A5053068389- Numerical methods for differential equations
- Quantum, superfluid, helium dynamics
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Chemical Physics Studies
- Quantum Chromodynamics and Particle Interactions
- High-Energy Particle Collisions Research
- Spectroscopy and Quantum Chemical Studies
- Physics of Superconductivity and Magnetism
- Quantum chaos and dynamical systems
- Matrix Theory and Algorithms
- Atomic and Subatomic Physics Research
- Nonlinear Photonic Systems
- Quantum and electron transport phenomena
- Nonlinear Waves and Solitons
- Particle physics theoretical and experimental studies
- Advanced Numerical Methods in Computational Mathematics
- Electromagnetic Simulation and Numerical Methods
- Model Reduction and Neural Networks
- Advanced Fiber Laser Technologies
- Pulsars and Gravitational Waves Research
- Advanced Thermodynamics and Statistical Mechanics
- Particle accelerators and beam dynamics
- Theoretical and Computational Physics
- Magnetic confinement fusion research
- Molecular spectroscopy and chirality
Texas A&M University
2014-2024
Mitchell Institute
2010
Johannes Kepler University of Linz
2010
Center for Theoretical Biological Physics
1990-2008
University of Michigan
1995
IBM (United States)
1985-1993
3M (United States)
1992
The King's College
1986-1991
Florida State University
1988
University of California, Los Angeles
1982-1985
This report presents a methodology for measuring the performance of supercomputers. It includes 13 Fortran programs that total over 50,000 lines source code. They represent applications in several areas engi neering and scientific computing, many cases codes are currently being used by computational re search development groups. We also present PERFECT standard, set guidelines allow portability to types machines. Furthermore, we some measures method ology recording sharing results among...
This Letter proposes, on the basis of Massachusetts Institute Technology bag model hadrons, that extended, massive, multiquark states possessing great strangeness may be metastable. Such novel matter would have to baryon-number ratio $\frac{|S|}{A}\ensuremath{\simeq}2$ with $A\ensuremath{\gtrsim}10$ and estimated lifetime \ensuremath{\gtrsim} ${10}^{\ensuremath{-}4}$ sec.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectron correlation effects in hyperpolarizabilities of p-nitroanilineFiona Sim, Steven Chin, Michel Dupuis, and Julia E. RiceCite this: J. Phys. Chem. 1993, 97, 6, 1158–1163Publication Date (Print):February 1, 1993Publication History Published online1 May 2002Published inissue 1 February 1993https://pubs.acs.org/doi/10.1021/j100108a010https://doi.org/10.1021/j100108a010research-articleACS PublicationsRequest reuse permissionsArticle...
We compute zero-temperature ground-state energies, one- and two-body densities, collective-excitation spectra, transition static dynamic structure functions of $^{4}\mathrm{He}$ clusters up to a cluster size N=112 particles. The properties are computed using second-order diffusion Monte Carlo algorithm with Jastrow triplet trial used for importance sampling. Excitation obtained by solving generalized Feynman eigenvalue equation. determine the systematic variation collective energies size,...
The electronic structure of the allyl radical C3H5 and polyene radicals C5H7, C7H9, C9H11, C11H13 have been calculated using linear combination Gaussian-type orbitals-local spin density method. In contrast to results obtained Hartree–Fock model, which show large errors, geometries are in excellent agreement with multiconfiguration self-consistent-field calculations experiment. LSD yields a C2v symmetry for radical, while polyenes C5H7 C–C bonds alternating between single double bonds....
We show that the method of factorizing evolution operator to fourth order with purely positive coefficients, in conjunction Suzuki’s implementing time-ordering operators, produces a new class powerful algorithms for solving Schrödinger equation time-dependent potentials. When applied Walker–Preston model diatomic molecule strong laser field, these can have error coefficients are three orders magnitude smaller than Forest–Ruth algorithm using same number fast Fourier transforms. Compared...
The diffusion Monte Carlo algorithm with and without importance sampling is analyzed in terms of the algorithm's underlying transfer matrix. crucial role played by Langevin importance-sampling process made explicit emphasized. failure existing second-order algorithms to converge quadratically for atomic many-body problems shown be caused nonperturbative convergence errors due intrinsic inability sample Slater orbitals. This can simply circumvented enforcing attractive cusp conditions on...
We present a new class of high-order imaginary time propagators for path integral Monte Carlo simulations that require no higher order derivatives the potential nor explicit quadratures Gaussian trajectories. Higher orders are achieved by an extrapolation primitive second-order propagator involving subtractions. By requiring all terms extrapolated to have same trajectory, subtraction only affects part integral. The resulting violation positivity has surprisingly little effects on accuracy...
Optimized variational calculations have been carried out for pure and doped clusters of $^{4}\mathrm{He}$ atoms up to a cluster size N=1000 particles. For small sizes with less than or equal 112 particles, where comparisions existing diffusion Monte Carlo results are possible, we find excellent agreement the ground-state energy, correlation, structure functions. larger our energies extrapolate smoothly toward bulk limit -7.2 K surface energy 0.272...
We investigate the effects of impurities and changing ring geometry on energetics quantum rings under different magnetic field strengths. show that as and/or electron number are/is increased, both quasiperiodic Aharonov-Bohm oscillations various phases become insensitive to whether is circular or square in shape. This qualitative agreement with experiments. However, we also find oscillation can be greatly phase shifted by only a few completely obliterated high level impurity density. In...
By invoking Bogoliubov's spectrum, we show that for the nonlinear Schr\"odinger equation, modulation instability (MI) of its $n=1$ Fourier mode on a finite background automatically triggers further cascading instability, forcing all higher modes to grow exponentially in locked step with mode. This fundamental insight, enslavement mode, explains formation triangular-shaped spectrum generates Akhmediev breather, predicts time analytically from initial amplitude, and shows Fermi-Pasta-Ulam...
Abstract Dipole moments and static dipole polarizabilities have been calculated for a number of small molecules using the linear combination Gaussian‐type orbitals–local spin density method. The effect augmenting standard orbital basis sets with polarization functions has investigated. A set optimum ζ d , use in calculating polarizabilities, derived first‐row atoms C, N, O, F. results this optimized doubly polarized double‐zeta compare well obtained augmented by four even‐tempered functions....
We describe a rapidly converging algorithm for solving the Schrödinger equation with local potentials in real space. The is based on imaginary time by factorizing evolution operator e−εH to fourth order purely positive coefficients. wave functions |ψj〉 and associated energies extracted from normalization factor e−εEj converge as O(ε4). computed directly expectation value, 〈ψj|H|ψj〉, O(ε8). When compared existing second-order split method, our at least of 100 more efficient. examine compare...
We show that the method of splitting operator ${\rm e}^{\epsilon(T+V)}$ to fourth order with purely positive coefficients produces excellent algorithms for solving time-dependent Schr\"odinger equation. These require knowing potential and gradient potential. One 4th algorithm only requires four Fast Fourier Transformations per iteration. In a one dimensional scattering problem, error these new are roughly 500 times smaller than negative coefficient, such as those based on traditional...
We compute the ground-state structure and collective-excitation energies of $^{4}\mathrm{He}$ droplets at zero temperature. The collective excitations are described by a generalized Feynman theory with inputs exact one- two-body densities sampled from second-order diffusion Monte Carlo algorithm. monopole transition density shows pronounced shell not accountable simple Jastrow-type variational trial functions.