16,111 research outputs found
Giant Charge Relaxation Resistance in the Anderson Model
We investigate the dynamical charge response of the Anderson model viewed as
a quantum RC circuit. Applying a low-energy effective Fermi liquid theory, a
generalized Korringa-Shiba formula is derived at zero temperature, and the
charge relaxation resistance is expressed solely in terms of static
susceptibilities which are accessible by Bethe ansatz. We identify a giant
charge relaxation resistance at intermediate magnetic fields related to the
destruction of the Kondo singlet. The scaling properties of this peak are
computed analytically in the Kondo regime. We also show that the resistance
peak fades away at the particle-hole symmetric point.Comment: 4 pages, 1 figur
Searching for signatures of planet formation in stars with circumstellar debris discs
(Abridged) Tentative correlations between the presence of dusty debris discs
and low-mass planets have been presented. In parallel, detailed chemical
abundance studies have reported different trends between samples of planet and
non-planet hosts. We determine in a homogeneous way the metallicity, and
abundances of a sample of 251 stars including stars with known debris discs,
with debris discs and planets, and only with planets. Stars with debris discs
and planets have the same [Fe/H] behaviour as stars hosting planets, and they
also show a similar -Tc trend. Different behaviour in the -Tc
trend is found between the samples of stars without planets and the samples of
planet hosts. In particular, when considering only refractory elements,
negative slopes are shown in cool giant planet hosts, whilst positive ones are
shown in stars hosting low-mass planets. Stars hosting exclusively close-in
giant planets show higher metallicities and positive -Tc slope. A
search for correlations between the -Tc slopes and the stellar
properties reveals a moderate but significant correlation with the stellar
radius and as well as a weak correlation with the stellar age. The fact that
stars with debris discs and stars with low-mass planets do not show neither
metal enhancement nor a different -Tc trend might indicate a
correlation between the presence of debris discs and the presence of low-mass
planets. We extend results from previous works which reported differences in
the -Tc trends between planet hosts and non hosts. However, these
differences tend to be present only when the star hosts a cool distant planet
and not in stars hosting exclusively low-mass planets.Comment: Accepted for publication in Astronomy and Astrophysic
Superconducting transport through a vibrating molecule
Nonequilibrium electronic transport through a molecular level weakly coupled
to a single coherent phonon/vibration mode has been studied for superconducting
leads. The Keldysh Green function formalism is used to compute the current for
the entire bias voltage range. In the subgap regime, Multiple Andreev
Reflection (MAR) processes accompanied by phonon emission cause rich structure
near the onset of MAR channels, including an even-odd parity effect that can be
interpreted in terms of an inelastic MAR ladder picture. Thereby we establish a
connection between the Keldysh formalism and the Landauer scattering approach
for inelastic MAR.Comment: 5 pages, 5 figures, version contains now more details, accepted by
PR
The low temperature Fulde-Ferrell-Larkin-Ovchinnikov phases in 3 dimensions
We consider the nature of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phases
in three dimensions at low temperature. We introduce a new method to handle the
quasiclassical equations for superconductors with space dependent order
parameter, which makes use of a Fourier expansion. This allows us to show that,
at T=0, an order parameter given by the linear combination of three cosines
oscillating in orthogonal directions is preferred over the standard single
cosine solution. The transition from the normal state to this phase is first
order, and quite generally the transition below the tricritical point to the
FFLO phases is always first order.Comment: 4 pages, revtex, 1 figur
Confinement-induced resonances for a two-component ultracold atom gas in arbitrary quasi-one-dimensional traps
We solve the two-particle s-wave scattering problem for ultracold atom gases
confined in arbitrary quasi-one-dimensional trapping potentials, allowing for
two different atom species. As a consequence, the center-of-mass and relative
degrees of freedom do not factorize. We derive bound-state solutions and obtain
the general scattering solution, which exhibits several resonances in the 1D
scattering length induced by the confinement. We apply our formalism to two
experimentally relevant cases: (i) interspecies scattering in a two-species
mixture, and (ii) the two-body problem for a single species in a non-parabolic
trap.Comment: 22 pages, 3 figure
Enabling science with Gaia observations of naked-eye stars
ESA's Gaia space astrometry mission is performing an all-sky survey of
stellar objects. At the beginning of the nominal mission in July 2014, an
operation scheme was adopted that enabled Gaia to routinely acquire
observations of all stars brighter than the original limit of G~6, i.e. the
naked-eye stars. Here, we describe the current status and extent of those
observations and their on-ground processing. We present an overview of the data
products generated for G<6 stars and the potential scientific applications.
Finally, we discuss how the Gaia survey could be enhanced by further exploiting
the techniques we developed.Comment: 16 pages, 8 figures. Submitted for the proceedings of the 2016 SPIE
Astronomical Instrumentation and Telescopes conference (SPIE 9904
Stochastic integration with respect to cylindrical semimartingales
In this work we introduce a theory of stochastic integration with respect to
general cylindrical semimartingales defined on a locally convex space .
Our construction of the stochastic integral is based on the theory of tensor
products of topological vector spaces and the property of good integrators of
real-valued semimartingales. This theory is further developed in the case where
is a complete, barrelled, nuclear space, where we obtain a complete
description of the class of integrands as -valued locally bounded and
weakly predictable processes. Several other properties of the stochastic
integral are proven, including a Riemann representation, a stochastic
integration by parts formula and a stochastic Fubini theorem. Our theory is
then applied to provide sufficient and necessary conditions for existence and
uniqueness of solutions to linear stochastic evolution equations driven by
semimartingale noise taking values in the strong dual of . In the
last part of this article we apply our theory to define stochastic integrals
with respect to a sequence of real-valued semimartingales
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