Deviation of light curves of gamma-ray burst pulses from standard forms due to the curvature effect of spherical fireballs or uniform jets

As revealed previously, under the assumption that some pulses of gamma-ray bursts are produced by shocks in spherical fireballs or uniform jets of large opening angles, there exists a standard decay form of the profile of pulses arising from very narrow or suddenly dimming local (or intrinsic) pulses due to the relativistic curvature effect (the Doppler effect over the spherical shell surface). Profiles of pulses arising from other local pulses were previously found to possess a reverse S-feature deviation from the standard decay form. We show in this paper that, in addition to the standard decay form shown in Qin et al. (2004), there exists a marginal decay curve associated with a local $\delta$ function pulse with a mono-color radiation. We employ the sample of Kocevski et al. (2003) to check this prediction and find that the phenomenon of the reverse S-feature is common, when compared with both the standard decay form and the marginal decay curve. We accordingly propose to take the marginal decay curve (whose function is simple) as a criteria to check if an observed pulse could be taken as a candidate suffered from the curvature effect. We introduce two quantities $A_1$ and $A_2$ to describe the mentioned deviations within and beyond the $FWHM$ position of the decay phase, respectively. The values of $A_1$ and $A_2$ of pulses of the sample are calculated, and the result suggests that for most of these pulses their corresponding local pulses might contain a long decay time relative to the time scale of the curvature effect.Comment: 24 pages, 7 figures, 1 table accepted for publication in MNRA

Study on the spectrum of the injected relativistic protons

About 10TeV gamma-ray emission within 10 pc region from the Galactic Center had been reported by 4 independent groups. Considering that this TeV gamma-ray emission is produced via a hadronic model, and the relativistic protons came from the tidal disruption of stars by massive black holes, we investigate the spectral nature of the injected relativistic protons required by the hadronic model. The calculation was carried on the tidal disruption of the different types of stars and the different propagation mechanisms of protons in the interstellar medium. Compared with the observation data from HESS, we find for the best fitting that the power-law index of the spectrum of the injected protons is about -1.9, when a red giant star is tidally disrupted, and the effective confinement of protons diffusion mechanism is adopted.Comment: 2 pages, IAU Symposium 25

Electron-doped phosphorene: A potential monolayer superconductor

We predict by first-principles calculations that the electron-doped phosphorene is a potential BCS-like superconductor. The stretching modes at the Brillouin-zone center are remarkably softened by the electron-doping, which results in the strong electron-phonon coupling. The superconductivity can be introduced by a doped electron density ($n_{2D}$) above $1.3 \times10^{14}$ cm$^{-2}$, and may exist over the liquid helium temperature when $n_{2D}>2.6 \times10^{14}$ cm$^{-2}$. The maximum critical temperature is predicted to be higher than 10 K. The superconductivity of phosphorene will significantly broaden the applications of this novel material

Negative refraction and plano-concave lens focusing in one-dimensional photonic crystals

Negative refraction is demonstrated in one-dimensional (1D) dielectric photonic crystals (PCs) at microwave frequencies. Focusing by plano-concave lens made of 1D PC due to negative refraction is also demonstrated. The frequency-dependent negative refractive indices, calculated from the experimental data matches very well with those determined from band structure calculations. The easy fabrication of one-dimensional photonic crystals may open the door for new applications.Comment: 3 pages and 5 figure