28,992 research outputs found
Symmetry Breaking Using Value Precedence
We present a comprehensive study of the use of value precedence constraints
to break value symmetry. We first give a simple encoding of value precedence
into ternary constraints that is both efficient and effective at breaking
symmetry. We then extend value precedence to deal with a number of
generalizations like wreath value and partial interchangeability. We also show
that value precedence is closely related to lexicographical ordering. Finally,
we consider the interaction between value precedence and symmetry breaking
constraints for variable symmetries.Comment: 17th European Conference on Artificial Intelligenc
Discussion of: A statistical analysis of multiple temperature proxies: Are reconstructions of surface temperatures over the last 1000 years reliable?
Discussion of "A statistical analysis of multiple temperature proxies: Are
reconstructions of surface temperatures over the last 1000 years reliable?" by
B.B. McShane and A.J. Wyner [arXiv:1104.4002]Comment: Published in at http://dx.doi.org/10.1214/10-AOAS398F the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
New Types of Thermodynamics from -Dimensional Black Holes
For normal thermodynamic systems superadditivity , homogeneity \H and
concavity \C of the entropy hold, whereas for -dimensional black holes
the latter two properties are violated. We show that -dimensional black
holes exhibit qualitatively new types of thermodynamic behaviour, discussed
here for the first time, in which \C always holds, \H is always violated
and may or may not be violated, depending of the magnitude of the black
hole mass. Hence it is now seen that neither superadditivity nor concavity
encapsulate the meaning of the second law in all situations.Comment: WATPHYS-TH93/05, Latex, 10 pgs. 1 figure (available on request), to
appear in Class. Quant. Gra
Higher Dimensional Taub-NUTs and Taub-Bolts in Einstein-Maxwell Gravity
We present a class of higher dimensional solutions to Einstein-Maxwell
equations in d-dimensions. These solutions are asymptotically locally flat,
de-Sitter, or anti-de Sitter space-times. The solutions we obtained depend on
two extra parameters other than the mass and the nut charge. These two
parameters are the electric charge, q and the electric potential at infinity,
V, which has a non-trivial contribution. We Analyze the conditions one can
impose to obtain Taub-Nut or Taub-Bolt space-times, including the
four-dimensional case. We found that in the nut case these conditions coincide
with that coming from the regularity of the one-form potential at the horizon.
Furthermore, the mass parameter for the higher dimensional solutions depends on
the nut charge and the electric charge or the potential at infinity.Comment: 11 pages, LaTe
Recommended from our members
Dietary manipulation of broiler breeder growth through the feeding of conjugated linoleic acid
Phenomenology of Dirac Neutrinogenesis in Split Supersymmetry
In Split Supersymmetry scenarios the possibility of having a very heavy
gravitino opens the door to alleviate or completely solve the worrisome
"gravitino problem'' in the context of supersymmetric baryogenesis models. Here
we assume that the gravitino may indeed be heavy and that Majorana masses for
neutrinos are forbidden as well as direct Higgs Yukawa couplings between left
and right handed neutrinos. We investigate the viability of the mechansim known
as Dirac leptogenesis (or neutrinogenesis), both in solving the baryogenesis
puzzle and explaining the observed neutrino sector phenomenology. To
successfully address these issues, the scenario requires the introduction of at
least two new heavy fields. If a hierarchy among these new fields is
introduced, and some reasonable stipulations are made on the couplings that
appear in the superpotential, it becomes a generic feature to obtain the
observed large lepton mixing angles. We show that in this case, it is possible
simultaneously to obtain both the correct neutrino phenomenology and enough
baryon number, making thermal Dirac neutrinogenesis viable. However, due to
cosmological constraints, its ability to satisfy these constraints depends
nontrivially on model parameters of the overall theory, particularly the
gravitino mass. Split supersymmetry with m_{3/2} between 10^{5} and 10^{10} GeV
emerges as a "natural habitat" for thermal Dirac neutrinogenesis.Comment: 37 pages, 8 figure
Exact Solutions of Relativistic Two-Body Motion in Lineal Gravity
We develop the canonical formalism for a system of bodies in lineal
gravity and obtain exact solutions to the equations of motion for N=2. The
determining equation of the Hamiltonian is derived in the form of a
transcendental equation, which leads to the exact Hamiltonian to infinite order
of the gravitational coupling constant. In the equal mass case explicit
expressions of the trajectories of the particles are given as the functions of
the proper time, which show characteristic features of the motion depending on
the strength of gravity (mass) and the magnitude and sign of the cosmological
constant. As expected, we find that a positive cosmological constant has a
repulsive effect on the motion, while a negative one has an attractive effect.
However, some surprising features emerge that are absent for vanishing
cosmological constant. For a certain range of the negative cosmological
constant the motion shows a double maximum behavior as a combined result of an
induced momentum-dependent cosmological potential and the gravitational
attraction between the particles. For a positive cosmological constant, not
only bounded motions but also unbounded ones are realized. The change of the
metric along the movement of the particles is also exactly derived.Comment: 37 pages, Latex, 24 figure
Kindergarten Dinosaurs and Rocks: An Example of Integrating a Field-tested Lesson Plan for Geoscientists into the Alberta Curriculum
Professional geoscientists have to make many presentations to colleagues, engineers, executives and accountants. However, panic is often felt when a note comes home from a child's educator looking for parents to help in teaching elementary school students. For the teacher, this is a chance to integrate many core subjects from the curriculum with the special and exciting resources available to geoscientists. This paper presents guidelines developed over time, and includes an understanding of how children learn and ask questions, the pace of the talk, and what children need to learn. In addition, data sources and gateways available to geoscientists have been included. While the premise outlined in the paper is applicable across Canada, it is based on the Alberta curriculum requirements. With these suggestions, the classroom experience is really no different than presenting to senior management, although you have to remember that your audience is shorter and does not drive a big BMW or Lexus.
RÉSUMÉ
Les géoscientifiques ont souvent à faire des exposés à des collègues, des ingénieurs, des dirigeants et des comptables. Cela dit, il arrive souvent qu'un sentiment de panique s'empare d'eux lorsqu'ils reçoivent une note des enseignants du primaire aux parents faisant appel aux compétences professionnelles des parents. Les enseignants y voient là une occasion de lier les thèmes du programme d'enseignement aux ressources fantastiques dont disposent les géoscientifiques. Le présent article présente les lignes directrices qui ont été validées avec le temps et décrit les modes d'apprentissage des enfants, leurs manières de poser des questions, le rythme particulier de présentation, ainsi que ce qu'ils ont besoin d'apprendre. L'article comporte aussi des références à des sources et des passerelles de données que les géoscientifiques peuvent consulter. Les principes de base présentés dans cet article peuvent s'appliquer partout à travers le pays, simplement, on les a appliqués aux exigences particulières du programme scolaire de l'Alberta. En tenant compte des suggestions offertes, on se rendra compte qu'une classe d'école n'est pas différente d'une d'un auditoire de gestionnaires; il faut simplement se souvenir que les membres de l'auditoire sont plus courts et ne conduisent pas des BM ou des Lexus
Thermal leptogenesis in brane world cosmology
The thermal leptogenesis in brane world cosmology is studied. In brane world
cosmology, the expansion law is modified from the four-dimensional standard
cosmological one at high temperature regime in the early universe. As a result,
the well-known upper bound on the lightest light neutrino mass induced by the
condition for the out-of-equilibrium decay of the lightest heavy neutrino,
eV, can be moderated to be in the case of with the
lightest heavy neutrino mass () and the ``transition temperature''
(), at which the modified expansion law in brane world cosmology is
smoothly connecting with the standard one. This implies that the degenerate
mass spectrum of the light neutrinos can be consistent with the thermal
leptogenesis scenario. Furthermore, as recently pointed out, the gravitino
problem in supersymmetric case can be solved if the transition temperature is
low enough GeV. Therefore, even in the supersymmetric
case, thermal leptogenesis scenario can be successfully realized in brane world
cosmology.Comment: 9 pages, final versio
Neutrino Models of Dark Energy
I consider a scenario proposed by Fardon, Nelson and Weiner where dark energy
and neutrinos are connected. As a result, neutrino masses are not constant but
depend on the neutrino number density. By examining the full equation of state
for the dark sector, I show that in this scenario the dark energy is equivalent
to having a cosmological constant, but one that "runs" as the neutrino mass
changes with temperature. Two examples are examined that illustrate the
principal feautures of the dark sector of this scenario. In particular, the
cosmological constant is seen to be negligible for most of the evolution of the
Universe, becoming inportant only when neutrinos become non-relativistic. Some
speculations on features of this scenario which might be present in a more
realistic theory are also presented.Comment: 12 pages, 6 figures. Added comments on why FNW scenario always leads
to a running cosmological constant and a few references. To be published in
Phys. Rev.
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