2,622 research outputs found
Black hole horizons can hide positive heat capacity
Regarding the volume as independent thermodynamic variable we point out that
black hole horizons can hide positive heat capacity and specific heat. Such
horizons are mechanically marginal, but thermally stable. In the absence of a
canonical volume definition, we consider various suggestions scaling
differently with the horizon radius. Assuming Euler-homogeneity of the entropy,
besides the Hawking temperature, a pressure and a corresponding work term
render the equation of state at the horizon thermally stable for any meaningful
volume concept that scales larger than the horizon area. When considering also
a Stefan--Boltzmann radiation like equation of state at the horizon, only one
possible solution emerges: the Christodoulou--Rovelli volume, scaling as , with an entropy .Comment: 5 pages, no figures, to be published in Phys. Lett.
Nuclear multifragmentation within the framework of different statistical ensembles
The sensitivity of the Statistical Multifragmentation Model to the underlying
statistical assumptions is investigated. We concentrate on its micro-canonical,
canonical, and isobaric formulations. As far as average values are concerned,
our results reveal that all the ensembles make very similar predictions, as
long as the relevant macroscopic variables (such as temperature, excitation
energy and breakup volume) are the same in all statistical ensembles. It also
turns out that the multiplicity dependence of the breakup volume in the
micro-canonical version of the model mimics a system at (approximately)
constant pressure, at least in the plateau region of the caloric curve.
However, in contrast to average values, our results suggest that the
distributions of physical observables are quite sensitive to the statistical
assumptions. This finding may help deciding which hypothesis corresponds to the
best picture for the freeze-out stageComment: 20 pages, 7 figure
The twistor geometry of three-qubit entanglement
A geometrical description of three qubit entanglement is given. A part of the
transformations corresponding to stochastic local operations and classical
communication on the qubits is regarded as a gauge degree of freedom. Entangled
states can be represented by the points of the Klein quadric a space
known from twistor theory. It is shown that three-qubit invariants are
vanishing on special subspaces of . An invariant vanishing for the
class is proposed. A geometric interpretation of the canonical
decomposition and the inequality for distributed entanglement is also given.Comment: 4 pages RevTeX
Modeling the growth effects of regional knowledge production: The GMR-Europe model and its applications for EU Framework Program policy impact simulations
This paper introduces the Geographic Macro and Regional (GMR) model for NUTS-2 regions of the Euro zone. This model consists of three blocks: the TFP, the SCGE and the MACRO blocks. The model is built for impact analysis of policies targeting intangible assets in the forms of R&D, human capital and social capital. The analysis can be done both at the regional and the EU macroeconomic levels. Policy simulations on the growth impacts of the 6th European Framework Program illustrate the capabilities of the complex model system.
Strange and charm quark-pair production in strong non-Abelian field
We have investigated strange and charm quark-pair production in the early
stage of heavy ion collisions. Our kinetic model is based on a Wigner function
method for fermion-pair production in strong non-Abelian fields. To describe
the overlap of two colliding heavy ions we have applied the time-dependent
color field with a pulse-like shape. The calculations have been performed in an
SU(2)-color model with finite current quark masses. For strange quark-pair
production the obtained results are close to the Schwinger limit, as we
expected. For charm quark the large inverse temporal width of the field pulse,
instead of the large charm quark mass, determines the efficiency of the
quark-pair production. Thus we do not observe the expected suppression of charm
quark-pair production connecting to the usual Schwinger-formalism, but our
calculation results in a relatively large charm quark yield. This effect
appears in Abelian models as well, demonstrating that particle-pair production
for fast varying non-Abelian gluon field strongly deviates from the Schwinger
limit for charm quark. We display our results on number densities for light,
strange, charm quark-pairs, and different suppression factors as the function
of characteristic time of acting chromo-electric field.Comment: 6 pages, 2 figures; to appear in the proceedings of the International
Conference on Strangeness in Quark matter (SQM2008), Beijing, China, Oct
6-10, 2008; version accepted to J. Phys.
Evaluation of color intensity enhanced by paprika as feed additive in goldfish and koi carp using computer-assisted image analysis
Body color intensity of red-colored koi carp Cyprinus carpio and goldfish Carassius auratus auratus varieties were measured to evaluate the effect of paprika used as a feed additive. Digital photos of the experimental fish were processed and analyzed by using special software. The red, green and blue (RGB) values of images were recorded and grayscale values of R, G and B were analyzed. The RGB values seem to play different roles in the development of the visible 'redness' of the two species. In most cases the B values decreased continuously during the administration of the paprika as a carotenoid feed additive, which seemed to have no effect on this process. The G values remained unchanged or decreased slightly as redness increased due to paprika feeding. The R values had a tendency to increase due to paprika feeding but significant differences can be expected only after 4 weeks at the feeding conditions applied here. Both the initial rate of redness and genetic background are thought to influence the rate of red color intensity change, which was observed to be different in the two fish species studied here
Noncommutative Common Cause Principles in Algebraic Quantum Field Theory
States in algebraic quantum field theory "typically" establish correlation
between spacelike separated events. Reichenbach's Common Cause Principle,
generalized to the quantum field theoretical setting, offers an apt tool to
causally account for these superluminal correlations. In the paper we motivate
first why commutativity between the common cause and the correlating events
should be abandoned in the definition of the common cause. Then we show that
the Noncommutative Weak Common Cause Principle holds in algebraic quantum field
theory with locally finite degrees of freedom. Namely, for any pair of
projections A, B supported in spacelike separated regions V_A and V_B,
respectively, there is a local projection C not necessarily commuting with A
and B such that C is supported within the union of the backward light cones of
V_A and V_B and the set {C, non-C} screens off the correlation between A and B
College admissions with stable score-limits
A common feature of the Hungarian, Irish, Spanish and Turkish higher education
admission systems is that the students apply for programmes and are ranked according
to their scores. Students who apply for a programme with the same score are tied.
Ties are broken by lottery in Ireland, by objective factors in Turkey (such as date
of birth) and other precisely defined rules in Spain. In Hungary, however, an equal
treatment policy is used, students applying for a programme with the same score
are all accepted or rejected together. In such a situation there is only one decision
to make, whether or not to admit the last group of applicants with the same score
who are at the boundary of the quota. Both concepts can be described in terms of
stable score-limits
. The strict rejection of the last group with whom a quota would be
violated corresponds to the concept of H-stable (i.e. higher-stable) score-limits that
is currently used in Hungary. We call the other solutions based on the less strict
admission policy as L-stable (i.e. lower-stable) score-limits. We show that the natural
extensions of the Gale-Shapley algorithms produce stable score-limits, moreover, the
applicant-oriented versions result in the lowest score-limits (thus optimal for students)
and the college-oriented versions result in the highest score-limits with regard to each
concept. When comparing the applicant-optimal H-stable and L-stable score-limits
we prove that the former limits are always higher for every college. Furthermore,
these two solutions provide upper and lower boundaries for any solution arising from
a tie-breaking strategy. Finally we show that both the H-stable and the L-stable
applicant-proposing score-limit algorithms are manipulable
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