198 citations · 1.8k across the 47 of their papers we have counts for
49 papers
Gravitating sources with zero energy density in cosmology
Özgür Akarsu, Cihad Kıbrıs, Burcu Öztürk +1
A cosmological source can have identically zero comoving energy density and still gravitate through its pressure. This differs from an energy density passing through zero at an iso…
Reconstructing sign-switching dark energy histories: Scalar-field regularity, conditional potential comparison, and representative dynamics
Shahnawaz A. Adil, Özgür Akarsu, Mariam Bouhmadi-López +3
Phenomenologically similar sign-switching dark-energy histories need not have comparable scalar-field realizations. We reconstruct minimally coupled scalars with fixed kinetic sign…
Action-selected currents and a singular conservation closure in two-fluid energy--momentum-squared cosmology
Özgür Akarsu, Bilal Bulduk, Nihan Katırcı
In multi-fluid, matter-type gravity, the Bianchi identity constrains the divergence of the total effective stress tensor but does not, by itself, determine the currents assigned to…
Defocusing dark energy: Raychaudhuri diagnostics beyond and the phantom divide
Özgür Akarsu, Antonio De Felice, N. Merve Uzun
In general relativity, cosmic acceleration is timelike defocusing of the comoving congruence and requires a negative total active gravitational mass density, $\mathcal{M}_{\rm tot}…
Background-level reconstruction of scalar-field potentials from dark-energy histories and comparison with analytic potential families
Shahnawaz A. Adil, Miguel A. Zapata, Özgür Akarsu +1
We present a unified \emph{background-level} framework that maps a prescribed late-time dark-energy density history onto an effective scalar-field description in a…
Probing dynamical dark energy with late-time data: Evidence, tensions, and the limits of the CDM framework
Tengpeng Xu, Suresh Kumar, Yun Chen +2
We test the dynamical dark-energy CDM (CPL) framework against CDM using CMB anisotropies and lensing together with DESI DR2, SDSS-IV, transverse/angular BAO (BAOtr), and…
k-inflation: Non-separable case meets ACT measurements
Tahere Fallahi Serish, Seyed Ali Hosseini Mansoori, Fereshteh Felegary +2
We investigate a non-separable subset of -essence in which the kinetic and potential sectors interact through an coupling, implemented via a potential-dependent prefac…
Linear matter density perturbations in the CDM model: Examining growth dynamics and addressing the tension
Özgür Akarsu, Arman Çam, Evangelos A. Paraskevas +1
We investigate linear matter density perturbations in the CDM, in which the is replaced by late-time () mirror AdS-dS transition, resulting in distinct growt…
Mapping the CDM scenario to modified gravity: Effects on structure growth rate
Mateus S. Souza, Ana M. Barcelos, Rafael C. Nunes +2
The concept of a rapidly sign-switching cosmological constant, interpreted as a mirror AdS-dS transition in the late universe and known as the CDM, has significantly imp…
Unexplored regions in teleparallel gravity: Sign-changing dark energy density
Ozgur Akarsu, Bilal Bulduk, Antonio De Felice +2
While gravity has shown considerable potential in addressing cosmological tensions, we explore previously overlooked solution spaces that hold further promise. We examine th…
Exploring new physics in the late Universe's expansion through non-parametric inference
Miguel A. Sabogal, Özgür Akarsu, Alexander Bonilla +2
In this study, we investigate deviations from the Planck-CDM model in the late universe () using the Gaussian Processes method, with minimal assumptions. Our goa…
CDM cosmology: Alleviating major cosmological tensions by predicting standard neutrino properties
Anita Yadav, Suresh Kumar, Cihad Kibris +1
We investigate a two-parameter extension of the CDM model by allowing variations in the effective number of neutrino species and their total mass $\sum m_ν…
Cosmological constraints on CDM scenario in a type II minimally modified gravity
Özgür Akarsu, Antonio De Felice, Eleonora Di Valentino +5
The idea of a rapid sign-switching cosmological constant (mirror AdS-dS transition) in the late universe at , known as the CDM model, has significantly improve…
CDM cosmology from a type-II minimally modified gravity
Özgür Akarsu, Antonio De Felice, Eleonora Di Valentino +5
We integrate CDM, a promising scenario for alleviating cosmological tensions, into VCDM, a type-II minimally modified gravity. This promotes the scenario to a fully pred…
Transition dynamics in the CDM model: Implications for bound cosmic structures
Evangelos A. Paraskevas, Arman Cam, Leandros Perivolaropoulos +1
We explore the predictions of CDM, a novel framework suggesting a rapid anti-de Sitter (AdS) to de Sitter (dS) vacua transition in the late Universe, on bound cosmic str…
CDM Tensions: Localising Missing Physics through Consistency Checks
Özgür Akarsu, Eoin Ó Colgáin, Anjan A. Sen +1
CDM tensions are by definition model dependent; one sees anomalies through the prism of CDM. Thus, progress towards tension resolution necessitates checking the consistency o…
Quadratic energy-momentum squared gravity: constraints from big bang nucleosynthesis
Ozgur Akarsu, Mariam Bouhmadi-López, Nihan Katirci +1
In this work, we extend the standard cosmological model within the quadratic energy-momentum squared gravity (qEMSG) framework, introducing a nonminimal interaction between the usu…
Equivalence of matter-type modified gravity theories to general relativity with nonminimal matter interaction
Özgür Akarsu, Mariam Bouhmadi-López, Nihan Katırcı +3
In this study, we first establish that gravity models incorporating matter-related terms, such as , , and , into the usu…
Omnipotent dark energy: A phenomenological answer to the Hubble tension
Shahnawaz A. Adil, Ozgur Akarsu, Eleonora Di Valentino +4
This paper introduces the class of omnipotent dark energy (DE) models characterized by nonmonotonic energy densities that are capable of attaining negative values with correspondin…
Model-independent reconstruction of the Interacting Dark Energy Kernel: Binned and Gaussian process
Luis A. Escamilla, Ozgur Akarsu, Eleonora Di Valentino +1
The cosmological dark sector remains an enigma, offering numerous possibilities for exploration. One particularly intriguing option is the (non-minimal) interaction scenario betwee…
Relativistic binary systems in scale-independent energy-momentum squared gravity
Ozgur Akarsu, Elham Nazari, Mahmood Roshan
In this paper, we study the gravitational-wave (GW) radiation and radiative behavior of relativistic binary systems in the scale-independent energy-momentum squared gravity (EMSG).…
Relaxing cosmological tensions with a sign switching cosmological constant: Improved results with Planck, BAO, and Pantheon data
Ozgur Akarsu, Suresh Kumar, Emre Ozulker +2
We present a further observational analysis of the CDM model proposed in Akarsu et al. [Phys. Rev. D 104, 123512 (2021)]. This model is based on the recent conjecture su…
Weak field and slow motion limits in energy-momentum powered gravity
Ozgur Akarsu, A. Kazim Camlibel, Nihan Katirci +2
We explore the weak field and slow motion limits, Newtonian and Post-Newtonian limits, of the energy-momentum powered gravity (EMPG), viz., the energy-momentum squared gravity (EMS…
Inevitable manifestation of wiggles in the expansion of the late Universe
Ozgur Akarsu, Eoin O. Colgain, Emre Ozulker +2
Using the fact that the comoving angular diameter distance to the last scattering surface is strictly constrained almost model independently, we show that, for any model agreeing w…