14,834 research outputs found
Strongly Interacting Matter at Finite Chemical Potential : Hybrid Model Approach
Search for a proper and realistic equation of state (EOS) for strongly
interacting matter used in the study of the QCD phase diagram still appears as
a challenging problem. Recently, we constructed a hybrid model description for
the quark gluon plasma (QGP) as well as hadron gas (HG) phases where we used an
excluded volume model for HG and a thermodynamically consistent quasiparticle
model for the QGP phase. The hybrid model suitably describes the recent lattice
results of various thermodynamical as well as transport properties of the QCD
matter at zero baryon chemical potential (). In this paper, we extend
our investigations further in obtaining the properties of QCD matter at finite
value of and compare our results with the most recent results of
lattice QCD calculation.Comment: 14 pages, 9 figure
QCD Phase Transition in a new Hybrid Model Formulation
Search of a proper and realistic equations of state (EOS) for strongly
interacting matter used in the study of QCD phase diagram still appears as a
challenging task. Recently, we have constructed a hybrid model description for
the quark gluon plasma (QGP) as well as hadron gas (HG) phases where we use a
new excluded-volume model for HG and a thermodynamically-consistent
quasiparticle model for the QGP phase. We attempt to use them to get a QCD
phase boundary and a critical point. We test our hybrid model by reproducing
the entire lattice QCD data for strongly interacting matter at zero baryon
chemical potential ()and predict the results at finite and
.Comment: 5 pages, 4 figures, to be published in proceedings of QGP MEET 2012
held at VECC, Kolkata, INDI
Critical Point on the QCD Deconfining Phase Boundary
Ambiguities regarding the physics and the existence of the critical point
(CP) on the QCD phase boundary still exist and the mist regarding the
conjectured QCD phase boundary has not yet cleared. In this paper we extend our
earlier study where we constructed a deconfining phase boundary using Gibbs'
equilibrium conditions after using a quasiparticle equation of state (EOS) for
quark gluon plasma (QGP) and an excluded volume EOS for the hadron gas (HG) and
find the presence of a critical point on this phase boundary where the first
order phase transition terminates. In this paper, we plot the difference in the
normalized entropy density () between HG and QGP phases along the
deconfining phase boundary and find that it vanishes at CP. Further we have
shown the variation of the square of speed of sound () for the HG
and QGP separately and find that the difference () between
them along the deconfining phase boundary again vanishes at the CP of the
boundary. We also plot the variation of shear viscosity to entropy density
ratio () in HG as well as in QGP phases separately with respect to
temperature at different baryonic chemical potential (). The presence
of a cusp like structure in again confirms the existence of CP on the
deconfining phase boundary as predicted by some authors. These studies thus
firmly indicate the precise location of CP as a second order phase transition
point.Comment: 15 pages, 4 figure
Holographic Dark Energy Model in Brans-Dicke Theory with Future Event Horizon
In this paper, we study the dynamics of non-interacting and interacting
holographic dark energy models in the framework of Brans-Dicke theory. As
system's infra-red cut-off we consider the future event horizon. The motivation
of this work is to use the logarithmic form of the Brans-Dicke scalar field,
, where and are constants and
`a' is the scalar factor as proposed Kumar and Singh in a recent work to study
the new agegraphic dark energy models. We find the time-dependent equation of
state parameter and deceleration parameter which describe the phase transition
of the universe. We observe that the model explains the early time inflation
and late time acceleration including matter-dominated phase. It is also
observed that the equation of state parameter may cross phantom divide line in
late time evolution. The cosmic coincidence problem is also discussed for both
the models. We observe that this logarithmic form of Brans-Dicke scalar field
is more appropriate to achieve a less acute coincidence problem in
non-interacting model whereas a soft coincidence can be achieved if coupling
parameter in interacting model has small value.Comment: 11 Page
Large scale shell model calculations for even-even Fe isotopes
The recently measured experimental data of Legnaro National Laboratories on
neutron rich even isotopes of Fe with A=62,64,66 have been
interpreted in the framework of large scale shell model. Calculations have been
performed with a newly derived effective interaction GXPF1A in full
space without truncation. The experimental data is very well explained for
Fe, satisfactorily reproduced for Fe and poorly fitted for
Fe. The increasing collectivity reflected in experimental data when
approaching N=40 is not reproduced in calculated values. This indicates that
whereas the considered valence space is adequate for Fe, inclusion of
higher orbits from shell is required for describing Fe.Comment: 10 pages, 6 figure
Structure of odd Se isotopes with proton and neutron excitations across AND
The recently measured experimental data of Se isotopes have been
interpreted in terms of shell model calculations. The calculations have been
performed in space with the recently derived interactions,
namely with JUN45 and jj44b. To study the importance of the proton excitations
across the shell in this region. We have also performed calculation in
valence space using an effective interaction with
Ca core and imposing a truncation. Excitation energies, values,
quadrupole moments and magnetic moments are compared with experimental data
when available. Present study reveals the importance of proton excitations
across the shell for predicting quadrupole and magnetic moments.Comment: 12 pages, 6 figures. arXiv admin note: text overlap with
arXiv:1210.579
Structure of odd Ge isotopes with
We have interpreted recently measured experimental data of Ge, and
also for Ge isotopes in terms of state-of-the-art shell model
calculations. Excitation energies, B(2) values, quadrupole moments and magnetic
moments are compared with experimental data when available. The calculations
have been performed with the recently derived interactions, namely with JUN45
and jj44b for space. We have also performed calculation for
valence space using an effective interaction with
Ca core and imposing a truncation to study the importance of the proton
excitations across the Z=28 shell in this region. The predicted results of
jj44b interaction are in good agreement with experimental data.Comment: 22 pages, 7 figures, Physics of Atomic Nucle
Comparison of shell model results for even-even Se isotopes
Comprehensive set of shell model calculations for Se isotopes have
been performed with recently derived interactions, namely JUN45 and jj44b for
space. To study the importance of the proton excitations
across Z=28 shell in this region mentioned by Cheal {\it et al.} [Phys. Rev.
Lett. {\bf104}, 252502 (2010)], calculation for valence space
using an effective interaction with Ca as core and imposing a
truncation has also been performed. Comparison of the calculations with
experimental data show that the predicted results of jj44b interaction are in
good agreement with experimental data.Comment: 15 pages, 6 figures, Accepted for publication in Physica Script
Shell-model results in and spaces for Co isotopes
Low-lying spectra and several high-spin states of odd--even Co
isotopes are calculated in two different shell-model spaces. First set of
calculations have been carried out in shell valence space (full
space for Co and a truncated one for Co) using two recently
derived shell interactions, namely GXPF1A and KB3G, with Ca as
core. Similarly, the second set of calculations have been performed in
valence space using an effective interaction due to
Sorlin {\it et al}., with Ca as core and imposing a truncation. It is
seen that the results of GXPF1A and KB3G are reasonable for Co. For
Co, shell-model results show that the interaction adopted in the
study is inadequate and also point out that it is necessary to include orbitals
higher than for neutron-rich Co isotopes.Comment: 19 pages, 3 figures, accepted for publication in Physics of Atomic
Nucle
Nuclear -decay half-lives for and shell nuclei
In the present work we calculate the allowed -decay half-lives of
nuclei with and N 50 systematically under the framework of
the nuclear shell model. A recent study shows that some nuclei in this region
belong to the island of inversion. We perform calculation for shell nuclei
using KB3G effective interaction. In the case of Ni, Cu, and Zn, we used JUN45
effective interaction. Theoretical results of values, half-lives,
excitation energies, log values, and branching fractions are discussed and
compared with the experimental data. In the Ni region, we also compared our
calculated results with recent experimental data [Z. Y. Xu {\it et al.},
\emph{Phys. Rev. Lett.} \textbf{113}, 032505, 2014]. Present results agree with
the experimental data of half-lives in comparison to QRPA.Comment: Accepted in Journal of Physics G: Nuclear and Particle Physic
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