large-N gauge theory. To understand entanglement in string theory, we consider the simpler context of two-dimensional large-N Yang-Mills theory, and its dual string theory description due to Gross and Taylor. We will show how entanglement in the gauge theory is described in terms of the string theory as thermal entropy of open strings whose endpoints are anchored on a stretched entangling surface which we call an entanglement brane.