1,214 research outputs found
Specific heat at constant volume in the thermodynamic model
A thermodynamic model for multifragmentation which is frequently used appears
to give very different values for specific heat at constant volume depending
upon whether canonical or grand canonical ensemble is used. The cause for this
discrepancy is analysed.Comment: Revtex, 7 pages including 4 figure
Negative specific heat in a thermodynamic model of multifragmentation
We consider a soluble model of multifragmentation which is similar in spirit
to many models which have been used to fit intermediate energy heavy ion
collision data. In this model is always positive but for finite nuclei
can be negative for some temperatures and pressures. Furthermore,
negative values of can be obtained in canonical treatment. One does not
need to use the microcanonical ensemble. Negative values for can persist
for systems as large as 200 paticles but this depends upon parameters used in
the model calculation. As expected, negative specific heats are absent in the
thermodynamic limit.Comment: Revtex, 13 pages including 6 figure
Is entanglement entropy proportional to area?
It is known that the entanglement entropy of a scalar field, found by tracing
over its degrees of freedom inside a sphere of radius , is
proportional to the area of the sphere (and not its volume). This suggests that
the origin of black hole entropy, also proportional to its horizon area, may
lie in the entanglement between the degrees of freedom inside and outside the
horizon. We examine this proposal carefully by including excited states, to
check probable deviations from the area law.Comment: 6 pages. Based on talk by S. Das at Theory Canada 1, Vancouver, 3
June, 2005. To be published in a special edition of the Canadian Journal of
Physics. Minor changes to match published versio
Hyperspherical partial wave theory applied to electron hydrogen-atom ionization calculation for equal energy sharing kinematics
Hyperspherical partial wave theory has been applied here in a new way in the
calculation of the triple differential cross sections for the ionization of
hydrogen atoms by electron impact at low energies for various
equal-energy-sharing kinematic conditions. The agreement of the cross section
results with the recent absolute measurements of R\"oder \textit {et al} [51]
and with the latest theoretical results of the ECS and CCC calculations [29]
for different kinematic conditions at 17.6 eV is very encouraging. The other
calculated results, for relatively higher energies, are also generally
satisfactory, particularly for large geometries. In view of the
present results, together with the fact that it is capable of describing
unequal-energy-sharing kinematics [35], it may be said that the hyperspherical
partial wave theory is quite appropriate for the description of ionization
events of electron-hydrogen type systems. It is also clear that the present
approach in the implementation of the hyperspherical partial wave theory is
very appropriate.Comment: 16 pages, 9 figures, LaTeX file and EPS figures. To appear in Phys.
Rev.
Model of multifragmentation, Equation of State and phase transition
We consider a soluble model of multifragmentation which is similar in spirit
to many models which have been used to fit intermediate energy heavy ion
collision data. We draw a p-V diagram for the model and compare with a p-V
diagram obtained from a mean-field theory. We investigate the question of
chemical instability in the multifragmentation model. Phase transitions in the
model are discussed.Comment: Revtex, 9 pages including 6 figures: some change in the text and Fig.
Characteristic length scales and formation of vortices in the Abelian Higgs model in the presence of a uniform background charge
In this brief report we consider a non-local Abelian Higgs model in the
presence of a neutralizing uniform background charge. We show that such a
system possesses vortices which key feature is a strong radial electric field.
We estimate the basic properties of such an object and characteristic length
scales in this model.Comment: Replaced with journal version. Some minor change
Metallothioneins pattern during ontogeny of coastal dolphin, Pontoporia blainvillei, from Argentina
Metallothioneins are signals of metal exposure and widely used in biomonitoring. Franciscana dolphin is an endemic cetacean from the Southwestern Atlantic Ocean, classified as Vulnerable A3d by the IUCN. Metallothionein, copper and zinc in Franciscana were assessed in two geographic groups; one inhabits La Plata River estuary, anthropogenically impacted, and the other inhabits marine coastal ecosystems, with negligible pollution. Despite the environment, hepatic and renal MT concentrations were similar, but there was a declining trend from early to later developmental stages. Metallothionein K/L, Cu and Zn levels corresponded to normal reported ranges. MT was not related with Cd. Fetal concentrations were higher than its mother. These results and the health status of dolphins are suggesting that MT correspond to physiological ranges for the species, and they are closely to homeostasis of Zn and Cu, according to its ontogenetic changes. The information constitutes the first MT information on Franciscana dolphin and can be considered as baseline for the species conservation
Comparisons of Statistical Multifragmentation and Evaporation Models for Heavy Ion Collisions
The results from ten statistical multifragmentation models have been compared
with each other using selected experimental observables. Even though details in
any single observable may differ, the general trends among models are similar.
Thus these models and similar ones are very good in providing important physics
insights especially for general properties of the primary fragments and the
multifragmentation process. Mean values and ratios of observables are also less
sensitive to individual differences in the models. In addition to
multifragmentation models, we have compared results from five commonly used
evaporation codes. The fluctuations in isotope yield ratios are found to be a
good indicator to evaluate the sequential decay implementation in the code. The
systems and the observables studied here can be used as benchmarks for the
development of statistical multifragmentation models and evaporation codes.Comment: To appear on Euorpean Physics Journal A as part of the Topical Volume
"Dynamics and Thermodynamics with Nuclear Degrees of Freedo
Vertical Confinement and Evolution of Reentrant Insulating Transition in the Fractional Quantum Hall Regime
We have observed an anomalous shift of the high field reentrant insulating
phases in a two-dimensional electron system (2DES) tightly confined within a
narrow GaAs/AlGaAs quantum well. Instead of the well-known transitions into the
high field insulating states centered around , the 2DES confined
within an 80\AA-wide quantum well exhibits the transition at .
Comparably large quantum lifetime of the 2DES in narrow well discounts the
effect of disorder and points to confinement as the primary driving force
behind the evolution of the reentrant transition.Comment: 5 pages, 4 figure
Probing neutralino properties in minimal supergravity with bilinear R-parity violation
Supersymmetric models with bilinear R-parity violation can account for the observed neutrino masses and mixing parameters indicated by neutrino oscillation data. We consider minimal supergravity versions of bilinear R-parity violation where the lightest supersymmetric particle is a neutralino. This is unstable, with a large enough decay length to be detected at the CERN Large Hadron Collider. We analyze the Large Hadron Collider potential to determine the lightest supersymmetric particle properties, such as mass, lifetime and branching ratios, and discuss their relation to neutrino properties
- …