Reflected Iron Line From a Source Above a Kerr Black Hole Accretion Disc

In this paper we present a fully relativistic approach to modelling both the continuum emission and the reflected fluorescent iron line from a primary X-ray source near a Kerr black hole. The X-ray source is located above an accretion disc orbiting around the black hole. The source is assumed to be a static point source located on an arbitrary position above the disc, on or off the axis of rotation. We carry out Monte Carlo simulations in order to estimate the iron line spectrum as well as its equivalent width. Because of the gravitational lensing effect, an enhancement of the iron line is expected when the primary source is located close to the central black hole. We find that for a source located on the axis of rotation the enhancement is relatively modest. An observer at inclination 30 degrees would measure an equivalent width of ~300eV in the extreme case of a maximally rotating black hole and a source located at height 1.5 gravitational radius from the centre. This corresponds to an equivalent width enhancement factor of about 2 compared to the classical value where no lensing effect comes into play. However, when allowing the source to be located off the axis of rotation, much stronger enhancement can be obtained. In the extreme case of a maximally rotating black hole and a source located just above the approaching side of the disc, an observer at inclination 30d egrees could measure an equivalent width as high as ~1.5 keV (i.e. ~10 times the classical value). We also find that observers located at high inclination angles observe a stronger line than observers at low inclination angles.Comment: 11 pages, 13 figures. Submitted to Monthly Notices of the Royal Astronomical Society (MNRAS

Easy 4G/LTE IMSI Catchers for Non-Programmers

IMSI Catchers are tracking devices that break the privacy of the subscribers of mobile access networks, with disruptive effects to both the communication services and the trust and credibility of mobile network operators. Recently, we verified that IMSI Catcher attacks are really practical for the state-of-the-art 4G/LTE mobile systems too. Our IMSI Catcher device acquires subscription identities (IMSIs) within an area or location within a few seconds of operation and then denies access of subscribers to the commercial network. Moreover, we demonstrate that these attack devices can be easily built and operated using readily available tools and equipment, and without any programming. We describe our experiments and procedures that are based on commercially available hardware and unmodified open source software

Negative Refraction in Ferromagnet/Superconductor Superlattices

Negative refraction, which reverses many fundamental aspects of classical optics, can be obtained in systems with negative magnetic permeability and negative dielectric permittivity. This Letter documents an experimental realization of negative refraction at millimeter waves, finite magnetic fields and cryogenic temperatures utilizing a multilayer stack of ferromagnetic and superconducting thin films. In the present case the superconducting YBa_2Cu_3O_7 layers provide negative permittivity while negative permeability is achieved via ferromagnetic (La:Sr)MnO_3 layers for frequencies and magnetic fields close to the ferromagnetic resonance. In these superlattices the refractive index can be switched between positive and negative regions using external magnetic field as tuning parameter.Comment: 4 Pages, 3 Figures, Phys. Rev. Lett., accepte

Non-commutative connections of the second kind

A connection-like objects, termed {\em hom-connections} are defined in the realm of non-commutative geometry. The definition is based on the use of homomorphisms rather than tensor products. It is shown that hom-connections arise naturally from (strong) connections in non-commutative principal bundles. The induction procedure of hom-connections via a map of differential graded algebras or a differentiable bimodule is described. The curvature for a hom-connection is defined, and it is shown that flat hom-connections give rise to a chain complex.Comment: 13 pages, LaTe

Star product formula of theta functions

As a noncommutative generalization of the addition formula of theta functions, we construct a class of theta functions which are closed with respect to the Moyal star product of a fixed noncommutative parameter. These theta functions can be regarded as bases of the space of holomorphic homomorphisms between holomorphic line bundles over noncommutative complex tori.Comment: 12 page

NA48/2 final results on charged semileptonic kaon decays and ∣V(us)∣|V_{(us)}|, NA48 measurements of the Kμ3K\mu3 form factors from KLK_{L} decays

Measured ratios of decay rates for $\Re_{Ke3/K2π}, \Re_{K\mu3/K2\pi}$ and $\Re_{K\mu 3/Ke3}$ are presented, based on $K^{\pm}$ decays collected in a dedicated run in 2003 by the NA48/2 experiment at CERN. The results obtained are $\Re_{Ke3/K2\pi} = 0.2470 \pm 0.0009_{stat} \pm 0.0004_{syst}$ and $\Re_{K\mu3/K2\pi} = 0.1637 \pm 0.0006_{stat} \pm 0.0003_{syst}$. Using the PDG average for the $K^{\pm} \rightarrow \pi^{\pm}\pi^{0}$ normalisation mode, both values are found to be larger than the current values given by the Particle Data Book [1] and lead to a larger magnitude of the $|V_{us}|$ element in the CabibboKobayashi-Maskawa (CKM) matrix than previously accepted. When combined with the latest Particle Data Book value of $|V_{ud}|$[1], the result is in agreement with unitarity of the CKM matrix. In addition, a new measured value of $Re_{K\mu3/K2\pi} = 0.663 \pm 0.003_{stat} \pm 0.001_{syst}$ is compared to the semi-empirical predictions based on the latest form factor measurements. The $K\mu 3$ form factors have been measured from a sample of $K_{L}$ decays in a dedicated run in 1999 by the NA48 experiment at CERN. Studying the Dalitz plot density, using the linear form factor approximation, a measurement was made of $\lambda_{+} = (26.7 \pm 0.6_{stat} \pm 0.8_{sys}) \times 10^{−3}$ and $\lambda_{0} = (11.7 \pm 0.7_{stat} \pm 1.0_{sys} \times 10^{−3}$ . Measurements were also made using the quadratic parameterisation, the pole parameterisation and the dispersive parameterisation. The results of all parameterisations will be presented

Why is the nuclear symmetry energy so uncertain at supra-saturation densities?

Within the interacting Fermi gas model for isospin asymmetric nuclear matter, effects of the in-medium three-body interaction and the two-body short-range tensor force due to the $\rho$ meson exchange as well as the short-range nucleon correlation on the high-density behavior of the nuclear symmetry energy are demonstrated respectively in a transparent way. Possible physics origins of the extremely uncertain nuclear symmetry energy at supra-saturation densities are discussed.Comment: Added discussions and revised format. Version to appear in Phys. Rev. C (2010