Searcharxiv⌕ Search

arXiv subjects

Jose A. Gonzalez

Publications and source records attributed to Jose A. Gonzalez.

24 records · Page 2Linked to original sources
arXiv2003

Quantum Mechanics on the cylinder

A new approach to deformation quantization on the cylinder considered as phase space is presented. The method is based on the standard Moyal formalism for R^2 adapted to (S^1 x R) by the Weil--Brezin--Zak transformation. The results are compared with other solutions of this problem presented by Kasperkovitz and Peev (Ann. Phys. vol. 230, 21 (1994)0 and by Plebanski and collaborators (Acta Phys. Pol. vol. B 31}, 561 (2000)). The equivalence of these three methods is proved.

quant-ph↗
arXiv2001

Local Constraints on the Oscillating G Model

We analyze the observational constraints on the effective Brans-Dicke parameter and on the temporal variation of the effective gravitational constant within the context of the oscillating G model, a cosmological model based on a massive scalar field non-minimally coupled to gravity. We show that these local constraints cannot be satisfied simultaneously once the values of the free parameters entering the model become fixed by the global attributes of our Universe. In particular, we show that the lower observational bound for the effective Brans-Dicke parameter and the upper bound of the variation of the effective gravitational constant lead to a specific value of the oscillation amplitude which lies well below the value required to explain the periodicity of 128 Mpc h^{-1} in the galaxy distribution observed in the pencil beam surveys.

astro-ph↗
arXiv2001

Scalar solitons in a 4-Dimensional curved space-time

There is a theorem known as a Virial theorem that restricts the possible existence of non-trivial static solitary waves with scalar fields in a flat space-time with 3 or more spatial dimensions. This raises the following question: Does the analogous curved space-time version hold?. We investigate the possibility of solitons in a 4-D curved space-time with a simple model using numerical analysis. We found that there exists a static solution of the proposed non linear wave equation. This proves that in curved space-time the possibilities of solitonic solutions is enhanced relative to the flat space-time case.

gr-qc↗
arXiv2000

Spatial Structure and Periodicity in the Universe

We analyze the possibility that the spatial periodicity of 128 h^{-1}Mpc in the galaxy count number observed recently in deep pencil-beam surveys could be explained by the mere existence of structure with the appropriate scale in the galaxy distribution in the Universe. We simulate a universe where the distribution of galaxies has an intrinsic length scale and then investigate the probability of observing in a given direction a spatial periodicity similar to that observed in the pencil-beam surveys of the galactic polar regions. A statistical analysis shows that this probability is of the order of 10^{-8}, a value which excludes the afore mentioned explanation. This result contrasts with the estimates based on Voronoi foam models which yield probabilities of the order 10^{-1} - 10^{-2}. The conclusion that emerges from these studies put together with the present one, is that although they can be obtained in some models, the presence of an intrinsic scale in the structure is not sufficient to achieve reasonable probabilities for observation of the detected periodicities.

astro-ph↗
arXiv1998

Coherent states on the circle

A careful study of the physical properties of a family of coherent states on the circle, introduced some years ago by de Bièvre and González in [DG 92], is carried out. They were obtained from the Weyl-Heisenberg coherent states in $L^2(\R)$ by means of the Weil-Brezin-Zak transformation, they are labeled by the points of the cylinder $S^1 \times \R$, and they provide a realization of $L^2(S^1)$ by entire functions (similar to the well-known Fock-Bargmann construction). In particular, we compute the expectation values of the position and momentum operators on the circle and we discuss the Heisenberg uncertainty relation.

quant-ph↗