3,977 research outputs found
Ancilla-based quantum simulation
We consider simulating the BCS Hamiltonian, a model of low temperature
superconductivity, on a quantum computer. In particular we consider conducting
the simulation on the qubus quantum computer, which uses a continuous variable
ancilla to generate interactions between qubits. We demonstrate an O(N^3)
improvement over previous work conducted on an NMR computer [PRL 89 057904
(2002) & PRL 97 050504 (2006)] for the nearest neighbour and completely general
cases. We then go on to show methods to minimise the number of operations
needed per time step using the qubus in three cases; a completely general case,
a case of exponentially decaying interactions and the case of fixed range
interactions. We make these results controlled on an ancilla qubit so that we
can apply the phase estimation algorithm, and hence show that when N \geq 5,
our qubus simulation requires significantly less operations that a similar
simulation conducted on an NMR computer.Comment: 20 pages, 10 figures: V2 added section on phase estimation and
performing controlled unitaries, V3 corrected minor typo
Legal Counseling and Lawyers\u27 Fees: A Quadrilogue
Discusses the relationship between legal counseling and lawyers\u27 fees. Attitudes of lawyers toward legal counseling; Area of legal counseling related to human needs and human interactions; Usefulness of counseling time
Legal Counseling and Lawyers\u27 Fees: A Quadrilogue
Discusses the relationship between legal counseling and lawyers\u27 fees. Attitudes of lawyers toward legal counseling; Area of legal counseling related to human needs and human interactions; Usefulness of counseling time
Health reform requires policy capacity
Health reform requires policy capacity
Pierre-Gerlier Forest
1
*
, Jean-Louis Denis
2
, Lawrence D. Brown
3
, David Helms
4
Abstract
Among the many reasons that may limit the adoption of promising reform ideas, policy capacity is the least recognized.
The concept itself is not widely understood. Although policy capacity is concerned with the gathering of information and
the formulation of options for public action in the initial phases of policy consultation and development, it also touches
on all stages of the policy process, from the strategic identification of a problem to the actual development of the policy,
its formal adoption, its implementation, and even further, its evaluation and continuation or modification. Expertise in
the form of policy advice is already widely available in and to public administrations, to well-established professional
organizations like medical societies and, of course, to large private-sector organizations with commercial or financial
interests in the health sector. We need more health actors to join the fray and move from their traditional position of
advocacy to a fuller commitment to the development of policy capacity, with all that it entails in terms of leadership and
social responsibilit
The Quantum States and the Statistical Entropy of the Charged Black Hole
We quantize the Reissner-Nordstr\"om black hole using an adaptation of
Kucha\v{r}'s canonical decomposition of the Kruskal extension of the
Schwarzschild black hole. The Wheeler-DeWitt equation turns into a functional
Schroedinger equation in Gaussian time by coupling the gravitational field to a
reference fluid or dust. The physical phase space of the theory is spanned by
the mass, , the charge, , the physical radius, , the dust proper time,
, and their canonical momenta. The exact solutions of the functional
Schroedinger equation imply that the difference in the areas of the outer and
inner horizons is quantized in integer units. This agrees in spirit, but not
precisely, with Bekenstein's proposal on the discrete horizon area spectrum of
black holes. We also compute the entropy in the microcanonical ensemble and
show that the entropy of the Reissner-Nordstr\"om black hole is proportional to
this quantized difference in horizon areas.Comment: 31 pages, 3 figures, PHYZZX macros. Comments on the wave-functional
in the interior and one reference added. To appear in Phys. Rev.
Hamiltonian thermodynamics of the Reissner-Nordstr\"om-anti-de Sitter black hole
We consider the Hamiltonian dynamics and thermodynamics of spherically
symmetric Einstein-Maxwell spacetimes with a negative cosmological constant. We
impose boundary conditions that enforce every classical solution to be an
exterior region of a Reissner-Nordstr\"om-anti-de Sitter black hole with a
nondegenerate Killing horizon, with the spacelike hypersurfaces extending from
the horizon bifurcation two-sphere to the asymptotically anti-de Sitter
infinity. The constraints are simplified by a canonical transformation, which
generalizes that given by Kucha\v{r} in the spherically symmetric vacuum
Einstein theory, and the theory is reduced to its true dynamical degrees of
freedom. After quantization, the grand partition function of a thermodynamical
grand canonical ensemble is obtained by analytically continuing the Lorentzian
time evolution operator to imaginary time and taking the trace. A~similar
analysis under slightly modified boundary conditions leads to the partition
function of a thermodynamical canonical ensemble. The thermodynamics in each
ensemble is analyzed, and the conditions that the (grand) partition function be
dominated by a classical Euclidean black hole solution are found. When these
conditions are satisfied, we recover in particular the Bekenstein-Hawking
entropy. The limit of a vanishing cosmological constant is briefly discussed.
(This paper is dedicated to Karel Kucha\v{r} on the occasion of his sixtieth
birthday.)Comment: 34 pages, REVTeX v3.0. (Minor corrections and presentational
revisions; added references.
Recommended from our members
Essential tremor associated with pathologic changes in the cerebellum
Background: Although essential tremor (ET) is one of the most common neurologic disorders, there have been few postmortem studies. We recently reported postmortem changes (torpedoes and Bergmann gliosis) in the cerebellar cortex in a few ET cases. Objective: To describe more extensive postmortem changes in the cerebellum in another ET case. Design: Case report. Results: A 90-year-old woman had a 30-year history of ET. At postmortem examination, there was segmental loss of Purkinje cells, presence of torpedoes, and Bergmann gliosis in the cerebellar cortex. Moreover, there were extensive changes in the dentate nucleus, in the form of neuronal loss, neuronal atrophy, microglial clusters, and reduction in the number of efferent fibers (ie, pallor of the hilum). Conclusions: The brain in the current case exhibited more marked cerebellar pathologic features than noted in previously reported ET cases and thereby extends the described cerebellar findings in this common, yet pathologically poorly characterized, neurologic disorder
Black Hole Thermodynamics and Two-Dimensional Dilaton Gravity Theory
We relate various black hole solutions in the near-horizon region to black
hole solutions in two-dimensional dilaton gravity theories in order to argue
that thermodynamics of black holes in D>=4 can be effectively described by
thermodynamics of black holes in two-dimensional dilaton gravity theories. We
show that the Bekenstein-Hawking entropies of single-charged dilatonic black
holes and dilatonic p-branes with an arbitrary dilaton coupling parameter in
arbitrary spacetime dimensions are exactly reproduced by the Bekenstein-Hawking
entropy of the two-dimensional black hole in the associated two-dimensional
dilaton gravity model. We comment that thermodynamics of non-extreme stringy
four-dimensional black hole with four charges and five-dimensional black hole
with three charges may be effectively described by thermodynamics of the black
hole solutions with constant dilaton field in two-dimensional dilaton gravity
theories.Comment: 15 pages, LaTeX, added reference
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