A5038303597- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Galaxies: Formation, Evolution, Phenomena
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Dark Matter and Cosmic Phenomena
- Relativity and Gravitational Theory
- Advanced Differential Geometry Research
- Particle physics theoretical and experimental studies
- Astronomy and Astrophysical Research
- Pulsars and Gravitational Waves Research
- Computational Physics and Python Applications
- Scientific Computing and Data Management
- Earth Systems and Cosmic Evolution
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Risk and Portfolio Optimization
- Supply Chain Resilience and Risk Management
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- Financial Markets and Investment Strategies
- Complex Systems and Time Series Analysis
- Stochastic processes and financial applications
- Text and Document Classification Technologies
- Quantum Chromodynamics and Particle Interactions
Istanbul Technical University
2015-2024
Üsküdar University
2022
The Abdus Salam International Centre for Theoretical Physics (ICTP)
2013-2020
Birla Institute of Technology and Science, Pilani
2018
Istanbul Bilgi University
2018
Koç University
2011-2015
Ege University
2009-2010
We present a further observational analysis of the ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{s}}\mathrm{CDM}$ model proposed in Akarsu et al. [Phys. Rev. D 104, 123512 (2021)]. This is based on recent conjecture suggesting Universe has transitioned from anti--de Sitter vacua to de (viz., cosmological constant switches sign negative positive), at redshift ${z}_{\ifmmode\dagger\else\textdagger\fi{}}\ensuremath{\sim}2$, inspired by graduated dark energy 101, 063528 (2020)]. was previously...
This paper introduces the class of omnipotent dark energy (DE) models characterized by nonmonotonic densities that are capable attaining negative values with corresponding equation state parameters featuring phantom divide line (PDL) crossings and singularities. These nontrivial features phenomenologically motivated findings previous studies reconstruct cosmological functions from observations, success extensions $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$, whose actual or effective DE...
Abstract In this work, we investigate a two-parameter extension of the Λ s CDM model, as well ΛCDM model for comparison, by allowing variations in effective number neutrino species ( N eff ) and their total mass (∑ m ν ). Our motivation is twofold: (i) to examine whether framework retains its success fitting data addressing major cosmological tensions, without suggesting need deviation from standard particle physics, (ii) determine indicate new physics that could potentially address either...
In this paper, we consider a simple form of expansion history Universe referred to as the hybrid law - product power-law and exponential type functions. The ansatz by construction mimics de Sitter cosmologies special cases but also provides an elegant description transition from deceleration cosmic acceleration. We point out Brans-Dicke realization under consideration. construct potentials for quintessence, phantom tachyon fields, which can give rise in general relativity. investigate...
We study the cosmological constant ($\Lambda$) in standard $\Lambda$CDM model by introducing \textit{graduated dark energy} (gDE) characterised a minimal dynamical deviation from null inertial mass density of $\Lambda$ form $\rho_{\rm inert}\propto \rho^{\lambda}<0$ with $\lambda<1$ being ratio two odd integers, for which its energy $\rho$ dynamically takes negative values finite past. For large $\lambda$, it creates phenomenological described smooth function that approximately describes...
Inspired by the recent conjecture originated from graduated dark energy that Universe has recently transitioned anti-de Sitter vacua to de vacua, we extend $\Lambda$CDM model a cosmological constant ($\Lambda_{\rm s}$) switches sign at certain redshift $z_\dagger$, and call this $\Lambda_{\rm s}$CDM. We discuss construction theoretical features of find out that, when consistency s}$CDM with CMB data is ensured, (i) $z_\dagger\gtrsim1.1$ implied condition monotonically expands, (ii) $H_0$...
We consider the simplest anisotropic generalization, as a correction, to standard $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model, by replacing spatially flat Robertson-Walker metric Bianchi type-I metric, which brings in new term ${\mathrm{\ensuremath{\Omega}}}_{\ensuremath{\sigma}0}{a}^{\ensuremath{-}6}$ (mimicking stiff fluid) average expansion rate $H(a)$ of Universe. From Hubble and Pantheon data, relevant late Universe ($z\ensuremath{\lesssim}2.4$), we obtain constraint...
Abstract The cosmological dark sector remains an enigma, offering numerous possibilities for exploration. One particularly intriguing option is the (non-minimal) interaction scenario between matter and energy. In this paper, to investigate scenario, we have implemented Binned Gaussian model-independent reconstructions kernel alongside equation of state; while using data from BAOs, Pantheon+ Cosmic Chronometers. addition reconstruction process, conducted a model selection analyze how our...
$\Lambda$CDM tensions are by definition model dependent; one sees anomalies through the prism of $\Lambda$CDM. Thus, progress towards tension resolution necessitates checking consistency to localise missing physics either in redshift or scale. Since Universe is dynamical and a proxy for time, it imperative first perform checks involving redshift, then scale, as next steps settle ``systematics versus new physics" debate foster informed building. We present review hierarchy assumptions...
In this study, we first establish that gravity models incorporating matter-related terms, such as $f({\mathcal{L}}_{\mathrm{m}})$, $f({g}_{\ensuremath{\mu}\ensuremath{\nu}}{T}^{\ensuremath{\mu}\ensuremath{\nu}})$, and $f({T}_{\ensuremath{\mu}\ensuremath{\nu}}{T}^{\ensuremath{\mu}\ensuremath{\nu}})$, into the usual matter Lagrangian density ${\mathcal{L}}_{\mathrm{m}}$, are equivalent to general relativity (GR) with nonminimal interactions. Through redefinition...
We investigate the dynamics and cosmological implications of dark energy (DE), modeled as a scalar field with hyperbolic tangent potential that induces smooth shift in effective constant (CC), encompassing transitions such AdS-dS, 0-dS, dS-dS, mirror AdS-dS particular case aligned $\Lambda_{\rm s}$CDM scenario. In our construction, phantom negative kinetic term drives bottom-up transition from an AdS-like vacuum at high redshifts to dS-like low redshifts, thereby providing physical...
We propose a modified theory of gravitation constructed by the addition term $f({T}_{\ensuremath{\mu}\ensuremath{\nu}}{T}^{\ensuremath{\mu}\ensuremath{\nu}})$ to Einstein-Hilbert action, and elaborate particular case $f({T}_{\ensuremath{\mu}\ensuremath{\nu}}{T}^{\ensuremath{\mu}\ensuremath{\nu}})=\ensuremath{\alpha}({T}_{\ensuremath{\mu}\ensuremath{\nu}}{T}^{\ensuremath{\mu}\ensuremath{\nu}}{)}^{\ensuremath{\eta}}$, where $\ensuremath{\alpha}$ $\ensuremath{\eta}$ are real constants, dubbed...
Deviations from the predictions of general relativity due to energy-momentum squared gravity (EMSG) are expected become pronounced in high density cores neutron stars. We derive hydrostatic equilibrium equations EMSG and solve them numerically obtain star mass-radius relations for four different realistic state. use existing observational measurements masses radii stars constrain free parameter, $\ensuremath{\alpha}$, that characterizes coupling between matter spacetime EMSG. show...
Using the fact that comoving angular diameter distance to last scattering surface is strictly constrained almost model independently, we show that, for any agreeing with standard $\mathrm{\ensuremath{\Lambda}}$CDM on its background dynamics at $z\ensuremath{\sim}0$ and size of sound horizon scattering, deviations Hubble radius from one must be a member set admissible wavelets. The family models characterized by this framework also offers nontrivial oscillatory behaviors in various functions...
ABSTRACT Hubble constant H0 and weighted amplitude of matter fluctuations S8 determinations are biased to higher lower values, respectively, in the late universe with respect early values inferred by Planck collaboration within flat ΛCDM cosmology. If these anomalies physical, that is, not due systematics, they naively suggest decreases increases effective redshift. Here, subjecting density today Ωm a prior, corresponding combination CMB BAO data, we perform consistency test Planck-ΛCDM...