16109922
Non-BPS D-branes in string theory
In this paper I shall discuss some aspects of non-BPS D-branes in string theory. PACS number: 1125
118381804
An Introduction to Duality Symmetries in String Theory
In this review I discuss some basic aspects of non-perturbative string theory. The topics include test of duality symmetries based on the analysis of the low energy effective action and the spectrum of BPS states, relationship between different duality symmetries, and an introduction to M-theory.
118614329
Reconstructing the interaction rate in holographic models of dark energy
Abstract We reconstruct the interaction rate of the holographic dark energy model recently proposed by Zimdahl and Pavon [W. Zimdahl, D. Pavon, Class. Quantum Grav. 24 (2007) 5461] in the redshift interval 0 z 1.8 with observational data from supernovae type Ia, baryon acoustic oscillations, gas mass fraction in galaxy clusters, and the growth factor. It shows a reasonable behavior in the sense that it increases with expansion from a small or vanishing value in the long past but starts decreasing at recent times. The later feature suggests that the equation of state parameter of dark energy does not cross the phantom divide.
14264374
Observational Constraints on Cardassian Expansion
In this work, we have studied the observational constraints on the Cardassian Model for the dark energy. We have compared the model with existing Supernova data. The dependence of the location of the Cosmic Microwave Background Radiation (CMBR) peaks on the parameters of the model have also been studied. We find, in particular that observational data arising from Archeops for the location of the first peak, BOOMERANG for the location of the third peak, together with the Supernova data, constrain significantly the parameter space.