[Crib-list] SPEAKER: JACOB BRINGEWATT (University of Maryland) / "Virtual" CRIBB Seminar / 12:00 PM - 1:00 PM / Friday, November 5, 2021

[Shirley Entzminger]

 	A   R E M I N D E R.....


 	      COMPUTATIONAL RESEARCH in BOSTON and BEYOND SEMINAR
 				 (CRIBB)


   ZOOM meeting info...

 	https://mit.zoom.us/j/96155042770

 	Meeting ID: 961 5504 2770

====================================

DATE:	Friday, November 5, 2021

TIME:	12:00 PM - 1:00 PM


TITLE:	Lefschetz Thimble Quantum Monte Carlo
 	 for Spin Systems


SPEAKER:   JACOB BRINGEWATT  (University of Maryland)


ABSTRACT:

Monte Carlo simulations are often useful tools for modeling quantum systems, but
in some cases they suffer from a sign problem, which manifests as an oscillating
phase attached to the probabilities being sampled. This sign problem generally
leads to an exponential slow down in the time taken by a Monte Carlo algorithm
to reach any given level of accuracy, and it has been shown that completely
solving the sign problem for an arbitrary quantum system is NP-hard. However, a
variety of techniques exist for mitigating the sign problem in specific cases;
in particular, the technique of deforming the Monte Carlo simulation's plane of
integration onto Lefschetz thimbles (that is, complex hypersurfaces of
stationary phase) has seen success for many problems of interest in the context
of quantum field theories. We extend this methodology to discrete spin systems
by utilizing spin coherent state path integrals to re-express the spin system's
partition function in terms of continuous variables. This translation to
continuous variables introduces additional challenges into the Lefschetz thimble
method, which we address. We show that these techniques do indeed work to lessen
the sign problem on some simple spin systems.

Based on: arXiv:2110.10699


=======================================

For information about the "Computational Research in Boston and Beyond Seminar"
(CRIBB), please visit:

 		https://math.mit.edu/sites/crib/


=================

Shirley A. Entzminger
Administrative Assistant II
Department of Mathematics
Massachusetts Institute of Technology
77 Massachusetts Avenue
Building 2, Room 350A
Cambridge, MA 02139
PHONE: 	(617) 253-4994
E-mail:	daisymae at math.mit.edu
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