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An appropriate iterative scheme for the minimization of the energy, based on the variational Monte Carlo (VMC) technique, is introduced and compared with existing stochastic schemes. We test the various methods for the 1D Heisenberg ring…

Strongly Correlated Electrons · Physics 2009-11-11 Sandro Sorella

In non-relativistic quantum mechanics of $N$ particles in three spatial dimensions, the wave function $\psi(q_1,\ldots,q_N,t)$ is a function of $3N$ position coordinates and one time coordinate. It is an obvious idea that in a relativistic…

Quantum Physics · Physics 2018-01-24 Matthias Lienert , Sören Petrat , Roderich Tumulka

We show a general phenomenon of the constrained functional value for densities satisfying general convexity conditions, which generalizes the observation in Bobkov and Madiman (2011) that the entropy per coordinate in a log-concave random…

Information Theory · Computer Science 2020-10-27 Yanjun Han

Density functional perturbation theory is a well-established method to study responses of molecules and solids, especially responses to atomic displacements or to different perturbing fields (electric, magnetic). Like for density functional…

Materials Science · Physics 2024-02-16 Xavier Gonze , Samare Rostami , Christian Tantardini

It would be interesting to investigate the accuracy of the results obtained in the variational method, because it is important for studying hadron spectra. One can define some criteria to judge the accuracy, or the quality of the trial…

High Energy Physics - Phenomenology · Physics 2007-05-23 Yi-Bing Ding , Xue-Qian Li , Peng-Nian Shen

Determining quantum excited states is crucial across physics and chemistry but presents significant challenges for variational methods, primarily due to the need to enforce orthogonality to lower-energy states, often requiring…

Quantum Physics · Physics 2025-05-01 Shi-Xin Zhang , Lei Wang

I present a new way to solve the Wheeler--de Witt equation using the invariance of the classical lagrangian under reparametrization. This property allows one to introduce an arbitrary function for each degree of freedom of the wave function…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Marco Cavaglià

Selection of physically meaningful solutions of the Wheeler-DeWitt equation for the wavefunction in quantum cosmology, can be attained by a reduction of the theory to the sector of true physical degrees of freedom and their canonical…

General Relativity and Quantum Cosmology · Physics 2014-05-06 A. O. Barvinsky , A. Yu. Kamenshchik

The Hartree-Fock approximation for bosons employs variational wave functions that are a combination of permanents. These are bosonic counterpart of the fermionic Slater determinants, but with the significant distinction that the…

Quantum Gases · Physics 2025-03-03 B. R. Que , J. M. Zhang , H. F. Song , Y. Liu

To avoid instabilities in the continuum semi-classical limit of loop quantum cosmology models, refinement of the underlying lattice is necessary. The lattice refinement leads to new dynamical difference equations which, in general, do not…

General Relativity and Quantum Cosmology · Physics 2008-12-18 William Nelson , Mairi Sakellariadou

The efficiency of the variational perturbation theory [Phys. Rev. C {\bf 62}, 045503 (2000)] formulated recently for many-particle systems is examined by calculating the ground state correlation energy of the 3D electron gas with the…

Strongly Correlated Electrons · Physics 2009-11-07 Sang Koo You , Noboru Fukushima

In the regime where traditional approaches to electronic structure cannot afford to achieve accurate energy differences via exhaustive wave function flexibility, rigorous approaches to balancing different states' accuracies become…

Chemical Physics · Physics 2017-11-22 Paul J. Robinson , Sergio D. Pineda Flores , Eric Neuscamman

We use the virial expansion to investigate the behavior of the two-component, attractive Fermi gas in the high-temperature limit, where the system smoothly evolves from weakly attractive fermions to weakly repulsive bosonic dimers as the…

Quantum Gases · Physics 2015-01-12 V. Ngampruetikorn , Meera M. Parish , Jesper Levinsen

A variational wave function constructed with correlated Hyperspherical Harmonic functions is used to describe the Helium trimer. This system is known to have a deep bound state. In addition, different potential models predict the existence…

Atomic and Molecular Clusters · Physics 2009-11-07 Paolo Barletta , Alejandro Kievsky

A novel concept of multiconfigurational self-consistent field method, the generalized occupation-restricted-multiple-active-space (GORMAS) is presented. GORMAS wave functions are defined by substituting the complete active space (CAS) in…

Chemical Physics · Physics 2021-12-01 Chen Yang , Yoshihiro Watanabe , Haruyuki Nakano

We employ a generalized variational principle to improve the stability, reliability, and precision of fully excited-state-specific complete active space self-consistent field theory. Compared to previous approaches that similarly seek to…

Chemical Physics · Physics 2022-09-05 Rebecca Hanscam , Eric Neuscamman

A method is developed that allows analysis of quantum Monte Carlo simulations to identify errors in trial wave functions. The purpose of this method is to allow for the systematic improvement of variational wave functions by identifying…

Strongly Correlated Electrons · Physics 2016-08-03 Kiel T. Williams , Lucas K. Wagner

A variational Perturbation theory based on the functional integral approach is formulated for many-particle systems. Using the variational action obtained through Jensen-Peierls' inequality, a perturbative expansion scheme for the…

Strongly Correlated Electrons · Physics 2009-10-31 Sang Koo You , Chul Koo Kim , Kyun Nahm , Hyun Sik Noh

Variational wave functions containing electronic pairing and suppressed charge fluctuations (i.e., projected BCS states) have been proposed as the paradigm for disordered magnetic systems (including spin liquids). Here we discuss the…

Strongly Correlated Electrons · Physics 2009-06-01 Federico Becca , Luca Capriotti , Alberto Parola , Sandro Sorella

A principle is proposed according to which the dynamics of a quantum particle in a one-dimensional configuration space (OCS) is determined by a variational problem for two functionals: one is based on the mean value of the Hamilton…

Quantum Physics · Physics 2023-08-15 N. L. Chuprikov