A5010870214- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- Noncommutative and Quantum Gravity Theories
- Computational Physics and Python Applications
- Advanced Differential Geometry Research
- Solar and Space Plasma Dynamics
- Relativity and Gravitational Theory
- Astronomy and Astrophysical Research
- Particle physics theoretical and experimental studies
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Nonlinear Waves and Solitons
- Advanced Thermodynamics and Statistical Mechanics
- Scientific Research and Discoveries
- Astro and Planetary Science
- Statistical Mechanics and Entropy
- Model Reduction and Neural Networks
- Meteorological Phenomena and Simulations
- Fractal and DNA sequence analysis
Institute for Nuclear Research and Nuclear Energy
2015-2025
Bulgarian Academy of Sciences
2015-2025
University of Sheffield
2024
Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Gran Sasso
2022
University of L'Aquila
2022
Istituto Nazionale di Fisica Nucleare
2022
Sofia University "St. Kliment Ohridski"
2010-2012
Joint Institute for Nuclear Research
2012
Abstract The unification of quantum mechanics and general relativity has long been elusive. Only recently have empirical predictions various possible theories gravity put to test, where a clear signal properties is still missing. dawn multi-messenger high-energy astrophysics tremendously beneficial, as it allows us study particles with much higher energies travelling longer distances than in terrestrial experiments, but more progress needed on several fronts. A thorough appraisal current...
Baryon acoustic oscillations (BAO) involve measuring the spatial distribution of galaxies to determine growth rate cosmic structures. We derive constraints on cosmological parameters from 17 uncorrelated BAO measurements that were collected 333 published data points in effective redshift range 0.106 ≤ z 2.36. test correlation subset using a random covariance matrix. The Λ cold dark matter (ΛCDM) model fit yields Ω m = 0.261 ± 0.028 and 0.733 0.021. Combining with Cosmic Chronometers data,...
A possible interaction between cold dark matter and energy, corresponding to a well-known interacting energy model discussed in the literature within context of resolving Hubble tension, has been investigated. We put constraints on it novel way, by creating new likelihoods with an analytical marginalization over parameter $H_0$, sound horizon $r_d$, supernova absolute magnitude $M_B$. Our aim is investigate impacts coupling model, $\xi$, equation state $w$ density $\Omega_{m,0}$. The...
The $H_0$ tension and the accompanying $r_d$ are a hot topic in current cosmology. In order to remove degeneracy between Hubble parameter sound horizon scale from Baryon Acoustic Oscillations (BAO) datasets, we redefine likelihood by marginalizing over $H_0 \cdot r_d$ then perform full Bayesian analysis for different models of dark energy (DE). We find that our uncalibrated early or late physics {datasets cannot} constrain DE properly without further assumptions. By adding type IA supernova...
We study the two-body problem in context of both dark energy and post-Newtonian modifications. In this unified framework, we demonstrate that plays role a critical period with T Λ = 2 π / c √Λ ≈ 60 Gyr. also show ratio between orbital periods naturally emerges from Kretschmann scalar, which is quadratic curvature invariant characterizing all binary systems effectively represented by de Sitter-Schwarzschild space-time. The suitability system constraining determined its Keplerian period, K , ....
We present a comprehensive comparison of different Markov Chain Monte Carlo (MCMC) sampling methods, evaluating their performance on both standard test problems and cosmological parameter estimation. Our analysis includes traditional Metropolis-Hastings MCMC, Hamiltonian (HMC), slice sampling, nested as implemented in dynesty, PolyChord. examine samplers through multiple metrics including runtime, memory usage, effective sample size, accuracy, testing scaling with dimension response to...
In this article, we continue our investigation on how the electromagnetic waves propagate in Friedman–Lemaître–Robertson–Walker spacetime. Unlike standard approach, which relies null geodesics and geometric optics approximation, derive explicit solutions for expanding spacetime examine their implications cosmological observations. particular, analysis reveals potential modifications to luminosity distance formula. Its effect other parameters, e.g., amount of cold dust matter Universe, is...
We present a comprehensive comparison of different Markov chain Monte Carlo (MCMC) sampling methods, evaluating their performance on both standard test problems and cosmological parameter estimation. Our analysis includes traditional Metropolis–Hastings MCMC, Hamiltonian (HMC), slice sampling, nested as implemented in dynesty, PolyChord. examine samplers through multiple metrics including runtime, memory usage, effective sample size, accuracy, testing scaling with dimension response to...
Although finding numerically the quasinormal modes of a nonrotating black hole is well-studied question, physics problem often hidden behind complicated numerical procedures aimed at avoiding direct solution spectral system in this case. In article, we use exact analytical solutions Regge-Wheeler equation and Teukolsky radial equation, written terms confluent Heun functions. both cases, obtain from condition The frequencies are compared with ones already published by Andersson other authors....
Extended gravity is widely constrained in different astrophysical and astronomical systems. Since these systems are based on scales it not trivial to get a combined constraint that phenomenology. Here, for the first time (to best of our knowledge), we combine constraints f(R) from late Cosmology orbital motion stars around galactic center. models give potentials tested directly The cosmological data set includes type Ia supernova baryon acoustic oscillations. For star center use published...
We investigated a possible interaction between cold dark matter and energy, corresponding to well-known interacting energy model discussed in the literature within context of resolving Hubble tension. put constraints on it novel way, by creating new likelihoods with an analytical marginalization over parameter H 0 , sound horizon r d supernova absolute magnitude M B . Our aim is investigate impacts coupling model, ξ equation state w density Ω m, The late-time cosmological probes used our...
The Hubble tension in cosmology is not showing signs of alleviation and thus, it important to look for alternative approaches it. One such example would be the eventual detection a time delay between simultaneously emitted high-energy low-energy photons gamma-ray bursts (GRB). This signal possible Lorentz Invariance Violation (LIV) case non-zero quantum gravity delay, can used study as well. In this work, we use various astrophysical datasets (BAO, Pantheon Plus CMB distance priors),...
It has been theorized that dynamical dark energy (DDE) could be a possible solution to Hubble tension. To avoid degeneracy between parameter H0 and sound horizon scale rd, in this article, we use their multiplication as one c/H0rd, it infer cosmological parameters for 6 models—ΛCDM 5 DDE parametrizations—the Chevallier–Polarski–Linder (CPL), the Barboza–Alcaniz (BA), low correlation (LC), Jassal–Bagla–Padmanabhan (JBP) Feng–Shen–Li-Li models. We choose dataset treats combination parameter,...
Abstract Putting constraints on a possible Lorentz Invariance Violation (LIV) from astrophysical sources such as gamma-ray bursts (GRBs) is essential for finding evidences of new theories quantum gravity (QG) that predict an energy-dependent speed light. This search has its own difficulties, so usually, the effect cosmological model understudied, with default being fixed-parameters ΛCDM.In this work, we use various datasets to study number dark energy models LIV constraints. To end, combine...
The Heun functions have wide application in modern physics and are expected to succeed the hypergeometrical physical problems of 21st century. numerical work with those functions, however, is complicated requires filling gaps theory also, creating new algorithms able them efficiently. We propose a algorithm for solving system two nonlinear transcendental equations complex variables based on Müller algorithm. particularly useful systems featuring them, gives distinctly better results than...
Recently, a model of modified gravity plus single scalar field was proposed, in which the couples both to standard Riemannian volume form given by square root determinant metric, as well another non-Riemannian terms an auxiliary maximal rank antisymmetric tensor gauge field. This provides exact unified description dark energy (via dynamically generated cosmological constant) and matter (as “dust” fluid due hidden nonlinear Noether symmetry). In this paper, we test against Supernovae type Ia...
We consider the propagation of electromagnetic waves in Friedman – Lemaître Robertson Walker metric. The exact solutions for plane and spherical wave are written down. corresponding redshift, amplitude change, dispersion discussed. also speculate about connection equation to Klein–Gordon equation.
We consider the cosmological application of a (variant of) relatively newly proposed model \cite{1609.06915} unifying inflation, dark energy, matter, and Higgs mechanism. The was originally defined using additional non-Riemannian measures but it can be reformulated into effective quintessential energy matter. Here we demonstrate numerically that is capable describing entire Universe evolution in seamless way, this requires some revision setup. main reason there strong friction model, feature...
We propose a new algorithm for solving system of two nonlinear transcendental equations with complex variables based on the Muller algorithm. The two-dimensional is tested systems different type and found to work comparably Newton's method Broyden's in many cases. particularly useful featuring Heun functions whose complexity may make already known algorithms not efficient enough or working at all. In those specific cases, gives distinctly better results than other methods. As an example its...