相关论文: Nucleosynthesis in slowly evolving Cosmologies
We present a case for Cosmological Nucleosynthesis in an FRW universe in which the scale factor expands linearly with time: $a(t) \sim t$. It is demonstrated that adequate amount of $^4He$ requires a baryon density that saturates mass…
We study the effect of neutrino degeneracy on primordial nucleosynthesis in a universe in which the cosmological scale factor evolves linearly with time. The degeneracy parameter of electron type neutrinos ($\xi_e$) determines the $n/p$…
Primordial nucleosynthesis is considered a success story of the standard big bang (SBB) cosmology. The cosmological and elementary particle physics parameters are believed to be severely constrained by the requirement of correct abundances…
Primordial nucleosynthesis is considered a success story of the standard big bang (SBB) cosmology. The cosmological and elementary particle physics parameters are believed to be severely constrained by the requirement of correct abundances…
Primordial nucleosynthesis is rightly hailed as one of the great successes of the standard cosmological model. Here we consider the initial forging of elements in the recently proposed Rh = ct universe, a cosmology that demands linear…
Primordial nucleosynthesis is a success story of the standard big bang (SBB) cosmology. We explore nucleosynthesis in possible models very different from SBB in which the cosmological scale factor increases linearly with time right through…
We have recently considered cosmologies in which the Universal scale factor varies as a power of the age of the Universe and concluded that they cannot satisfy the observational constraints on the present age, the magnitude-redshift…
Recent observation of the power spectrum of Cosmic Microwave Background (CMB) Radiation has exhibited that the flat cosmology is most likely. This suggests too large universal baryon-density parameter $\Omega_b h^2 \approx 0.022 \sim 0.030$…
We review some important observed properties of massive stars. Then we discuss how mass loss and rotation affect their evolution and help in giving better fits to observational constraints. Consequences for nucleosynthesis at different…
We demonstrate that nucleosynthesis in rapid, high-entropy expansions of proton-rich matter from high temperature and density can result in a wider variety of abundance patterns than heretofore appreciated. In particular, such expansions…
We present what we know on nucleosynthesis in the Universe and hypotheses that have been made in this regard. A brief description of the Universe's evolution during its different stages is offered, indicating which are the periods and…
Following a brief introduction to early Universe cosmology, the current of status of big bang nucleosynthesis is reviewed and the concordance between theory and observation is examined in detail. The abundances of He4 and Li7 determine the…
Stars more massive than $\sim$ 20 - 25 \ms form a black hole at the end of their evolution. Stars with non-rotating black holes are likely to collapse "quietly" ejecting a small amount of heavy elements (Faint supernovae). In contrast,…
A strictly linear evolution of the cosmological scale factor is surprisingly an excellent fit to a host of cosmological observations. Any model that can support such a coasting presents itself as a falsifiable model as far as classical…
We study the cosmological evolution of massless single-field scalar-tensor theories of gravitation from the time before the onset of $e^+e^-$ annihilation and nucleosynthesis up to the present. The cosmological evolution together with the…
Starting from astrophysical indications that the fine structure constant might undergo a small cosmological time shift, we discuss the implications of such an effect from the point of view of particle physics. Grand unification implies…
The origins of the elements and isotopes of cosmic material is a critical aspect of understanding the evolution of the universe. Nucleosynthesis typically requires physical conditions of high temperatures and densities. These are found in…
Recently conformal Weyl gravity has been considered as a candidate alternative gravity theory. This fourth-order theory is attractive because it is the only metric theory of gravity which is invariant under local conformal transformations…
Observation indicates that the expansion of the Universe is accelerating and favours a dynamical cosmological constant, \Lambda(t). We consider the possibility that this is due to a scalar field which has undergone a very recent phase…
Big Bang Nucleosynthesis provides us with an observational insight into the very early Universe. Since this mechanism of light element synthesis comes out of the standard model of particle cosmology which follows directly from General…