2,222 research outputs found
The dynamics of neutron star crusts: Lagrangian perturbation theory for a relativistic superfluid-elastic system
The inner crust of a mature neutron star is composed of an elastic lattice of
neutron-rich nuclei penetrated by free neutrons. These neutrons can flow
relative to the crust once the star cools below the superfluid transition
temperature. In order to model the dynamics of this system, which is relevant
for a range of problems from pulsar glitches to magnetar seismology and
continuous gravitational-wave emission from rotating deformed neutron stars, we
need to understand general relativistic Lagrangian perturbation theory for
elastic matter coupled to a superfluid component. This paper develops the
relevant formalism to the level required for astrophysical applications.Comment: 31 pages, double spacing, minor typos fixe
Carter's constant revealed
A new formulation of Carter's constant for geodesic motion in Kerr black
holes is given. It is shown that Carter's constant corresponds to the total
angular momentum plus a precisely defined part which is quadratic in the linear
momenta. The characterization is exact in the weak field limit obtained by
letting the gravitational constant go to zero. It is suggested that the new
form can be useful in current studies of the dynamics of extreme mass ratio
inspiral (EMRI) systems emitting gravitational radiation.Comment: Minor changes to match published versio
Energy and temperature fluctuations in the single electron box
In mesoscopic and nanoscale systems at low temperatures, charge carriers are
typically not in thermal equilibrium with the surrounding lattice. The
resulting, non-equilibrium dynamics of electrons has only begun to be explored.
Experimentally the time-dependence of the electron temperature (deviating from
the lattice temperature) has been investigated in small metallic islands.
Motivated by these experiments we investigate theoretically the electronic
energy and temperature fluctuations in a metallic island in the Coulomb
blockade regime, tunnel coupled to an electronic reservoir, i.e. a single
electron box. We show that electronic quantum tunnelling between the island and
the reservoir, in the absence of any net charge or energy transport, induces
fluctuations of the island electron temperature. The full distribution of the
energy transfer as well as the island temperature is derived within the
framework of full counting statistics. In particular, the low-frequency
temperature fluctuations are analysed, fully accounting for charging effects
and non-zero reservoir temperature. The experimental requirements for measuring
the predicted temperature fluctuations are discussed.Comment: 20 pages, 4 figures, submitted to NJP special issue on Quantum
Thermodynamic
Shot noise of photon-excited electron-hole pairs in open quantum dots
We investigate shot noise of photon-excited electron-hole pairs in open
multi-terminal, multi-channel chaotic dots. Coulomb interactions in the dot are
treated self-consistently giving a gauge-invariant expression for the finite
frequency correlations. The Coulomb interactions decrease the noise, the strong
interaction limit coincides with the non-interacting adiabatic limit. Inelastic
scattering and dephasing in the dot are described by voltage and dephasing
probe models respectively. We find that dephasing leaves the noise invariant,
but inelastic scattering decreases correlations eventually down to zero.Comment: 4 pages, 1 figure; minor changes, 3 references adde
Elastic Stars in General Relativity: II. Radial perturbations
We study radial perturbations of general relativistic stars with elastic
matter sources. We find that these perturbations are governed by a second order
differential equation which, along with the boundary conditions, defines a
Sturm-Liouville type problem that determines the eigenfrequencies. Although
some complications arise compared to the perfect fluid case, leading us to
consider a generalisation of the standard form of the Sturm-Liouville equation,
the main results of Sturm-Liouville theory remain unaltered. As an important
consequence we conclude that the mass-radius curve for a one-parameter sequence
of regular equilibrium models belonging to some particular equation of state
can be used in the same well-known way as in the perfect fluid case, at least
if the energy density and the tangential pressure of the background solutions
are continuous. In particular we find that the fundamental mode frequency has a
zero for the maximum mass stars of the models with solid crusts considered in
Paper I of this series.Comment: 22 pages, no figures, final version accepted for publication in
Class. Quantum Grav. The treatment of the junction conditions has been
improve
Full counting statistics for voltage and dephasing probes
We present a stochastic path integral method to calculate the full counting
statistics of conductors with energy conserving dephasing probes and
dissipative voltage probes. The approach is explained for the experimentally
important case of a Mach-Zehnder interferometer, but is easily generalized to
more complicated setups. For all geometries where dephasing may be modeled by a
single one-channel dephasing probe we prove that our method yields the same
full counting statistics as phase averaging of the cumulant generating
function.Comment: 4 pages, 2 figure
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