In this talk, I explore the determination of an event horizon candidate for slowly evolving dynamical black holes (BHs). Such a candidate has been termed as a slowly evolving null surface (SENS). Such surfaces are of interest because they coincide with the event horizon and are causal, unlike apparent horizons. Moreover, known laws of BH mechanics can be established for these slowly evolving...
In this talk, I will define the photon surface conditions using Cartan scalars within an invariant spin frame which offers a comprehensive description of the local spacetime geometry. By employing this approach, one can gain novel insights into the geometry and dynamics of photon surfaces, independent of the global spacetime structure. I will first discuss the photon surface conditions in a...
Abstract:
Marginally outer trapped surfaces (MOTS) are surfaces from which outgoing light rays neither converge nor diverge. In recent years they have been found to be a key tool for understanding black hole geometries. In particular, the stability operator provides information as to whether the MOTS bounds a trapped region. This study investigates the eigenvalue problem associated with the...
The null-surface formulation (NSF) of general relativity is equivalent to standard general relativity but uses null surfaces instead of a metric or a connection. The NSF, itself, exists in two distinct but mathematically equivalent versions: (a) Future-directed light rays leave a spacetime point and intersect null-infinity. The resulting light-cone cut encodes the properties of the spacetime;...
We are interested in the static spherically symmetric geometries in F(T) teleparallel gravity with physical importance. We have found the general forms of the spherically symmetric frame with zero curvature, metric compatible and non-zero spin connection. We then analyse the antisymmetric field equations (the solutions splitting into two separate cases), and derive and analyse the resulting...
The construction of an averaged theory of gravity based on Einstein's General Relativity is challenging due in one part to the difficulty in defining a mathematically precise covariant averaging procedure for tensor fields over differentiable manifolds. Even if one is able to address the first problem, a second problem has to deal with the non-linear nature of the gravitational field...
Is GR open to EDI concepts? Are relativists considering inclusivity in their research and teaching? In this talk, I will try to draw a picture of GR with an EDI perspective and show my students' perspective as first-time relativity learners.
Black hole evaporation is perhaps the most commonly studied way for a black hole to end. However there is another way that is both entirely classical and whose consequences have been observed hundreds of times by LIGO/VIRGO. One can sensibly understand black hole mergers as representing the formation of a new black hole followed by the destruction of the two original ones. The destruction...
I will present a study on the quantum gravitational collapse of spherically symmetric pressureless dust. Using an effective equation derived from a polymer quantization in the connection-triad phase space variables of general relativity, numerics show, for a variety of initial dust configurations, that (i) trapped surfaces form and disappear as an initially collapsing density profile evolves...
Developing a Theory of Everything has been a long-standing, yet elusive goal. Even so, approaches exist that may be able to remedy this. In this presentation, we will explore one such approach: The Newton-Schrödinger System. Presented here will be numerical analysis on how such a system behaves in the domain of a circle with various Gaussian initial conditions, as well as the motion of test...
We derive a “classical-quantum” approximation scheme for a broad class of bipartite quantum systems from fully quantum dynamics. In this approximation, one subsystem evolves via classical equations of motion with quantum corrections, and the other subsystem evolves quantum mechanically with equations of motion informed by the evolving classical degrees of freedom. Using perturbation theory, we...
We study the classical-quantum (CQ) hybrid dynamics of homogeneous cosmology from a Hamiltonian perspective where the classical gravitational phase space variables and matter state evolve self-consistently with full backreaction. We compare numerically the classical and CQ dynamics for isotropic and anisotropic models, including quantum scalar-field induced corrections to the Kasner exponents....
It is widely believed that quantum gravity should be background independent. Perhaps the most radical way to realize this is to imagine a quantum theory in which the abode of gravity, that is to say, the fabric of spacetime itself, becomes an emergent, rather than an inherent, entity. Group field theories constitute a concrete attempt at such a formulation of quantum gravity. However, in such...
In this talk, I will show how cosmological physics emerge from the collective behavior of spacetime quanta within the Group Field Theory (GFT) approach to quantum gravity. In particular, I will review key aspects of the resulting quantum cosmological physics, including the resolution of the initial singularity into a quantum bounce, the presence of a purely quantum geometric inflationary...
Group field theory (GFT) is a background independent approach to quantum gravity that exhibits a rich phenomenology in the cosmological setting. In this talk we will explore a recent proposal that reconstructs an effective metric directly from the quantum theory. This is achieved by relating metric components to the expectation values of novel operators that are based on symmetries of the GFT...
I will attempt a brief overview of a few ideas about quantum gravity and what they might reveal about a final theory.
I will introduce a dynamical system formulation for inhomogeneous LRS-II spacetimes using the covariant 1+1+2 decomposition approach, that we recently proposed in 2404.01161. Our approach describes the LRS-II dynamics from the point of view of a comoving observer. Promoting the covariant radial derivatives of the covariant dynamical quantities to new dynamical variables and utilizing the...
We investigate the exponential 𝑓 (𝑄) symmetric teleparallel gravitation, namely 𝑓 (𝑄) = 𝑄 + 𝛼𝑄_0(1 − 𝑒^(−𝛽√𝑄/𝑄_0)) using ME-GADGET code to probe the structure formation with box sizes 𝐿_box = 10/100 Mpc/ℎ and middle resolution 𝑁^1/3 = 512. To reproduce viable cosmology within the aforementioned modified gravity theory, we first perform Markov Chain Monte Carlo (MCMC) sampling on...
