33,255 research outputs found
Wiedemann-Franz Law For Hot QCD Matter in a Color String Percolation Scenario
Transport coefficients serve as important probes in characterizing the QCD
matter created in high-energy heavy-ion collisions. Thermal and electrical
conductivities as transport coefficients have got special significance in
studying the time evolution of the created matter. We have adopted color string
percolation approach for the estimation of thermal conductivity (),
electrical conductivity () and their ratio, which is popularly
known as Wiedemann-Franz law in condensed matter physics. The ratio
, which is also known as Lorenz number () is
studied as a function of temperature and is compared with various theoretical
calculations. We observe that the thermal conductivity for hot QCD medium is
almost temperature independent in the present formalism and matches with the
results obtained in ideal equation of state (EOS) for quark-gluon plasma with
fixed coupling constant (). The obtained Lorenz number is compared
with the Stefan-Boltzmann limit for an ideal gas. We observe that a hot QCD
medium with color degrees of freedom behaves like a free electron gas.Comment: No change in the MS. arXiv admin note: text overlap with
arXiv:1804.0798
Electrical conductivity of Hot and Dense QCD matter at RHIC BES energies: A Color String Percolation Approach
Recently, transport coefficients viz. shear viscosity, electrical
conductivity etc. of strongly interacting matter produced in heavy-ion
collisions have drawn considerable interest. We study the normalised electrical
conductivity (/T) of hot QCD matter as a function of
temperature (T) using the Color String Percolation Model (CSPM). We also study
the temperature dependence of shear viscosity and its ratio with electrical
conductivity for the QCD matter. We compare CSPM estimations with various
existing results and lattice Quantum Chromodynamics (lQCD) predictions with
(2+1) dynamical flavours. We find that /T in CSPM has a very
weak dependence on the temperature. We compare CSPM results with those obtained
in Boltzmann Approach to Multi-Parton Scatterings (BAMPS) model. A good
agreement is found between CSPM results and predictions of BAMPS with fixed
strong coupling constant.Comment: Same as published versio
Analyzing research performance: proposition of a new complementary index
A researcher collaborating with many groups will normally have more papers
(and thus higher citations and -index) than a researcher spending all
his/her time working alone or in a small group. While analyzing an author's
research merit, it is therefore not enough to consider only the collective
impact of the published papers, it is also necessary to quantify his/her share
in the impact. For this quantification, here I propose the -index which is
defined as an author's percentage share in the total citations that his/her
papers have attracted. It is argued that this -index does not directly
depend on the most of the subjective issues like an author's influence,
affiliation, seniority or career break. A simple application of the Central
Limit Theorem shows that, the scheme of equidistribution of credit among the
coauthors of a paper will give us the most probable value of the -index
(with an associated small standard deviation which decreases with increasing
-index). I show that the total citations (), the -index and the
-index are three independent parameters (within their bounds), and together
they give a comprehensive idea of an author's overall research performance.Comment: minor changes made; accepted for publication in Scientometrics; this
version is essentially the same as the accepted one, visit link.springer.com
for the final published articl
Observation of Radiative B^0 -> \phi K^0 \gamma Decays and Measurements of Their Time-Dependent CP Violation
We report the first observation of the radiative decay B^0->\phi K^0\gamma
using a data sample of 772x10^6 BBar pairs collected at the Y(4S) resonance
with the Belle detector at the KEKB asymmetric-energy e+e- collider. We observe
a signal of 35+/-8 events with a significance of 5.4 standard deviations
including systematic uncertainties. The measured branching fraction is , where the
uncertainties are statistical and systematic, respectively. We also report the
first measurement of time-dependent CP violation parameters:
and . We also precisely measure . The observed mass
spectrum differs significantly from that expected in a three-body phase-space
decay. These results are preliminary.Comment: 4 pages, 6 figures, To be published in the proceedings of 35th
International Conference of High Energy Physics (ICHEP 2010), Paris, France,
July 22-28, 201
Exclusive Radiative B meson decays at Belle
In this proceeding, we discuss recent results on exclusive radiative B meson
decays from the Belle Collaboration. These decays are sensitive to right-handed
currents from New Physics. In particular, we measure time-dependent CP
violation parameters in B^0->K_S\pi^0\gamma and B^0->K_S\rho^0\gamma decays,
using high-statistics data samples collected at the Y(4S) resonance with the
Belle detector at the KEKB asymmetric-energy e^+e^- collider. With the present
statistics, these measurements are consistent with the standard model
predictions. We also search for the radiative decay B^0->\phiK^0\gamma and
report the first observation with a significance of 5.4 \sigma, including
systematic uncertainties.Comment: 6 pages, 16 figures, To be published in the proceedings of DPF-2009,
Detroit, MI, July 2009, eConf C09072
A periodic varying deceleration parameter in gravity
The phenomenon of accelerated expansion of the present universe and a cosmic
transit aspect is explored in the framework of a modified gravity theory known
as gravity (where is the Ricci scalar and is the trace of the
energy momentum tensor of the matter content). The cosmic transit phenomenon
signifies a signature flipping behaviour of the deceleration parameter. We
employ a periodic varying deceleration parameter and obtained the exact
solution of field equations. The dynamical features of the model including the
oscillatory behaviour of the EOS parameter are studied. We have also explored
the obvious violation of energy momentum conservation in gravity. The
periodic behaviour of energy conditions for the model are also discussed with a
wide range of the free parameters.Comment: 19 pages, 14 figures, Accepted version in MPL
Inverse Vector Operators
In different branches of physics, we frequently deal with vector del operator
(). This del operator is generally used to find curl or
divergence of a vector function or gradient of a scalar function. In many
important cases, we need to know the parent vector whose curl or divergence is
known or require to find the parent scalar function whose gradient is known.
But the task is not very easy, especially in case of finding vector potential
whose curl is known. Here,'inverse curl', 'inverse divergence' and 'inverse
gradient' operators are defined to solve those problems easily. All operators
are defined in the orthogonal curvilinear co-ordinate system.Comment: 8 pages; rewritten with more clarit
Performance Comparison of Packet Scheduling Algorithms for Video Traffic in LTE Cellular Network
In this paper we have studied downlink packet scheduling algorithms proposed
for LTE cellular networks. The study emphasize on three most promising
scheduling algorithms such as: FLS, EXP rule and LOG rule. The performance of
these three algorithms is conducted over video traffic in a vehicular
environment using LTE-Sim simulator. The simulation was setup with varying
number of users from 10 - 60 in fixed bounded regions of 1 km radius. The main
goal this study is to provide results that will help in the design process of
packet scheduler for LTE cellular networks, aiming to get better overall
performance users. Simulation results show that, the FLS scheme outperforms in
terms of average system throughput, average packet delay, PLR; and with a
satisfactory level of fairness index
Limiting fragmentation in high-energy nuclear collisions at the CERN Large Hadron Collider
The hypothesis of limiting fragmentation (LF) or it is called otherwise
recently, as extended longitudinal scaling, is an interesting phenomena in high
energy multiparticle production process. This paper discusses about different
regions of phase space and their importance in hadron production, giving
special emphasis on the fragmentation region. Although it was conjectured as a
universal phenomenon in high energy physics, with the advent of higher
center-of-mass energies, it has become prudent to analyse and understand the
validity of such hypothesis in view of the increasing inelastic nucleon-nucleon
cross-section (). In this work, we revisit the phenomenon of
limiting fragmentation for nucleus-nucleus (A+A) collisions in the
pseudorapidity distribution of charged particles at various energies. We use
energy dependent to transform the charged particle
pseudorapidity distributions () into differential
cross-section per unit pseudorapidity () of charged
particles and study the phenomenon of LF. We find that in LF seems to be violated at LHC energies while considering the energy
dependent . We also perform a similar study using A
Multi-Phase Transport (AMPT) Model with string melting scenario and also find
that LF is violated at LHC energies.Comment: Published versio
String theory: big problem for small size
String theory is the most promising candidate theory for a unified
description of all fundamental forces exist in the nature. It provides a
mathematical framework that combine quantum theory with Einstein's general
theory of relativity. But due to the extremely small size of strings, nobody
has been able to detect it directly in the laboratory till today. In this
article, we have presented a general introduction to string theory.Comment: 12 pages, 2 figure
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