15,555 research outputs found
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.
Efficiency of a Brownian information machine
A Brownian information machine extracts work from a heat bath through a
feedback process that exploits the information acquired in a measurement. For
the paradigmatic case of a particle trapped in a harmonic potential, we
determine how power and efficiency for two variants of such a machine operating
cyclically depend on the cycle time and the precision of the positional
measurements. Controlling only the center of the trap leads to a machine that
has zero efficiency at maximum power whereas additional optimal control of the
stiffness of the trap leads to an efficiency bounded between 1/2, which holds
for maximum power, and 1 reached even for finite cycle time in the limit of
perfect measurements.Comment: 9 pages, 2 figure
Entropy bounds in terms of the w parameter
In a pair of recent articles [PRL 105 (2010) 041302 - arXiv:1005.1132; JHEP
1103 (2011) 056 - arXiv:1012.2867] two of the current authors have developed an
entropy bound for equilibrium uncollapsed matter using only classical general
relativity, basic thermodynamics, and the Unruh effect. An odd feature of that
bound, S <= A/2, was that the proportionality constant, 1/2, was weaker than
that expected from black hole thermodynamics, 1/4. In the current article we
strengthen the previous results by obtaining a bound involving the (suitably
averaged) w parameter. Simple causality arguments restrict this averaged
parameter to be <= 1. When equality holds, the entropy bound saturates at the
value expected based on black hole thermodynamics. We also add some clarifying
comments regarding the (net) positivity of the chemical potential. Overall, we
find that even in the absence of any black hole region, we can nevertheless get
arbitrarily close to the Bekenstein entropy.Comment: V1: 14 pages. V2: One reference added. V3: This version accepted for
publication in JHE
New possibilities for the gauging of chiral bosons
We study a new mechanism for the electromagnetic gauging of chiral bosons
showing that new possibilities emerge for the interacting theory of chiral
scalars. We introduce a chirally coupled gauge field necessary to mod out the
degree of freedom that obstructs gauge invariance in a system of two opposite
chiral bosons soldering them together.Comment: 11 pages, Latex. Accepted for publication in Physical Review
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
Charmonium Suppression by Comover Scattering in Pb+Pb Collisions
The first reports of and production from experiment NA50 at
the CERN SPS are compared to predictions based on a hadronic model of
charmonium suppression. Data on centrality dependence and total cross sections
are in good accord with these predictions.Comment: 9 pages, latex, 6 figures, epsf, figure added and text modified to
clarify result
Interference Phenomenon for the Faddeevian Regularization of 2D Chiral Fermionic Determinants
The classification of the regularization ambiguity of 2D fermionic
determinant in three different classes according to the number of second-class
constraints, including the new faddeevian regularization, is examined and
extended. We found a new and important result that the faddeevian class, with
three second-class constraints, possess a free continuous one parameter family
of elements. The criterion of unitarity restricts the parameter to the same
range found earlier by Jackiw and Rajaraman for the two-constraints class. We
studied the restriction imposed by the interference of right-left modes of the
chiral Schwinger model () using Stone's soldering formalism. The
interference effects between right and left movers, producing the massive
vectorial photon, are shown to constrain the regularization parameter to belong
to the four-constraints class which is the only non-ambiguous class with a
unique regularization parameter.Comment: 15 pages, Revtex. Final version to be published in Phys. Rev.
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