V. C. Kuriakose

Quasinormal modes of Reissner–Nördstrom black hole surrounded by quintessence

We evaluate the complex frequencies of the normal modes for the charged scalar field perturbations around a Reissner–Nördstrom black hole surrounded by a static and spherically symmetric quintessence using third order WKB approximation approach. Quintessence decreases the oscillation frequency and increases the damping time of quasinormal frequencies. We studied the variation of quasinormal frequencies with charge of the black bole, mass and charge of perturbing scalar field and the quintessential parameters.

Self-written waveguide in methylene blue sensitized poly(vinyl alcohol)/acrylamide photopolymer material

We report the observation of a self-written waveguide inside a bulk methylene blue sensitized poly/vinyl alcohol)/acrylamide photopolymer material. Light from a low power He-Ne laser is focused into the material, and the evolution of the beam is monitored. The refractive index of the material is modulated in the region of high intensity due to photobleaching and photopolymerization effects occurring in the material. As a result, the beam propagates through the medium without any diffraction effects.

Optical soliton with damping and frequency chirping in fibre media

Abstract Nonlinear Schrodinger (NLS) equation which governs the propagation of single field in the fibre medium with pulse chirping and gain (loss) is considered. The integrability condition of NLS equation is arrived from the linear eigenvalue problem and is studied by using the Painleve singularity structure analysis. From the Lax pair, soliton solution is constructed by using the Darboux–Backlund transformation technique. From the results, we show that the soliton is alive, i.e., pulse area is conserved with the inclusion of damping and pulse chirping effects.

The thermodynamics and thermodynamic geometry of the Park black hole

We study the thermodynamics and thermodynamic geometry of the Park black hole in Hořava gravity. By incorporating the ideas of differential geometry, we investigate the thermodynamics by using the Weinhold and the Ruppeiner geometry. We have also analyzed it in the context of the newly developed geometrothermodynamics (GTD). The divergence of the specific heat is associated with a second-order phase transition. Here in the context of the Park black hole, both Weinhold’s metric and Ruppeiner’s metric well explain this phase transition. But these explanations depend on the choice of the potential. Hence the Legendre invariant GTD is used, and with the true singularities in the curvature scalar, they well explain the second-order phase transition. All these methods together give an exact idea of all the behaviors of the Park black hole thermodynamics.

Absorption cross section of RN black hole

The behavior of a charged scalar field in the RN black hole space time is studied using WKBapproximation. In the present work it is assumed that matter waves can get reflected from the eventhorizon. Using this effect, the Hawking temperature and the absorption cross section for RN blackhole placed in a charged scalar field are calculated. The absorption cross section σ

Phase transition, quasinormal modes and Hawking radiation of Schwarzschild black hole in quintessence field

Black hole thermodynamic stability can be determined by studying the nature of heat capacity of the system. For Schwarzschild black hole the heat capacity is negative, but in the quintessence field, this system shows a second-order phase transition, implying the existence of a stable phase. We further discuss the equation of state of the present system. While analyzing the quasinormal modes (QNM), we find that the massive scalar QNM frequencies in the complex ω plane shows a dramatic change when we plot it as a progressive function of quintessence state parameter. We also find the Hawking temperature of the system via the method of tunneling.

Phase synchronization in an array of driven Josephson junctions

We consider an array of N Josephson junctions connected in parallel and explore the condition for chaotic synchronization. It is found that the outer junctions can be synchronized while they remain uncorrelated to the inner ones when an external biasing is applied. The stability of the solution is found out for the outer junctions in the synchronization manifold. Symmetry considerations lead to a situation wherein the inner junctions can synchronize for certain values of the parameter. In the presence of a phase difference between the applied fields, all the junctions exhibit phase synchronization. It is also found that chaotic motion changes to periodic in the presence of phase differences.

Generation of pedestal-free ultrashort soliton pulses and optimum dispersion profile in real dispersion-decreasing fibre

In this paper, we study the generation of high-quality ultrashort soliton pulses in dispersion-decreasing fibres with the inclusion of fibre loss in the integrable case. Five closely shaped profiles, namely linear, hyperbolic, exponential, logarithmic, and Gaussian, have been considered. The effects of these dispersion profiles and fibre loss on the performance of pulse compression in dispersion-decreasing fibres have been analysed. The pulse is compressed adiabatically by keeping the soliton property of conservation of pulse area provided the fibre loss is less than the critical value. Both analytical and graphical results show that, out of the five different profiles considered, the Gaussian profile is the optimum profile for achieving maximum pulse compression.

Phase effects on synchronization by dynamical relaying in delay-coupled systems.

Synchronization in an array of mutually coupled systems with a finite time delay in coupling is studied using the Josephson junction as a model system. The sum of the transverse Lyapunov exponents is evaluated as a function of the parameters by linearizing the equation about the synchronization manifold. The dependence of synchronization on damping parameter, coupling constant,and time delay is studied numerically. The change in the dynamics of the system due to time delay and phase difference between the applied fields is studied. The case where a small frequency detuning between the applied fields is also discussed.

Photometric Scaling Relations for Bulges of Galaxies

We describe the photometric parameters of the bulges of galaxies of different Hubble types including ellipticals, lenticulars, early and late type spirals and early type dwarf galaxies. Analyzing the distributions of various photometric parameters and two- and three-dimensional correlations between them, we find that there is a difference in the correlations exhibited by bright (