# Spacetime and Quantum Mechanics Seminar

As part of the program on Spacetime and Quantum Mechanics, the CMSA will be hosting a weekly seminar on Thursdays at 2:30pm in room G10.

Date Speaker Title/Abstract

9/12/2019

Pasha Pylyavskyy (University of Minnesota)

19/18/2019

2:00pm

G02

Francis Brown (University of Oxford)

Title: Amplitudes, Polylogs and Moduli Spaces

9/19/2019

Chuck Doran (University of Alberta)

Abstract: I will present an overview of the algebraic and transcendental features of the computation of N-loop sunset Feynman integrals.

Starting from the realization of arbitrary Feynman graph hypersurfaces as (generalized) determinantal varieties, we describe the Calabi-Yau subvarieties of permutohedral varieties that arise from the N-loop sunset Feynman graphs and some key features of their geometry and moduli.

These include: (1) an iterated fibration structure which allows one to “bootstrap” both periods and Picard-Fuchs equations from lower N cases; (2) specialization to and interpretation of coincident mass loci (“jump loci”) in moduli; (3) a significant generalization of the Griffiths-Dwork algorithm via “creative telescoping”; and (4) the realization of Calabi-Yau pencils as Landau-Ginzburg models mirror to weak Fano varieties.

Details of each of these will be discussed in later lectures this semester. This is joint work with Pierre Vanhove and Andrey Novoseltsev.

9/26/2019

Tomasz Taylor (Northeastern)

Title: Celestial Amplitudes

10/3/2019

Simon Caron-Huot (McGill)

10/10/2019

3:30pm

Yutin Huang (National Taiwan University)

10/15/2019

Tuesday

3:30pm

Sergey Fomin (Univ. of Michigan)

10/18/2019

Friday

G02

Sebastian Franco (The City College of New York)

10/31/2019

Junjie Rao (Albert Einstein Institute)

11/1/2019

SC 232

1:30pm

George Lusztig (MIT)

11/12/2019

Tuesday

G02

3:30pm

11/14/2019

G02

11/21/2019

Cristian Vergu (Niels Bohr Institute)

Title: The Octagonal Alphabet

11/26/2019

Stephan Stieberger (IAS)

12/4/2019

Title: BCJ numerators, $\mathcal{M}_{0,n}$, and ABHY

Abstract: We relate the BCJ numerator Jacobi property to the classical fact that the top homology group of $\mathcal{M}_{0,n}$ is isomorphic to a component of the free Lie algebra. We describe ways to get BCJ numerators, and caution that the BCJ Jacobi property doesn’t imply the existence of what has been called a ‘kinematic algebra.’

12/5/2019 David Kosower (IAS)

Title: From scattering amplitudes to classical observables

12/10/2019

Ramis Movassagh (MIT)

Abstract: In recent years, there has been a surge of activities in proposing “exactly solvable” quantum spin chains with surprising high amount of ground state entanglement–exponentially more than the critical systems that have $\log(n)$ von Neumann entropy. We discuss these models from first principles. For a spin chain of length $n$, we prove that the ground state entanglement entropy scales as $\sqrt(n)$ and in some cases even extensive (i.e., as $n$) despite the underlying Hamiltonian being: (1) Local (2) Having a unique ground state and (3) Translationally invariant in the bulk. These models have rich connections with combinatorics, random walks, Markov chains, and universality of Brownian excursions. Lastly, we develop techniques for proving the gap. As a consequence, the gap of Motzkin and Fredkin spin chains are proved to vanish as 1/n^c with c>2; this rules out the possibility of these models to be relativistic conformal field theories in the continuum limit. Time permitting we will discuss more recent developments in this direction and ‘generic’ aspects of local spin chains.