2,111 research outputs found
Statistics of conductance and shot-noise power for chaotic cavities
We report on an analytical study of the statistics of conductance, , and
shot-noise power, , for a chaotic cavity with arbitrary numbers of
channels in two leads and symmetry parameter . With the theory
of Selberg's integral the first four cumulants of and first two cumulants
of are calculated explicitly. We give analytical expressions for the
conductance and shot-noise distributions and determine their exact asymptotics
near the edges up to linear order in distances from the edges. For a
power law for the conductance distribution is exact. All results are also
consistent with numerical simulations.Comment: 7 pages, 3 figures. Proc. of the 3rd Workshop on Quantum Chaos and
Localisation Phenomena, Warsaw, Poland, May 25-27, 200
Correlation functions of impedance and scattering matrix elements in chaotic absorbing cavities
Wave scattering in chaotic systems with a uniform energy loss (absorption) is
considered. Within the random matrix approach we calculate exactly the energy
correlation functions of different matrix elements of impedance or scattering
matrices for systems with preserved or broken time-reversal symmetry. The
obtained results are valid at any number of arbitrary open scattering channels
and arbitrary absorption. Elastic enhancement factors (defined through the
ratio of the corresponding variance in reflection to that in transmission) are
also discussed.Comment: 10 pages, 2 figures (misprints corrected and references updated in
ver.2); to appear in Acta Phys. Pol. A (Proceedings of the 2nd Workshop on
Quantum Chaos and Localization Phenomena, May 19-22, 2005, Warsaw
Issues in health reform: How changes in eligibility may move millions back and forth between Medicaid and insurance exchanges
The Affordable Care Act will extend health insurance coverage by both expanding Medicaid eligibility and offering premium subsidies for the purchase of private health insurance through state health insurance exchanges. But by definition, eligibility for these programs is sensitive to income and can change over time with fluctuating income and changes in family composition. The law specifies no minimum enrollment period, and subsidy levels will also change as income rises and falls. Using national survey data, we estimate that within six months, more than 35 percent of all adults with family incomes below 200 percent of the federal poverty level will experience a shift in eligibility from Medicaid to an insurance exchange, or the reverse; within a year, 50 percent, or 28 million, will. To minimize the effect on continuity and quality of care, states and the federal government should adopt strategies to reduce the frequency of coverage transitions and to mitigate the disruptions caused by those transitions. Options include establishing a minimum guaranteed eligibility period and “dually certifying” some plans to serve both Medicaid and exchange enrollees
The spherical spin glass model: an exactly solvable model for glass to spin-glass transition
We present the full phase diagram of the spherical spin glass model
with . The main outcome is the presence of a new phase with both
properties of Full Replica Symmetry Breaking (FRSB) phases of discrete models,
e.g, the Sherrington-Kirkpatrick model, and those of One Replica Symmetry
Breaking (1RSB). The phase, which separates a 1RSB phase from FRSB phase, is
described by an order parameter function with a continuous part (FRSB)
for and a discontinuous jump (1RSB) at . This phase has a finite
complexity which leads to different dynamic and static properties.Comment: 5 pages, 2 figure
Statistical properties of random density matrices
Statistical properties of ensembles of random density matrices are
investigated. We compute traces and von Neumann entropies averaged over
ensembles of random density matrices distributed according to the Bures
measure. The eigenvalues of the random density matrices are analyzed: we derive
the eigenvalue distribution for the Bures ensemble which is shown to be broader
then the quarter--circle distribution characteristic of the Hilbert--Schmidt
ensemble. For measures induced by partial tracing over the environment we
compute exactly the two-point eigenvalue correlation function.Comment: 8 revtex pages with one eps file included, ver. 2 - minor misprints
correcte
How often is a random quantum state k-entangled?
The set of trace preserving, positive maps acting on density matrices of size
d forms a convex body. We investigate its nested subsets consisting of
k-positive maps, where k=2,...,d. Working with the measure induced by the
Hilbert-Schmidt distance we derive asymptotically tight bounds for the volumes
of these sets. Our results strongly suggest that the inner set of
(k+1)-positive maps forms a small fraction of the outer set of k-positive maps.
These results are related to analogous bounds for the relative volume of the
sets of k-entangled states describing a bipartite d X d system.Comment: 19 pages in latex, 1 figure include
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