1,151 research outputs found
Influence of the Rashba effect on the Josephson current through a superconductor/Luttinger liquid/superconductor tunnel junction
The Josephson current through a 1D quantum wire with Rashba spin-orbit and
electron-electron interactions is calculated. We show that the interplay of
Rashba and Zeeman interactions gives rise to a supercurrent through the 1D
conductor that is anomalous in the sense that it persists in the absence of any
phase difference between the two superconducting leads to which it is attached.
The electron dispersion asymmetry induced by the Rashba interaction in a
Luttinger-liquid wire plays a significant role for poorly transmitting
junctions. It is shown that for a weak or moderate electron-electron
interaction the spectrum of plasmonic modes confined to the normal part of the
junction becomes quasi-random in the presence of dispersion asymmetry.Comment: 25 pages, 3 figure
Dispersionless Hirota equations and the genus 3 hyperelliptic divisor
Equations of dispersionless Hirota type have been thoroughly investigated in
the mathematical physics and differential geometry literature. It is known that
the parameter space of integrable Hirota type equations in 3D is 21-dimensional
and the action of the natural equivalence group Sp(6, R) on the parameter space
has an open orbit. However the structure of the `master-equation' corresponding
to this orbit remained elusive. Here we prove that the master-equation is
specified by the vanishing of any genus 3 theta constant with even
characteristic. The rich geometry of integrable Hirota type equations sheds new
light on local differential geometry of the genus 3 hyperelliptic divisor, in
particular, the integrability conditions can be viewed as local
differential-geometric constraints that characterise the hyperelliptic divisor
uniquely modulo Sp(6, C)-equivalence.Comment: amended version, to appear in Comm. Math. Phys., 15 page
Light-like mesons and deep inelastic scattering in finite-temperature AdS/CFT with flavor
We use the holographic dual of a finite-temperature, strongly-coupled, gauge
theory with a small number of flavors of massive fundamental quarks to study
meson excitations and deep inelastic scattering (DIS) in the low-temperature
phase, where the mesons are stable. We show that a high-energy flavor current
with nearly light-like kinematics disappears into the plasma by resonantly
producing mesons in highly excited states. This mechanism generates the same
DIS structure functions as in the high temperature phase, where mesons are
unstable and the current disappears through medium-induced parton branching. To
establish this picture, we derive analytic results for the meson spectrum,
which are exact in the case of light-like mesons and which corroborate and
complete previous, mostly numerical, studies in the literature. We find that
the meson levels are very finely spaced near the light-cone, so that the
current can always decay, without a fine-tuning of its kinematics.Comment: 43 pages, 6 figure
Non uniform rotating vortices and periodic orbits for the two-dimensional Euler Equations
This paper concerns the study of some special ordered structures in turbulent
flows. In particular, a systematic and relevant methodology is proposed to
construct non trivial and non radial rotating vortices with non necessarily
uniform densities and with different --fold symmetries, . In
particular, a complete study is provided for the truncated quadratic density
, with the unit disc. We
exhibit different behaviors with respect to the coefficients and
describing the rarefaction of bifurcating curves.Comment: 115 pages, 1 figur
A family of lowered isothermal models
We present a family of self-consistent, spherical, lowered isothermal models,
consisting of one or more mass components, with parameterised prescriptions for
the energy truncation and for the amount of radially biased pressure
anisotropy. The models are particularly suited to describe the phase-space
density of stars in tidally limited, mass-segregated star clusters in all
stages of their life-cycle. The models extend a family of isotropic,
single-mass models by Gomez-Leyton and Velazquez, of which the well-known
Woolley, King and Wilson (in the non-rotating and isotropic limit) models are
members. We derive analytic expressions for the density and velocity dispersion
components in terms of potential and radius, and introduce a fast model solver
in PYTHON (LIMEPY), that can be used for data fitting or for generating
discrete samples.Comment: 17 pages, 10 figures, 4 appendices, MNRAS, updated to match final
journal styl
Stellar Dynamics around Black Holes in Galactic Nuclei
We classify orbits of stars that are bound to central black holes in galactic
nuclei. The stars move under the combined gravitational influences of the black
hole and the central star cluster. Within the sphere of influence of the black
hole, the orbital periods of the stars are much shorter than the periods of
precession. We average over the orbital motion and end up with a simpler
problem and an extra integral of motion: the product of the black hole mass and
the semimajor axis of the orbit. Thus the black hole enforces some degree of
regularity in its neighborhood. Well within the sphere of influence, (i)
planar, as well as three dimensional, axisymmetric configurations-both of which
could be lopsided-are integrable, (ii) fully three dimensional clusters with no
spatial symmetry whatsover must have semi-regular dynamics with two integrals
of motion. Similar considerations apply to stellar orbits when the black hole
grows adiabatically. We introduce a family of planar, non-axisymmetric
potential perturbations, and study the orbital structure for the harmonic case
in some detail. In the centered potentials there are essentially two main
families of orbits: the familiar loops and lenses, which were discussed in
Sridhar and Touma (1997, MNRAS, 287, L1-L4). We study the effect of
lopsidedness, and identify a family of loop orbits, whose orientation
reinforces the lopsidedness, an encouraging sign for the construction of
self-consistent models of eccentric, discs around black holes, such as in M31
and NGC 4486B.Comment: to appear in MNRAS, 10 pages, latex, 20 POstScript figure
Electron Spin Relaxation in a Transition-Metal Dichalcogenide Quantum Dot
We study the relaxation of a single electron spin in a circular quantum dot
in a transition-metal dichalcogenide monolayer defined by electrostatic gating.
Transition-metal dichalcogenides provide an interesting and promising arena for
quantum dot nano-structures due to the combination of a band gap, spin-valley
physics and strong spin-orbit coupling. First we will discuss which bound state
solutions in different B-field regimes can be used as the basis for qubits
states. We find that at low B-fields combined spin-valley Kramers qubits to be
suitable, while at large magnetic fields pure spin or valley qubits can be
envisioned. Then we present a discussion of the relaxation of a single electron
spin mediated by electron-phonon interaction via various different relaxation
channels. In the low B-field regime we consider the spin-valley Kramers qubits
and include impurity mediated valley mixing which will arise in disordered
quantum dots. Rashba spin-orbit admixture mechanisms allows for relaxation by
in-plane phonons either via the deformation potential or by piezoelectric
coupling, additionally direct spin-phonon mechanisms involving out-of-plane
phonons give rise to relaxation. We find that the relaxation rates scale as
for both in-plane phonons coupling via deformation potential and
the piezoelectric effect, while relaxation due to the direct spin-phonon
coupling scales independant to B-field to lowest order but scales strongly on
device mechanical tension. We will also discuss the relaxation mechanisms for
pure spin or valley qubits formed in the large B-field regime.Comment: 10 pages, 4 figure
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