Conveners
Ph.D. Students Workshop
- Tomasz Denkiewicz (Szczecin University)
Ph.D. Students Workshop
- Adam Balcerzak
The GRAVITY Collaboration achieved the remarkable detection of the orbital precession of the S2 star around the Galactic Centre supermassive black hole, providing yet another proof of the validity of the General Relativity. The departure from the Schwarzschild precession is encoded in the parameter $f_{\rm SP}$ which multiplies the predicted general relativistic precession. Such a parameter...
The late universe contains a wealth of information about fundamental physics and gravity, wrapped up in non-Gaussian fields. To make use of as much information as possible it is necessary to go beyond power spectra. Rather than going to higher order N-point correlation functions, this talk will demonstrate that the probability distribution function (PDF) of spheres in the matter field (a...
We reconstruct the Hubble function using late-time cosmological data sets and use it to draw out Horndeski theories that are fully anchored on the expansion history. We discuss various formalisms for the inversion of the modified Friedmann equations and complement this with the reconstructed Hubble data to obtain predictive constraints on the Horndeski potentials and the dark energy equation of state.
Screening mechanisms in Extended Theories of Gravity (ETGs) are essential to make theories able to pass Solar System constraints and, at the same time, possibly driving the accelerated expansion of the Universe at large scales (thus behaving as dark energy). In our work, we have considered an ETG belonging to the family of Degenerate High-Order Scalar-Tensor theories (DHOST) and characterized...
The non-product spectral geometry may lead to models that possess features characteristic to bimetric gravity theories. Starting from the pair of Friedmann–Lemaître–Robertson–Walker metrics on the product geometry and mildly modifying the Dirac operator we end up with a class of models that have a nontrivial interacting potential term, and their solutions are stable for several cosmological...
General relativity has been very successful in describing gravity. However, cosmological observations such as the dark sector of the universe, the value of the cosmological constant, and the Hubble constant give indications to new physics. This might be explained by modified theories of gravity. What has often been overlooked is that general relativity has different equivalent descriptions....
The polynomial affine gravity is an alternative model to describe gravitational interactions using the affine connection as the sole mediator. The action is built using a sort of dimensional analysis technique and preserving the invariance under diffeomorphisms. Interestingly, the coupling constants are dimensionless, which is desirable from a quantum field stand point. In $3+1$ dimensions...
From the study of relativistic dynamics of fluids out of equilibrium in a curved background, a new cosmological framework, dubbed Ricci Cosmology, has emerged in which linear terms in Ricci scalar and Ricci tensor lead to modifications of the equilibrium pressure in the energy-momentum tensor in the fluids filling the Universe. The coefficients in front of such terms are called second order...
Abstract
After the recent detection of GW170817, the most interesting terms of Horndeski theory were severely
constrained. Nevertheless, the analog of Horndeski theory in the Teleparallel Gravity framework is far richer in structure since the extra term in the Lagrangian, Ltele emerges.
As a result, the terms that were eliminated in standard Horndeski theory could, in this case,...
Scalar Tensor Vector Gravity (STVG) is a metric theory of gravity with dynamical scalar fields and a massive vector field introduced in addition to the metric tensor. In the weak field approximation STVG modifies the Newtonian acceleration with a Yukawa like repulsive term due to Maxwell-Proca type Lagrangian. This associates matter with a fifth force and a modified equation of motion.STVG has...
CDT is a numerical approach to quantum gravity which attempts to describe our Universe with the help of Regge Calculus and Path Integral formalism. The study of the past years revealed the rich phase-diagram of the model, which contains a physical de Sitter phase with higher order phase-transitions on its boarders. Recently we added scalar fields to the model. The classical fields were used as...
Interpreting the cosmological constant ($\Lambda$) as the vacuum energy, and under a minimum amount of assumptions, leads to a deformation in the vicinity of a black hole and a new Kerr–de Sitter solution. The new Kerr–de Sitter solution is a more straightforward and has richer geometric structure than the original one. Interestingly, there exist minimum ($M_{min}$) and maximum ($M_{min}$)...
