3,468 research outputs found
Non-Fermi-Liquid Specific Heat of Normal Degenerate Quark Matter
We compute the low-temperature behavior of the specific heat of normal
(non-color-superconducting) degenerate quark matter as well as that of an
ultradegenerate electron gas. Long-range magnetic interactions lead to
non-Fermi-liquid behavior with an anomalous leading term.
Depending on the thermodynamic potential used as starting point, this effect
appears as a consequence of the logarithmic singularity in the fermion
self-energy at the Fermi surface or directly as a contribution from the only
weakly screened quasistatic magnetic gauge bosons. We show that a calculation
of Boyanovsky and de Vega claiming the absence of a leading term
missed it by omitting vector boson contributions to the internal energy. Using
a formulation which collects all nonanalytic contributions in bosonic ring
diagrams, we systematically calculate corrections beyond the well-known
leading-log approximation. The higher-order terms of the low-temperature
expansion turn out to also involve fractional powers and we
explicitly determine their coefficients up to and including order as
well as the subsequent logarithmically enhanced term . We derive
also a hard-dense-loop resummed expression which contains the infinite series
of anomalous terms to leading order in the coupling and which we evaluate
numerically. At low temperatures, the resulting deviation of the specific heat
from its value in naive perturbation theory is significant in the case of
strongly coupled normal quark matter and thus of potential relevance for the
cooling rates of (proto-)neutron stars with a quark matter component.Comment: REVTEX, 26 pages, 5 postscript figures. v3: new chapter added which
performs a complete hard-dense-loop resummation, covering the infinite series
of anomalous terms and extending the range of applicability to all T << m
Caracterização molecular de fungos entomopatogênicos utilizados no controle biológico de pragas do milho - Beauveria bassiana versus Spodoptera frugiperda.
bitstream/item/25658/1/Com-93.pd
Monte-Carlo calculation of longitudinal and transverse resistivities in a model Type-II superconductor
We study the effect of a transport current on the vortex-line lattice in
isotropic type-II superconductors in the presence of strong thermal
fluctuations by means of 'driven-diffusion' Monte Carlo simulations of a
discretized London theory with finite magnetic penetration depth. We calculate
the current-voltage (I-V) characteristics for various temperatures, for
transverse as well as longitudinal currents I. From these characteristics, we
estimate the linear resistivities R_xx=R_yy and R_zz and compare these with
equilibrium results for the vortex-lattice structure factor and the helicity
moduli. From this comparison a consistent picture arises, in which the melting
of the flux-line lattice occurs in two stages for the system size considered.
In the first stage of the melting, at a temperature T_m, the structure factor
drops to zero and R_xx becomes finite. For a higher temperature T_z, the second
stage takes place, in which the longitudinal superconducting coherence is lost,
and R_zz becomes finite as well. We compare our results with related recent
numerical work and experiments on cuprate superconductors.Comment: 4 pages, with eps figure
Ultraviolet and Infrared Divergences in Implicit Regularization: a Consistent Approach
Implicit Regularization is a 4-dimensional regularization initially conceived
to treat ultraviolet divergences. It has been successfully tested in several
instances in the literature, more specifically in those where Dimensional
Regularization does not apply. In the present contribution we extend the method
to handle infrared divergences as well. We show that the essential steps which
rendered Implicit Regularization adequate in the case of ultraviolet
divergences have their counterpart for infrared ones. Moreover we show that a
new scale appears, typically an infrared scale which is completely independent
of the ultraviolet one. Examples are given.Comment: 9 pages, version to appear in Mod. Phys. Lett.
- …