The Baryon-Dark Matter Ratio Via Moduli Decay After Affleck-Dine Baryogenesis

Low-scale supersymmetry breaking in string motivated theories implies the presence of O(100) TeV scale moduli, which generically lead to a significant modification of the history of the universe prior to Big Bang Nucleosynthesis. Such an approach implies a non-thermal origin for dark matter resulting from scalar decay, where the lightest supersymmetric particle can account for the observed dark matter relic density. We study the further effect of the decay on the baryon asymmetry of the universe, and find that this can satisfactorily address the problem of the over-production of the baryon asymmetry by the Affleck-Dine mechanism in the MSSM. Remarkably, there is a natural connection between the baryon and dark matter abundances today, which leads to a solution of the `Cosmic Coincidence Problem'.Comment: 12 pages, no figure. v2: references adde

Heterotic strings on G_2 orbifolds

We study compactification of heterotic strings to three dimensions on orbifolds of G_2 holonomy. We consider the standard embedding and show that the gauge group is broken from E_8 x E_8 or SO(32) to F_4 x E_8 or SO(25) respectively. We also compute the spectrum of massless states and compare with the results obtained from reduction of the 10-dimensional fields. Non-standard embeddings are discussed briefly. For type II compactifications we verify that IIB and IIA have equal massless spectrum.Comment: LaTex, 21 page

Phase transition and hybrid star in a SU(2) chiral sigma model

We use a modified SU(2) chiral sigma model to study nuclear matter at high density using mean field approach. We also study the phase transition of nuclear matter to quark matter in the interior of highly dense neutron stars. Stable solutions of Tolman-Oppenheimer-Volkoff equations representing hybrid stars are obtained with a maximum mass of 1.69 $M_{\odot}$, radii around 9.3 kms and a quark matter core constituting nearly 55-85 % of the star radii.Comment: 19 pages, 9 figures, accepted for Mod. Phys. Letts.

Broadband study of blazar 1ES 1959+650 during flaring state in 2016

Aim : The nearby TeV blazar 1ES 1959+650 (z=0.047) was reported to be in flaring state during June - July 2016 by Fermi-LAT, FACT, MAGIC and VERITAS collaborations. We studied the spectral energy distributions (SEDs) in different states of the flare during MJD 57530 - 57589 using simultaneous multiwaveband data to understand the possible broadband emission scenario during the flare. Methods : The UV/optical and X-ray data from UVOT and XRT respectively on board Swift and high energy $\gamma$-ray data from Fermi-LAT are used to generate multiwaveband lightcurves as well as to obtain high flux states and quiescent state SEDs. The correlation and lag between different energy bands is quantified using discrete correlation function. The synchrotron self Compton (SSC) model was used to reproduce the observed SEDs during flaring and quiescent states of the source. Results : A decent correlation is seen between X-ray and high energy $\gamma$-ray fluxes. The spectral hardening with increase in the flux is seen in X-ray band. The powerlaw index vs flux plot in $\gamma$-ray band indicates the different emission regions for 0.1 - 3 GeV and 3-300 GeV energy photons. Two zone SSC model satisfactorily fits the observed broadband SEDs. The inner zone is mainly responsible for producing synchrotron peak and high energy $\gamma$-ray part of the SED in all states. The second zone is mainly required to produce less variable optical/UV and low energy $\gamma$-ray emission. Conclusions : Conventional single zone SSC model does not satisfactorily explain broadband emission during observation period considered. There is an indication of two emission zones in the jet which are responsible for producing broadband emission from optical to high energy $\gamma$-rays.Comment: 11 pages, 12 figures, Accepted in A&

Superconformal field theories from crystal lattices

We propose a brane configuration for the (2+1)d, $\mathcal{N}=2$ superconformal theories (CFT$_3$) arising from M2-branes probing toric Calabi-Yau 4-fold cones, using a T-duality transformation of M-theory. We obtain intersections of M5-branes on a three-torus which form a 3d bipartite crystal lattice in a way similar to the 2d dimer models for CFT$_4$. The fundamental fields of the CFT$_3$ are M2-brane discs localized around the intersections, and the super-potential terms are identified with the atoms of the crystal. The model correctly reproduces the complete BPS spectrum of mesons and baryons.Comment: 4 pages, 4 figures, revtex; v2. references added, minor correction

Rotating membranes on G_2 manifolds, logarithmic anomalous dimensions and N=1 duality

We show that the $E-S \sim \log S$ behaviour found for long strings rotating on $AdS_5\times S^5$ may be reproduced by membranes rotating on $AdS_4\times S^7$ and on a warped $AdS_5$ M-theory solution. We go on to obtain rotating membrane configurations with the same $E-K \sim \log K$ relation on $G_2$ holonomy backgrounds that are dual to ${\mathcal{N}}=1$ gauge theories in four dimensions. We study membrane configurations on $G_2$ holonomy backgrounds systematically, finding various other Energy-Charge relations. We end with some comments about strings rotating on warped backgrounds.Comment: 1+44 pages. Latex. No figures. Minor corrections to make all membrane configurations consistent. One configuration is now noncompac

A Note on Mirror Symmetry for Manifolds with Spin(7) Holonomy

Starting from the superconformal algebras associated with $G_2$ manifolds, I extend the algebra to the manifolds with spin(7) holonomy. I show how the mirror symmetry in manifolds with spin(7) holonomy arises as the automorphism in the extended sperconformal algebra. The automorphism is realized as 14 kinds of T-dualities on the supersymmetric $T^4$ toroidal fibrations. One class of Joyce's orbifolds are pairwise identified under the symmetry.Comment: 12 pages, harvmac bi

Study on the morphometric and meristic characteristics of splendid silver belly Leiognathus splendens (Cuvier) from Bombay coast

Ten morphometric and six meristic characters of Leiognathus splendens (Cuvier) of Bombay Coast have been studied sexwise. Regression and sexwise difference if any between the compared morphometric characteristics have been worked out. Range, mode, standard deviation, co-efficient of variation of 6 meristic characters have been analysed. There was no significant difference between the sexes in morphometric and any deviation in the meristic characters