GCG Parametrization for Growth Function and Current Constraints

We study the linear growth function $f$ for large scale structures in a cosmological scenario where Generalised Chaplygin Gas (GCG) serves as dark energy candidate. We parametrize the growth index parameter as a function of redshift and do a comparative study between the theoretical growth rate and the proposed parametrization. Moreover, we demonstrate that growth rates for a wide range of dark energy models can be modeled accurately by our proposed parametrization. Finally, we compile a data set consisting of 28 data points within redshift range (0.15,3.8) to constrain the growth rate. It includes direct growth data from various projects/surveys including the latest data from the Wiggle-Z measurements. It also includes data constraining growth indirectly through the rms mass fluctuation $\sigma_8(z)$ inferred from Ly-$\alpha$ measurements at various redshifts. By fitting our proposed parametrization for $f$ to these data, we show that growth history of large scale structures of the universe although allows a transient acceleration, one cannot distinguish it at present with an eternally accelerating universe.Comment: 19 pages, Latex Style, 5 EPS figures, 3 Tables, Revised and improved versio

SUSY at ATLAS

This talk focuses on SUSY search at ATLAS with initial data taking

An Imaging Polarimeter(IMPOL) for multi-wavelength observations

Taking advantage of the advances in array detector technology, an imaging polarimeter (IMPOL) has been constructed for measuring linear polarization in the wavelength band from 400-800 nm. It makes use of a Wollaston prism as the analyser to measure simultaneously the two orthogonal polarization components that define a Stoke's parameter. An achromatic half-wave plate is used to rotate the plane of polarization with respect to the axis of the analyser so that the second Stoke's parameter also can be determined. With a field of view correponding to about 30x30 sq. mm for a 1.2 m, f/13 telescope, a sensitive, liquid-nitrogen cooled CCD camera as the detector and a built-in acquisition and guidance unit, the instrument can be used for studying stellar fields or extended objects with an angular resolution close to 2 arcsec. The instrumental polarization is less than 0.05% and the accuracies of measurement are primarily limited by photon noise for typical observations.Comment: 10 pages including 5 embedded figures; submitted to Astronomy and Astrophysics Supplement Series; available on request to A. N. Ramaprakash ([email protected] or [email protected]); quote report n

Frequency-dependent (ac) Conduction in Disordered Composites: a Percolative Study

In a recent paper [Phys. Rev. B{\bf57}, 3375 (1998)], we examined in detail the nonlinear (electrical) dc response of a random resistor cum tunneling bond network ($RRTN$, introduced by us elsewhere to explain nonlinear response of metal-insulator type mixtures). In this work which is a sequel to that paper, we consider the ac response of the $RRTN$-based correlated $RC$ ($CRC$) model. Numerical solutions of the Kirchoff's laws for the $CRC$ model give a power-law exponent (= 0.7 near $p = p_c$) of the modulus of the complex ac conductance at moderately low frequencies, in conformity with experiments on various types of disordered systems. But, at very low frequencies, it gives a simple quadratic or linear dependence on the frequency depending upon whether the system is percolating or not. We do also discuss the effective medium approximation ($EMA$) of our $CRC$ and the traditional random $RC$ network model, and discuss their comparative successes and shortcomings.Comment: Revised and reduced version with 17 LaTeX pages plus 8 JPEG figure

Conflict, Aid and Poverty: Cause, Effect and Prediction

Recent studies and reports suggest that foreign aid/intervention has been somewhat futile in eradicating conflict. In this study, we develop a simultaneous donor/recipient model of foreign aid and terrorism. Thereafter, we extend our theoretical propositions through a machine learning algorithm of inductive causation. We find that terrorism increases foreign aid, however foreign assistance is futile in mitigating terrorism. Additionally, socio-economic factors influence foreign aid given by the donors. But foreign assistance is unsuccessful in enhancing the livelihoods of the underprivileged. We conclude that foreign aid policies need to be more efficient.Food Security and Poverty, International Relations/Trade,

Coexistence of Bound and Virtual-bound States in Shallow-core to Valence Spectroscopies

We develop the theory for shallow-core to valence excitations when the multiplet spread is larger than the core-hole attraction, e.g., if the core and valence orbitals have the same principal quantum number. This results in a cross-over from bound to virtual-bound excited states with increasing energy and in large differences between dipole and high-order multipole transitions, as observed in inelastic x-ray scattering. The theory is important to obtain ground state information from x-ray spectroscopies of strongly correlated transition metal, rare-earth and actinide systems.Comment: 5 pages, 3 figures. Submitted to Phys. Rev. Let