6,496 research outputs found
Chiral Symmetry Breaking and the Dirac Spectrum at Nonzero Chemical Potential
The relation between the spectral density of the QCD Dirac operator at
nonzero baryon chemical potential and the chiral condensate is investigated. We
use the analytical result for the eigenvalue density in the microscopic regime
which shows oscillations with a period that scales as 1/V and an amplitude that
diverges exponentially with the volume . We find that the discontinuity
of the chiral condensate is due to the whole oscillating region rather than to
an accumulation of eigenvalues at the origin. These results also extend beyond
the microscopic regime to chemical potentials .Comment: 4 pages, 1 figur
Research reports: 1985 NASA/ASEE Summer Faculty Fellowship Program
A compilation of 40 technical reports on research conducted by participants in the 1985 NASA/ASEE Summer Faculty Fellowship Program at Marshall Space Flight Center (MSFC) is given. Weibull density functions, reliability analysis, directional solidification, space stations, jet stream, fracture mechanics, composite materials, orbital maneuvering vehicles, stellar winds and gamma ray bursts are among the topics discussed
Research Reports: 1984 NASA/ASEE Summer Faculty Fellowship Program
A NASA/ASEE Summer Faulty Fellowship Program was conducted at the Marshall Space Flight Center (MSFC). The basic objectives of the programs are: (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate an exchange of ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of the participants' institutions; and (4) to contribute to the research objectives of the NASA Centers. The Faculty Fellows spent ten weeks at MSFC engaged in a research project compatible with their interests and background and worked in collaboration with a NASA/MSFC colleague. This document is a compilation of Fellows' reports on their research during the summer of 1984. Topics covered include: (1) data base management; (2) computational fluid dynamics; (3) space debris; (4) X-ray gratings; (5) atomic oxygen exposure; (6) protective coatings for SSME; (7) cryogenics; (8) thermal analysis measurements; (9) solar wind modelling; and (10) binary systems
Research Reports: 1983 NASA/ASEE Summer Faculty Fellowship Program
Thirty-five technical reports contain results of investigations in information and electronic systems; materials and processing; systems dynamics; structures and propulsion; and space sciences. Ecology at KSC, satellite de-spin, and the X-ray source monitor were also studied
Individual complex Dirac eigenvalue distributions from random matrix theory and comparison to quenched lattice QCD with a quark chemical potential
We analyze how individual eigenvalues of the QCD Dirac operator at nonzero
quark chemical potential are distributed in the complex plane. Exact and
approximate analytical results for both quenched and unquenched distributions
are derived from non-Hermitian random matrix theory. When comparing these to
quenched lattice QCD spectra close to the origin, excellent agreement is found
for zero and nonzero topology at several values of the quark chemical
potential. Our analytical results are also applicable to other physical systems
in the same symmetry class.Comment: 4 pages, 4 figures, minor changes, as published in Phys. Rev. Let
Large harmonic softening of the phonon density of states of uranium
Phonon density-of-states curves were obtained from inelastic neutron scattering spectra from the three crystalline phases of uranium at temperatures from 50 to 1213 K. The alpha -phase showed an unusually large thermal softening of phonon frequencies. Analysis of the vibrational power spectrum showed that this phonon softening originates with the softening of a harmonic solid, as opposed to vibrations in anharmonic potentials. It follows that thermal excitations of electronic states are more significant thermodynamically than are the classical volume effects. For the alpha-beta and beta-gamma phase transitions, vibrational and electronic entropies were comparable
Phase Diagram of the Dirac Spectrum at Nonzero Chemical Potential
The Dirac spectrum of QCD with dynamical fermions at nonzero chemical
potential is characterized by three regions, a region with a constant
eigenvalue density, a region where the eigenvalue density shows oscillations
that grow exponentially with the volume and the remainder of the complex plane
where the eigenvalue density is zero. In this paper we derive the phase diagram
of the Dirac spectrum from a chiral Lagrangian. We show that the constant
eigenvalue density corresponds to a pion condensed phase while the strongly
oscillating region is given by a kaon condensed phase. The normal phase with
nonzero chiral condensate but vanishing Bose condensates coincides with the
region of the complex plane where there are no eigenvalues.Comment: 17 pages, 3 figure
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