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

[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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