198 citations · 1.8k across the 47 of their papers we have counts for
6 papers · 1 filter
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…