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We present a quantum Monte Carlo (QMC) technique for calculating the exact finite-temperature properties of Bose-Fermi mixtures. The Bose-Fermi Auxiliary-Field Quantum Monte Carlo (BF-AFQMC) algorithm combines two methods, a…

Quantum Gases · Physics 2012-12-04 Brenda M. Rubenstein , Shiwei Zhang , David R. Reichman

Frustrated spin systems generically suffer from the negative sign problem inherent to Monte Carlo methods. Since the severity of this problem is formulation dependent, optimization strategies can be put forward. We introduce a phase pinning…

Strongly Correlated Electrons · Physics 2021-08-18 Toshihiro Sato , Fakher F. Assaad

Phaseless Auxiliary-Field Quantum Monte Carlo (ph-AFQMC) has recently emerged as a promising method for the production of benchmark-level simulations of medium to large-sized molecules, due to its accuracy and favorable polynomial scaling…

The ability to accurately predict the finite temperature properties of realistic quantum solids is central to uncovering new phases and engineering materials with novel properties. Nonetheless, there remain comparatively few many-body…

Strongly Correlated Electrons · Physics 2020-07-21 Yuan Liu , Tong Shen , Hang Zhang , Brenda Rubenstein

We present three distinct examples where phaseless auxiliary-field Quantum Monte Carlo (ph-AFQMC) can be reliably performed with a single-determinant trial wavefunction with essential symmetry breaking. We first utilized essential…

Chemical Physics · Physics 2020-04-20 Joonho Lee , Fionn D. Malone , Miguel A. Morales

We provide a negative-sign-free formulation of the auxiliary field quantum Monte Carlo algorithm for generalized Kitaev models with higher symmetries. Our formulation is based on the Abrikosov fermion representation of the spin-1/2 degree…

Strongly Correlated Electrons · Physics 2022-10-19 Toshihiro Sato , Fakher F. Assaad

We applied a mean-field approach associated to Monte Carlo simulations in order to study the spin-1 ferromagnetic Blume-Capel model in the square and the linear lattice. This new technique, which we call MFT-MC, determines the molecular…

Statistical Mechanics · Physics 2016-07-06 J. Roberto Viana , Octavio D. Rodriguez Salmon , Minos A. Neto

We outline how auxiliary-field quantum Monte Carlo (AFQMC) can leverage graphical processing units (GPUs) to accelerate the simulation of solid state sytems. By exploiting conservation of crystal momentum in the one- and two-electron…

Computational Physics · Physics 2020-08-21 Fionn D. Malone , Shuai Zhang , Miguel A. Morales

In this thesis, the properties of mixtures of Bose-Einstein condensates at $T = 0$ have been investigated using quantum Monte Carlo (QMC) methods and Density Functional Theory (DFT) with the aim of understanding physics beyond the…

Quantum Gases · Physics 2021-05-05 Viktor Cikojević

We describe a new algorithm for the numerical simulation of quantum spin and boson systems. The method is based on the Trotter decomposition in imaginary time and a decoupling by auxiliary Ising spins. It can be applied, in principle, to…

Disordered Systems and Neural Networks · Physics 2009-10-31 M. Ulmke , R. T. Scalettar

We develop an all-electron quantum Monte Carlo (QMC) method for solids that does not rely on pseudopotentials, and use it to construct a primary ultra-high pressure calibration based the equation of state of cubic boron nitride(c-BN). We…

Materials Science · Physics 2015-05-14 K. P. Esler , R. E. Cohen , B. Militzer , Jeongnim Kim , R. J. Needs , M. D. Towler

Quantum Monte Carlo methods have recently been employed to study properties of nuclei and infinite matter using local chiral effective field theory interactions. In this work, we present a detailed description of the auxiliary field…

Nuclear Theory · Physics 2018-05-02 D. Lonardoni , S. Gandolfi , J. E. Lynn , C. Petrie , J. Carlson , K. E. Schmidt , A. Schwenk

The bond dissociation energies of a set of 44 3d transition metal-containing diatomics are computed with phaseless auxiliary-field quantum Monte Carlo (ph-AFQMC) utilizing a correlated sampling technique. We investigate molecules with H, N,…

The many-body diffusion quantum Monte Carlo (DMC) method with twist-averaged boundary conditions is used to calculate the ground-state equation of state and the energetics of point defects in fcc aluminum using supercells up to 1331 atoms.…

Materials Science · Physics 2012-10-22 Randolph Q. Hood , P. R. C. Kent , Fernando A. Reboredo

The chromium dimer (Cr2) presents an outstanding challenge for many-body electronic structure methods. Its complicated nature of binding, with a formal sextuple bond and an unusual potential energy curve, is emblematic of the competing…

Computational Physics · Physics 2015-02-17 Wirawan Purwanto , Shiwei Zhang , Henry Krakauer

Nearest-neighbor Heisenberg antiferromagnet on a face-centered cubic lattice is studied by extensive Monte Carlo simulations in zero magnetic field. The parallel tempering algorithm is utilized, which allows to overcome a slow relaxation of…

Statistical Mechanics · Physics 2007-05-23 M. V. Gvozdikova , M. E. Zhitomirsky

This paper describes a method of numerical evaluating high-order QED contributions to the electron anomalous magnetic moment. The method is based on subtraction of infrared and ultraviolet divergences in Feynman-parametric space before…

High Energy Physics - Phenomenology · Physics 2018-11-07 Sergey Volkov

We discuss the pseudogap regime in the cold atomic unitary Fermi gas, with a particular emphasis on the auxiliary-field quantum Monte Carlo (AFMC) approach. We discuss possible signatures of the pseudogap, review experimental results, and…

Quantum Gases · Physics 2019-03-27 S. Jensen , C. N. Gilbreth , Y. Alhassid

In this paper, we present two multiple scalar auxiliary variable (MSAV)-based, finite element numerical schemes for the Abels-Garcke-Gr{\"u}n (AGG) model, which is a thermodynamically consistent phase field model of two-phase incompressible…

Numerical Analysis · Mathematics 2024-08-09 Jiancheng Wang , Maojun Li , Cheng Wang

Magnetization processes of the spin-1/2 antiferromagnetic $XXZ$ model in two and three spatial dimensions are studied using quantum Monte Carlo method based on stochastic series expansions. Recently developed operator-loop algorithm enables…

Strongly Correlated Electrons · Physics 2009-11-07 Seiji Yunoki