7,337 research outputs found
Aharonov-Bohm oscillations and resonant tunneling in strongly correlated quantum dots
We investigate Aharonov-Bohm oscillations of the current through a strongly
correlated quantum dot embedded in an arbitrary scattering geometry.
Resonant-tunneling processes lead to a flux-dependent renormalization of the
dot level. As a consequence we obtain a fine structure of the current
oscillations which is controlled by quantum fluctuations. Strong Coulomb
repulsion leads to a continuous bias voltage dependent phase shift and, in the
nonlinear response regime, destroys the symmetry of the differential
conductance under a sign change of the external flux.Comment: RevTex, 5 pages, 3 PostScript figures. Accepted for publication in
Phys. Rev. Let
Solid-State Quantum Communication With Josephson Arrays
Josephson junction arrays can be used as quantum channels to transfer quantum
information between distant sites. In this work we discuss simple protocols to
realize state transfer with high fidelity. The channels do not require
complicate gating but use the natural dynamics of a properly designed array. We
investigate the influence of static disorder both in the Josephson energies and
in the coupling to the background gate charges, as well as the effect of
dynamical noise. We also analyze the readout process, and its backaction on the
state transfer
The Impact of Fiscal Restraint on Budgetary Allocations for Women's Programs
How did the fiscal restraints exercised during the time of fiscal difficulties in 1997-2003 affect the gender/women-targeted programs of the Philippine government? What does a close scrutiny of the government budget reveal regarding the implicit gender implications of such restraints? Manasan and Villanueva disclose some of their findings.budget analysis, gender analysis, women's programs
Looking Closely on Who Benefits from Public Subsidies in Health Care: a Gender Perspective
Do men benefit more than women from government expenditures in health care? Or do women have the upper hand? Using a sex-differentiated incidence analysis of the various Department of Health program expenditures, this Notes' authors assess who indeed benefits from such expenditures in terms of gender. And why.gender, benefit incidence analysis, gender analysis, public spending in health, sex-differentiated incidence analysis
Anomalous density of states of a Luttinger liquid in contact with a superconductor
We study the frequency and space dependence of the local tunneling density of
states of a Luttinger liquid (LL) which is connected to a superconductor. This
coupling {\em strongly} modifies the single-particle properties of the LL. It
significantly enhances the density of states near the Fermi level, whereas this
quantity vanishes as a power law for an isolated LL. The enhancement is due to
the interplay between electron-electron interactions and multiple
back-scattering processes of low-energy electrons at the interface between the
LL and the superconductor. This anomalous behavior extends over large distances
from the interface and may be detected by coupling normal probes to the system.Comment: 8 pages Revtex, two postscript figure
Relations between entanglement and purity in non-Markovian dynamics
Knowledge of the relationships among different features of quantumness, like
entanglement and state purity, is important from both fundamental and practical
viewpoints. Yet, this issue remains little explored in dynamical contexts for
open quantum systems. We address this problem by studying the dynamics of
entanglement and purity for two-qubit systems using paradigmatic models of
radiation-matter interaction, with a qubit being isolated from the environment
(spectator configuration). We show the effects of the corresponding local
quantum channels on an initial two-qubit pure entangled state in the
concurrence-purity diagram and find the conditions which enable dynamical
closed formulas of concurrence, used to quantify entanglement, as a function of
purity. We finally discuss the usefulness of these relations in assessing
entanglement and purity thresholds which allow noisy quantum teleportation. Our
results provide new insights about how different properties of composite open
quantum systems behave and relate each other during quantum evolutions.Comment: 16 Pages, 10 Figures. One author added. Improved version with more
references and comment
The Nuclear Outflow in NGC 2110
We present a HST/STIS spectroscopic and optical/radio imaging study of the
Seyfert NGC 2110 aiming to measure the dynamics and understand the nature of
the nuclear outflow in the galaxy. Previous HST studies have revealed the
presence of a linear structure in the Narrow-Line Region (NLR) aligned with the
radio jet. We show that this structure is strongly accelerated, probably by the
jet, but is unlikely to be entrained in the jet flow. The ionisation properties
of this structure are consistent with photoionisation of dusty, dense gas by
the active nucleus. We present a plausible geometrical model for the NLR,
bringing together various components of the nuclear environment of the galaxy.
We highlight the importance of the circum-nuclear disc in determining the
appearance of the emission line gas and the morphology of the jet. From the
dynamics of the emission line gas, we place constraints on the accelerating
mechanism of the outflow and discuss the relative importance of radio source
synchrotron pressure, radio jet ram pressure and nuclear radiation pressure in
accelerating the gas. While all three mechanisms can account for the energetics
of the emission line gas, gravitational arguments support radio jet ram
pressure as the most likely source of the outflow.Comment: 15 pages, 7 figures; accepted to MNRA
An Empirical Investigation of Debt Contract Design: The Determinants of the Choice of Debt Terms in Eurobond Issues
This paper provides a comprehensive analysis of the determinants for the optimal choice of contract terms on Eurobonds issued by UK companies. We examine predictions of extant theories that associate the choice of debt features namely, maturity, call options, convertible options, and protective covenants to firm and market characteristics. Like in Correia (2003), a simultaneous equations approach is adopted to test the alternative use of contract features for mitigating debt-contracting costs. The evidence provides strong support to the prediction that both callable and short-term debt and convertible and debt with protective covenants are used as alternative control devises to mitigate agency costs. Further evidence suggests, however, that contrary to the fundamentals guiding the choice of maturity and callability structures, the use of conversion options and protective covenants in Eurobond contracts seems to be determined by equity agency costs rather than debt agency costs. Also, some support is found for the risk uncertainty theory underlying the use of convertibles and for liquidity risk arguments regarding the choice to include protective covenants.
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