709 research outputs found
Neutron Dripline in Odd and Even Mass Calcium and Nickel Nuclei
Neutron rich Ca and Ni nuclei have been studied in spherical Relativistic
Mean Field formalism in co-ordinate space. A delta interaction has been has
been adopted to treat the pairing correlations for the neutrons. Odd nuclei
have been treated in the blocking approximation. The effect of the positive
energy continuum and the role of pairing in the stability of nuclei have been
investigated using the resonant-BCS (rBCS) approach. In Ca isotopes, N=50 is no
longer a magic number while in Ni nuclei, a new magic number emerges at N=70.
There is a remarkable difference in the relative positions of the drip lines
for odd and even isotopes. In Ca isotopes, the last bound even and odd nuclei
are found to be Ca and Ca, respectively. In Ni isotopes, the
corresponding nuclei are Ni and Ni, respectively. The origin of
this difference in relative positions of the dripline in even and odd isotopes
in the two chain is traced to the difference in the single particle level
structures and consequent modification in the magic numbers in the two
elements. Pairing interaction is seen to play a major role. The effect of the
width of the resonance states on pairing has also been investigated.Comment: To appear in Physical Review
Evolution of primordial black holes in Jordan-Brans-Dicke cosmology
We consider the evolution of primordial black holes in a generalyzed
Jordan-Brans-Dicke cosmological model where both the Brans-Dicke scalar field
and its coupling to gravity are dynamical functions determined from the
evolution equations. The evaporation rate for the black holes changes compared
to that in standard cosmology. We show that accretion of radiation can proceed
effectively in the radiation dominated era. The black hole lifetime shortens
for low initial mass, but increases for high initial mass, and is thus
considerably modified compared to the case of standard cosmology. We derive a
cut-off value for the initial black hole mass, below which primordial black
holes evaporate out in the radiation dominated era, and above which they
survive beyond the present era.Comment: 5 pages, Latex; uses MNRAS stylefiles; minor changes; accepted for
publication in MNRA
Analytic study of properties of holographic p-wave superconductors
In this paper, we analytically investigate the properties of p-wave
holographic superconductors in -Schwarzschild background by two
approaches, one based on the Sturm-Liouville eigenvalue problem and the other
based on the matching of the solutions to the field equations near the horizon
and near the asymptotic region. The relation between the critical
temperature and the charge density has been obtained and the dependence of the
expectation value of the condensation operator on the temperature has been
found. Our results are in very good agreement with the existing numerical
results. The critical exponent of the condensation also comes out to be 1/2
which is the universal value in the mean field theory.Comment: Latex, To appear in JHE
Formulation, Interpretation and Application of non-Commutative Quantum Mechanics
In analogy with conventional quantum mechanics, non-commutative quantum
mechanics is formulated as a quantum system on the Hilbert space of
Hilbert-Schmidt operators acting on non-commutative configuration space. It is
argued that the standard quantum mechanical interpretation based on Positive
Operator Valued Measures, provides a sufficient framework for the consistent
interpretation of this quantum system. The implications of this formalism for
rotational and time reversal symmetry are discussed. The formalism is applied
to the free particle and harmonic oscillator in two dimensions and the physical
signatures of non commutativity are identified.Comment: 11 page
Analytic study of Gauss-Bonnet holographic superconductors in Born-Infeld electrodynamics
Using Sturm-Liouville (SL) eigenvalue problem, we investigate several
properties of holographic s-wave superconductors in Gauss-Bonnet gravity with
Born-Infeld electrodynamics in the probe limit. Our analytic scheme has been
found to be in good agreement with the numerical results. From our analysis it
is quite evident that the scalar hair formation at low temperatures is indeed
affected by both the Gauss-Bonnet as well as the Born-Infeld coupling
parameters. We also compute the critical exponent associated with the
condensation near the critical temperature. The value of the critical exponent
thus obtained indeed suggests a universal mean field behavior.Comment: 9 pages, Latex, minor modifications, To appear in JHE
Noncommutativity In The Mechanics Of A Free Massless Relativistic Particle
We show the existence of a noncommutative spacetime structure in the context
of a complete discussion on the underlying spacetime symmetries for the
physical system of a free massless relativistic particle. The above spacetime
symmetry transformations are discussed for the first-order Lagrangian of the
system where the transformations on the coordinates, velocities and momenta
play very important roles. We discuss the dynamics of this system in a
systematic manner by exploiting the symplectic structures associated with the
four dimensional (non-)commutative cotangent (i.e. momentum phase) space
corresponding to a two dimensional (non-)commutative configuration (i.e.
target) space. A simple connection of the above noncommutativity (NC) is
established with the NC associated with the subject of quantum groups where
transformations play a decisive role.Comment: LaTeX file, 19 page
Optical absorption and photoluminescence spectroscopy of the growth of silver nanoparticles
Results obtained from the optical absorption and photoluminescence (PL)
spectroscopy experiments have shown the formation of excitons in the
silver-exchanged glass samples. These findings are reported here for the first
time. Further, we investigate the dramatic changes in the photoemission
properties of the silver-exchanged glass samples as a function of postannealing
temperature. Observed changes are thought to be due to the structural
rearrangements of silver and oxygen bonding during the heat treatments of the
glass matrix. In fact, photoelectron spectroscopy does reveal these chemical
transformations of silver-exchanged soda glass samples caused by the thermal
effects of annealing in a high vacuum atmosphere. An important correlation
between temperature-induced changes of the PL intensity and thermal growth of
the silver nanoparticles has been established in this Letter through precise
spectroscopic studies.Comment: 15 pages,4 figures,PDF fil
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