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We present an algorithm for rigid body diffusion Monte Carlo with importance sampling, which is based on a rigorous short-time expansion of the Green's function for rotational motion in three dimensions. We show that this short-time…

Computational Physics · Physics 2009-11-07 Alexandra Viel , Mehul V. Patel , Parhat Niyaz , K. Birgitta Whaley

We derive a formula to calculate the local change to the log of any density of states for smooth real observables. Using this in Monte-Carlo simulations, we are able to calculate the expectation value of the observable with a precision…

High Energy Physics - Lattice · Physics 2024-01-03 Rasmus Normann Larsen

We introduce a neural network-based approach for modeling wave functions that satisfy Bose-Einstein statistics. Applying this model to small $^4He_N$ clusters (with N ranging from 2 to 14 atoms), we accurately predict ground state energies,…

Atomic and Molecular Clusters · Physics 2023-12-20 William Freitas , S. A. Vitiello

Monte Carlo computer simulations are virtually the only way to analyze the thermodynamic behavior of a system in a precise way. However, the various existing methods exhibit extreme differences in their efficiency, depending on model…

Statistical Mechanics · Physics 2011-07-05 Michael Bachmann

We report an accurate Monte Carlo calculation of the phase diagram and clustering properties of the restricted primitive model with non-additive hard-sphere diameters. At high density the positively non-additive fluid shows more clustering…

Soft Condensed Matter · Physics 2013-07-11 Riccardo Fantoni , Giorgio Pastore

Computational codes based on the Diffusion Monte Carlo method can be used to determine the quantum state of two-electron systems confined by external potentials of various nature and geometry. In this work, we show how the application of…

Chemical Physics · Physics 2021-02-24 Gaia Micca Longo , Carla Maria Coppola , Domenico Giordano , Savino Longo

We demonstrate the existence of different density-density functionals designed to retain selected properties of the many-body ground state in a non-interacting solution starting from the standard density functional theory ground state. We…

Other Condensed Matter · Physics 2009-11-13 F. A. Reboredo , P. R. C. Kent

Monte-Carlo simulations are routinely used for estimating the scaling exponents of complex systems. However, due to finite-size effects, determining the exponent values is often difficult and not reliable. Here we present a novel technique…

Computational Physics · Physics 2013-03-05 Indrek Mandre , Jaan Kalda

Warm dense matter (WDM) is an active field of research, with applications ranging from astrophysics to inertial confinement fusion. Ionization degree and continuum lowering are important quantities to understand how materials behave under…

Monte Carlo simulations have been performed in order to evaluate the efficiencies of several light ions identification techniques. The detection system was composed with layers of scintillating material to measure either the deposited…

Nuclear Experiment · Physics 2013-10-02 S. Salvador , M. Labalme , J. M. Fontbonne , J. Dudouet , J. Colin , D. Cussol

A phenomenological method based on the natural orbital representation is applied to construct the ground state one-body density matrix which describes correctly both density and momentum distributions in $^{4}He$, $^{16}O$ and $^{40}Ca$…

We combine a Monte Carlo radiative transfer code with an SPH code, so that -- assuming thermal equilibrium -- we can calculate dust-temperature fields, spectral energy distributions, and isophotal maps, for the individual time-frames…

Astrophysics · Physics 2009-11-11 Dimitris Stamatellos , Anthony Whitworth

The configuration-interaction shell model approach provides an attractive framework for the calculation of nuclear level densities in the presence of correlations, but the large dimensionality of the model space has hindered its application…

Nuclear Theory · Physics 2016-01-05 Y. Alhassid , G. F. Bertsch , C. N. Gilbreth , H. Nakada , C. Özen

The "gravitational million-body problem," to model the dynamical evolution of a self-gravitating, collisional N-body system with ~10^6 particles over many relaxation times, remains a major challenge in computational astrophysics.…

Instrumentation and Methods for Astrophysics · Physics 2018-12-07 Carl L. Rodriguez , Bharath Pattabiraman , Sourav Chatterjee , Alok Choudhary , Wei-keng Liao , Meagan Morscher , Frederic A. Rasio

We present a formalism of the transition matrix Monte Carlo method. A stochastic matrix in the space of energy can be estimated from Monte Carlo simulation. This matrix is used to compute the density of states, as well as to construct…

Statistical Mechanics · Physics 2011-12-30 Jian-Sheng Wang , Robert H. Swendsen

The High Energy cosmic-Radiation Detection (HERD) facility onboard China's Space Station is planned for operation starting around 2020 for about 10 years. It is designed as a next generation space facility focused on indirect dark matter…

Instrumentation and Methods for Astrophysics · Physics 2015-06-22 M. Xu , G. M. Chen , Y. W. Dong , J. G. Lu , Z. Quan , L. Wang , Z. G. Wang , B. B. Wu , S. N. Zhang

We provide a pedagogical introduction to the two main variants of real-space quantum Monte Carlo methods for electronic-structure calculations: variational Monte Carlo (VMC) and diffusion Monte Carlo (DMC). Assuming no prior knowledge on…

Chemical Physics · Physics 2015-08-13 Julien Toulouse , Roland Assaraf , C. J. Umrigar

Non-perturbative study of "real-time" field theories is difficult due to the sign problem. We use Bold Schwinger-Dyson (SD) equations to study the real-time $\phi^4$ theory in $d=4$ beyond the perturbative regime. Combining SD equations in…

High Energy Physics - Phenomenology · Physics 2015-12-17 Navid Abbasi , Ali Davody

We use a two-fluid model combining the quantum Green's function technique for the electrons and a classical HNC description for the ions to calculate the high-density equation of state of hydrogen. This approach allows us to describe fully…

Plasma Physics · Physics 2011-08-25 J. Vorberger , D. O. Gericke , W. -D. Kraeft

We introduce a class of unbiased Monte Carlo estimators for the multivariate density of max-stable fields generated by Gaussian processes. Our estimators take advantage of recent results on exact simulation of max-stable fields combined…

Computation · Statistics 2017-02-28 Jose Blanchet , Zhipeng Liu