5,524 research outputs found
The Pioneer's acceleration anomaly and Hubble's constant
The reported anomalous acceleration acting on the Pioneers spacecrafts could
be seen as a consequence of the existence of some local curvature in light
geodesics when using the coordinate speed of light in an expanding space-time.
The effect is related with the non synchronous character of the underlying
metric and therefore, planets closed orbits can not reveal it. It is shown that
the cosmic expansion rate -the Hubble parameter H- has been indeed detected.
Additionally, a relation for an existing annual term is obtained which depends
on the cosine of the ecliptic latitude of the spacecraft, suggestingan
heuristic analogy between the effect and Foucault's experiment - light rays
playing a similar role in the expanding space than Foucault's Pendulum does
while determining Earth's rotation. This statement could be seen as a benchmark
for future experiments.Comment: 8 pages, LaTex, minor changes for submissio
The Pioneer's Anomalous Doppler Drift as a Berry Phase
The detected anomalous frequency drift acceleration in Pioneer's radar data
finds its explanation in a Berry phase that obtains the quantum state of a
photon that propagates within an expanding space-time. The clock acceleration
is just the adiabatic expansion rate and an analogy between the effect and
Foucault's experiment is fully suggested. In this sense, light rays play a
similar role in the expanding space than Foucault's Pendulum does while
determining Earth's rotation. On the other hand, one could speculate about a
suitable future experiment at "laboratory" scales able to measure the local
cosmological expansion rate using the procedure outlined in this paper.Comment: 7 pages, The references are now correc
Supersymmetric Cosmology and Dark Energy
Using the superfield approach we construct the n = 2 supersymmetric
lagrangian for the FRW Universe with perfect fluid as matter fields. The
obtained supersymmetric algebra allowed us to take the square root of the
Wheeler-DeWitt equation and solve the corresponding quantum constraint. This
model leads to the relation between the vacuum energy density and the energy
density of the dust matter.Comment: This article is a contribution to the anniversary volume "The
Problems of Modern Cosmology". On the occasion of the 50th birthday of Prof.
S.D. Odintsov. Editor Prof. P.M. Lavro
Anti-self-dual gravity and supergravity from a pure connection formulation
We introduce a complex pure connection action with constraints which is
diffeomorphism and gauge invariant. Taking as an internal group , we
obtain, from the equations of motion, anti-self-dual Einstein spaces together
with the zero torsion condition thanks to Bianchi identity. By applying the
same procedure, we take as internal symmetry the super group and by
means of the Bianchi identity and integrability conditions, the equations of
motion are those that come from anti-self-dual supergravity with
cosmological constant sector
General scalar interaction in the supersymmetric FRW model
In this work we have constructed the most general action for a set of complex
homogeneous scalar supermultiplets interacting with the scale factor in the
supersymmetric FRW model. It is shown, that local conformal time supersymmetry
leads to the scalar fields potential, which is defined in the same combination:
K\"ahler potential and superpotential as in supergravity (or effective
superstring) theories. This scalar fields potential depends on arbitrary
parameter , which is not fixed by conformal time supersymmetry.Comment: 10 pages, Latex, no figures, submitted to MPL
Extended supersymmetry for the Bianchi-type cosmological models
In this paper we propose a superfield description for all Bianchi-type
cosmological models. The action is invariant under world-line local
supersymmetry with internal symmetry. Due to the
invariance of the action we obtain the constraints, which form a closed
superalgebra of the supersymmetric quantum mechanics. This procedure
provides the inclusion of supermatter in a sistematic way.Comment: 9 pages, accepted in Mod. Phys. Lett.
Discrete canonical analysis of three dimensional gravity with cosmological constant
We discuss the interplay between standard canonical analysis and canonical
discretization in three-dimensional gravity with cosmological constant. By
using the Hamiltonian analysis, we find that the continuum local symmetries of
the theory are given by the on-shell space-time diffeomorphisms, which at the
action level, corresponds to the Kalb-Ramond transformations. At the time of
discretization, although this symmetry is explicitly broken, we prove that the
theory still preserves certain gauge freedom generated by a constant curvature
relation in terms of holonomies and the Gauss's law in the lattice approach.Comment: 19 pages, 1 figure. arXiv admin note: text overlap with
arXiv:1310.3759, arXiv:gr-qc/0512065, arXiv:1111.1879 by other author
A semilattice structure for the set of numerical semigroups with fixed Frobenius number
We present a procedure to enumerate the whole set of numerical semigroups
with a given Frobenius number F, S(F). The methodology is based on the
construction of a partition of S(F) by a congruence relation. We identify
exactly one irreducible and one homogeneous numerical semigroup at each class
in the relation, and from those two elements we reconstruct the whole class. An
alternative more efficient method is proposed based on the use of the
Kunz-coordinates vectors of the elements in S(F).Comment: 11 page
Learning Generative Models of Similarity Matrices
We describe a probabilistic (generative) view of affinity matrices along with
inference algorithms for a subclass of problems associated with data
clustering. This probabilistic view is helpful in understanding different
models and algorithms that are based on affinity functions OF the data. IN
particular, we show how(greedy) inference FOR a specific probabilistic model IS
equivalent TO the spectral clustering algorithm.It also provides a framework
FOR developing new algorithms AND extended models. AS one CASE, we present new
generative data clustering models that allow us TO infer the underlying
distance measure suitable for the clustering problem at hand. These models seem
to perform well in a larger class of problems for which other clustering
algorithms (including spectral clustering) usually fail. Experimental
evaluation was performed in a variety point data sets, showing excellent
performance.Comment: Appears in Proceedings of the Nineteenth Conference on Uncertainty in
Artificial Intelligence (UAI2003
The tree of irreducible numerical semigroups with fixed Frobenius number
In this paper we present a procedure to build the set of irreducible
numerical semigroups with a fixed Frobenius number. The construction gives us a
rooted tree structure for this set. Furthermore, by using the notion of
Kunz-coordinates vector we translate the problem of finding such a tree into
the problem of manipulating 0-1 vectors with as many component as the Frobenius
number.Comment: 10 page
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