36,102 research outputs found
Double distributions: Loose ends
We point out that double distributions need not vanish at their boundary.
Boundary terms do not change the ambiguity inherent in defining double
distributions; instead, boundary conditions must be satisfied in order to
switch between different decompositions. We analyze both the spin zero and spin
one-half cases.Comment: 4 pages, 0 figures, RevTex 4, Brief Repor
Hadron annihilation into two photons and backward dVCS in the scaling regime of QCD
We study the scaling regime of hadron-(anti)-hadron annihilation into a
deeply virtual photon and a real photon, H anti-H -> gamma^* gamma, and deep
backward virtual Compton scattering, gamma^* H -> H gamma. We advocate that
there is a kinematical region where the scattering amplitude factorizes into a
short-distance matrix element and a long-distance dominated object: a
transition distribution amplitude which describes the hadron to photon
transition.Comment: 4 pages, 1 .eps figure, to be published in Phys. Rev. D Rapid Com
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
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
On a differential inclusion related to the Born-Infeld equations
We study a partial differential relation that arises in the context of the
Born-Infeld equations (an extension of the Maxwell's equations) by using
Gromov's method of convex integration in the setting of divergence free fields
Unfolding and unzipping of single-stranded DNA by stretching
We present a theoretical study of single-stranded DNA under stretching.
Within the proposed framework, the effects of basepairing on the mechanical
response of the molecule can be studied in combination with an arbitrary
underlying model of chain elasticity. In a generic case, we show that the
stretching curve of ssDNA exhibits two distinct features: the second-order
"unfolding" phase transition, and a sharp crossover, reminiscent of the
first-order "unzipping" transition in dsDNA. We apply the theory to the
particular cases of Worm-like Chain (WLC) and Freely-Joint Chain (FJC) models,
and discuss the universal and model--dependent features of the mechanical
response of ssDNA. In particular, we show that variation of the width of the
unzipping crossover with interaction strength is very sensitive to the
energetics of hairpin loops. This opens a new way of testing the elastic
properties of ssDNA.Comment: 7 pages, 4 figures, substantially revised versio
Calorons in SU(3) lattice gauge theory
We examine the semiclassical content of SU(3) Yang Mills theory on the
lattice at finite temperature. Employing the cooling method, a set of classical
fields is generated from a Monte Carlo ensemble. Various operators are used to
inspect this set with respect to topological properties. We find pseudoparticle
fields, so-called caloron solutions, possessing the remarkable features of
(superpositions of) Kraan-van Baal solutions, i.e. extensions of
Harrington-Shepard calorons to generic values of the holonomy.Comment: 14 pages, 16 figure
- …