2026-04-13T13:40:57Zhttps://recercat.cat/oai/request

oai:recercat.cat:2117/275272026-01-21T10:36:30Zcom_2072_1033col_2072_452950

urn:hdl:2117/27527 Quantum Monte Carlo estimation of complex-time correlations for the study of the ground-state dynamic structure function Rota, R Casulleras Ambrós, Joaquín Mazzanti Castrillejo, Fernando Pablo Boronat Medico, Jordi Àrees temàtiques de la UPC::Física Monte Carlo method Quantum systems Path integrals Analytic continuation Analytic continuation Path-integrals Maximum-entropy Rate constants Systems Simulations Monte Carlo, Mètode de Quàntums, Teoria dels Integrals We present a method based on the path integral Monte Carlo formalism for the calculation of ground-state time correlation functions in quantum systems. The key point of the method is the consideration of time as a complex variable whose phase d acts as an adjustable parameter. By using high-order approximations for the quantum propagator, it is possible to obtain Monte Carlo data all the way from purely imaginary time to d values near the limit of real time. As a consequence, it is possible to infer accurately the spectral functions using simple inversion algorithms. We test this approach in the calculation of the dynamic structure function S(q, omega) of two one-dimensional model systems, harmonic and quartic oscillators, for which S(q, omega) can be exactly calculated. We notice a clear improvement in the calculation of the dynamic response with respect to the common approach based on the inverse Laplace transform of the imaginary-time correlation function. (C) 2015 AIP Publishing LLC. Postprint (author’s final draft) 2015-03-21 Article http://scitation.aip.org/content/aip/journal/jcp/142/11/10.1063/1.4914995 http://creativecommons.org/licenses/by-nc-nd/3.0/es/ Open Access Attribution-NonCommercial-NoDerivs 3.0 Spain