5,990 research outputs found
Transverse energy distributions and production in Pb+Pb collisions
We have analyzed the latest NA50 data on transverse energy distributions and
suppression in Pb+Pb collisions. The transverse energy distribution
was analysed in the geometric model of AA collisions. In the geometric model,
fluctuations in the number of NN collisions at fixed impact parameter are taken
into account. Analysis suggests that in Pb+Pb collisions, individual NN
collisions produces less , than in other AA collisions. The nucleons are
more transparent in Pb+Pb collisions. The transverse energy dependence of the
suppression was obtained following the model of Blaizot et al, where
charmonium suppression is assumed to be 100% effective above a threshold
density. With fluctuations in number of NN collisions taken into account, good
fit to the data is obtained, with a single parameter, the threshold density.Comment: Revised version with better E_T fit. 4 pages, 2 figure
suppression in Pb+Pb collisions and broadening
We have analysed the NA50 data, on the centrality dependence of
broadening of 's, in Pb+Pb collisions, at the CERN-SPS. The data were
analysed in a QCD based model, where 's are suppressed in 'nuclear'
medium. Without any free parameter, the model could explain the NA50
broadening data. The data were also analysed in a QGP based threshold model,
where suppression is 100% above a critical density. The QGP based
model could not explain the NA50 broadening data. We have also predicted
the centrality dependence of suppression and broadening at RHIC
energy. Both the models, the QGP based threshold model and the QCD based
nuclear absorption model, predict broadening very close to each other.Comment: The paper was completely revised. The conclusion is also changed. 5
pages, 4 figure
Differentially Private Model Selection with Penalized and Constrained Likelihood
In statistical disclosure control, the goal of data analysis is twofold: The
released information must provide accurate and useful statistics about the
underlying population of interest, while minimizing the potential for an
individual record to be identified. In recent years, the notion of differential
privacy has received much attention in theoretical computer science, machine
learning, and statistics. It provides a rigorous and strong notion of
protection for individuals' sensitive information. A fundamental question is
how to incorporate differential privacy into traditional statistical inference
procedures. In this paper we study model selection in multivariate linear
regression under the constraint of differential privacy. We show that model
selection procedures based on penalized least squares or likelihood can be made
differentially private by a combination of regularization and randomization,
and propose two algorithms to do so. We show that our private procedures are
consistent under essentially the same conditions as the corresponding
non-private procedures. We also find that under differential privacy, the
procedure becomes more sensitive to the tuning parameters. We illustrate and
evaluate our method using simulation studies and two real data examples
Equilibrium glassy phase in a polydisperse hard sphere system
The phase diagram of a polydisperse hard sphere system is examined by
numerical minimization of a discretized form of the Ramakrishnan-Yussouff free
energy functional. Crystalline and glassy local minima of the free energy are
located and the phase diagram in the density-polydispersity plane is mapped out
by comparing the free energies of different local minima. The crystalline phase
disappears and the glass becomes the equilibrium phase beyond a "terminal"
value of the polydispersity. A crystal to glass transition is also observed as
the density is increased at high polydispersity. The phase diagram obtained in
our study is qualitatively similar to that of hard spheres in a quenched random
potential.Comment: 4 pages, 4 figure
Enhancement of gluonic dissociation of in viscous QGP
We have investigated the effect of viscosity on the gluonic dissociation of
in an equilibrating plasma. Suppression of due to gluonic
dissociation depend on the temperature and also on the chemical equilibration
rate. In an equilibrating plasma, viscosity affects the temperature evolution
and also the chemical equilibration rate, requiring both of them to evolve
slowly compared to their ideal counter part. For Au+Au collisions at RHIC and
LHC energies, gluonic dissociation of increases for a viscous plasma.
Low 's are found to be more suppressed due to viscosity than the
high ones. Also the effect is more at LHC energy than at RHIC energy.Comment: 3 pages, 1 figur
Laser induced reentrant freezing in two-dimensional attractive colloidal systems
The effects of an externally applied one-dimensional periodic potential on
the freezing/melting behaviour of two-dimensional systems of colloidal
particles with a short-range attractive interaction are studied using Monte
Carlo simulations. In such systems, incommensuration results when the
periodicity of the external potential does not match the length-scale at which
the minimum of the attractive potential occurs. To study the effects of this
incommensuration, we consider two different models for the system. Our
simulations for both these models show the phenomenon of reentrant freezing as
the strength of the periodic potential is varied. Our simulations also show
that different exotic phases can form when the strength of the periodic
potential is high, depending on the length-scale at which the minimum of the
attractive pair-potential occurs.Comment: 24 pages (including figures) in preprint forma
Study on Noncommutative Representations of Galilean Generators
The representations of Galilean generators are constructed on a space where
both position and momentum coordinates are noncommutating operators. A
dynamical model invariant under noncommutative phase space transformations is
constructed. The Dirac brackets of this model reproduce the original
noncommutative algebra. Also, the generators in terms of noncommutative phase
space variables are abstracted from this model in a consistent manner. Finally,
the role of Jacobi identities is emphasised to produce the noncommuting
structure that occurs when an electron is subjected to a constant magnetic
field and Berry curvature.Comment: Title changed, new references added, published in Int. J. Mod. Phys.
Deconfinement and the Hagedorn Transition in String Theory
Superseded and extended in hep-th/0105110 and hep-th/0208112.Comment: Superseded and extended in hep-th/0105110 and hep-th/020811
On Generalizations of Network Design Problems with Degree Bounds
Iterative rounding and relaxation have arguably become the method of choice
in dealing with unconstrained and constrained network design problems. In this
paper we extend the scope of the iterative relaxation method in two directions:
(1) by handling more complex degree constraints in the minimum spanning tree
problem (namely, laminar crossing spanning tree), and (2) by incorporating
`degree bounds' in other combinatorial optimization problems such as matroid
intersection and lattice polyhedra. We give new or improved approximation
algorithms, hardness results, and integrality gaps for these problems.Comment: v2, 24 pages, 4 figure
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