The study of gravitational collapse model in higher dimensional space-time

We investigate the end state of the gravitational collapse of an inhomogeneous dust cloud in higher dimensional space-time. The naked singularities are shown to be developing as the final outcome of non-marginally bound collapse. The naked singularities are found to be gravitationally strong in the sense of Tipler .Comment: 6 Latex pages, No figure, Revtex styl

Quasi-spherical gravitational collapse and the role of initial data, anisotropy and inhomogeneity

In this paper, the role of anisotropy and inhomogeneity has been studied in quasi-spherical gravitational collapse. Also the role of initial data has been investigated in characterizing the final state of collapse. Finally, a linear transformation on the initial data set has been presented and its impact has been discussed.Comment: RevTex, 7 Latex pages, No figure

The effect of Pressure in Higher Dimensional Quasi-Spherical Gravitational Collapse

We study gravitational collapse in higher dimensional quasi-spherical Szekeres space-time for matter with anisotropic pressure. Both local and global visibility of central curvature singularity has been studied and it is found that with proper choice of initial data it is possible to show the validity of CCC for six and higher dimensions. Also the role of pressure in the collapsing process has been discussed.Comment: 11 pages, 6 figures, RevTeX styl

Tripartite Entanglement versus Tripartite Nonlocality in Three-Qubit Greenberger-Horne-Zeilinger-Class States

We analyze the relationship between tripartite entanglement and genuine tripartite nonlocality for three-qubit pure states in the Greenberger-Horne-Zeilinger class. We consider a family of states known as the generalized Greenberger-Horne-Zeilinger states and derive an analytical expression relating the three-tangle, which quantifies tripartite entanglement, to the Svetlichny inequality, which is a Bell-type inequality that is violated only when all three qubits are nonlocally correlated. We show that states with three-tangle less than 1/2 do not violate the Svetlichny inequality. On the other hand, a set of states known as the maximal slice states does violate the Svetlichny inequality, and exactly analogous to the two-qubit case, the amount of violation is directly related to the degree of tripartite entanglement.We discuss further interesting properties of the generalized Greenberger-Horne-Zeilinger and maximal slice states

Collapse Dynamics of a Star of Dark Matter and Dark Energy

In this work, we study the collapse dynamics of an inhomogeneous spherically symmetric star made of dark matter (DM) and dark energy (DE). The dark matter is taken in the form of a dust cloud while anisotropic fluid is chosen as the candidate for dark energy. It is investigated how dark energy modifies the collapsing process and is examined whether dark energy has any effect on the Cosmic Censorship Conjecture. The collapsing star is assumed to be of finite radius and the space time is divided into three distinct regions $\Sigma$ and $V^{\pm}$, where $\Sigma$ represents the boundary of the star and $V^{-}(V^{+})$ denotes the interior (exterior) of the star. The junction conditions for matching $V^{\pm}$ over $\Sigma$ are specified. Role of Dark energy in the formation of apparent horizon is studied and central singularity is analyzed.Comment: 13 page

QPO Evolution in 2005 Outburst of the Galactic Nano Quasar GRO J1655-40

GRO J1655-40 showed significant X-ray activity in the last week of February, 2005 and remained active for the next 260 days. The rising and the decline phases of this particular outburst show evidence for systematic movements of the Comptonizing region, assumed to be a CENBOL, which causes the Quasi-periodic Oscillations or QPOs. We present both the spectral and the timing results of the RXTE/PCA data taken from these two hard spectral states. Assuming that the QPOs originate from an oscillating shock CENBOL, we show how the shock slowly moves in through the accretion flow during the rising phase at a constant velocity and accelerate away outward during the later part of the decline phase. By fitting the observed frequencies with our solution, we extract time variation of various disk parameters such as the shock locations, velocity etc.Comment: 5 Pages, 2 Figures, Proceeding of the 2nd Kolkata Conference on "Observational Evidence for the Black Holes in the Universe", Published in AIP, 200

Scaling, self-similar solutions and shock waves for V-shaped field potentials

We investigate a (1+1)-dimensional nonlinear field theoretic model with the field potential $V(\phi)| = |\phi|.$ It can be obtained as the universal small amplitude limit in a class of models with potentials which are symmetrically V-shaped at their minima, or as a continuum limit of certain mechanical system with infinite number of degrees of freedom. The model has an interesting scaling symmetry of the 'on shell' type. We find self-similar as well as shock wave solutions of the field equation in that model.Comment: Two comments and one reference adde

Gravitational collapse due to dark matter and dark energy in the brane world scenario

Gravitational collapse of FRW brane world embedded in a conformaly flat bulk is considered for matter cloud consists of dark matter and dark energy with equation of state $p=\epsilon \rho$ $(\epsilon<-{1/3})$. The effect of dark matter and dark energy is being considered first separately and then a combination of them both with and without interaction. In some cases the collapse leads to black hole in some other cases naked singularity appears.Comment: 10 Latex Pages, RevTex style, 4 figure

Instruments of RT-2 Experiment onboard CORONAS-PHOTON and their test and evaluation II: RT-2/CZT payload

Cadmium Zinc Telluride (CZT) detectors are high sensitivity and high resolution devices for hard X-ray imaging and spectroscopic studies. The new series of CZT detector modules (OMS40G256) manufactured by Orbotech Medical Solutions (OMS), Israel, are used in the RT-2/CZT payload onboard the CORONAS-PHOTON satellite. The CZT detectors, sensitive in the energy range of 20 keV to 150 keV, are used to image solar flares in hard X-rays. Since these modules are essentially manufactured for commercial applications, we have carried out a series of comprehensive tests on these modules so that they can be confidently used in space-borne systems. These tests lead us to select the best three pieces of the 'Gold' modules for the RT-2/CZT payload. This paper presents the characterization of CZT modules and the criteria followed for selecting the ones for the RT-2/CZT payload. The RT-2/CZT payload carries, along with three CZT modules, a high spatial resolution CMOS detector for high resolution imaging of transient X-ray events. Therefore, we discuss the characterization of the CMOS detector as well.Comment: 26 pages, 19 figures, Accepted for publication in Experimental Astronomy (in press