Varying Speed Of Light Cosmology Research Articles

Normal DGP in varying speed of light cosmology

Varying speed of light (VSL) has been used in cosmological models in which the physical constants vary over time. On the other hand, the Dvali, Gabadadze and Porrati (DGP) brane world model, especially its normal branch, has been extensively discussed to justify the current cosmic acceleration. In this article we show that the normal branch of DGP in VSL cosmology leads to a self-accelerating behavior and therefore can interpret cosmic acceleration. Applying statefinder diagnostics demonstrates that our result slightly deviates from the ΛCDM model.

SOLUTIONS OF COSMOLOGICAL MODELS WITH VARYING SPEED OF LIGHT

In recent years, there has been some renewed interest in cosmological models in which the constants of nature vary with time. In one of these, one supposes a dependence on the redshift of the fine structure constant as suggested by some astronomical observations of quasars. This has led, among others, to the proposal that the speed of light varies with the cosmological time. A Varying Speed of Light (VSL) would be able to solve some long standing problems of the standard cosmological model, without the need for inflation. In this work we study two models in which (1) c varies according to a power law of the scale factor c(t) ∝ a-r and (2) c is proportional to the Hubble parameter c(t) ∝ Hu. We present solutions for these two types of VSL cosmologies. We find that for a flat (k = 0) Friedmann–Robertson–Walker (FRW) universe, the variation of c is coupled to a cosmological Λ-term and both singular and non-singular solutions are possible.

Cosmologies with varying speed of light: A historical perspective

The possibility that natural laws and constants may not be true constants, but vary over cosmic periods of time, has recently attracted much attention. In this paper, I provide some historical background to the issue and consider, in the form of a historical review, some of the more spectacular developments within recent years. The focus of the paper is on the hypothesis of a varying speed of light, which appeared shortly after the announcement of the expanding universe. After a brief account of the history of this hypothesis, I consider in more details the varying c theories that have appeared during the last decade and were originally introduced as an alternative to the inflationary model. These so-called varying speed of light (VSL) theories have been surprisingly popular and created a flood of physics and cosmology papers. However, they have also been severely criticized from conceptual points of view and their status is as yet uncertain. Although a research programme in development, a historical perspective on VSL cosmology may not be out of place.

Unusual features of varying speed of light cosmologies

We contrast features of simple varying speed of light (VSL) cosmologies with inflationary universe models. We present new features of VSL cosmologies and show that they face problems explaining the cosmological isotropy problem. We also find that if c falls fast enough to solve the flatness and horizon problems then the quantum wavelengths of massive particle states and the radii of primordial black holes can grow to exceed the scale of the particle horizon. This may provide VSL cosmologies with a self-reproduction property. The constraint of entropy increase is also discussed. The new problems described in the this Letter provide a set of bench tests for more sophisticated VSL theories to pass.

Variable-speed-of-light cosmology and second law of thermodynamics

We examine whether cosmologies with a varying speed of light (VSL) are compatible with the second law of thermodynamics. We find that the VSL cosmology with a varying fundamental constant is severely constrained by the second law of thermodynamics, whereas the bimetric cosmological models are less constrained.

Brane world cosmologies with varying speed of light

We study cosmologies in the Randall-Sundrum models, incorporating the possibility of time-varying speed of light and Newton's constant. The cosmologies with varying speed of light (VSL) were proposed by Moffat and by Albrecht and Magueijo as an alternative to inflation for solving the cosmological problems. We consider the case in which the speed of light varies with time after the radion or the scale of the extra dimension has been stabilized. We elaborate on the conditions under which the flatness problem and the cosmological constant problem can be resolved. We find that the RS models are more restrictive about possible desirable VSL cosmological models than the standard general relativity. Particularly, the VSL cosmologies may provide with a possible mechanism for bringing the quantum corrections to the fine-tuned brane tensions after the SUSY breaking under control.

Cosmonumerology and empiricism: The Dirac-Gamow dialogue

The possibility that natural laws and constants may not be true constants, but vary over cosmic periods of time, has recently attracted much attention. In this paper, I provide some historical background to the issue and consider, in the form of a historical review, some of the more spectacular developments within recent years. The focus of the paper is on the hypothesis of a varying speed of light, which appeared shortly after the announcement of the expanding universe. After a brief account of the history of this hypothesis, I consider in more details the varying c theories that have appeared during the last decade and were originally introduced as an alternative to the inflationary model. These so-called varying speed of light (VSL) theories have been surprisingly popular and created a flood of physics and cosmology papers. However, they have also been severely criticized from conceptual points of view and their status is as yet uncertain. Although a research programme in development, a historical perspective on VSL cosmology may not be out of place.