40,501 research outputs found
Law Behind Second Law of Thermodynamics --Unification with Cosmology--
In an abstract setting of a general classical mechanical system as a model
for the universe we set up a general formalism for a law behind the second law
of thermodynamics, i.e. really for "initial conditions". We propose a
unification with the other laws by requiring similar symmetry and locality
properties.Comment: 17 page
Local aspects of disentanglement induced by spontaneous emission
We consider spontaneous emission of two two-level atoms interacting with
vacuum fluctuations. We study the process of disentanglement in this system and
show the possibility of changing disentanglement time by local operations.Comment: 7 pages, 2 figure
Ethnicity, gender, social class and citizenship: comparative views from England and Sweden
Please note.
What follows is a summary of the second stage of ongoing research comparing the experiences of students and teachers of Citizenship Education in Sweden and England. A more complete and detailed version is expected to appear in a leading refereed journal later in the year, and a book proposal relating to all stages of the research is currently under consideration. While we await confirmation of the submitted proposals we cannot identify the journal or the prospective book publisher, but it is in those sources that more detailed and nuanced analysis and explanation will be located.
Introduction
The National Curriculum provision for Citizenship Education in England clearly requires that the subject must be taught throughout KS 3 and KS 4, with content indicated and a public examination available at KS4; until recently, there was also an A level. In Sweden - where Citizenship Education is not a separate subject - the content is vague and teachers’ interpretations of the assignment differ distinctively between the different schools and programmes. This contrasting provision between two countries which have both prided themselves on their welfare provision and policies of inclusive citizenship was considered ideal to examine the extent to which different approaches produce more or less aware, articulate and active citizens
Generalized dual symmetry of nonabelian theories, monopoles and dyons
In the present talk we present an investigation of nonabelian SU(N) gauge
theories, describing a system of fields with non--dual g and dual \tilde g
charges and revealing the generalized dual symmetry. The Zwanziger type action
is suggested. The renormalization group equations for pure nonabelian theories,
in particular for pure SU(3)\times\widetilde{SU(3)} gauge theory (as an
example) are analysed. We consider not only monopoles, but also dyons. The
behaviour of the QCD total beta--function is investigated. It was shown that
this beta--function is antisymmetric under the interchange
\alpha\leftrightarrow\frac 1\alpha (here \alpha\equiv\alpha_s), and has zero
("fixed point") at \alpha = 1. Monopoles, or dyons, are responsible for the
phase transition. Considering critical points at \alpha_1\approx 0.4 and
\alpha_2\approx 2.5, we give an explanation of the freezing of \alpha_s.Comment: 15 pages, 5 figures, Presented at the 12th Lomonosov Conference on
Elementary Particle Physics, Moscow State University, Moscow, 25-31 August,
200
Quantum discord in finite XY chains
We examine the quantum discord between two spins in the exact ground state of
finite spin 1/2 arrays with anisotropic XY couplings in a transverse field B.
It is shown that in the vicinity of the factorizing field B_s, the discord
approaches a common finite non-negligible limit which is independent of the
pair separation and the coupling range. An analytic expression of this limit is
provided. The discord of a mixture of aligned pairs in two different
directions, crucial for the previous results, is analyzed in detail, including
the evaluation of coherence effects, relevant in small samples and responsible
for a parity splitting at B_s. Exact results for finite chains with first
neighbor and full range couplings and their interpretation in terms of such
mixtures are provided.Comment: 9 pages, 6 figure
Gravitational Lorentz anomaly from the overlap formula in 2-dimensions
In this letter we show that the overlap formulation of chiral gauge theories
correctly reproduces the gravitational Lorentz anomaly in 2-dimensions. This
formulation has been recently suggested as a solution to the fermion doubling
problem on the lattice. The well known response to general coordinate
transformations of the effective action of Weyl fermions coupled to gravity in
2-dimensions can also be recovered.Comment: 7 pages, late
Description of thermal entanglement with the static path plus random-phase approximation
We discuss the application of the static path plus random phase approximation
(SPA+RPA) and the ensuing mean field+RPA treatment to the evaluation of
entanglement in composite quantum systems at finite temperature. These methods
involve just local diagonalizations and the determination of the generalized
collective vibrational frequencies. As illustration, we evaluate the pairwise
entanglement in a fully connected XXZ chain of spins at finite temperature
in a transverse magnetic field . It is shown that already the mean field+RPA
provides an accurate analytic description of the concurrence below the mean
field critical region (), exact for large , whereas the full
SPA+RPA is able to improve results for finite systems in the critical region.
It is proved as well that for weak entanglement also arises when the
ground state is separable (), with the limit temperature for pairwise
entanglement exhibiting quite distinct regimes for .Comment: 20 pages, 5 figure
Thermal entanglement in fully connected spin systems and its RPA description
We examine the thermal pairwise entanglement in a symmetric system of
spins fully connected through anisotropic -type couplings embedded in a
transverse magnetic field. We consider both the exact evaluation together with
that obtained with the static path + random phase approximation (RPA) and the
ensuing mean field + RPA. The latter is shown to provide an accurate analytic
description of both the parallel and antiparallel thermal concurrence in large
systems. We also analyze the limit temperature for pairwise entanglement, which
is shown to increase for large fields and to decrease logarithmically with
increasing . Special finite size effects are as well discussed.Comment: 9 pages, 5 figure
-kaon cross section in meson exchange model
We calculate the cross section for the dissociation of by kaons
within the framework of a meson exchange model including anomalous parity
interactions. Off-shell effects at the vertices were handled with QCD sum rule
estimates for the running coupling constants. The total -kaon cross
section was found to be mb for 4.1\leq\sqrt{s}\leq5 \GeV.Comment: 13 pages, 4 eps figure
- …