36,468 research outputs found
Casimir energy density in closed hyperbolic universes
The original Casimir effect results from the difference in the vacuum
energies of the electromagnetic field, between that in a region of space with
boundary conditions and that in the same region without boundary conditions. In
this paper we develop the theory of a similar situation, involving a scalar
field in spacetimes with compact spatial sections of negative spatial
curvature.Comment: 10 pages. Contribution to the "Fifth Alexander Friedmann
International Seminar on Gravitation and Cosmology," Joao Pessoa, Brazil,
2002. Revised version, with altered Abstract and one new referenc
Weak hyperon decays in heavy baryon chiral perturbation theory: Renormalization and applications
The complete renormalization of the weak Lagrangian to chiral order q^2 in
heavy baryon chiral perturbation theory is performed using heat kernel
techniques. The results are compared with divergences appearing in the
calculation of Feynman graphs for the nonleptonic hyperon decay Lambda -> p
pi^- and an estimate for the size of the counterterm contributions to the
s-wave amplitudes in nonleptonic hyperon decays is given.Comment: 21 pages, 2 figure
A role for doctors in assisted dying? An analysis of legal regulations and medical professional positions in six European countries
An extensive debate about assisted suicide and euthanasia has been taking place in westernized countries during the last twenty years. Traditionally, the medical profession has maintained a clear distance from euthanasia and assisted suicide, but this distance can no longer be justified by simply referring to the law.
This paper analyses the legal and, in particular, medical professional positions with respect to the doctor’s role in assisted dying in certain Western European countries (Belgium, Germany, Netherlands, Norway, Switzerland, United Kingdom) and discusses their implications for doctors
Nanoscale tunnel field effect transistor based on a complex oxide lateral heterostructure
We demonstrate a tunnel field effect transistor based on a lateral
heterostructure patterned from an electron gas.
Charge is injected by tunneling from the /
contacts and the current through a narrow channel of insulating
is controlled via an electrostatic side gate. Drain-source
I/V-curves have been measured at low and elevated temperatures. The transistor
shows strong electric-field and temperature-dependent behaviour with a steep
sub-threshold slope %of up to as small as and a
transconductance as high as . A fully
consistent transport model for the drain-source tunneling reproduces the
measured steep sub-threshold slope.Comment: 20 pages, 6 figures, Supplementary material: 4 pages, 2 figure
Lyapunov Spectra in SU(2) Lattice Gauge Theory
We develop a method for calculating the Lyapunov characteristic exponents of
lattice gauge theories. The complete Lyapunov spectrum of SU(2) gauge theory is
obtained and Kolmogorov-Sinai entropy is calculated. Rapid convergence with
lattice size is found.Comment: 7pp, DUKE-TH-93-5
Accurate simulation estimates of cloud points of polydisperse fluids
We describe two distinct approaches to obtaining cloud point densities and
coexistence properties of polydisperse fluid mixtures by Monte Carlo simulation
within the grand canonical ensemble. The first method determines the chemical
potential distribution (with the polydisperse attribute)
under the constraint that the ensemble average of the particle density
distribution matches a prescribed parent form. Within the region
of phase coexistence (delineated by the cloud curve) this leads to a
distribution of the fluctuating overall particle density n, p(n), that
necessarily has unequal peak weights in order to satisfy a generalized lever
rule. A theoretical analysis shows that as a consequence, finite-size
corrections to estimates of coexistence properties are power laws in the system
size. The second method assigns such that an equal peak weight
criterion is satisfied for p(n)\mu(\sigma)$. We show how to ascertain the
requisite weight factor operationally. A theoretical analysis of the second
method suggests that it leads to finite-size corrections to estimates of
coexistence properties which are {\em exponentially small} in the system size.
The scaling predictions for both methods are tested via Monte Carlo simulations
of a novel polydisperse lattice gas model near its cloud curve, the results
showing excellent quantitative agreement with the theory.Comment: 8 pages, 6 figure
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