IF Colloquium No.26 – SOME WORDS ABOUT GRAVITATIONAL ENTROPY AND PENROSE’S WEYL CURVATURE CONJECTURE

📣 IF invites you to the No.26 IF Colloquium (Online Seminar Series)
——————————————–

📌 Title: ” SOME WORDS ABOUT GRAVITATIONAL ENTROPY AND PENROSE’S WEYL CURVATURE CONJECTURE ”

📌 Speaker : Daniele Gregoris, (Ph.D. in Physics, Stockholm University within the Erasmus Mundus program, Sweden), Associate Professor at Jiangsu University of Science and Technology, China

📌 Abstract : My seminar will be divided into two parts exploring the notion of gravitational entropy in cosmology and in black hole physics, respectively. First of all, I will critically inspect Penrose’s conjecture according to which the gravitational entropy of a cosmological model should be quantified via its Weyl curvature, with the Clifton-Ellis-Tavakol entropy being one specific realization of this proposal. In fact, I will show that in some exact inhomogeneous and anisotropic cosmological models in general relativity, the Clifton-Ellis-Tavakol gravitational entropy is increasing in time despite the decrease of the magnitude of the Weyl curvature: this is possible thanks to the growth of the spacetime shearing effects. The matter content driving the dynamics of this model comes in the form of a massless chameleon scalar field. The values of the free parameters entering the metric tensor we work with are those consistent with the holographic principle and the second law of thermodynamics. I will mention the possible formation of some primordial astrophysical structures, like the Large Quasar Groups, in this class of models as suggested by the growth of gravitational entropy, and whose existence cannot be accounted for by standard perturbation techniques over a Friedman background. In the second part, I will discuss an appropriate combination of curvature scalars fully based on the Weyl curvature which can serve as density of gravitational entropy reproducing the celebrated Hawking-Bekenstein area law for black holes. I will emphasize that our formalism, unlike previous ones, works well both for empty space black holes and electrically charged ones, e.g. regardless the energy density outside their horizon. Then, I will interpret black hole entropy as a manifestation of tidal effects, putting our result in the perspective of modified gravity theories as well. The talk will be based on Phys. Rev. D 102, 023539 (2020) & PRD 105, 104017 (2022).

📌 Keywords : Gravitational Entropy, Penrose’s Weyl curvature conjecture

📌 IF Channel : https://www.youtube.com/watch?v=U0UtWmg3_NM

——————————————–
#Cosmology #Physics #TheoreticalPhysics #IFNU #PhysicsNaresuan #IFColloquium