5,756 research outputs found
Inclusion of Quantum Fluctuations in Wave Packet Dynamics
We discuss a method by which quantum fluctuations can be included in
microscopic transport models based on wave packets that are not energy
eigenstates. By including the next-to-leading order term in the cumulant
expansion of the statistical weight, which corresponds to the wave packets
having Poisson energy distributions, we obtain a much improved global
description of the quantum statistical properties of the many-body system. In
the case of atomic nuclei, exemplified by 12C and 40Ca, the standard
liquid-drop results are reproduced at low temperatures and a phase
transformation to a fragment gas occurs as the temperature is raised. The
treatment can be extended to dynamical scenarios by means of a Langevin force
emulating the transitions between the wave packets. The general form of the
associated transport coefficients is derived and it is shown that the
appropriate microcanonical equilibrium distribution is achieved in the course
of the time evolution. Finally, invoking Fermi's golden rule, we derive
specific expressions for the transport coefficients and verify that they
satisfy the fluctuation-dissipation theorem.Comment: uuencoded revtex body and 8 ps figures (16 pages total
Statistical Properties of Fermionic Molecular Dynamics
Statistical properties of Fermionic Molecular Dynamics are studied. It is
shown that, although the centroids of the single--particle wave--packets follow
classical trajectories in the case of a harmonic oscillator potential, the
equilibrium properties of the system are the quantum mechanical ones. A system
of weakly interacting fermions as well as of distinguishable particles is found
to be ergodic and the time--averaged occupation probabilities approach the
quantum canonical ones of Fermi--Dirac and Boltzmann statistics, respectively.Comment: 16 pages, several postscript figures, uses 'epsfig.sty'. More
information is available at http://www.gsi.de/~schnack/fmd.htm
INCORPORATION OF QUANTUM STATISTICAL FEATURES IN MOLECULAR DYNAMICS
We formulate a method for incorporating quantum fluctuations into molecular-
dynamics simulations of many-body systems, such as those employed for energetic
nuclear collision processes. Based on Fermi's Golden Rule, we allow spontaneous
transitions to occur between the wave packets which are not energy eigenstates.
The ensuing diffusive evolution in the space of the wave packet parameters
exhibits appealing physical properties, including relaxation towards quantum-
statistical equilibrium.Comment: 8 latex pages + 1 uuencoded ps figur
Tables of Hyperonic Matter Equation of State for Core-Collapse Supernovae
We present sets of equation of state (EOS) of nuclear matter including
hyperons using an SU_f(3) extended relativistic mean field (RMF) model with a
wide coverage of density, temperature, and charge fraction for numerical
simulations of core collapse supernovae. Coupling constants of Sigma and Xi
hyperons with the sigma meson are determined to fit the hyperon potential
depths in nuclear matter, U_Sigma(rho_0) ~ +30 MeV and U_Xi(rho_0) ~ -15 MeV,
which are suggested from recent analyses of hyperon production reactions. At
low densities, the EOS of uniform matter is connected with the EOS by Shen et
al., in which formation of finite nuclei is included in the Thomas-Fermi
approximation. In the present EOS, the maximum mass of neutron stars decreases
from 2.17 M_sun (Ne mu) to 1.63 M_sun (NYe mu) when hyperons are included. In a
spherical, adiabatic collapse of a 15 star by the hydrodynamics
without neutrino transfer, hyperon effects are found to be small, since the
temperature and density do not reach the region of hyperon mixture, where the
hyperon fraction is above 1 % (T > 40 MeV or rho_B > 0.4 fm^{-3}).Comment: 23 pages, 6 figures (Fig.3 and related comments on pion potential are
corrected in v3.
Epitaxial growth and transport properties of Nb-doped SrTiO thin films
Nb-doped SrTiO epitaxial thin films have been prepared on (001)
SrTiO substrates using pulsed laser deposition. A high substrate
temperature () was found to be necessary to achieve
2-dimensional growth. Atomic force microscopy reveals atomically flat surfaces
with 3.9 \AA steps. The films show a metallic behavior, residual
resistivity ratios between 10 and 100, and low residual resistivity of the
order of 10cm. At 0.3 K, a sharp superconducting transition,
reaching zero resistance, is observed.Comment: 4 pages, 4 figure
Characterisation of High Current Density Resonant Tunneling Diodes for THz Emission Using Photoluminescence Spectroscopy
We discuss the numerical simulation of high current density InGaAs/AlAs/InP resonant tunneling diodes with a view to
their optimization for application as THz emitters. We introduce a figure of merit based upon the ratio of maximum
extractable THz power and the electrical power developed in the chip. The aim being to develop high efficiency emitters
as output power is presently limited by catastrophic failure. A description of the interplay of key parameters follows,
with constraints on strained layer epitaxy introduced. We propose an optimized structure utilizing thin barriers paired
with a comparatively wide quantum well that satisfies strained layer epitaxy constraints
A genome-based approach to create a minimally mutated, Corynebacterium glutamicm strain for efficient L-lysine production
The original publication is available at www.springerlink.com.ArticleJournal of Industrial Microbiology & Biotechnology. 33(7): 610-615 (2006)journal articl
Characterization of mutations induced by N-methyl-N '-nitro-N-nitrosoguanidine in an industrial Corynebacterium glutamicum strain
ArticleMUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS. 649(1-2): 239-244 (2008)journal articl
Search for a Ridge Structure Origin with Shower Broadening and Jet Quenching
We investigate the role of jet and shower parton broadening by the strong
colour field in the - correlation of high
particles. When anisotropic momentum broadening () is
given to jet and shower partons in the initial stage, a ridge-like structure is
found to appear in the two hadron correlation. The ratio of the peak to the
pedestal yield is overestimated.Comment: Talk given at 20th Int. Conf. on Ultra-Relativistic Nucleus-Nucleus
Collisions, Jaipur, India, Feb.4-10, 200
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