27,395 research outputs found
Does the Third Law of Thermodynamics hold in the Quantum Regime?
The first in a long series of papers by John T. Lewis,
G. W. Ford and the present author, considered the problem of the most general
coupling of a quantum particle to a linear passive heat bath, in the course of
which they derived an exact formula for the free energy of an oscillator
coupled to a heat bath in thermal equilibrium at temperature T. This formula,
and its later extension to three dimensions to incorporate a magnetic field,
has proved to be invaluable in analyzing problems in quantum thermodynamics.
Here, we address the question raised in our title viz. Nernst's third law of
thermodynamics
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
Solvable glassy system: static versus dynamical transition
A directed polymer is considered on a flat substrate with randomly located
parallel ridges. It prefers to lie inside wide regions between the ridges. When
the transversel width is exponential in the
longitudinal length , there can be a large number of
available wide states. This ``complexity'' causes a phase transition from a
high temperature phase where the polymer lies in the widest lane, to a glassy
low temperature phase where it lies in one of many narrower lanes. Starting
from a uniform initial distribution of independent polymers, equilibration up
to some exponential time scale induces a sharp dynamical transition. When the
temperature is slowly increased with time, this occurs at a tunable
temperature. There is an asymmetry between cooling and heating. The structure
of phase space in the low temperature non-equilibrium glassy phase is of a
one-level tree.Comment: 4 pages revte
Quantum description of spherical spins
The spherical model for spins describes ferromagnetic phase transitions well,
but it fails at low temperatures. A quantum version of the spherical model is
proposed. It does not induce qualitative changes near the phase transition.
However, it produces a physical low temperature behavior. The entropy is
non-negative. Model parameters can be adapted to the description of real
quantum spins. Several applications are discussed. Zero-temperature quantum
phase transitions are analyzed for a ferromagnet and a spin glass in a
transversal field. Their crossover exponents are presented.Comment: 4 pages postscript. Revised version, to appear in Phys. Rev. Let
Resolving HD 100546 disc in the mid-infrared: Small inner disc and asymmetry near the gap
A region of roughly half of the solar system scale around the star HD 100546
is largely cleared of gas and dust, in contrast to the bright outer disc.
However, some material is observed in the immediate vicinity of the star. We
investigate how the dust is distributed within and outside the gap, and
constrain the disc geometry with mid-infrared interferometric observations
using VLTI/MIDI. With baseline lengths of 40m, our long baseline observations
are sensitive to the inner few AU from the star, and we combined them with
observations at shorter, 15m baselines, to probe emission beyond the gap at up
to 20AU from the star. We modelled the mid-infrared emission using radial
temperature profiles. Our model is composed of infinitesimal concentric annuli
emitting as black bodies, and it has distinct inner and outer disc components.
We derived an upper limit of 0.7AU for the radial size of the inner disc, from
our longest baseline data. This small dusty disc is separated from the edge of
the outer disc by a large, roughly 10AU wide gap. Our short baseline data place
a bright ring of emission at 11+-1AU, consistent with prior observations of the
transition region between the gap and the outer disc, known as the disc wall.
The inclination and position angle are constrained by our data to i=53+-8deg
and PA=145+-5deg. Compared to the rim and outer disc geometry this suggests
co-planarity. Brightness asymmetry is evident in both short and long baseline
data, and it is unequivocally discernible from any atmospheric or instrumental
effects. The origin of the asymmetry is consistent with the bright disc wall,
which we find to be 1-2AU wide. The gap is cleared of micron-sized dust, but we
cannot rule out the presence of larger particles and/or perturbing bodies.Comment: 12 pages, 9 figures, accepted for publication in A&
Frequency Metrology on single trapped ions in the weak binding limit: The 3s1/2-3p3/2 transition in 24-Mg+
We demonstrate a method for precision spectroscopy on trapped ions in the
limit of unresolved motional sidebands. By sympathetic cooling of a chain of
crystallized ions we suppress adverse temperature variations induced by the
spectroscopy laser that usually lead to a distorted line profle and obtain a
Voigt profile with negligible distortions. We applied the method to measure the
absolute frequency of the astrophysically relevant D2 transition in single
24-Mg+ ions and find 1072082934.33(16)MHz, a nearly 400fold improvement over
previous results. Further, we find the excited state lifetime to be 3.84(10)
ns.Comment: 4 pages, 5 figure
Laser-Cluster-Interaction in a Nanoplasma-Model with Inclusion of Lowered Ionization Energies
The interaction of intense laser fields with silver and argon clusters is
investigated theoretically using a modified nanoplasma model. Single pulse and
double pulse excitations are considered. The influence of the dense cluster
environment on the inner ionization processes is studied including the lowering
of the ionization energies. There are considerable changes in the dynamics of
the laser-cluster interaction. Especially, for silver clusters, the lowering of
the ionization energies leads to increased yields of highly charged ions.Comment: 10 pages, 11 figure
Multipole moments in Kaluza-Klein theories
This paper contains discussion of the problem of motion of extended i.e. non
point test bodies in multidimensional space. Extended bodies are described in
terms of so called multipole moments. Using approximated form of equations of
motion for extended bodies deviation from geodesic motion is derived. Results
are applied to special form of space-time.Comment: 11 pages, AMS-TeX, few misprints corrected, to appear in Classical
and Quantum Gravit
Distributions of inherent structure energies during aging
We perform extensive simulations of a binary mixture Lennard-Jones system
subjected to a temperature jump in order to study the time evolution of
fluctuations during aging. Analyzing data from 1500 different aging
realizations, we calculate distributions of inherent structure energies for
different aging times and contrast them with equilibrium. We find that the
distributions initially become narrower and then widen as the system
equilibrates. For deep quenches, fluctuations in the glassy system differ
significantly from those observed in equilibrium. Simulation results are
partially captured by theoretical predictions only when the final temperature
is higher than the mode coupling temperature.Comment: 5 pages, 4 figure
Sampling functions for multimode homodyne tomography with a single local oscillator
We derive various sampling functions for multimode homodyne tomography with a
single local oscillator. These functions allow us to sample multimode
s-parametrized quasidistributions, density matrix elements in Fock basis, and
s-ordered moments of arbitrary order directly from the measured quadrature
statistics. The inevitable experimental losses can be compensated by proper
modification of the sampling functions. Results of Monte Carlo simulations for
squeezed three-mode state are reported and the feasibility of reconstruction of
the three-mode Q-function and s-ordered moments from 10^7 sampled data is
demonstrated.Comment: 12 pages, 8 figures, REVTeX, submitted Phys. Rev.
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