AR-2019-2020

tational error of a previous version. This work has been done in collaboration with Sweta Sarmah. Magnetic field creation by solar mass neutrino jets Parity violation and its effects for neutrinos in as- trophysical contexts have been considered earlier in pioneering papers of Hawking and Vilenkin. But because even the largest magnetic moments pre- dicted by physics beyond the Standard Model are some twelve orders of magnitude smaller than the Bohr magneton, their implications for magnetic field generation and neutrino oscillations are gen- erally considered insignificant. Here, we show that since in astrophysical scenarios a huge number of neutrinos may be emitted, the smallness of the magnetic moment, when coupled with parity viola- tion, is compensated by the sheer number of neu- trinos. The merger of neutron stars would leave be- hind a short pulse of electromagnetic synchrotron radiation even if the neutrino jet in the merger points away from the neutrino detectors. We show that the magnetic field can be as large as 10 6 Gauss and comment on the possibility of direct detection. Observation of such a pulse would lend strong sup- port for neutrino magnetic moments and resolve the missing neutrino problem in neutron star merg- ers. This work has been done in collaboration with Cheng-Yang Lee. G. Ambika Classification of close binary stars using recurrence networks. In close binary stars, the component stars are close enough such that they can exchange mass and/or energy. They are subdivided into semi-detached, overcontact or ellipsoidal binary stars. A challeng- ing problem in the context of close binary stars is their classification into these subclasses, based solely on their light curves. Conventionally, this is done by observing subtle features in the light curves like the depths of adjacent minima, which is tedious when dealing with large datasets. In this work, we suggest the use of machine learn- ing algorithms applied to measures of recurrence networks and nonlinear time series analysis to dif- ferentiate between classes of close binary stars. We show that overcontact binary stars occupy a region different from semi-detached and ellipsoidal binary stars in a plane of characteristic path length (CPL) and average clustering coefficient (CC), computed from their recurrence networks. We use standard clustering algorithms and report that the clusters formed correspond to the standard classes with a high degree of accuracy. This work has been in collabration with Sandip V. George, and Ranjeev Misra. Synapse loss and progress of Alzheimer’s disease - A network model. We present observational evidence from studies on primary cortical cultures from AD transgenic mice, APPSwe/PS1ΔE9 (APP/PS1) mice, for significant decrease in total spine density at DIV-15 and on- ward. This indicates reduction in potential healthy synapses and strength of connections among neu- rons. Based on this, a network model of neu- rons is developed, that explains the consequent loss of coordinated activity and transmission ef- ficiency among neurons that manifests over time. The critical time when structural connectivity in the brain undergoes a phase-transition, from ini- tial robustness to irreparable breakdown, is esti- mated from this model. We also show how the global efficiency of signal transmission in the net- work decreases over time. Moreover, the num- ber of multiple paths of high efficiency decreases rapidly as the disease progresses, indicating loss of structural plasticity and inefficiency in choos- ing alternate paths or desired paths for any pat- tern of activity. Thus, loss of spines caused by β -Amyloid (A β ) peptide results in disintegration of the neuronal network over time with consequent cognitive dysfunctions in Alzheimers Disease (AD). This work has been done in collaboration with G. Srikanth Kashyap, Deepti Bapat, D. Das, Ruturaj Gowaikar, Ravindra E. Amritkar, et al. Arunima Banerjee The specific angular momenta of superthin galax- ies: Cue to their origin? Superthin galaxies are low surface brightness (LSB) bulgeless disc galaxies having stellar discs with un- usually high planar-to-vertical axes ratio b/a > 10 - 20, the formation and evolution of which is not well-understood. We calculate the specific angu- lar momenta of a sample of six superthins and nine other bulgeless LSBs using stellar photome- try, atomic hydrogen (HI) surface density and high resolution HI rotation curves available in the lit- erature. We find that the stellar specific angu-