2,597 research outputs found
Superadiabatic transitions in quantum molecular dynamics
We study the dynamics of a moleculeâs nuclear wave function near an avoided crossing of two electronic energy levels for one nuclear degree of freedom. We derive the general form of the Schrödinger equation in the nth superadiabatic representation for all n Ń N. Using these results, we obtain closed formulas for the time development of the component of the wave function in an initially unoccupied energy subspace when a wave packet travels through the transition region. In the optimal superadiabatic representation, which we define, this component builds up monotonically. Finally, we give an explicit formula for the transition wave function away from the avoided crossing, which is in excellent agreement with high-precision numerical calculations
Large Nc Continuum Reduction and the Thermodynamics of QCD
It is noted that if large Nc continuum reduction applies to an observable,
then that observable is independent of temperature for all temperatures below
some critical value. This fact, plus the fact that mesons and glueballs are
weakly interacting at large Nc is used as the basis for a derivation of large
Nc continuum reduction for the chiral condensate. The structure of this
derivation is quite general and can be extended to a wide class of observables
The Hagedorn temperature Revisited
The Hagedorn temperature, T_H is determined from the number of hadronic
resonances including all mesons and baryons. This leads to a stable result T_H
= 174 MeV consistent with the critical and the chemical freeze-out temperatures
at zero chemical potential. We use this result to calculate the speed of sound
and other thermodynamic quantities in the resonance hadron gas model for a wide
range of baryon chemical potentials following the chemical freeze-out curve. We
compare some of our results to those obtained previously in other papers.Comment: 13 pages, 4 figure
Micro-canonical pentaquark production in \ee annihilations
The existence of pentaquarks, namely baryonic states made up of four quarks
and one antiquark, became questionable, because the candidates, i.e. the
peak, are seen in certain reactions, i.e. p+p collisions, but not in
others, i.e. \ee annihilations. In this paper, we estimate the production of
and in \ee annihilations at different
energies using Fermi statistical model as originally proposed in its
microcanonical form. The results is compared with that from pp collisions at
SPS and RHIC energies. We find that, if pentaquark states exist, the production
is highly possible in \ee annihilations. For example, at LEP energy
=91.2 GeV, both and yield more
than in pp collisions at SPS and RHIC energy.Comment: 7 pages 2 figure
Is there a black hole minimum mass?
Applying the first and generalised second laws of thermodynamics for a
realistic process of near critical black hole formation, we derive an entropy
bound, which is identical to Bekenstein's one for radiation. Relying upon this
bound, we derive an absolute minimum mass ,
where and is the effective degrees of freedom for the
initial temparature and the Planck mass, respectively. Since this minimum mass
coincides with the lower bound on masses of which black holes can be regarded
as classical against the Hawking evaporation, the thermodynamical argument will
not prohibit the formation of the smallest classical black hole. For more
general situations, we derive a minimum mass, which may depend on the initial
value for entropy per particle. For primordial black holes, however, we show
that this minimum mass can not be much greater than the Planck mass at any
formation epoch of the Universe, as long as is within a reasonable
range. We also derive a size-independent upper bound on the entropy density of
a stiff fluid in terms of the energy density.Comment: 4 pages, accepted for publication in Physical Review D, minor
correctio
Avoided crossings in mesoscopic systems: electron propagation on a non-uniform magnetic cylinder
We consider an electron constrained to move on a surface with revolution
symmetry in the presence of a constant magnetic field parallel to the
surface axis. Depending on and the surface geometry the transverse part of
the spectrum typically exhibits many crossings which change to avoided
crossings if a weak symmetry breaking interaction is introduced. We study the
effect of such perturbations on the quantum propagation. This problem admits a
natural reformulation to which tools from molecular dynamics can be applied. In
turn, this leads to the study of a perturbation theory for the time dependent
Born-Oppenheimer approximation
The Detection of Methionine Sulfoxide in Tubulin and Glyceraldehyde 3-Phosphate Dehydrogenase
Oxidative stress is an imbalance between the production of reactive oxygen species (ROS) and antioxidant defenses (1). Free radicals are an unavoidable by-product of many biochemical processes, and in the case of activated neutrophils, are deliberately formed. Oxidative stressors such as infection, inflammation, metabolic abnormalities, or environmental contaminants overwhelm the body\u27s defense mechanisms allowing reactive oxygen species concentrations to increase. This increase in ROS can cause damage to biological macromolecules including proteins, lipids and DNA. An accumulation of oxidative damage is the underlying cause of many diseases because oxidative metabolism is an essential part of every cell\u27s metabolism (2). It has been suggested that accumulation over a long period of time plays a significant role in the aging process, inflammatory diseases (arthritis, vasculitis), heart disease, and several neurodegenerative diseases such as Alzheimer\u27s and Parkinson\u27s diseases
Strangeness, Equilibration, Hadronization
In these remarks I explain the motivation which leads us to consider chemical
nonequilibrium processes in flavor equilibration and in statistical
hadroniziation of quark--gluon plasma (QGP). Statistical hadronization allowing
for chemical non-equilibrium is introduced. The reesults of fits to
RHIC-130 results, including multistrange hadrons, are shown to agree only
with the model of an exploding QGP fireball.Comment: 8 pages including one figure, discussion contribution at Strange
Quark Matter 2001, Frankfurt, submitted to J. Phys.
Crossover transition in bag-like models
We formulate a simple model for a gas of extended hadrons at zero chemical
potential by taking inspiration from the compressible bag model. We show that a
crossover transition qualitatively similar to lattice QCD can be reproduced by
such a system by including some appropriate additional dynamics. Under certain
conditions, at high temperature, the system consist of a finite number of
infinitely extended bags, which occupy the entire space. In this situation the
system behaves as an ideal gas of quarks and gluons.Comment: Corresponds to the published version. Added few references and
changed the titl
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