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

Naked Singularities in Higher Dimensional Szekeres Space-time

In this paper we study the quasi-spherical gravitational collapse of (n+2) dimensional Szekeres space-time. The nature of the central shell focusing singularity so formed is analyzed by studying both the radial null and time-like geodesic originated from it. We follow the approach of Barve et al to analyze the null geodesic and find naked singularity in different situations.Comment: 11 Latex Pages, 4 figures, RevTex styl

A possible disk mechanism for the 23d QPO in Mkn~501

Optically thin two-temperature accretion flows may be thermally and viscously stable, but acoustically unstable. Here we propose that the O-mode instability of a cooling-dominated optically thin two-temperature inner disk may explain the 23-day quasi-periodic oscillation (QPO) period observed in the TeV and X-ray light curves of Mkn~501 during its 1997 high state. In our model the relativistic jet electrons Compton upscatter the disk soft X-ray photons to TeV energies, so that the instability-driven X-ray periodicity will lead to a corresponding quasi-periodicity in the TeV light curve and produce correlated variability. We analyse the dependence of the instability-driven quasi-periodicity on the mass (M) of the central black hole, the accretion rate ($\rm{\dot{M}}$) and the viscous parameter ($\alpha$) of the inner disk. We show that in the case of Mkn~501 the first two parameters are constrained by various observational results, so that for the instability occurring within a two-temperature disk where $\alpha=0.05-1.0$, the quasi-period is expected to lie within the range of 8 to 100 days, as indeed the case. In particular, for the observed 23-day QPO period our model implies a viscosity coefficient $\alpha \leq 0.28$, a sub-Eddington accretion rate $\dot{M} \simeq 0.02 \dot{M}_{\rm Edd}$ and a transition radius to the outer standard disk of $r_0 \sim 60 r_g$, and predicts a period variation $\delta P/P \sim 0.23$ due to the motion of the instability region.Comment: 18 pages, 1 figure, accepted by AP

Emergence of triggerfishes (Family: Balistidae) as an alternate lucrative target fishery for trawls along the Tuticorin coast in Gulf of Mannar

Fishes of the family Balistidae are commonly known as trigger fishes. Globally the family is represented by about 40 species belonging to 11 genera. The name triggerfish arose as the second dorsal spine act as a trigger to the first dorsal fin. Locally they are known as ‘Kilathi’ in Tamil. Though they used to occur in trawl catch of Tuticorin coast from time immemorial, they were thrown back into the sea by fishermen mainly due to lack of market demand and also for want of onboard storage space. Trawlers used to avoid areas of their congregation as they considered it a menace leading to wastage of energy and time

Feeding congregation of ribbonfish, Trichiurus lepturus juveniles in oceanic waters and their targeted exploitation by deepsea trawlers along the Tuticorin coast in Gulf of Mannar

Ribbonfishes supported commercial fishery at Tuticorin prior to nineteen nineties. But reports suggested that their stock and fishery declined considerably thereafter. Their fishery during 2000- 2006 was represented by occasional landings of small quantity of ribbonfish by trawls. Average production by trawls at Tuticorin fishing harbour during the period was 250 t. They represent about 0.7% of the total fish catch of the period

मान्नार की खाडी में टूटिकोरिन तट पर सागरी जलक्षेत्रों में फीतामीन ट्राइक्यूरस लेप्टुयूरस किशोरों का जमाव और गभीर सागर आनायकों द्वारा इसका लक्षित विदोहन

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