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

Year: 2015

Authors: Rota R., Casulleras J., Mazzanti F., Boronat J.

Autors Affiliation: Univ Trento, Dipartimento Fis, I-38123 Povo, Trento, Italy; Univ Trento, INO CNR BEC Ctr, I-38123 Povo, Trento, Italy; Univ Politecn Cataluna, Dept Fis & Engn Nucl, E-08034 Barcelona, Spain.

Abstract: 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.

Journal/Review: JOURNAL OF CHEMICAL PHYSICS

Volume: 142 (11)      Pages from: 114114-1  to: 114114-11

More Information: This research was supported under the MICINN-Spain, Grant No. FIS2011-25275, ERC through the QGBE Grant, and Provincia Autonoma di Trento. Additional support was provided by a Grant from the Qatar National Research Fund No. NPRP 5-674-1-114.
KeyWords: Analytic Continuation; Path-integrals; Rate Constants; Systems
DOI: 10.1063/1.4914995

Citations: 9
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