Fractal Measures and Nonlinear Dynamics of Overcontact Binaries

Overcontact binary stars are systems of two stars where the component stars are in contact with each other. This implies that they share a common envelope of gas. In this work we seek signatures of nonlinearity and chaos in these stars by using time series analysis techniques. We use three main techniques, namely the correlation dimension,f (\alpha) spectrum and the bicoherence. The former two are calculated from the reconstructed dynamics, while the latter is calculated from the Fourier transforms of the time series of intensity variations(light curves) of these stars. Our dataset consists of data from 463 overcontact binary stars in the Kepler field of view [1]. Our analysis indicates nonlinearity and signatures of chaos in almost all the light curves. We also explore whether the underlying nonlinear properties of the stars are related to their physical properties like fill-out-factor, a measure of the extend of contact between the components of an overcontact binary system . We observe that significant correlations exist between the fill out factor and the nonlinear quantifiers. This correlation is more pronounced in specific subcategories constructed based on the mass ratios and effective temperatures of the binaries. The correlations observed can be indicative of variations in the nonlinear properties of the star as it ages. We believe that this study relating nonlinear and astrophysical properties of binary stars is the first of its kind and is an important starting point for such studies in other astrophysical objects displaying nonlinear dynamical behaviour.Comment: 17 pages, 12 figures, submitted to Communications in Nonlinear Science and Numerical Simulatio

Up-Down Asymmetry of Neutral Current Events as a Diagnostic for Nu_mu - Nu-st Versus Nu_mu- Nu_tau Oscillations

We show that the asymmetry in the neutral current events (e.g. Nu N -> Nu N pi^0) can be used to discriminate between Nu_mu - Nu_tau and Nu_mu - Nu_st mixing as being responsible for the atmospheric neutrino anomaly. Specifically, A_N vanishes for Nu_mu - Nu_tau mixing and is about 2/3 A_mu for Nu_mu - Nu_st mixing.Comment: 3pages, 1 figur

CP Violation in Hyperon Decays from Supersymmetry

It was pointed out recently that supersymmetry can generate flavor-changing gluonic dipole operators with sufficiently large coefficients to dominate the observed value of epsilon'/epsilon. We point out that the same operators contribute to direct CP violation in hyperon decay and can generate a CP violating asymmetry A(\Lambda^0_-) in the range probed by the current E871 experiment. Interestingly, models that naturally reproduce the relation lambda = sqrt{m_d/m_s} do not generate epsilon'/epsilon but could lead to an A(\Lambda^0_-) of O(10^{-3}).Comment: 4 page

Determination of Weak Amplitudes using Bose Symmetry and Dalitz Plots

We present a new method using Dalitz plot and Bose symmetry of pions that allows the complete determination of the magnitudes and phases of weak decay amplitudes. We apply the method to process like B->K^* pi, with the subsequent decay of K^* -> K pi. Our approach enables the additional measurement of an isospin amplitude without any theoretical assumption. This advance will help in measuring weak phase and probing for new physics beyond standard model with fewer assumptions.Comment: 5 pages, 1 figure; Title changed; Conclusions unchanged; Accepted for publication in Physical Review Letter

Classification of galaxies using fractal dimensions

The classification of galaxies is morphological. Shapes of the galaxies range from the very simple (e.g. elliptical galaxies) to the highly complex (e.g. irregular galaxies). Analyzing a measure of complexity for such shapes could lead to automatic classification. Fractal dimension, a quantity related to the complexity of a given shape, could be such a measure. Capacity dimension and correlation dimension are two of the several types of fractal dimensions. In this project, correlation dimensions and the capacity dimensions of the contours generated around different intensity levels of the galaxy images, versus the intensity levels were computed. It was found that elliptical galaxies tend to have a lower value of the average correlation dimension (computed for a selected range of intensity levels) than spirals