19,074 research outputs found
Spin-Charge Decoupling and Orthofermi Quantum Statistics
Currently Gutzwiller projection technique and nested Bethe ansatz are two
main methods used to handle electronic systems in the infinity limit. We
demonstrate that these two approaches describe two distinct physical systems.
In the nested Bethe ansatz solutions, there is a decoupling between the spin
and charge degrees of freedom. Such a decoupling is absent in the Gutzwiller
projection technique. Whereas in the Gutzwiller approach, the usual
antisymmetry of space and spin coordinates is maintained, we show that the
Bethe ansatz wave function is compatible with a new form of quantum statistics,
viz., orthofermi statistics. In this statistics, the wave function is
antisymmetric in spatial coordinates alone. This feature ultimately leads to
spin-charge decoupling.Comment: 12 pages, LaTex Journal_ref: A slightly abridged version of this
paper has appeared as a brief report in Phys. Rev. B, Vol. 63, 132405 (2001
Interior gap superfluidity in a two-component Fermi gas of atoms
A new superfluid phase in Fermi matter, termed as "interior gap" (IG) or
"breached pair", has been recently predicted by Liu and Wilczek [Phys.Rev.Lett.
{\bf 90}, 047002 (2003)]. This results from pairing between fermions of two
species having essentially different Fermi surfaces. Using a nonperturbative
variational approach, we analyze the features, such as energy gap, momentum
distributions, and elementary excitations associated with the predicted phase.
We discuss possible realization of this phase in two-component Fermi gases in
an optical trap.Comment: 5 page
Hot Nuclear Matter : A Variational Approach
We develop a nonperturbative technique in field theory to study properties of
infinite nuclear matter at zero temperature as well as at finite temperatures.
Here we dress the nuclear matter with off-mass shell pions. The techniques of
thermofield dynamics are used for finite temperature calculations. Equation of
state is derived from the dynamics of the interacting system in a self
consistent manner. The transition temperature for nuclear matter appears to be
around 15 MeV.Comment: 16 pages, IP/BBSR/91-3
Neutron matter - Quark matter phase transition and Quark star
We consider the neutron matter quark matter phase transition along with
possible existence of hybrid quark stars. The equation of state for neutron
matter is obtained using a nonperturbative method with pion dressing of the
neutron matter and an analysis similar to that of symmetric nuclear matter. The
quark matter sector is treated perturbatively in the small distance domain. For
bag constant =148 MeV, a first order phase transition is seen. In the
context of neutron quark hybrid stars, Tolman-Oppenheimer-Volkoff equations are
solved using the equations of state for quark matter and for neutron matter
with a phase transition as noted earlier. Stable solutions for such stars are
obtained with the Chandrasekhar limit as 1.58 and radius around 10
km. The bulk of the star is quark matter with a thin crust of neutron matter of
less than a kilometer.Comment: 28 pages including 9 figures, Revtex, IP/BBSR/92-8
BCS BEC crossover and phase structure of relativistic system: a variational approach
We investigate here the BCS BEC crossover in relativistic systems using a
variational construct for the ground state and the minimization of the
thermodynamic potential. This is first studied in a four fermion point
interaction model and with a BCS type ansatz for the ground state with fermion
pairs. It is shown that the antiparticle degrees of freedom play an important
role in the BCS BEC crossover physics, even when the ratio of fermi momentum to
the mass of the fermion is small. We also consider the phase structure for the
case of fermion pairing with imbalanced populations. Within the ansatz,
thermodynamically stable gapless modes for both fermions and anti fermions are
seen for strong coupling in the BEC regime. We further investigate the effect
of fluctuations of the condensate field by treating it as a dynamical field and
generalize the BCS ansatz to include quanta of the condensate field also in a
boson fermion model with quartic self interaction of the condensate field. It
is seen that the critical temperature decreases with inclusion of fluctuations.Comment: 18 pages, 13 figures, one more section added, title modified, version
to appear in Phys Rev
Color superconducting 2SC+s quark matter and gapless modes at finite temperatures
We investigate the phase diagram of color superconducting quark matter with
strange quarks (2SC+s quark matter) in beta equliibrium at zero as well as
finite temperatures within a Nambu-Jona-Lasinio model. The variational method
as used here allows us to investigate simultaneous formation of condensates in
quark--antiquark as well as in diquark channels. Color and electric charge
neutrality conditions are imposed in the calculation of the thermodynamic
potential. Medium dependance of strange quark mass plays a sensitve role in
maintaining charge neutrality conditions. At zero temperature the system goes
from gapless phase to usual BCS phase through an intermediate normal phase as
density is increased. The gapless modes show a smooth behaviour with respect to
temperature vanishing above a critical temperature which is larger than the BCS
transition temperature. We observe a sharp transition from gapless
superconducting phase to the BCS phase as density is increased for the color
neutral matter at zero temperature. As temperature is increased this however
becomes a smooth transition.Comment: 18 pages, 14 figure
First order sensitivity analysis of symplectic eigenvalues
For every positive definite matrix there are positive
numbers associated with called the
symplectic eigenvalues of It is known that are continuous functions
of but are not differentiable in general. In this paper, we show that the
directional derivative of exists and derive its expression. We also
discuss various subdifferential properties of such as Clarke and
Michel-Penot subdifferentials.Comment: 24 page
Reasons for female neonaticide in India
Invited commentary on ‘Neonaticide in India and the stigma of female gender: report of two cases’, Mishra et al
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