Cosmological model with time varying deceleration parameter in F(R, G) gravity

In this paper, we study the dynamical behaviour of the universe in the F (R, G) theory of gravity, where R and G respectively denote the Ricci scalar and Gauss-Bonnet invariant. Our wide analysis encompasses the energy conditions, cosmographic parameters, Om(z) diagnostic, stability and the viability of reconstructing the referred model through a scalar field formalism. The model obtained here shows the quintessence like behaviour at late times.

Limiting fluctuations in quantum gravity to diffeomorphisms

Within the background field formalism of quantum gravity, I show that if the quantum fluctuations are limited to diffeomorphic gauge transformations rather than the physical degrees of freedom, as in conventional quantum field theory, all the quantum corrections vanish on shell and the effective action is equivalent to the classical action. In principle, the resulting theory is finite and unitary, and requires no renormalization. I also show that this is the unique parameterization that renders the path integral independent of the on-shell condition for the background field, a form of background independence. Thus, a connection is established between background independence and renormalizability and unitarity.

A sharp transition in quantum chaos and thermodynamics of mass deformed SYK model

We review our recent work [1] where we studied the chaotic property of the two coupled Sachdev-Ye-Kitaev systems exhibiting a Hawking-Page like phase transition. By computing the out-of-time-ordered correlator in the large NN limit by using the bilocal field formalism, we found that the chaos exponent of this model shows a discontinuous fall-off at the phase transition temperature. Hence in this model the Hawking-Page like transition is correlated with a transition in chaoticity, as expected from the relation between a black hole geometry and the chaotic behavior in the dual field theory.

Structural and decay properties of nuclei appearing in the α-decay chains of 296,298,300,302,304120 within the relativistic mean field formalism

An extensive study of [Formula: see text]-decay half-lives for various decay chains of isotopes of [Formula: see text] is performed within the axially deformed relativistic mean-field (RMF) formalism by employing the NL3, NL3[Formula: see text], and DD-ME2 parameter set. The structural properties of the nuclei appearing in the decay chains are explored. The binding energy, quadrupole deformation parameter, root-mean-square charge radius, and pairing energy are calculated for the even–even isotopes of [Formula: see text], which are produced in five different [Formula: see text]-decay chains, namely, [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]. A superdeformed prolate ground state is observed for the heavier nuclei, and gradually the deformation decreases towards the lighter nuclei in the considered decay chains. The RMF results are compared with various theoretical predictions and experimental data. The [Formula: see text]-decay energies are calculated for each decay chain. To determine the relative numerical dependency of the half-life for a specific [Formula: see text]-decay energy, the decay half-lives are calculated using four different formulas, namely, Viola–Seaborg, Alex–Brown, Parkhomenko–Sobiczewski and Royer for the above said five [Formula: see text]-decay chain. We notice a firm dependency of the half-life on the [Formula: see text]-decay formula in terms of [Formula: see text]-values for all decay chains. Further, this study also strengthens the prediction for the island of stability in terms of magic number at the superheavy valley in the laboratories.