13 papers
ACT-DR6 consistent inflation in generalised entropic cosmology and gravity
Shin'ichi Nojiri, Sergei D. Odintsov
Within the framework of generalised entropic cosmology and its equivalent gravity, we construct inflationary scenarios consistent with recent Atacama Cosmology Telescope (AC…
May Negative Mass Objects exist in the sky?
Shin'ichi Nojiri, S. D. Odintsov
We conjecture the possibility of negative mass objects (NMOs) existing in the sky. It is shown that they may not be so exotic as usually expected. We show that NMOs appear as solut…
Observational signatures of negative mass wormholes through their shadows
Shin'ichi Nojiri, Sergei D. Odintsov, Diego Sáez-Chillón Gómez
Systems containing objects with negative mass (NMOs) are considered. Such a system consists of one object with positive mass and one NMO, where a bound state exists even though the…
Apparent Phantom Crossing in Gauss-Bonnet Gravity
Shin'ichi Nojiri, Sergei D. Odintsov, V. K Oikonomou
The recent observations of the Dark Energy Spectroscopic Instrument (DESI) indicated the possibility that the dark energy equation of state parameter might change from t…
Wormhole spacetimes in an expanding universe: Energy conditions and future singularities
Taishi Katsuragawa, Shin'ichi Nojiri, Sergei D. Odintsov
We study wormhole geometries embedded in an expanding universe within a four-scalar non-linear model, where the target-space metric is identified with the spacetime Ricci tens…
Dynamical Black Hole in the accelerating Universe approaching the future singularity -- Possible origin of (super-)massive black holes
Shin'ichi Nojiri, Sergei D. Odintsov
We construct and investigate the dynamical black hole spacetime embedded in the expanding universe filled with cosmic fluid, such as dark energy. When the equation of state (EoS) p…