46,855 research outputs found

    CP violating effects in the decay Z -> mu^+mu^-gamma induced by ZZgamma and Zgammagamma couplings

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    We analyze possible CP-violating effects induced in the ZZ decay with hard photon radiation by γZZ\gamma ZZ and γγZ\gamma\gamma Z anomalous vertices. We estimate the sensibility of future linear collider experiments on these couplings coming from CP-odd asymmetries associated to angular correlations of the three particle final state in e+e−→Z→μ+μ−γe^+e^- \to Z \to \mu^+\mu^-\gamma. We find that a linear collider with an integrated luminosity of 500 fb−1fb^{-1} and s=0.05\sqrt{s} = 0.05 TeV can place the bound ∣h1γ,Z∣<0.92|h_1^{\gamma,Z}| < 0.92 at the 90% confidence level for these couplings.Comment: Added references, 2 graphics 5 pages, LaTeX; typos added, 4 graphics remove

    Evolution of Vacuum Bubbles Embeded in Inhomogeneous Spacetimes

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    We study the propagation of bubbles of new vacuum in a radially inhomogeneous background filled with dust or radiation, and including a cosmological constant, as a first step in the analysis of the influence of inhomogeneities in the evolution of an inflating region. We also compare the cases with dust and radiation backgrounds and show that the evolution of the bubble in radiation environments is notably different from that in the corresponding dust cases, both for homogeneous and inhomogeneous ambients, leading to appreciable differences in the evolution of the proper radius of the bubble.Comment: 18 pages, 15 figures, accepted for publication in Journal of Cosmology and Astroparticle Physics (new version with a few cosmetic changes w.r.t. the published one

    Anisotropic thermal emission from magnetized neutron stars

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    The thermal emission from isolated neutron stars is not well understood. The X-ray spectrum is very close to a blackbody but there is a systematic optical excess flux with respect to the extrapolation to low energy of the best blackbody fit. This fact, in combination with the observed pulsations in the X-ray flux, can be explained by anisotropies in the surface temperature distribution.We study the thermal emission from neutron stars with strong magnetic fields in order to explain the origin of the anisotropy. We find (numerically) stationary solutions in axial symmetry of the heat transportequations in the neutron star crust and the condensed envelope. The anisotropy in the conductivity tensor is included consistently. The presence of magnetic fields of the expected strength leads to anisotropy in the surface temperature. Models with toroidal components similar to or larger than the poloidal field reproduce qualitatively the observed spectral properties and variability of isolated neutron stars. Our models also predict spectral features at energies between 0.2 and 0.6 keV.Comment: 18 pages, 19 figures, version accepted for publication in A&

    Analysis of the acoustic cut-off frequency and HIPs in six Kepler stars with stochastically excited pulsations

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    Gravito-acoustic modes in the Sun and other stars propagate in resonant cavities with a frequency below a given limit known as the cut-off frequency. At higher frequencies, waves are no longer trapped in the stellar interior and become traveller waves. In this article we study six pulsating solar-like stars at different evolutionary stages observed by the NASA Kepler mission. These high signal-to-noise targets show a peak structure that extends at very high frequencies and are good candidates for studying the transition region between the modes and the interference peaks or pseudo-modes. Following the same methodology successfully applied on Sun-as-a-star measurements, we uncover the existence of pseudo-modes in these stars with one or two dominant interference patterns depending on the evolutionary stage of the star. We also infer their cut-off frequency as the midpoint between the last eigenmode and the first peak of the interference patterns. By using ray theory we show that, while the period of one of the interference pattern is very close to half the large separation the other, one depends on the time phase of mixed waves, thus carrying additional information on the stellar structure and evolution.Comment: Accepted for publication in A&A. 14 pages, 28 figure

    Self-organized evolution in socio-economic environments

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    We propose a general scenario to analyze social and economic changes in modern environments. We illustrate the ideas with a model that incorporating the main trends is simple enough to extract analytical results and, at the same time, sufficiently complex to display a rich dynamic behavior. Our study shows that there exists a macroscopic observable that is maximized in a regime where the system is critical, in the sense that the distribution of events follow power-laws. Computer simulations show that, in addition, the system always self-organizes to achieve the optimal performance in the stationary state.Comment: 4 pages RevTeX; needs epsf.sty and rotate.sty; submitted to Phys Rev Let

    Brans-Dicke wormholes in nonvacuum spacetime

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    Analytical wormhole solutions in Brans-Dicke theory in the presence of matter are presented. It is shown that the wormhole throat must not be necessarily threaded with exotic matter.Comment: Minor corrections, to be published in Phys. Rev.
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