AR_final file_2018-19

shift and velocity dispersion to test whether lenses lie in different environments from similar non-lens galaxies. It is found that lens fields contain higher number counts of galaxies compared to the control fields, but this effect arises from the local environ- ment of the lens. Once galaxies in the lens plane are removed, the lens lines of sight are consistent with the control sample. The local environments of the lenses are overdense compared to the con- trol sample, and are slightly overdense compared to those of the twin sample, although the signifi- cance is marginal. There is no significant evidence of the evolution of the local overdensity of lens en- vironments with redshift. Gravitational Waves Gravitational wave signature of a mini creation event In light of the recent discoveries of binary black hole events by the advanced LIGO (aLIGO) and advanced Virgo (aVirgo) detectors, Sanjeev V. Dhurandhar and Jayant V. Narlikar propose a new astrophysical source, namely, the mini creation event (MCE) as a possible source of gravitational waves (GW) to be detected by advanced detectors. The MCE is at the heart of the quasi steady state cosmology (QSSC), and is not expected to occur in standard cosmology. Generically, the MCE is anisotropic and they assume a Bianchi tpye I model for its description. They compute its signature waveform and assume masses, distances analogous to the events detected by aLIGO and aVirgo. By matched filtering the signal, they find that for a broad range of model parameters, the signal to noise ratio of the randomly oriented MCE is suf- ficiently high for a confident detection by aLIGO. They, therefore, propose the MCE as a viable as- trophysical source of GW. The detection or non- detection of such a source also holds implications for QSSC, namely, whether it is a viable cosmology or not. Hierarchical search for detecting grav- itational waves from compact coalesc- ing binaries Standard searches are currently restricted to a smaller parameter space which assumes aligned spins. Construction of a larger and denser param- eter space, and optimising the resultant increase in false alarms, pose a serious computational chal- lenge. Bhooshan Gadre , Sanjit Mitra , and Sanjeev V. Dhurandhar present a hierarchical strategy to search for compact coalescing binaries from a network of detectors, and demonstrate the computational advantage of about 20 over the flat search in real data. Optimal chi squared vetos for Sine- Gaussian glitches The traditional chi squared veto has been applied to the gravitational wave data with fair amount of success. However, this test is ad hoc and is not guaranteed to be optimal. Sanjeev Dhurandhar , Sukanta Bose , and Rahul Dhurkunde have con- structed an optimal chi squaredtest for glitches in the data, which can be modelled as Sine Gaussians, and which are ubiquitous. The method for con- structing any chi squared has been fully discussed in the previous work on unified chi squares. The pa- rameter space of Sine-Gaussians is adequately sam- pled and a subspace of the space of data trains is obtained. Using the singular value decomposition, one may construct subspace of much lower dimen- sion and orthogonal to the signal. This is then the required chi squared. Cosmic Magnetic Fields Varying the forcing scale in low Prandtl number dynamos Small-scale dynamos are expected to operate in all astrophysical fluids that are turbulent and electrically conducting, for example, the interstel- lar medium, stellar interiors, and accretion disks, where they may also be affected by or competing ( 69 )