[seminar] 30. 09. 2022. Stuart C. Althorpe: Real-time dynamics from imaginary-time path-integrals: Theory and practice

[Sanjin Benić]

Drage kolegice i kolege,
Drago mi je da mogu najaviti sljedeći Seminar Fizičkog odsjeka:

Dear colleagues,
I would like to invite you to the following Seminar of the Department of
Physics:

petak/Friday 30.09.2022. u 11:15 u F201

Real-time dynamics from imaginary-time path-integrals: Theory and practice

Stuart C. Althorpe

Yusuf Hamied Department of Chemistry, University of

Cambridge, Cambridge, UK

Imaginary-time path-integrals or ``ring-polymers" are a

long-established practical technique for simulating quantum Boltzmann

statistics. More recently, they have also been used to simulate

real-time dynamics, using the centroid molecular dynamics (CMD) and

(thermostatted) ring-polymer molecular dynamics ((T)RPMD) methods. Here,

we show that the theoretical basis of CMD and RPMD is a classical

dynamics which arises when the exact quantum dynamics is represented

using path-integrals and is coarse-grained to make it a smooth and

differentiable function of imaginary-time. This ``Matsubara" dynamics

cannot be used as a practical method (because of a severe sign problem),

but can be used to critique and refine heuristic methods such as CMD and

RPMD, which turn out to be approximations to Matsubara dynamics that

avoid the phase. In particular, we will show how to extend quantum

simulations of the infrared spectrum of liquid water and ice to lower

temperatures (150 K) than hitherto possible.

Cjeloviti oglas je u prilogu./Formatted announcement is attached.

Lijep pozdrav / Best regards
Sanjin Benic i Damjan Pelc
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