20,288 research outputs found
A model-independent analysis of the dependence of the anomalous J/psi suppression on the number of participant nucleons
A recently published experimental dependence of the J/psi to Drell-Yan ratio
on the measured, by a zero degree calorimeter, forward energy E_ZDC in Pb+Pb
collisions at the CERN SPS is analyzed. Using a model-independent approach it
is shown that the data are at variance with an earlier published experimental
dependence of the same quantity on the transverse energy of neutral hadrons
E_T. The discrepancy is related to a moderate centrality region: 100 < N_p <
200 (N_p is the number of participant nucleons) and is peculiar only to the
data obtained within the `minimum bias' analysis (using the `theoretical
Drell-Yan'). This could result from systematic experimental errors in the
minimum bias sample. A possible source of the errors is discussed.Comment: 10 pages, LaTeX, 3 PS-figures. V2: Misprints are correcte
Lagrangian formulation for noncommutative nonlinear systems
In this work we use the well known formalism developed by Faddeev and Jackiw
to introduce noncommutativity within two nonlinear systems, the SU(2) Skyrme
and O(3) nonlinear sigma models. The final result is the Lagrangian
formulations for the noncommutative versions of both models. The possibility of
obtaining different noncommutative versions for these nonlinear systems is
demonstrated.Comment: 8 pages. Revex 4.
Gauge Fluctuations in Superconducting Films
In this paper we consider a superconducting film modeled by the
Ginzburg-Landau model, confined between two parallel planes a distance
apart from one another. Our approach is based on the Gaussian effective
potential in the transverse unitarity gauge, which allows to treat gauge
contributions in a compact form. Using techniques from dimensional and
-function regularizations, modified by the confinement conditions, we
investigate the critical temperature as a function of the film thickness .
The contributions from the scalar self-interaction and from the gauge
fluctuations are clearly identified. The model suggests the existence of a
minimal critical thickness below which superconductivity is suppressed.Comment: 6 pages Revtex, no figure
Magnetic effects on spontaneous symmetry breaking/restoration in a toroidal topology
We study temperature and finite-size effects on the spontaneous symmetry
breaking/restoration for a scalar field model under the influence of an
external magnetic field, at finite chemical potential. We use the 2PI formalism
and consider the large- limit. We find that there is a minimal size of the
system to sustain the broken phase, which diminishes as the applied field
increases but is independent of the chemical potential. We analyze the critical
curves and show that the magnetic field enhances the broken-phase regions,
while increasing the chemical potential leads to a diminishement of the
critical temperature.Comment: Five pages, five figures, version as accepted for publication in
Phys. Rev.
Thermotoga maritima and Caldicellulosiruptor sacharolyticus co-culture for biohydrogen production
T. maritima and C. saccharolyticus co-culture (1:3) is advantageous for hydrogen production from mixture of glucose and xylose. The higher hydrogen production observed in co-culture was associated to lower lactic acid formation
Open string with a background B-field as the first order mechanics, noncommutativity and soldering formalism
To study noncommutativity properties of the open string with constant B-field
we construct a mechanical action which reproduces classical dynamics of the
string sector under consideration. It allows one to apply the Dirac
quantization procedure for constrained systems in a direct and unambiguous way.
The mechanical action turns out to be the first order system without taking the
strong field limit . In particular, it is true for zero
mode of the string coordinate which means that the noncommutativity is
intrinsic property of this mechanical system. We describe the arbitrariness in
the relation existent between the mechanical and the string variables and show
that noncommutativity of the string variables on the boundary can be removed.
It is in correspondence with the result of Seiberg and Witten on relation among
noncommutative and ordinary Yang-Mills theories. The recently developed
soldering formalism helps us to establish a connection between the original
open string action and the Polyakov action.Comment: Revtex4, 8 pages. To appear in Physical Review
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