52 research outputs found

    Qualitative Properties of Magnetic Fields in Scalar Field Cosmology

    Get PDF
    We study the qualitative properties of the class of spatially homogeneous Bianchi VI_o cosmological models containing a perfect fluid with a linear equation of state, a scalar field with an exponential potential and a uniform cosmic magnetic field, using dynamical systems techniques. We find that all models evolve away from an expanding massless scalar field model in which the matter and the magnetic field are negligible dynamically. We also find that for a particular range of parameter values the models evolve towards the usual power-law inflationary model (with no magnetic field) and, furthermore, we conclude that inflation is not fundamentally affected by the presence of a uniform primordial magnetic field. We investigate the physical properties of the Bianchi I magnetic field models in some detail.Comment: 12 pages, 2 figures in REVTeX format. to appear in Phys. Rev.

    Magnetogenesis and the dynamics of internal dimensions

    Full text link
    The dynamical evolution of internal space-like dimensions breaks the invariance of the Maxwell's equations under Weyl rescaling of the (conformally flat) four-dimensional metric. Depending upon the number and upon the dynamics of internal dimensions large scale magnetic fields can be created. The requirements coming from magnetogenesis together with the other cosmological constraints are examined under the assumption that the internal dimensions either grow or shrink (in conformal time) prior to a radiation dominated epoch. If the internal dimensions are growing the magnitude of the generated magnetic fields can seed the galactic dynamo mechanism.Comment: 27 in RevTex style, four figure

    Questioni di teoria generale del diritto pubblico nelle disposizioni in materia di terrorismo.

    No full text
    Tema della trattazione è la ricerca attorno alle questioni di teoria dello Stato e del diritto costituzionale che è dato di discernere, oltre agli aspetti penalistici di immediata percezione, nella legislazione italiana, definita come di carattere emergenziale, contro il terrorismo fondamentalista, con particolare riguardo alle mutazioni introdotte sull'ordinamento stauale dalla minaccia jihadista in rapporto ai valori fondamentali delle istituzioni liberaldemocratiche degli Stati e dell'ordinamento internazionale. Particolare attenzione è dedicata alla forma e al contenuto delle disposizioni introdotte dal Legislatore italiano. La redazione dei primi sei paragrafi è opera di Silvia Illari (Osservazioni prelimiari, Sulla c.d. "guerra" al terrorismo; L'emergenza terrorismo tra costanza e novità nei caratteri fondamentali dei poteri di eccezione; La legislazione italiana di emergenza in relazione ai pericoli del terrorismo; Aspetti particolari della prassi in tema di ricorso alla legislazione di emergenza; Qualche riferimento agli insegnamenti di Carl Schmitt). A Pietro Giuseppe Grasso sono dovute le "Osservazioni finali" (par. 7)

    PSA mass screening: Is there enough evidence?

    No full text
    Prostate cancer plays an important role in widely understood aspects of men's health, and is becoming a growing problem in terms of public life. Prostate cancer is one of the most common neoplasms among men. Male patients can live with prostate cancer for a long time so it is important to offer appropriate males adequate diagnostic tools and treatments. Prostate cancer and PSA potentially represent a "pair" of a disease and an appropriate indicator to be used in mass screening, but regardless of that there is still active debate about it. Extensive use of PSA screening has modified epidemiology of the diseases. Randomized controlled studies provided sufficient results regarding a reduction in mortality through PSA mass screening, while all agreed on risks of overdiagnosis and overtreatment. New and accurate screening tools are necessary, along with adequate counseling and risk stratification
    • …
    corecore