25,613 research outputs found
Properties of a magnetic superconductor with weak magnetization - application to
Using a Ginsburg-Landau free energy functional, we study the phase
diagram of a weak magnetic superconductor, where the magnetization from the
magnetic component is marginal in supporting a spontaneous vortex phase in
absence of external magnetic field. In particular, the competition between the
spiral state and spontaneous vortex phase is analysed. Our theory is applied to
understand the magnetic properties of .Comment: 13 pages, 4 postscript figure
Dynamical stability of entanglement between spin ensembles
We study the dynamical stability of the entanglement between the two spin
ensembles in the presence of an environment. For a comparative study, we
consider the two cases: a single spin ensemble, and two ensembles linearly
coupled to a bath, respectively. In both circumstances, we assume the validity
of the Markovian approximation for the bath. We examine the robustness of the
state by means of the growth of the linear entropy which gives a measure of the
purity of the system. We find out macroscopic entangled states of two spin
ensembles can stably exist in a common bath. This result may be very useful to
generate and detect macroscopic entanglement in a common noisy environment and
even a stable macroscopic memory.Comment: 4 pages, 1 figur
A COEVOLUTIONARY APPROACH TO UNDERSTANDING THE PARADOX OF SOCIAL PRESSURES VERSUS ECONOMIC EFFICIENCY ACROSS THE WORLD'S FOOD CHAINS
Institutional and Behavioral Economics,
Probabilities on Sentences in an Expressive Logic
Automated reasoning about uncertain knowledge has many applications. One
difficulty when developing such systems is the lack of a completely
satisfactory integration of logic and probability. We address this problem
directly. Expressive languages like higher-order logic are ideally suited for
representing and reasoning about structured knowledge. Uncertain knowledge can
be modeled by using graded probabilities rather than binary truth-values. The
main technical problem studied in this paper is the following: Given a set of
sentences, each having some probability of being true, what probability should
be ascribed to other (query) sentences? A natural wish-list, among others, is
that the probability distribution (i) is consistent with the knowledge base,
(ii) allows for a consistent inference procedure and in particular (iii)
reduces to deductive logic in the limit of probabilities being 0 and 1, (iv)
allows (Bayesian) inductive reasoning and (v) learning in the limit and in
particular (vi) allows confirmation of universally quantified
hypotheses/sentences. We translate this wish-list into technical requirements
for a prior probability and show that probabilities satisfying all our criteria
exist. We also give explicit constructions and several general
characterizations of probabilities that satisfy some or all of the criteria and
various (counter) examples. We also derive necessary and sufficient conditions
for extending beliefs about finitely many sentences to suitable probabilities
over all sentences, and in particular least dogmatic or least biased ones. We
conclude with a brief outlook on how the developed theory might be used and
approximated in autonomous reasoning agents. Our theory is a step towards a
globally consistent and empirically satisfactory unification of probability and
logic.Comment: 52 LaTeX pages, 64 definiton/theorems/etc, presented at conference
Progic 2011 in New Yor
Idealized Slab Plasma approach for the study of Warm Dense Matter
Recently, warm dense matter (WDM) has emerged as an interdisciplinary field
that draws increasing interest in plasma physics, condensed matter physics,
high pressure science, astrophysics, inertial confinement fusion, as well as
materials science under extreme conditions. To allow the study of well-defined
WDM states, we have introduced the concept of idealized-slab plasmas that can
be realized in the laboratory via (i) the isochoric heating of a solid and (ii)
the propagation of a shock wave in a solid. The application of this concept
provides new means for probing the dynamic conductivity, equation of state,
ionization and opacity. These approaches are presented here using results
derived from first-principles (density-functional type) theory, Thomas-Fermi
type theory, and numerical simulations.Comment: 37 pages, 21 figures, available, pdf file only. To appear in: Laser
and Particle beams. To appear more or less in this form in Laser and Particle
beam
A Chemical Survey of the Batang Belungkung River and the Gombak River
A chemical survey of water quality in the Batang Belungkung River and the Gombak River was conducted
to assess the degree of pollution due to the continuing discharge of rubber and domestic wastes.
Levels of dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD),
nutrients (phosphorus and nitrogen), solid and trace elements (sodium, potassium, calcium and magnesium)
were monitored sequentially downriver. The Batang Belungkung River was found to be severely polluted
with anaerobic conditions existing downriver. The upper region of the Gombak River was relatively unpolluted
while the lower region of the Gombak River was found to be severely polluted. An increase of
approximately fourteen-fold was found in the oxygen demand in the lower region of the Gombak River
over the ten year period from 1968/69 to 1978/79
Pulsar Wind Nebulae in EGRET Error Boxes
A remarkable number of pulsar wind nebulae (PWN) are coincident with EGRET
gamma-ray sources. X-ray and radio imaging studies of unidentified EGRET
sources have resulted in the discovery of at least 6 new pulsar wind nebulae
(PWN). Stationary PWN (SPWN) appear to be associated with steady EGRET sources
with hard spectra, typical for gamma-ray pulsars. Their toroidal morphologies
can help determine the geometry of the pulsar which is useful for constraining
models of pulsed gamma-ray emission. Rapidly moving PWN (RPWN) with more
cometary morphologies seem to be associated with variable EGRET sources in
regions where the ambient medium is dense compared to what is typical for the
ISM.Comment: 8 pages, 5 figures, to appear in the proceedings of "The
Multiwavelength Approach to Unidentified Sources", ed. G. Romero & K.S. Chen
Frustrated multiband superconductivity
We show that a clean multiband superconductor may display one or several
phase transitions with increasing temperature from or to frustrated
configurations of the relative phases of the superconducting order parameters.
These transitions may occur when more than two bands are involved in the
formation of the superconducting phase and when the number of repulsive
interband interactions is odd. These transitions are signalled by slope changes
in the temperature dependence of the superconducting gaps.Comment: 5 pages, 3 figure
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