1,678 research outputs found
Superstrings and WZNW Models
We give a brief review of our approach to the quantization of superstrings.
New is a covariant derivation of the measure at tree level and a path integral
formula for this measure.Comment: 12 pp, LaTeX, Contribution to the QTS3 Conference Proceeding
Thermodynamic description of a dynamical glassy transition
For the dynamical glassy transition in the -spin mean field spin glass
model a thermodynamic description is given. The often considered marginal
states are not the relevant ones for this purpose. This leads to consider a
cooling experiment on exponential timescales, where lower states are accessed.
The very slow configurational modes are at quasi-equilibrium at an effective
temperature. A system independent law is derived that expresses their
contribution to the specific heat. -scaling in the aging regime of
two-time quantities is explained.Comment: 5 pages revte
Thermodynamics of the glassy state: effective temperature as an additional system parameter
A system is glassy when the observation time is much smaller than the
equilibration time. A unifying thermodynamic picture of the glassy state is
presented. Slow configurational modes are in quasi-equilibrium at an effective
temperature. It enters thermodynamic relations with the configurational entropy
as conjugate variable. Slow fluctuations contribute to susceptibilities via
quasi-equilibrium relations, while there is also a configurational term.
Fluctuation-dissipation relations also involve the effective temperature.
Fluctuations in the energy are non-universal, however. The picture is supported
by analytically solving the dynamics of a toy model.Comment: 5 pages, REVTEX. Phys. Rev. Lett, to appea
Thermodynamic picture of the glassy state
A picture for thermodynamics of the glassy state is introduced. It assumes
that one extra parameter, the effective temperature, is needed to describe the
glassy state. This explains the classical paradoxes concerning the Ehrenfest
relations and the Prigogine-Defay ratio. As a second part, the approach
connects the response of macroscopic observables to a field change with their
temporal fluctuations, and with the fluctuation-dissipation relation, in a
generalized non-equilibrium way.Comment: Proceedings of the Conference "Unifying Concepts in Glass Physics",
ICTP, Trieste, 15 - 18 September 199
Self-Dual Conformal Supergravity and the Hamiltonian Formulation
In terms of Dirac matrices the self-dual and anti-self-dual decomposition of
a conformal supergravity is given and a self-dual conformal supergravity theory
is developed as a connection dynamic theory in which the basic dynamic variabes
include the self-dual spin connection i.e. the Ashtekar connection rather than
the triad. The Hamiltonian formulation and the constraints are obtained by
using the Dirac-Bergmann algorithm.
PACS numbers: 04.20.Cv, 04.20.Fy,04.65.+
Thermodynamics of black holes: an analogy with glasses
The present equilibrium formulation of thermodynamics for black holes has
several drawbacks, such as assuming the same temperature for black hole and
heat bath. Recently the author formulated non-equilibrium thermodynamics for
glassy systems. This approach is applied to black holes, with the cosmic
background temperature being the bath temperature, and the Hawking temperature
the internal temperature. Both Hawking evaporation and absorption of background
radiation are taken into account.
It is argued that black holes did not form in the very early universe.Comment: 4 pages revtex; submitted to Phys. Rev. Let
Ehrenfest relations at the glass transition: solution to an old paradox
In order to find out whether there exists a thermodynamic description of the
glass phase, the Ehrenfest relations along the glass transition line are
reconsidered. It is explained that the one involving the compressibility is
always satisfied, and that the one involving the specific heat is principally
incorrect.
Thermodynamical relations are presented for non-ergodic systems with a
one-level tree in phase space. They are derived for a spin glass model, checked
for other models, and expected to apply, e.g., to glass forming liquids. The
second Ehrenfest relation gets a contribution from the configurational entropy.Comment: 4 pages revtex, to appear in Phys. Rev. Let
Exactly solvable model of a quantum spin glass
A mean field spherical model with random couplings between pairs, quartets,
and possibly higher multiplets of spins is considered. It has the same critical
behavior as the Sherrington-Kirkpatrick model. It thus exhibits replica
symmetry breaking. The order parameter function is solved exactly in the whole
low temperature phase. The zero field cooled susceptibility remains finite at
low . Next a quantum version of the system is considered. Whereas the
magnetic properties are not altered qualitatively, the thermodynamics is now
regular at small temperatures.Comment: 4 pages postscript. Revised version, to appear in Phys. Rev. Let
Walks of molecular motors in two and three dimensions
Molecular motors interacting with cytoskeletal filaments undergo peculiar
random walks consisting of alternating sequences of directed movements along
the filaments and diffusive motion in the surrounding solution. An ensemble of
motors is studied which interacts with a single filament in two and three
dimensions. The time evolution of the probability distribution for the bound
and unbound motors is determined analytically. The diffusion of the motors is
strongly enhanced parallel to the filament. The analytical expressions are in
excellent agreement with the results of Monte Carlo simulations.Comment: 7 pages, 2 figures, to be published in Europhys. Let
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