Search Results

Advanced search parameters have been applied.
open access

24-th Order high temperature expansion for the 3-d Ising model

Description: The authors present the series for the free energy and their estimate for the critical exponent {alpha}, as computed by a recursive bookkeeping algorithm on the CM5. They begin with a discussion of the algorithm to compute the High-Temperature expansion on finite 3-D Ising lattices.
Date: December 1, 1994
Creator: Glaessner, U.; Schilling, K.; Bhanot, G. & Creutz, M.
Partner: UNT Libraries Government Documents Department
open access

2D PERT. A TWO-DIMENSIONAL PERTURBATION CODE

Description: Given multigroup fluxes and adjoint fluxes of any cylindrical R-Z configuration, 2D PERT may compute: the prompt-neutron lifetime; the relative worth of various delayed neutrons; the integrals of capture, fission, etc., of given materials over any given region; local perturbations, i.e., danger coefflcients; and integrated perturbations, i.e., reactivity effect of uniform variation in the cross sections affecting a whole region. 2D PERT is programmed for a 32K IBM-704 using 3 tape units. The co… more
Date: May 1, 1962
Creator: Chaumont, J. M. & Koerner, J. A.
Partner: UNT Libraries Government Documents Department
open access

Ab Initio and Ab Exitu No-Core Shell Model

Description: We outline two complementary approaches based on the no core shell model (NCSM) and present recent results. In the ab initio approach, nuclear properties are evaluated with two-nucleon (NN) and three-nucleon interactions (TNI) derived within effective field theory (EFT) based on chiral perturbation theory (ChPT). Fitting two available parameters of the TNI generates good descriptions of light nuclei. In a second effort, an ab exitu approach, results are obtained with a realistic NN interaction … more
Date: October 2, 2007
Creator: Vary, J. P.; Navratil, P.; Gueorguiev, V. G.; Ormand, W. E.; Nogga, A.; Maris, P. et al.
Partner: UNT Libraries Government Documents Department
open access

Ab initio and density functional studies of hydrocarbon adsorption in zeolites.

Description: The adsorption energies of methane and ethane in zeolites are investigated with ab initio molecular orbital theory and density functional theory. In this work we have used zeolite cluster models containing two, three, and five tetrahedral (Si, Al) atoms and have found equilibrium structures for complexes of methane, ethane, and propane with an acid site. If a large enough cluster is used and correlation effects are included via perturbation theory, the calculated adsorption energy for ethane is… more
Date: August 21, 1998
Creator: Curtiss, L. A.
Partner: UNT Libraries Government Documents Department
open access

Ab Initio No-Core Shell Model

Description: A long-standing goal of nuclear theory is to determine the properties of atomic nuclei based on the fundamental interactions among the protons and neutrons (i.e., nucleons). By adopting nucleon-nucleon (NN), three-nucleon (NNN) and higher-nucleon interactions determined from either meson-exchange theory or QCD, with couplings fixed by few-body systems, we preserve the predictive power of nuclear theory. This foundation enables tests of nature's fundamental symmetries and offers new vistas for t… more
Date: April 11, 2011
Creator: Barrett, B R; Navratil, P & Vary, J P
Partner: UNT Libraries Government Documents Department
open access

Ab Initio Study of 40Ca with an Importance Truncated No-Core Shell Model

Description: We propose an importance truncation scheme for the no-core shell model, which enables converged calculations for nuclei well beyond the p-shell. It is based on an a priori measure for the importance of individual basis states constructed by means of many-body perturbation theory. Only the physically relevant states of the no-core model space are considered, which leads to a dramatic reduction of the basis dimension. We analyze the validity and efficiency of this truncation scheme using differen… more
Date: May 22, 2007
Creator: Roth, R & Navratil, P
Partner: UNT Libraries Government Documents Department
open access

Accelerating the Loop Expansion

Description: This thesis introduces a new non-perturbative technique into quantum field theory. To illustrate the method, I analyze the much-studied phi/sup 4/ theory in two dimensions. As a prelude, I first show that the Hartree approximation is easy to obtain from the calculation of the one-loop effective potential by a simple modification of the propagator that does not affect the perturbative renormalization procedure. A further modification then susggests itself, which has the same nice property, and w… more
Date: July 29, 1986
Creator: Ingermanson, R.
Partner: UNT Libraries Government Documents Department
open access

Adaptive Perturbation Theory I: Quantum Mechanics

Description: Adaptive perturbation is a new method for perturbatively computing the eigenvalues and eigenstates of quantum mechanical Hamiltonians that heretofore were not believed to be treatable by such methods. The novel feature of adaptive perturbation theory is that it decomposes a given Hamiltonian, H, into an unperturbed part and a perturbation in a way which extracts the leading non-perturbative behavior of the problem exactly. This paper introduces the method in the context of the pure anharmonic o… more
Date: October 19, 2005
Creator: Weinstein, Marvin
Partner: UNT Libraries Government Documents Department
open access

Adaptive Perturbation Theory: Quantum Mechanics and Field Theory

Description: Adaptive perturbation is a new method for perturbatively computing the eigenvalues and eigenstates of quantum mechanical Hamiltonians that are widely believed not to be solvable by such methods. The novel feature of adaptive perturbation theory is that it decomposes a given Hamiltonian, H, into an unperturbed part and a perturbation in a way which extracts the leading non-perturbative behavior of the problem exactly. In this talk I will introduce the method in the context of the pure anharmonic… more
Date: October 19, 2005
Creator: Weinstein, Marvin
Partner: UNT Libraries Government Documents Department
open access

AGS-2000: Experiments for the 21. Century. Proceedings of the workshop held at Brookhaven National Laboratory, May 13--17, 1996

Description: The AGS has a vital and interesting potential for new research. The reasons for this are a fortunate concomitance of the energy chosen for the AGS and the steady stream of technological advances which have both increased the intensity and flexibility of the AGS beams, and the capability of detectors to use these new beam parameters. The physics potentials of the future AGS program can be roughly divided into three broad areas. (1) fundamental elementary particle studies (based on rare kaon deca… more
Date: October 1, 1996
Creator: Littenberg, L. & Sandweiss, J.
Partner: UNT Libraries Government Documents Department
open access

Alfven cyclotron instability and ion cyclotron emission

Description: Two-dimensional solutions of compressional Alfven eigenmodes (CAE) are studied in the cold plasma approximation. For finite inverse aspect ratio tokamak plasmas the two-dimensional eigenmode envelope is localized at the low magnetic field side with the radial and poloidal localization on the order of a/{radical}m and a/(fourth root of m), respectively, where m is the dominant poloidal mode number. Charged fusion product driven Alfven Cyclotron Instability (ACI) of the compressional Alfven eigen… more
Date: July 1995
Creator: Gorelenkov, N. N. & Cheng, C. Z.
Partner: UNT Libraries Government Documents Department
open access

All-Optical Time-Resolved Measurement of Laser Energy Modulation in a Relativistic Electron Beam

Description: Hamiltonian light-front theory has been proposed as a promising method for solving bound states problems in quantum field theory a long time ago, see, e.g., the review article[1] for its various advantages compared to the traditional instant-form theories. Recently the Basis Light-Front Quantization (BLFQ) approach [2, 3] has been developed as a nonperturbative approach to solve Hamiltonian light-front quantum field theory. Numerical efficiency is a key advantage of this approach. The basic ide… more
Date: February 15, 2012
Creator: Xiang, D.; Colby, E.; Dunning, M.; Gilevich, S.; Hast, C.; Jobe, K. et al.
Partner: UNT Libraries Government Documents Department
open access

An Analogue Solution of a Reactor Perturbation Initiated by a Metallurgical Phase Transformation of the Fuel

Description: The analysis of a reactor model that is thermally nonlinear is presented. The significant sources of feadback in the closed-loop model ane dilatational changes of the fuel due to axial expansion caused by temperature and metallurgical phase changes. Ths dynamics of this phenomenon has been represented on the Pace electronic analog com puter. The model was subjected to unusually large inputs of sinusoidal power and did not show any drastic tendencies toward being unstable. (auth)
Date: January 1, 1961
Creator: Bryant, L. T.; Carter, J. C. & Janicke, M. J.
Partner: UNT Libraries Government Documents Department
open access

Analysis of Br(anti-B ---> X(s gamma)) at NNLO With a Cut on Photon Energy

Description: By combining a recent estimate of the total {bar B} {yields} X{sub s}{gamma} branching fraction at O({alpha}{sub s}{sup 2}) with a detailed analysis of the effects of a cut E{sub {gamma}} {ge} 1.6 GeV on photon energy, a prediction for the partial {bar B} {yields} X{sub s}{gamma} branching fraction at next-to-next-to-leading order in renormalization-group improved perturbation theory is obtained, in which contributions from all relevant scales are properly factorized. The result Br({bar B} {yie… more
Date: October 1, 2006
Creator: Becher, Thomas & Neubert, Matthias
Partner: UNT Libraries Government Documents Department
open access

Analytic Expressions for Optimal ICF Hohlraum Wall Density and Wall Loss

Description: Solutions to the radiation diffusion equation predict the absorbed energy (''wall loss'') within an inertial confinement fusion (ICF) hohlraum. Comparing supersonic vs. subsonic solutions suggests that a high Z metallic foam as hohlraum wall material will reduce hydrodynamic losses, and hence, net absorbed energy by {approx}20%. We derive an analytic expression for the optimal density (for any given drive temperature and pulse-length) that will achieve this reduction factor and which agrees wel… more
Date: May 25, 2004
Creator: Rosen, M D & Hammer, J H
Partner: UNT Libraries Government Documents Department
open access

Analytical Approach to Eigen-Emittance Evolution in Storage Rings

Description: This dissertation develops the subject of beam evolution in storage rings with nearly uncoupled symplectic linear dynamics. Linear coupling and dissipative/diffusive processes are treated perturbatively. The beam distribution is assumed Gaussian and a function of the invariants. The development requires two pieces: the global invariants and the local stochastic processes which change the emittances, or averages of the invariants. A map based perturbation theory is described, providing explicit … more
Date: May 16, 2006
Creator: Nash, Boaz
Partner: UNT Libraries Government Documents Department
open access

Analytical solutions of moisture flow equations and their numerical evaluation

Description: The role of analytical solutions of idealized moisture flow problems is discussed. Some different formulations of the moisture flow problem are reviewed. A number of different analytical solutions are summarized, including the case of idealized coupled moisture and heat flow. The evaluation of special functions which commonly arise in analytical solutions is discussed, including some pitfalls in the evaluation of expressions involving combinations of special functions. Finally, perturbation the… more
Date: April 1, 1981
Creator: Gibbs, A. G.
Partner: UNT Libraries Government Documents Department
open access

Anomalous dimensions of multiquark bound states

Description: The evolution of six-quark color-singlet state distribution amplitudes is formulated as an application of perturbative quantum chromodynamics to nuclear wave functions. We present a general method of solving the evolution equation for multiquark bound states and predict the asymptotic Q/sup 2/ slope for the deuteron charge form factor as a result.
Date: July 1, 1986
Creator: Ji, Cheung-Ryong
Partner: UNT Libraries Government Documents Department
open access

Anomalous {gamma} {r_arrow} 3{pi} amplitude in a bound-state approach

Description: The form factor for the anomalous process {gamma}{pi}{sup +} {r_arrow} pi{sub +}{pi}{sup 0}, which is presently being measured at CEBAF, is calculated in the Schwinger-Dyson approach in conjunction with an impulse approximation. The form factors obtained by the author are compared with the ones predicted by the simple constituent quark loop model, vector meson dominance and chiral perturbation theory, as well as the scarce already available data.
Date: January 1, 2000
Creator: Bistrovic, Bojan & Klabucar, Dubravko
Partner: UNT Libraries Government Documents Department
Back to Top of Screen