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in subjects: "Hamiltonians"

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A scaling theory for the assignment of spectra in the irregular region. Continuation progress report

The ultimate object of our program is to learn how to extract information about molecular rovibrational motions from experimental spectra or calculated energy levels. This goal of spectroscopy and theoretical chemistry has historically only been possible in the regular spectral region. Our project is one of several which are aimed at spectral interpretation in the chaotic or mixed chaotic plus regular regions. Our particular tools involve a scaling theory developed under our previous DOE suppor… more

Date: June 1, 1998

Creator: Taylor, H.S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Theory of gain in group-III nitride lasers

A microscopic theory of gain in a group-III nitride quantum well laser is presented. The approach, which treats carrier correlations at the level of quantum kinetic theory, gives a consistent account of plasma and excitonic effects in an inhomogeneously broadened system.

Date: June 1, 1997

Creator: Chow, W.W.; Wright, A.F. & Girndt, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Symbolic derivation of high-order Rayleigh-Schroedinger perturbation energies using computer algebra: Application to vibrational-rotational analysis of diatomic molecules

Rayleigh-Schroedinger perturbation theory is an effective and popular tool for describing low-lying vibrational and rotational states of molecules. This method, in conjunction with ab initio techniques for computation of electronic potential energy surfaces, can be used to calculate first-principles molecular vibrational-rotational energies to successive orders of approximation. Because of mathematical complexities, however, such perturbation calculations are rarely extended beyond the second o… more

Date: July 1, 1997

Creator: Herbert, J. M.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

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Crab crossing in a large hadron collider

Since its invention by Palmer in 1988, crab crossing has been explored by many people for both linear and storage ring collides to allow for an angle crossing without a loss of luminosity. Various crab crossing scenarios have been incorporated in the design of newly proposed linear collides and {Beta}-factory projects. For a hadron collider, this scheme can also be employed to lower {Beta}* at the interaction point for a higher luminosity. In this paper, we first review the principle and operat… more

Date: December 1, 1996

Creator: Wei, Jie

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Alfven-wave particle interaction in finite-dimensional self-consistent field model

A low-dimensional Hamiltonian model is derived for the acceleration of ions in finite amplitude Alfven waves in a finite pressure plasma sheet. The reduced low-dimensional wave-particle Hamiltonian is useful for describing the reaction of the accelerated ions on the wave amplitudes and phases through the self-consistent fields within the envelope approximation. As an example, the authors show for a single Alfven wave in the central plasma sheet of the Earth`s geotail, modeled by the linear pinc… more

Date: October 9, 1998

Creator: Padhye, N. & Horton, W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Round table discussion. Relativistic approaches to hadrons and nuclei at medium energies

The purpose of these discussions is to illuminate a variety of different approaches to the nonperturbative dynamics of hadrons and nuclei at medium energies.

Date: December 1, 1995

Creator: Coester, F.; Karmanov, V.A. & Lev, F.M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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A Model of Shape Memory Materials with Hierarchical Twinning: Statics and Dynamics

We consider a model of shape memory material in which hierarchical twinning near the habit plane (austenite-martensite interface) is a new and crucial ingredient. The model includes (1) a triple-well potential ({phi} model) in local shear strain, (2) strain gradient terms up to second order in strain and fourth order in gradient, and (3) all symmetry allowed compositional fluctuation induced strain gradient terms. The last term favors hierarchy which enables communication between macroscopic (c… more

Date: July 1, 1995

Creator: Saxena, A.; Bishop, A. R.; Shenoy, S. R.; Wu, Y. & Lookman, T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Variational Monte Carlo Calculations of {sup 3}He and {sup 4}He with a Relativistic Hamiltonian - II

In relativistic Hamiltonians the two-nucleon interaction is expressed as a sum of {tilde v}{sub ij}, the interaction in the P{sub ij}=0 rest frame, and the ''boost interaction'' {delta}v(P{sub ij}) which depends upon the total momentum P{sub ij} and vanishes in the rest frame. The {delta}v can be regarded as a sum of four terms: {delta}v{sub RE}, {delta}v{sub LC}, {delta}v{sub TP} and {delta}v{sub QM}; the first three originate from the relativistic energy-momentum relation, Lorentz contraction… more

Date: October 1, 1994

Creator: Forest, J.L.; Pandharipande, V.R.; Carlson, J. & Schiavilla, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Arbitrary order transfer maps for RF cavities

Current modeling of transfer maps for superconducting RF cavities at CEBAF includes only linear effects. Here we extend the transfer mapping modeling capability to include arbitrary order field information generated from the MAFIA field data. We include coupler kicks, normal and skew quadrupole focussing and higher order effects.

Date: December 31, 1995

Creator: van Zeijts, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Mesoscale modeling of irreversible volume growth in powders of anisotropic crystals

Careful thermometric analysis (TMA) on powders of micron-sized triamino-trinitrobenzene (TATB) crystallites are shown to display irreversible growth in volume when subjected to repeated cycles of heating and cooling. Such behavior is counter-intuitive to typical materials response to simulated annealing cycles in atomic-scale molecular dynamics. However, through coarse-grained simulations using a mesoscale Hamiltonian we quantitatively reproduce irreversible growth behavior in such powdered mat… more

Date: May 5, 2006

Creator: Gee, R.; Maiti, A. & Fried, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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An Algebraic Approach to the Evolution of Emittances upon Crossing the Linear Coupling Difference Resonance

One of the hallmarks of linear coupling is the resonant exchange of oscillation amplitude between the horizontal and vertical planes when the difference between the unperturbed tunes is close to an integer. The standard derivation of this phenomenon (known as the difference resonance) can be found, for example, in the classic papers of Guignard [1, 2]. One starts with an uncoupled lattice and adds a linear perturbation that couples the two planes. The equations of motion are expressed in hamilt… more

Date: September 1, 2008

Creator: Gardner,C.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Transverse Mode Coupling Instability in a Double RF System

The equations for transverse mode coupling in a storage ring with a double rf system are derived from a Hamiltonian formalism. The resulting integral equation is expanded into a set of orthogonal polynomials, and the expansion coefficients are then given by the solution of an infinite determinant. Truncation of this determinant permits solution of the problem on a computer, and a code has been written which finds the complex mode frequencies. The stability limits of LEP with a third harmonic ar… more

Date: February 1, 1993

Creator: Chin, Y.-H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Dynamical Effects Due to Fringe Field of the Magnets in Circular Accelerators

The leading Lie generators, including the chromatic effects, due to hard-edge fringe field of single multipole and solenoid are derived from the vector potentials within a Hamiltonian system. These nonlinear generators are applied to the interaction region of PEP-II to analyze the linear errors due to the feed-down from the off-centered quadrupoles and solenoid. The nonlinear effects of tune shifts at large amplitude, the synchro-betatron sidebands near half integer and their impacts on the dyn… more

Date: May 16, 2005

Creator: Cai, Y. & Nosochkov, Yu

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Shell Model in a First Principles Approach

We develop and apply an ab-initio approach to nuclear structure. Starting with the NN interaction, that fits two-body scattering and bound state data, and adding a theoretical NNN potential, we evaluate nuclear properties in a no-core approach. For presently feasible no-core model spaces, we evaluate an effective Hamiltonian in a cluster approach which is guaranteed to provide exact answers for sufficiently large model spaces and/or sufficiently large clusters. A number of recent applications a… more

Date: January 8, 2004

Creator: Navratil, P; Nogga, A; Lloyd, R; Vary, J P; Ormand, W E & Barrett, B R

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Composite fermion excitations in fractional quantum Hall systems

In two dimensional systems in a strong magnetic field, electrons can be transformed into composite Fermions (CF) by attaching to each a fictitious flux tube (carrying flux {Phi}) and fictitious charge q, where the product q{sup {Phi}} is a multiple of 2 {Pi}. In the mean field approximation, this transformation converts a fractionally filled electron Landau level into an integrally filled CF Landau level. This integrally filled CF Landau level corresponds to the ground state of a Laughlin incom… more

Date: April 1, 1995

Creator: Quinn, John J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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On the robustness of the localized spatiotemporal structures in electron-positron-ion plasmas

It is shown that, in an electron-positron plasma with a small fraction of ions, large-amplitude localized spatiotemporal structures (light bullets) can be readily generated and sustained. These light bullets are found to be exceptionally robust: they can emerge from a large variety of initial field distributions and are remarkably stable.

Date: April 1, 1998

Creator: Mahajan, S. M.; Berezhiani, V. I. & Miklaszewski, R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Modelling crystal-field interaction for f-elements in LaCl{sub 3}

The results of crystal field calculations in the framework of exchange charge model (ECM) are reported for trivalent lanthanide and actinide ions doped into LaCl{sub 3}. Whereas the scalar strength of the model crystal field parameters are consistent with that previously determined by fitting the experimental data, the sign of the second-order parameter is found to be negative, in contrast to previous reports. The contribution from long-range electrostatic interactions exceeds that from the nea… more

Date: September 1, 1997

Creator: Zhorin, V. V. & Liu, G. K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Nonlinear instability and chaos in plasma wave-wave interactions. II. Numerical methods and results

In Part I of this work and Physics of Plasmas, June 1995, the behavior of linearly stable, integrable systems of waves in a simple plasma model was described using a Hamiltonian formulation. It was shown that explosive instability arises from nonlinear coupling between modes of positive and negative energy, with well-defined threshold amplitudes depending on the physical parameters. In this concluding paper, the nonintegrable case is treated numerically. Several sets of waves are considered, co… more

Date: May 1, 1995

Creator: Kueny, C.S. & Morrison, P.J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Collective instabilities and halo formation of space-charge dominated beams in a particle-beam nonlinear-Dynamics approach

Nonlinear dynamics deals with parametric resonances and diffusion, which are usually beam-intensity independent and rely on a particle Hamiltonian. Collective instabilities deal with beam coherent motion, where the Vlasov equation is frequently used in conjunction with a beam-intensity dependent Hamiltonian. The authors address the questions: Are the two descriptions the same? Are collective instabilities the results of encountering parametric resonances whose driving force is intensity depende… more

Date: August 23, 2000

Creator: Ng, King-Yuen

Item Type: Article

Partner: UNT Libraries Government Documents Department

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High-Energy Colliding Crystals - A Theoretical Study

Recent theoretical investigations of beam crystallization using computer modeling based on the method of molecular dynamics (MD) and analytical approach based on the phonon theory are motivated by the study of colliding crystalline beams [4]. Analytical study of crystal stability in an alternating-gradient (AG) focusing ring was previously limited to the smooth approximation. In a typical ring, results obtained under such approximation largely agrees with that obtained with the MD simulation. H… more

Date: September 10, 2007

Creator: Wei, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Small-action Resonance in Hamiltonian Systems and Redistribution of Energetic Ions in Tokamaks

It has been found that an arbitrary small perturbation in an integrable Hamiltonian system typically leads to driven resonance in the regions of the phase space where at least one of the action variables is sufficiently small. In particular, such a small-action resonance is shown to play a dominant role in the sawtooth-crash-induced disappearance of a strongly localized gamma-ray and neutron emitting region in a tokamak plasma, which was observed experimentally.

Date: July 1, 1999

Creator: White, R. B.; Lutsenko, V. V.; Kolesnichenko, Ya. I. & Yakovenko, Yu. V.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Coarse-Grained Molecular Dynamics: Dissipation Due to Internal Modes

We describe progress on the issue of pathological elastic wave reflection in atomistic and multiscale simulation. First we briefly review Coarse-Grained Molecular Dynamics (CGMD). Originally CGMD was formulated as a Hamiltonian system in which energy is conserved. This formulation is useful for many applications, but recently CGMD has been extended to include generalized Langevin forces. Here we describe how Langevin dynamics arise naturally in CGMD, and we examine the implication for elastic w… more

Date: December 21, 2001

Creator: Rudd, R E

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Determination of linear optics functions from TBT data

A method for evaluation of coupled optics functions, detection of strong perturbing elements, determination of BPM calibration errors and tilts using turn-by-turn (TBT) data is presented as well as the new version of the Hamiltonian perturbation theory of betatron oscillations the method is based upon. An example of application of the considered method to the Tevatron is given.

Date: May 1, 2006

Creator: Alexahin, Y. & Gianfelice-Wendt, E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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GAUGE INVARIANCE IN A Z2 HAMILTONIAN LATTICE GUAGE THEORY.

We propose an efficient variational method for Z{sub 2} lattice gauge theory based on the matrix product ansatz. The method is applied to ladder and square lattices. The Gauss law needs to be imposed on quantum states to guarantee gauge invariance when one studies gauge theory in hamiltonian formalism. On the ladder lattice, we identify gauge invariant low-lying states by evaluating expectation values of the Gauss law operator after numerical diagonalization of the gauge hamiltonian. On the squ… more

Date: July 25, 2005

Creator: SUGIHARA, T.

Item Type: Article

Partner: UNT Libraries Government Documents Department