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Nuclear level densities are crucial for estimating statistical nuclear reaction rates. The shell model Monte Carlo method is a powerful approach for microscopic calculation of state densities in very large model spaces. However, these state…

Nuclear Theory · Physics 2013-04-29 Y. Alhassid , M. Bonett-Matiz , S. Liu , H. Nakada

The test particle Monte-Carlo models for neutral particles are often used in the tokamak edge modelling codes. The drawback of this approach is that the self-consistent solution suffers from random error introduced by the statistical…

Plasma Physics · Physics 2017-04-19 Vladislav Kotov

The calculation of the ground state and thermodynamics of mass-imbalanced Fermi systems is a challenging many-body problem. Even in one spatial dimension, analytic solutions are limited to special configurations and numerical progress with…

Quantum Gases · Physics 2018-07-20 Lukas Rammelmüller , William J. Porter , Joaquín E. Drut , Jens Braun

We present a practical solution to the "sign problem" in the auxiliary field Monte Carlo approach to the nuclear shell model. The method is based on extrapolation from a continuous family of problem-free Hamiltonians. To demonstrate the…

Nuclear Theory · Physics 2008-11-26 Y. Alhassid , D. J. Dean , S. E. Koonin , G. Lang , W. E. Ormand

We describe and discuss a recently proposed quantum Monte Carlo algorithm to compute the ground-state properties of various systems of interacting fermions. In this method, the ground state is projected from an initial wave function by a…

Condensed Matter · Physics 2009-10-28 Shiwei Zhang , J. Carlson , J. E. Gubernatis

Path integral Monte Carlo with Green's function analysis allows the sampling of quantum mechanical properties of molecules at finite temperature. While a high-precision computation of the energy of the Born-Oppenheimer surface from path…

Quantum Physics · Physics 2007-05-23 Daejin Shin , Ming-Chak Ho , J. Shumway

A method is proposed to handle the sign problem in the simulation of systems having indefinite or complex-valued measures. In general, this new approach, which is based on renormalisation blocking, is shown to yield statistical errors…

High Energy Physics - Lattice · Physics 2009-10-28 J. F. Markham , T. D. Kieu

Ultracold atomic systems have been of great research interest in the past, with more recent attention being paid to systems of mixed species. In this work we carry out non-perturbative Path Integral Monte Carlo (PIMC) simulations of N…

Quantum Gases · Physics 2017-10-19 William G. Dawkins , Alexandros Gezerlis

We present a simple, general purpose, quantum Monte-Carlo algorithm for out-of-equilibrium interacting nanoelectronics systems. It allows one to systematically compute the expansion of any physical observable (such as current or density) in…

Mesoscale and Nanoscale Physics · Physics 2015-07-08 Rosario E. V. Profumo , Christoph Groth , Laura Messio , Olivier Parcollet , Xavier Waintal

We present the first Green's function Monte Carlo calculations of light nuclei with nuclear interactions derived from chiral effective field theory up to next-to-next-to-leading order. Up to this order, the interactions can be constructed…

Nuclear Theory · Physics 2014-11-11 J. E. Lynn , J. Carlson , E. Epelbaum , S. Gandolfi , A. Gezerlis , A. Schwenk

The recently proposed full configuration interaction quantum Monte Carlo method allows access to essentially exact ground-state energies of systems of interacting fermions substantially larger than previously tractable without knowledge of…

Computational Physics · Physics 2012-12-17 J. S. Spencer , N. S. Blunt , W. M. C. Foulkes

The nonequilibrium spectral properties of the Anderson impurity model with a chemical potential bias are investigated within a numerically exact real time quantum Monte Carlo formalism. The two-time correlation function is computed in a…

Strongly Correlated Electrons · Physics 2014-04-11 Guy Cohen , Emanuel Gull , David R. Reichman , Andrew J. Millis

A variational Monte Carlo method is used to generate sets of orthogonal trial functions, Psi_T(J^pi,T), for given quantum numbers in various light p-shell nuclei. These Psi_T are then used as input to Green's function Monte Carlo…

Nuclear Theory · Physics 2008-11-26 Steven C. Pieper , R. B. Wiringa , J. Carlson

Quantum Monte Carlo (QMC) methods offer exact solutions for quantum many-body systems but face severe limitations in fermionic systems like atomic nuclei due to the sign problem. While sign-problem-free QMC algorithms exist and provide…

Nuclear Theory · Physics 2026-01-06 Zhong-Wang Niu , Bing-Nan Lu

We present a novel quantum Monte Carlo method based on a path integral in Fock space, which allows to compute finite-temperature properties of a many-body nuclear system with a monopole pairing interaction in the canonical ensemble. It…

Nuclear Theory · Physics 2009-01-23 N. J. Cerf

The recently developed auxiliary field diffusion Monte Carlo method is applied to compute the equation of state and the compressibility of neutron matter. By combining diffusion Monte Carlo for the spatial degrees of freedom and auxiliary…

Nuclear Theory · Physics 2009-11-10 A. Sarsa , S. Fantoni , K. E. Schmidt , F. Pederiva

We calculate the equation of state of neutron matter at zero temperature by means of the auxiliary field diffusion Monte Carlo method (AFDMC) combined with a fixed-phase approximation. The calculation of the energy is carried out by…

Nuclear Theory · Physics 2009-06-30 S. Gandolfi , A. Yu. Illarionov , K. E. Schmidt , F. Pederiva , S. Fantoni

A precise dynamical characterization of quantum impurity models with multiple interacting orbitals is challenging. In quantum Monte Carlo methods, this is embodied by sign problems. A dynamical sign problem makes it exponentially difficult…

Mesoscale and Nanoscale Physics · Physics 2024-07-02 Andre Erpenbeck , Thomas Blommel , Lei Zhang , Wei-Ting Lin , Guy Cohen , Emanuel Gull

We point out that Monte Carlo simulations of theories with severe sign problems can be profitably performed over manifolds in complex space different from the one with fixed imaginary part of the action. We describe a family of such…

High Energy Physics - Lattice · Physics 2016-03-22 Andrei Alexandru , Gokce Basar , Paulo F. Bedaque , Gregory W. Ridgway , Neill C. Warrington

We study a trapped system of fermions with an attractive zero-range two-body interaction using the Shell-Model Monte Carlo method. The method provides {\em ab initio} results in the low $N$ limit where mean-field theory is not applicable.…

Superconductivity · Physics 2008-08-04 N. T. Zinner , K. Mølmer , C. Özen , K. Langanke , D. J. Dean