Narrow Results

In this paper, we discuss cosmic age problem in the case of ghost dark energy (GDE) model. To this end, we use two observational data sets to constrain the free parameter space of the models. Next, we try to set new limits on the mentioned free parameter space using the age of the universe. In this work, both of these tasks are done for the GDE model in the presence of the sign-changeable interaction terms. To this end, three classes of interaction terms are considered that provide a sign-changeability possibility. For one of these cases, the age problem passes completely and there is no new bound of free parameters. For two others the age test sets some constrains on the models. In addition to cosmic age problem, we investigate some other properties of these three models including ability to cross the phantom line, accelerating phase of cosmic expansion and the stability against cosmic perturbations.

If one is willing to consider the current cosmic microwave back ground temperature as a quantum gravitational effect of the evolving primordial cosmic black hole (universe that constitutes dynamic space-time and exhibits quantum behavior) automatically general theory of relativity and quantum mechanics can be combined into a ‘scale independent’ true unified model of quantum gravity. By considering the ‘Planck mass’ as the initial mass of the baby Hubble volume, past and current physical and thermal parameters of the cosmic black hole can be understood. Current rate of cosmic black hole expansion is being stopped by the microscopic quantum mechanical lengths. In this new direction authors observed 5 important quantum mechanical methods for understanding the current cosmic deceleration. To understand the ground reality of current cosmic rate of expansion, sensitivity and accuracy of current methods of estimating the magnitudes of current CMBR temperature and current Hubble constant must be improved and alternative methods must be developed. If it is true that galaxy constitutes so many stars, each star constitutes so many hydrogen atoms and light is coming from the excited electron of galactic hydrogen atom, then considering redshift as an index of ‘whole galaxy’ receding may not be reasonable. During cosmic evolution, at any time in the past, in hydrogen atom emitted photon energy was always inversely proportional to the CMBR temperature. Thus past light emitted from older galaxy's excited hydrogen atom will show redshift with reference to the current laboratory data. As cosmic time passes, in future, the absolute rate of cosmic expansion can be understood by observing the rate of increase in the magnitude of photon energy emitted from laboratory hydrogen atom. Aged super novae dimming may be due to the effect of high cosmic back ground temperature. Need of new mathematical methods & techniques, computer simulations, advanced engineering skills seem to be essential in this direction.