14,746 research outputs found
Hamiltonian Derivations of the Generalized Jarzynski Equalities under Feedback Control
In the presence of feedback control by "Maxwell's demon," the second law of
thermodynamics and the nonequilibrium equalities such as the Jarzynski equality
need to be generalized. In this paper, we derive the generalized Jarzynski
equalities for classical Hamiltonian dynamics based on the Liouville's theorem,
which is the same approach as the original proof of the Jarzynski equality
[Phys. Rev. Lett. 78, 2690 (1997)]. The obtained equalities lead to the
generalizations of the second law of thermodynamics for the Hamiltonian systems
in the presence of feedback control.Comment: Proceedings of "STATPHYS - Kolkata VII", November 26-30, 2010,
Kolkata, Indi
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
Axial Anomaly from the BPHZ regularized BV master equation
A BPHZ renormalized form for the master equation of the field antifiled (or
BV) quantization has recently been proposed by De Jonghe, Paris and Troost.
This framework was shown to be very powerful in calculating gauge anomalies. We
show here that this equation can also be applied in order to calculate a global
anomaly (anomalous divergence of a classically conserved Noether current),
considering the case of QED. This way, the fundamental result about the
anomalous contribution to the Axial Ward identity in standard QED (where there
is no gauge anomaly) is reproduced in this BPHZ regularized BV framework.Comment: 10 pages, Latex, minor changes in the reference
Charmonium properties in deconfinement phase in anisotropic lattice QCD
J/Psi and eta_c above the QCD critical temperature T_c are studied in
anisotropic quenched lattice QCD, considering whether the c\bar c systems above
T_c are spatially compact (quasi-)bound states or scattering states. We adopt
the standard Wilson gauge action and O(a)-improved Wilson quark action with
renormalized anisotropy a_s/a_t =4.0 at \beta=6.10 on 16^3\times (14-26)
lattices, which correspond to the spatial lattice volume V\equiv
L^3\simeq(1.55{\rm fm})^3 and temperatures T\simeq(1.11-2.07)T_c. We
investigate the c\bar c system above T_c from the temporal correlators with
spatially-extended operators, where the overlap with the ground state is
enhanced. To clarify whether compact charmonia survive in the deconfinement
phase, we investigate spatial boundary-condition dependence of the energy of
c\bar c systems above T_c. In fact, for low-lying S-wave c \bar c scattering
states, it is expected that there appears a significant energy difference
\Delta E \equiv E{\rm (APBC)}-E{\rm (PBC)}\simeq2\sqrt{m_c^2+3\pi^2/L^2}-2m_c
(m_c: charm quark mass) between periodic and anti-periodic boundary conditions
on the finite-volume lattice. In contrast, for compact charmonia, there is no
significant energy difference between periodic and anti-periodic boundary
conditions. As a lattice QCD result, almost no spatial boundary-condition
dependence is observed for the energy of the c\bar c system in J/\Psi and
\eta_c channels for T\simeq(1.11-2.07)T_c. This fact indicates that J/\Psi and
\eta_c would survive as spatially compact c\bar c (quasi-)bound states below
2T_c. We also investigate a -wave channel at high temperature with maximally
entropy method (MEM) and find no low-lying peak structure corresponding to
\chi_{c1} at 1.62T_c.Comment: 13 pages, 11 figure
Weakly correlated electrons on a square lattice: a renormalization group theory
We study the weakly interacting Hubbard model on the square lattice using a
one-loop renormalization group approach. The transition temperature T_c between
the metallic and (nearly) ordered states is found. In the parquet regime, (T_c
>> |mu|), the dominant correlations at temperatures below T_c are
antiferromagnetic while in the BCS regime (T_c << |mu|) at T_c the d-wave
singlet pairing susceptibility is most divergent.Comment: 12 pages, REVTEX, 3 figures included, submitted to Phys. Rev. Let
Anisotropic suppression in nuclear collisions
The nuclear overlap zone in non-central relativistic heavy ion collisions is
azimuthally very asymmetric. By varying the angle between the axes of
deformation and the transverse direction of the pair momenta, the suppression
of and will oscillate in a characteristic way. Whereas the
average suppression is mostly sensitive to the early and high density stages of
the collision, the amplitude is more sensitive to the late stages. This effect
provides additional information on the suppression mechanisms such as
direct absorption on participating nucleons, comover absorption or formation of
a quark-gluon plasma. The behavior of the average suppression and its
amplitude with centrality of the collisions is discussed for SPS, RHIC and LHC
energies with and without a phase transition.Comment: Revised and extended version, new figure
Sound Speeds, Cracking and Stability of Self-Gravitating Anisotropic Compact Objects
Using the the concept of cracking we explore the influence of density
fluctuations and local anisotropy have on the stability of local and non-local
anisotropic matter configurations in general relativity. This concept,
conceived to describe the behaviour of a fluid distribution just after its
departure from equilibrium, provides an alternative approach to consider the
stability of selfgravitating compact objects. We show that potentially unstable
regions within a configuration can be identify as a function of the difference
of propagations of sound along tangential and radial directions. In fact, it is
found that these regions could occur when, at particular point within the
distribution, the tangential speed of sound is greater than radial one.Comment: 17 pages, 8 figures, 4 new references added. typos correcte
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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