AR-2019-2020

anisotropy irrelevant to make a significant change in the CMB quadrupole temperature, whereas the constraint from the cosmological data in our model provides the temperature change up to ∼ 11 mK, though it is much beyond the CMB quadrupole temperature. This work has been done in collab- oration with Ozgur Akarsu, Shivani Sharma, and Luigi Tedesco. Smriti Mahajan Galaxy And Mass Assembly (GAMA): Properties and evolution of red spiral galaxies We use multiwavelength data from the Galaxy And Mass Assembly (GAMA) survey to explore the cause of red optical colours in nearby (0 . 002 < z < 0 . 06) spiral galaxies. We show that the colours of red spiral galaxies are a direct consequence of some environment-related mechanism(s) that has removed dust and gas, leading to a lower star for- mation rate. We conclude that this process acts on long time-scales (several Gyr) due to a lack of morphological transformation associated with the transition in optical colour. The specific star for- mation rate (sSFR) and dust-to-stellar mass ratio of red spiral galaxies is found to be statistically lower than blue spiral galaxies. On the other hand, red spirals are on average 0.9 dex more massive, and reside in environments 2.6 times denser than their blue counterparts. We find no evidence of excessive nuclear activity, or higher inclination an- gles to support these as the major causes for the red optical colours seen in ≥ 47 per cent of all spirals in our sample. Furthermore, for a small subsam- ple of our spiral galaxies that are detected in H I, we find that the SFR of gas-rich red spiral galax- ies is lower by 1 dex than their blue counterparts. This work has been done in collabration with Kirti Kamal Gupta, Rahul Rane, Michael J. I. Brown, Steven Phillipps, Joss Bland-Hawathorn, et. al. Titus K. Mathew First law of thermodynamics and emergence of cos- mic space in a non-flat universe The emergence of cosmic space as cosmic time pro- gresses is an exciting idea advanced by Padman- abhan to explain the accelerated expansion of the universe. The generalization of Padmanabhan’s conjecture to the non-flat universe has resulted in scepticism about the choice of volume such that the law of emergence can not be appropriately for- mulated if one uses proper invariant volume. The deep connection between the first law of thermody- namics and the law of emergence, motivate us to explore the status of the first law in a non-flat uni- verse when one uses proper invariant volume. We have shown that the first law of thermodynamics, dE = T dS + WdV cannot be formulated properly for a non-flat universe using proper invariant vol- ume. We have also investigated the status of the first law of the form − dE = T dS in a non-flat uni- verse. We have shown that the energy change dE V within the horizon and the outward energy flux are not equivalent to each other in a non-flat universe when we use the proper invariant volume. We fur- ther point out that the consistency between the above two forms of the first law claimed in will hold only with the use of the real volume of the horizon. The failure in formulating the first law of thermo- dynamics with the use of invariant volume shows that the invariant volume will be a poor choice to describe any thermodynamic process in cosmology. This work has been done in collaboration with Ha- reesh Thuruthipilly, and P.B. Krishna. Dynamical system analysis and thermal evolution of the causal dissipative model The dynamical system behaviour and thermal evo- lution of a homogeneous and isotropic dissipative universe are analyzed. The dissipation is driven by the bulk viscosity and the evolution of bulk viscous pressure is described using the full causal Israel- Stewart theory. We find that for s = 1 / 2, the model possesses a prior decelerated epoch,which is unsta- ble and a stable future accelerated epoch. From the thermodynamic analysis, we have verified that the local as well as the generalised second law of thermodynamics are satisfied throughout the evo- lution of the universe. We also show that the con- vexity condition is satisfied at the end stage of the universe, which implies an upper bound to the evo- lution of the entropy. For, the case s < 1 / 2 is ruled out since it does not predict the conventional evolu- tionary stages of the universe. On the other hand, the case s > 1 / 2 does imply a prior decelerated and a late de Sitter epochs, but both of them are unstable fixed points. The thermal evolution cor- responding to the same case implies that GSL is satisfied at both the epochs but convexity condi- tion is violated by both, so that entropy growth is unbounded. Hence for s > 1 / 2, the model does not