Related papers: Decelerating universes older than their Hubble tim…
We study a parametrization of the deceleration parameter in a tilted universe, namely a cosmological model equipped with two families of observers. The first family follows the smooth Hubble flow, while the second are the real observers…
The dynamics of galaxies in an expanding universe is often determined for gravitational and dark matter in an Einstein-de Sitter universe, or alternatively by modifying the gravitational long-range attractions in the Newtonian dynamics…
Recent observations on the large-scale structure of the universe indicate that the cosmological constant cannot be the definitive answer to the nature of dark energy. Therefore, it is a good time to propose alternatives to understand the…
If the current acceleration of our Universe is due to a cosmological constant, then a Coleman-De Luccia bubble will nucleate in our Universe. In this work, we consider that our observations could be likely in this framework, consisting in…
A new speculative model for the expansion of our universe has been under development by the author for the last two decades, which correctly predicts astronomical measurements with no dark matter or dark energy. This new closed model (no…
The universe might experience many cycles with different vacua. The slow-roll inflation may be preceded by kinetic-dominated contraction occurring in "adjacent" vacua during some cycles. In this report we briefly show this phenomenon may…
Local and distant measurements of the Hubble constant are in significant tension: local measurements of the Hubble constant appear to show a Universe that is significantly contracted when compared to distant measurements. From the point of…
The unexpected faintness of high-redshift Type Ia supernovae (SNe Ia), as measured by two teams, has been interpreted as evidence that the expansion of the Universe is accelerating. We review the current challenges to this interpretation…
The secular evolution process, which slowly transforms the morphology of a galaxy over its lifetime, could naturally account for observed properties of the great majority of physical galaxies if both stellar and gaseous accretion processes…
Dark energy is inferred from a Hubble expansion which is slower at epochs which are earlier than ours. But evidence reviewed here shows $H_0$ for nearby galaxies is actually less than currently adopted and would instead require {\it…
Although the current galaxy models yield calculations consistent with much of the data, many irregularities exist, exceptions have been found to the current models, the $\Lambda$CDM model apparently fails on galaxy scales, dark matter…
Twenty years after the discovery that the expansion of the Universe is accelerating, a new finding is now challenging our understanding of the cosmos. Recent studies have shown that the Hubble constant, the speed of expansion measured…
The conventional background solution for the evolution of a single canonical inflaton field performs admirably in extreme scenarios such as the slow-roll phase (where the slow-roll parameter is much less than one) and the deep reheating era…
Hubble's name is associated closely with the idea of an expanding universe as he discovered the relation between the recession velocity and distances of galaxies. Hubble also did a lot of pioneering work on the distribution of galaxies in…
One of the strongest arguments against the cosmological constant as an explanation of the current epoch of accelerated cosmic expansion is the existence of an earlier, dynamical acceleration, i.e. inflation. We examine the likelihood that…
Equations of cosmic dynamics for a model of the opaque Universe are derived and tested on supernovae (SNe) Ia observations. The model predicts a cyclic expansion/contraction evolution of the Universe within a limited range of scale factors.…
A major outstanding challenge in cosmology is the persistent discrepancy between the Hubble constant obtained from early and late universe measurements -- the Hubble tension. Examining cosmological evolution through the lens of information…
The apparent cosmological conflict between the age of the Universe, predicted in the standard Friedman cosmology by using the recent measurement of the larger Hubble constant from a direct calibration of the distance to the Virgo galaxy…
The cosmological vacuum, which is perfectly uniform, dominates by density over all the forms of cosmic matter. It makes the Universe be actually more uniform than it could be seen from the visible picture of the highly non-uniform matter…
An occurrence of an oscillating Universe is showed using an inhomogeneous equation of state for dark energy fluid. The Hubble parameter described presents a periodic behavior such that early and late time acceleration are unified under the…