A Model for Quantum Stochastic Absorption in Absorbing Disordered Media

Wave propagation in coherently absorbing disordered media is generally modeled by adding a complex part to the real part of the potential. In such a case, it is already understood that the complex potential plays a duel role; it acts as an absorber as well as a reflector due to the mismatch of the phase of the real and complex parts of the potential. Although this model gives expected results for weakly absorbing disordered media, it gives unphysical results for the strong absorption regime where it causes the system to behave like a perfect reflector. To overcome this issue, we develop a model here using stochastic absorption for the modeling of absorption by "fake", or "side", channels obviating the need for a complex potential. This model of stochastic absorption eliminates the reflection that is coupled with the absorption in the complex potential model and absorption is proportional to the magnitude of the absorbing parameter. Solving the statistics of the reflection coefficient and its phase for both the models, we argue that stochastic absorption is a potentially better way of modeling absorbing disordered media.Comment: 5 pages, 4 figure

Recommendation for consideration in the development of Nepal's Irrigation Master Plan. Part 1 - Management of irrigation systems for effective O & M and resource mobilization; Part 2 - Farmer managed irrigation systems. Occasional paper

Irrigation management / Farmer managed irrigation systems / Resource management / Agricultural production / Nepal

Some Inhomogeneous Magnetized Viscous Fluid Cosmological Models with Varying Λ\Lambda

Some cylindrically symmetric inhomogeneous viscous fluid cosmological models with electro-magnetic field are obtained. To get a solution a supplementary condition between metric potentials is used. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density. Without assumin g any {\it ad hoc} law, we obtain a cosmological constant as a decreasing function of time. The behaviour of the electro-magnetic field tensor together with some p hysical aspects of the model are also discussed.Comment: 17 pages, 1 figur

String Cosmology in Anisotropic Bianchi-II Space-time

The present study deals with a spatially homogeneous and anisotropic Bianchi-II cosmological model representing massive strings. The energy-momentum tensor, as formulated by Letelier (1983), has been used to construct a massive string cosmological model for which the expansion scalar is proportional to one of the components of shear tensor. The Einstein's field equations have been solved by applying a variation law for generalized Hubble's parameter that yields a constant value of deceleration parameter in Bianchi-II space-time. A comparative study of accelerating and decelerating modes of the evolution of universe has been carried out in the presence of string scenario. The study reveals that massive strings dominate the early Universe. The strings eventually disappear from the Universe for sufficiently large times, which is in agreement with the current astronomical observations.Comment: 11 pages, 6 figures (To appear in Mod. Phys. Lett. A) In this version, the cosmic string has been directed along z-direction and the resultant field equations have been solved exactl