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different background Cosmological models, namely, the vanilla LCDM model, non-
interacting DE with constant and evolving EoS, and interacting dark sectors.
6. An EFT framework was developed to study NBD initial states respecting the recently
proposed Swampland Criteria and Trans-Planckian Censorship Conjecture that put
together stringent theoretical constraints on slow roll inflation. Reflections on future
CMB missions have also been investigated.
7. Possible constraints on invisible sectors (Dark Matter, Neutrino) and their interactions
from Cosmological observations have been searched for. In particular, light scale sub-
MeV thermal DM model and its annihilation into Neutrinos during the CMB era have
been analyzed from the Planck18 data.

We would like to take up the following projects in the coming years:

1. To find out possible signatures of evolving DE as well as DE perturbations in future
observations, in particular, in intermediate and high redshift observations like SKA,
TMT, eLISA etc via evolution of EoS, estimation of cosmic shear, sound speed of DE
etc.
2. To explore Neutrino Cosmology in details by finding out observational constraints on
its interactions with some other invisible sectors and to forecast on upcoming missions
like 21 cm observations.
3. To develop consistent EFT of LSS/ Redshift Space Distortion; and to corroborate that
with EFT of inflation followed by confrontation with data.
4. To do a forecast analysis for upcoming CMB missions and missions like EINSTEIN
telescope for tensor non-Gaussianities and mixed correlators.
5. To propose and analyze the next generation CMB features and to investigate for
prospects of detectability.

(Supratik Pal)

Graviytation and Cosmology

Effect of time crystal like behavior for higher derivative (in particular quadratic) gravity and
its effect in cosmology are being investigated. Non-trivial perturbative, stable ground states
with time or spatial crystal-like behaviour are shown to exist. Propagation of matter in this type
of non-uniform background is being investigated.

Related papers :

• Non-trivial ground state for gravitational perturbation in quadratic gravity,
(communicated) Authors:Sumanta Chakraborty, Subir Ghosh; arXiv:2001.04680 gr-
qc hep-th quant-ph

In the context of analogue gravity it has been shown, using Hamiltonian-Jacobi scheme, that
metamateria-normal dielectric composite can induce Hawking temperature at the junction. This
work will be extended this work using Bogoliubov approach and also utilise different stuctures
of effective metric scenario.

Related papers :

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