The Dirac oscillator in a spinning cosmic string spacetime

We examine the effects of gravitational fields produced by topological defects on a Dirac field and a Dirac oscillator in a spinning cosmic string spacetime. We obtain the eigenfunctions and the energy levels of the relativistic field in that background and consider the effect of various parameters, such as the frequency of the rotating frame, the oscillator's frequency, the string density and other quantum numbers.Comment: 12 pages, 3 figure

Path-integral quantization of Galilean Fermi fields

The Galilei-covariant fermionic field theories are quantized by using the path-integral method and five-dimensional Lorentz-like covariant expressions of non-relativistic field equations. Firstly, we review the five-dimensional approach to the Galilean Dirac equation, which leads to the Levy-Leblond equations, and define the Galilean generating functional and Green's functions for positive- and negative-energy/mass solutions. Then, as an example of interactions, we consider the quartic self-interacting potential ${\lambda} (\bar{\Psi} {\Psi})^2$, and we derive expressions for the 2- and 4-point Green's functions. Our results are compatible with those found in the literature on non-relativistic many-body systems. The extended manifold allows for compact expressions of the contributions in $(3+1)$ space-time. This is particularly apparent when we represent the results with diagrams in the extended $(4+1)$ manifold, since they usually encompass more diagrams in Galilean $(3+1)$ space-time.Comment: LATEX file, 27 pages, 8 figures; typos in the journal version are removed, equation (1) in Introduction is correcte

Fast Variations of Gamma-Ray Emission in Blazars

The largest group of sources identified by EGRET are Blazars. This sub-class of AGN is well known to vary in flux in all energy bands on time-scales ranging from a few minutes (in the optical and X-ray bands) up to decades (radio and optical regimes). In addition to variations of the gamma-ray flux between different viewing periods, the brightest of these sources showed a few remarkable gamma-ray flares on time-scales of about one day, confirming the extension of the ``Intraday-Variability (IDV)'' phenomenon into the GeV range. We present first results of a systematic approach to study fast variability with EGRET data. This statistical approach confirms the existence of IDV even during epochs when no strong flares are detected. This provides additional constraints on the site of the gamma-ray emission and allows cross-correlation analyses with light curves obtained at other frequencies even during periods of low flux. We also find that some stronger sources have fluxes systematically above threshold even during quiescent states. Despite the low count rates this allows explicit comparisons of flare amplitudes with other energy bands.Comment: 5 pages including figures, LaTex, uses aipproc.sty, to appear in the proceedings of the 4th Compton Symposium at Williamsburg, V

L'élargissement du concept de « détention », premier jalon d'une véritable protection contre l'auto-incrimination?

Le concept de détention ne peut se définir uniquement en fonction de considérations linguistiques; au contraire, son élaboration est largement influencée par la conciliation toujours à refaire entre la protection de la société et le respect de l'individu. À partir d'une analyse serrée de l'arrêt Therens, l'auteur procède à un examen de la jurisprudence récente et tente de cerner les principales difficultés auxquelles se heurtent les tribunaux. Si la contrainte physique et la coercition légale soulèvent relativement peu d'ambiguïtés, il n'en va pas de même de la détention résultant d'un élément de contrainte psychologique. Parce que cette extension du concept de détention est la plus novatrice et potentiellement la plus lourde de conséquence pour l'administration de la justice criminelle, un développement particulier y est consacré. Après avoir fait état de la problématique particulière que soulève cette forme de détention, l'auteur actualise la discussion en s'attardant plus particulièrement aux interrogatoires policiers. L'examen de certaines décisions contradictoires rendues par les cours d'appel du pays en cette matière, du droit américain ainsi que des règles qui gouvernent la recevabilité des preuves et des déclarations obtenues par les policiers, permet de mieux visualiser le lien étroit qui unit le concept de détention et l'étendue (ainsi que les fondements) des droits qu'il confère. En conclusion, l'auteur se dit d'avis que la définition du concept de détention doit fournir l'occasion de repenser l'harmonisation des droits individuels et de la sécurité collective, et souhaite que la Cour suprême tienne compte pour ce faire du rôle clé que doit nécessairement jouer le droit à l'avocat dans la protection contre l'auto-incrimination.The concept of detention should not be solely defined on the basis of linguistic considerations ; indeed, its development is largely influenced by the on-going reconciliation between protection of society and respect for the individual. From a narrow analysis of the Therens decision, the author examines recent case-law and attempts to determine the principal difficulties with which the courts are faced. While physical constraint and legal coercion may raise few ambiguities, the same cannot be said with regard to detention resulting from a psychological constraint. Particular consideration is given to this extension of the concept of detention because it is the most innovative and potentially the most burdensome on the administration of criminal justice. After establishing the particular problems raised by psychological constraint, the author centers his discussion on contemporary problems related to police interrogations. By examining certain contradictory decisions issuing from Canadian courts of appeal and from American law, plus rules governing the admissibility of evidence, it becomes easier to see the connection uniting the concept of detention and the scope land basis of the rights it engenders. In conclusion, the author maintains that the definition of the concept of detention must allow for the opportunity to rethink the balance of individual rights and collective security, and thus hopes that the Supreme Court will consider in achieving this end, the key role that the right to counsel plays in the protection against self-incrimination