Competing unconventional superconductivity and antiferromagnetism widely exist in several strongly correlated quantum materials whose direct simulation generally suffers from fermion sign problem. Here we report unbiased Quantum Monte Carlo (QMC) simulations on a sign-problem-free repulsive toy model with same onsite symmetries as the standard Hubbard 2D square lattice. Using QMC, supplemented ...

This article provides an overview of some interfaces between the theory of quasi-Monte Carlo (QMC) methods and applications. We summarize three QMC theoretical settings: first order QMC methods in the unit cube [0, 1] and in R, and higher order QMC methods in the unit cube. One important feature is that their error bounds can be independent of the dimension s under appropriate conditions on the...

The LDA+DMFT approach merges conventional band structure theory in the local density approximation (LDA) with a state-of-the-art many-body technique, the dynamical mean-field theory (DMFT). This new computational scheme has recently become a powerful tool for ab initio investigations of real materials with strong electronic correlations. In this paper an introduction to the basic ideas and the ...

We present an efficient scheme for representing many-body wave functions in quantum Monte Carlo (QMC) calculations. The scheme is based on B splines (blip functions), which consist of localized cubic splines centered on the points of a regular grid. We show that blip functions are unbiased, systematically improvable, and conveniently obtained from any standard plane-wave density functional theo...

Abstract First-principles approaches based on density functional theory (DFT) for calculating positron states and annihilation characteristics in condensed matter are presented. The treatment of electron-positron correlation effects is shown to play a crucial role when calculating affinities and annihilation rates. A generalized gradient approximation (GGA) takes the strong inhomogeneities of t...

We present an efficient low-rank updating algorithm for updating the trial wave functions used in quantum Monte Carlo (QMC) simulations. The algorithm is based on low-rank updating of the Slater determinants. In particular, the computational complexity of the algorithm is O(kN) during the kth step compared to traditional algorithms that require O(N(2)) computations, where N is the system size. ...

This paper collects together some properties of multidimensional definitions of the total variation of a real valued function. The subject has been studied for a long time. Many of the results presented here date back at least to the early 1900s. The main reason for revisiting this topic is that there has been much recent work in theory and applications of Quasi-Monte Carlo (QMC) sampling. For ...

An OpenMP version of a Quantum Monte Carlo (QMC) code has been developed. The original parallel MPI version of the QMC code was developed by the Electronic Structure of Solids HPCI consortium in collaboration with EPCC. This code has been highly successful, and has resulted in numerous publications based on results generated on the National Cray MPP systems at EPCC. Recent interest has focussed...

We investigate the behavior of flux lines in the presence of both columnar and point disorder in 1+1 dimension using Renormalization Group (RG) and world-line Quantum Monte Carlo (QMC) techniques. In particular, we calculate the transverse wandering correlation function for a single boson and recover known results for point and columnar disorder separately. We then examine the existence of a lo...

We perform the projector quantum Monte Carlo (QMC) simulation to study trion formation and phase transition in half filled attractive SU(3) Hubbard model on a honeycomb lattice. With increasing interaction, our simulations demonstrate continuous from semimetal charge-density wave (CDW) at critical coupling ${U}_{c}/t=\ensuremath{-}1.52(2)$. The exponents $\ensuremath{\nu}=0.82(3)$ $\ensuremath{...