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

[Shirley Entzminger]

 	     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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