29,537 research outputs found
Relative Quasiconvexity using Fine Hyperbolic Graphs
We provide a new and elegant approach to relative quasiconvexity for
relatively hyperbolic groups in the context of Bowditch's approach to relative
hyperbolicity using cocompact actions on fine hyperbolic graphs. Our approach
to quasiconvexity generalizes the other definitions in the literature that
apply only for countable relatively hyperbolic groups. We also provide an
elementary and self-contained proof that relatively quasiconvex subgroups are
relatively hyperbolic.Comment: 21 pages, 6 figures. New section on fine graphs. Version to appear in
AG
Phase transitions in charged topological black holes dressed with a scalar hair
Phase transitions in charged topological black holes dressed with a scalar
field are studied. These black holes are solutions of the Einstein-Maxwell
theory with a negative cosmological constant and a conformally coupled real
self-interacting scalar field. Comparing, in the grand canonical ensemble, the
free energies of the hairy and undressed black holes two different phase
transitions are found. The first of them is one of second-order type and it
occurs at a temperature defined by the value of the cosmological constant.
Below this temperature an undressed black hole spontaneously acquires a scalar
hair. The other phase transition is one of first-order type. The corresponding
critical temperature, which is bounded from above by the one of the previous
case, strongly depends on the coupling constant of the quartic self-interaction
potential, and this transition only appears when the coupling constant is less
than a certain value. In this case, below the critical temperature the
undressed black is thermodynamically favored. However, when the temperature
exceeds the critical value a hairy black hole is likely to be occur.Comment: Four pages, two figure
Supernova neutrinos and nucleosynthesis
Observations of metal-poor stars indicate that at least two different
nucleosynthesis sites contribute to the production of r-process elements. One
site is responsible for the production of light r-process elements Z<~50 while
the other produces the heavy r-process elements. We have analyzed recent
observations of metal-poor stars selecting only stars that are enriched in
light r-process elements and poor in heavy r-process elements. We find a strong
correlation between the observed abundances of the N=50 elements (Sr, Y and Zr)
and Fe. It suggest that neutrino-driven winds from core-collapse supernova are
the main site for the production of these elements. We explore this possibility
by performing nucleosynthesis calculations based on long term Boltzmann
neutrino transport simulations. They are based on an Equation of State that
reproduces recent constrains on the nuclear symmetry energy. We predict that
the early ejecta is neutron-rich with Ye ~ 0.48, it becomes proton rich around
4 s and reaches Ye = 0.586 at 9 s when our simulation stops. The
nucleosynthesis in this model produces elements between Zn and Mo, including
92Mo. The elemental abundances are consistent with the observations of the
metal-poor star HD 12263. For the elements between Ge and Mo, we produce mainly
the neutron-deficient isotopes. This prediction can be confirmed by
observations of isotopic abundances in metal-poor stars. No elements heavier
than Mo (Z=42) and no heavy r-process elements are produced in our
calculations.Comment: 18 pages, 5 figures, submitted to J. Phys. G: Nucl. Part. Phys.
(Focus issue "Nucleosynthesis and the role of neutrinos", ed. Baha Balantekin
and Cristina Volpe
Linearization of nonlinear connections on vector and affine bundles, and some applications
A linear connection is associated to a nonlinear connection on a vector
bundle by a linearization procedure. Our definition is intrinsic in terms of
vector fields on the bundle. For a connection on an affine bundle our procedure
can be applied after homogenization and restriction. Several applications in
Classical Mechanics are provided
Time-Delayed transfer functions simulations for LMXBs
Recent works (Steeghs & Casares 2002, Casares et al. 2003, Hynes et al. 2003)
have demonstrated that Bowen flourescence is a very efficient tracer of the
companion star in LMXBs. We present a numerical code to simulate time-delayed
transfer functions in LMXBs, specific to the case of reprocessing in emission
lines. The code is also able to obtain geometrical and binary parameters by
fitting observed (X-ray + optical) light curves using simulated annealing
methods. In this work we present the geometrical model for the companion star
and the analytical model for the disc and show synthetic time-delay transfer
functions for different orbital phases and system parameters.Comment: Contribution presented at the conference "Interacting Binaries:
Accretion, Evolution and Outcomes", held in Cefalu, Sicily (Italy) in July
2004. To be published by AIP (American Institute of Physics), eds. L. A.
Antonelli, L. Burderi, F. D'Antona, T. Di Salvo, G.L. Israel, L. Piersanti,
O. Straniero, A. Tornambe. 4 pages, 4 figure
Is justice blind? An examination of disparities in homicide sentencing in Colombia, 1980-2000
Evidence has repeatedly shown that disparities in crime sentences can be attributed to certain variables considered outside the legal dimensions of the case. The majority of research that investigates factors that contribute to such disparities has primarily focused on crimes of varying severities adjudicated in the U.S. court system. We expand research on this topic by focusing on disparities in homicide sentences using data from over 9000 homicide cases tried in Colombia from 1980 - 2000. We specifically explore whether judges use substantive rationality when deciding the length of the offender´s sentence and if the sentence should be above the legal minimum set for the severity of the crime according to the criminal code under which it is adjudicated. Results reveal that disparities in homicida sentences can be attributed to extra-legal variables such as: the city in which the homicide trial took place, where the body of the victim was retrieved, and whether the defendant was identified by an ID parade. However, we also find evidence that suggests that legal variables such as the defendant´s previous criminal record and the aggravating circumstances of the case engender greater differences in sentence outcomes than non-legal variables previously mentioned. Explanations and policy implications are discussed.Sentence Disparities, Homicide, Colombian Criminal Law
A non self-referential expression of Tsallis' probability distribution function
The canonical probability distribution function (pdf) obtained by optimizing
the Tsallis entropy under the linear mean energy constraint (first formalism)
or the escort mean energy constraint (third formalism) suffer
self-referentiality. In a recent paper [Phys. Lett. A {\bf335} (2005) 351-362]
the authors have shown that the pdfs obtained in the two formalisms are
equivalent to the pdf in non self-referential form. Based on this result we
derive an alternative expression, which is non self-referential, for the
Tsallis distributions in both first and third formalisms.Comment: 3 page
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