25,016 research outputs found
Scanning the critical fluctuations -- application to the phenomenology of the two-dimensional XY-model --
We show how applying field conjugated to the order parameter, may act as a
very precise probe to explore the probability distribution function of the
order parameter. Using this `magnetic-field scanning' on large-scale numerical
simulations of the critical 2D XY-model, we are able to discard the conjectured
double-exponential form of the large-magnetization asymptote.Comment: 4 pages, 4 figure
Passive States for Essential Observers
The aim of this note is to present a unified approach to the results given in
\cite{bb99} and \cite{bs04} which also covers examples of models not presented
in these two papers (e.g. -dimensional Minkowski space-time for ).
Assuming that a state is passive for an observer travelling along certain
(essential) worldlines, we show that this state is invariant under the isometry
group, is a KMS-state for the observer at a temperature uniquely determined by
the structure constants of the Lie algebra involved and fulfills (a variant of)
the Reeh-Schlieder property. Also the modular objects associated to such a
state and the observable algebra of an observer are computed and a version of
weak locality is examined.Comment: 27 page
Single Field Baryogenesis
We propose a new variant of the Affleck-Dine baryogenesis mechanism in which
a rolling scalar field couples directly to left- and right-handed neutrinos,
generating a Dirac mass term through neutrino Yukawa interactions. In this
setup, there are no explicitly CP violating couplings in the Lagrangian. The
rolling scalar field is also taken to be uncharged under the quantum
numbers. During the phase of rolling, scalar field decays generate a
non-vanishing number density of left-handed neutrinos, which then induce a net
baryon number density via electroweak sphaleron transitions.Comment: 4 pages, LaTe
Noise-Activated Escape from a Sloshing Potential Well
We treat the noise-activated escape from a one-dimensional potential well of
an overdamped particle, to which a periodic force of fixed frequency is
applied. We determine the boundary layer behavior, and the physically relevant
length scales, near the oscillating well top. We show how stochastic behavior
near the well top generalizes the behavior first determined by Kramers, in the
case without forcing. Both the case when the forcing dies away in the weak
noise limit, and the case when it does not, are examined. We also discuss the
relevance of various scaling regimes to recent optical trap experiments.Comment: 9 pages, no figures, REVTeX, expanded versio
Reduced Gutzwiller formula with symmetry: case of a finite group
We consider a classical Hamiltonian on , invariant by a
finite group of symmetry , whose Weyl quantization is a
selfadjoint operator on . If is an irreducible
character of , we investigate the spectrum of its restriction
to the symmetry subspace of
coming from the decomposition of Peter-Weyl. We give
reduced semi-classical asymptotics of a regularised spectral density describing
the spectrum of near a non critical energy . If
is compact, assuming that periodic orbits are
non-degenerate in , we get a reduced Gutzwiller trace formula
which makes periodic orbits of the reduced space appear. The
method is based upon the use of coherent states, whose propagation was given in
the work of M. Combescure and D. Robert.Comment: 20 page
Electron-electron interaction corrections to the thermal conductivity in disordered conductors
We evaluate the electron-electron interaction corrections to the electronic
thermal conductivity in a disordered conductor in the diffusive regime. We use
a diagrammatic many-body method analogous to that of Altshuler and Aronov for
the electrical conductivity. We derive results in one, two and three dimensions
for both the singlet and triplet channels, and in all cases find that the
Wiedemann-Franz law is violated.Comment: 8 pages, 2 figures Typos corrected in formulas (15) and (A.4) and
Table 1; discussion of previous work in introduction extended; reference
clarifying different definitions of parameter F adde
A near-field scanned microwave probe for spatially localized electrical metrology
We have developed a near-field scanned microwave probe with a sampling volume
of approximately 10 micron in diameter, which is the smallest one achieved in
near-field microwave microscopy. This volume is defined to confine close to 100
percent of the probe net sampling reactive energy, thus making the response
virtually independent on the sample properties outside of this region. The
probe is formed by a 4 GHz balanced stripline resonator with a few-micron tip
size. It provides non-contact, non-invasive measurement and is uniquely suited
for spatially localized electrical metrology applications, e.g. on
semiconductor production wafers.Comment: 6 pages, 3 figures, submitted to Appl. Phys. Let
Clock-Comparison Tests of Lorentz and CPT Symmetry in Space
Clock-comparison experiments conducted in space can provide access to many
unmeasured coefficients for Lorentz and CPT violation. The orbital
configuration of a satellite platform and the relatively large velocities
attainable in a deep-space mission would permit a broad range of tests with
Planck-scale sensitivity.Comment: 4 page
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