2,954 research outputs found
Acoustic gravity waves: A computational approach
This paper discusses numerical solutions of a hyperbolic initial boundary value problem that arises from acoustic wave propagation in the atmosphere. Field equations are derived from the atmospheric fluid flow governed by the Euler equations. The resulting original problem is nonlinear. A first order linearized version of the problem is used for computational purposes. The main difficulty in the problem as with any open boundary problem is in obtaining stable boundary conditions. Approximate boundary conditions are derived and shown to be stable. Numerical results are presented to verify the effectiveness of these boundary conditions
On the Large Load Characteristics of Vapour Pumps
The different characteristics of vapour pumps under various leak-load
and forepressure conditions are studied. The leak load position dependence of forepressure is investigated from which different conditions of critical forepressure are distinguished
Energy and momentum relaxation of heavy fermion in dense and warm plasma
We determine the drag and the momentum diffusion coefficients of heavy
fermion in dense plasma. It is seen that in degenerate matter drag coefficient
at the leading order mediated by transverse photon is proportional to
while for the longitudinal exchange this goes as . We
also calculate the longitudinal diffusion coefficient to obtain the Einstein
relation in a relativistic degenerate plasma. Finally, finite temperature
corrections are included both for the drag and the diffusion coefficients.Comment: 8 pages, 1 eps figure, typos corrected and paragraphs rearranged.
Accepted for publication in Physical Review
Matter induced charge symmetry breaking and pion form factor in nuclear medium
Medium modification of pion form factor has been evaluated in asymmetric
nuclear matter. It is shown that both the shape and the pole position of the
pion form factor in dense asymmetric nuclear matter is different from its
vacuum counterpart with - mixing. This is due to the density and
asymmetry dependent - mixing which could even dominate over its
vacuum counterpart in matter. Effect of the in-medium pion factor on
experimental observables {\it e.g.}, invariant mass distribution of lepton
pairs has been demonstrated.Comment: Final Version to appear in Jour. Phys.
Thermal Radiation from Au + Au Collisions at \sqrt{s} = 200 GEV/A Energy
The transverse momentum distribution of the direct photons measured by the
PHENIX collaboration in collisions at GeV/A has been
analyzed. It has been shown that the data can be reproduced reasonably well
assuming a deconfined state of thermalized quarks and gluons with initial
temperature more than the transition temperature for deconfinement inferred
from lattice QCD. The value of the initial temperature depends on the equation
of state of the evolving matter. The sensitivities of the results on various
input parameters have been studied. The effects of the modifications of
hadronic properties at non-zero temperature have been discussed.Comment: minor modifications in the text, accepted for publicatio
Aspects of meson properties in dense nuclear matter
We investigate the modification of meson spectral densities in dense nuclear
matter at zero temperature. These effects are studied in a fully relativistic
mean field model which goes beyond the linear density approximation and also
includes baryon resonances. In particular, the role of N*(1520) and N*(1720) on
the rho meson spectral density is highlighted. Even though the nucleon-nucleon
loop and the nucleon-resonance loop contribute with the opposite sign, an
overall reduction of rho meson mass is still observed at high density.
Importantly, it is shown that the resonances cause substantial broadening of
the rho meson spectral density in matter and also induces non-trivial momentum
dependence. The spectral density of the a0 meson is also shown. We study the
dispersion relations and collective oscillations induced by the rho meson
propagation in nuclear matter together with the influence of the mixing of rho
with the a0 meson. The relevant expression for the plasma frequency is also
recovered analytically in the appropriate limit.Comment: 19 pages, 17 figure
Normal Utilization as the Adjusting Variable in Neo-Kaleckian Growth Models: A Critique
As well-known, the canonical Neo-Kaleckian growth model fails to reconcile actual and normal rates of utilization in equilibrium. Some recent contributions revive an old proposal for solving this problem – making the normal rate of utilization an endogenous variable that converges to the actual utilization rate – justifying it with new, micro-founded premises. We argue that these new justifications for the convergence of normal to actual utilization do not stand closer scrutiny. First, the proposed microeconomic model relies on various restrictive assumptions, some of which are mutually inconsistent. Second, the derivation of the macroeconomic adjustment mechanism from the microeconomic analysis involves a logical leap, that can be justified only by a very arbitrary assumption with little economic justification. Finally, we discuss the way in which this mechanism has been incorporated into the Neo-Kaleckian growth model by proposers of this approach. We show that, even if one puts aside, for the sake of argument, the first two points, the existence of autonomous components of demand is sufficient to invalidate the resulting macroeconomic model
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