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Title: Quantum Monte Carlo estimation of complex-time correlations for the study of the ground-state dynamic structure function

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 δ 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 δ 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, ω) of two one-dimensional model systems, harmonic and quartic oscillators, for which S(q, ω) 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.
Authors:
 [1] ; ; ;  [2]
  1. Dipartimento di Fisica and INO-CNR BEC Center, Università degli Studi di Trento, I-38123 Povo, Trento (Italy)
  2. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Campus Nord B4-B5, E-08034 Barcelona (Spain)
Publication Date:
OSTI Identifier:
22415528
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 11; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALGORITHMS; APPROXIMATIONS; CORRELATION FUNCTIONS; CORRELATIONS; GROUND STATES; LAPLACE TRANSFORMATION; MONTE CARLO METHOD; ONE-DIMENSIONAL CALCULATIONS; OSCILLATORS; PATH INTEGRALS; PROPAGATOR; QUANTUM SYSTEMS; SPECTRAL FUNCTIONS; STRUCTURE FUNCTIONS