Varying Speed Of Light Research Articles

Variable speed of light cosmology, primordial fluctuations and gravitational waves

A variable speed of light (VSL) cosmology is described in which the causal mechanism of generating primordial perturbations is achieved by varying the speed of light in a primordial epoch. This yields an alternative to inflation for explaining the formation of the cosmic microwave background (CMB) and the large scale structure (LSS) of the universe. The initial value horizon and flatness problems in cosmology are solved. The model predicts primordial scalar and tensor fluctuation spectral indices $n_s=0.96$ and $n_t=- 0.04$, respectively. We make use of the $\delta{\cal N}$ formalism to identify signatures of primordial nonlinear fluctuations, and this allows the VSL model to be distinguished from inflationary models. In particular, we find that the parameter $f_{\rm NL}=5$ in the variable speed of light cosmology. The value of the parameter $g_{\rm NL}$ evolves during the primordial era and shows a running behavior.

Constraints on primordial magnetic fields from inflation

We present generic bounds on magnetic fields produced from cosmic inflation. By investigating field bounds on the vector potential, we constrain both the quantum mechanical production of magnetic fields and their classical growth in a model independent way. For classical growth, we show that only if the reheating temperature is as low as Treh ≲ 102 MeV can magnetic fields of 10−15 G be produced on Mpc scales in the present universe. For purely quantum mechanical scenarios, even stronger constraints are derived. Our bounds on classical and quantum mechanical scenarios apply to generic theories of inflationary magnetogenesis with a two-derivative time kinetic term for the vector potential. In both cases, the magnetic field strength is limited by the gravitational back-reaction of the electric fields that are produced simultaneously. As an example of quantum mechanical scenarios, we construct vector field theories whose time diffeomorphisms are spontaneously broken, and explore magnetic field generation in theories with a variable speed of light. Transitions of quantum vector field fluctuations into classical fluctuations are also analyzed in the examples.

Bulk viscosity in Friedmann universe with a varying speed of light described by modified equation of state

We solve the Freidmann equations by considering a universe media as a bulk viscosity described by a modified equation of state (EOS) of the form p = (γ - 1)ρc2 + Λ(t). A completely integrable dynamical equation to the scale factor is obtained and gives out the exact solution by assuming that the time-dependent parameter Λ and the bulk viscosity are linear combination of two and three terms, respectively and is expressed as: [Formula: see text] and [Formula: see text], where R is a scale factor and Λ0, Λ1, ζ0, ζ1, ζ2, are constants. For a special choice of the parameters, we discuss the acceleration expansion of the universe evolution and future singularities in the framework of variable speed of light (VSL) theory.

Bianchi type i cosmological model with varying G, Λ & σ2 in VSL theory

In this paper we study the Bianchi type I cosmological model in the framework of variable speed of light (VSL) theory. The cosmological field equations are solved for variable G，c and Λ coupled with shear parameter σ2. It is shown for the large value of t the resulting model reduces to FLRW model with Λ approaches to constant. We also derived exact expressions for the look back time, proper distance, luminosity distance and angular diameter distance versus redshift in the framework of VSL theory as already discussed by Khadekar and Kamdi [Int. Jour. Theo. Phys. 48 314% (2009)] in differ­ent context.

Varying constants quantum cosmology

We discuss minisuperspace models within the framework of varying physical constants theories including Λ-term. In particular, we consider the varying speed of light (VSL) theory and varying gravitational constant theory (VG) using the specific ansätze for the variability of constants: c(a) = c0 an and G(a)=G0 aq. We find that most of the varying c and G minisuperspace potentials are of the tunneling type which allows to use WKB approximation of quantum mechanics. Using this method we show that the probability of tunneling of the universe ``from nothing'' (a=0) to a Friedmann geometry with the scale factor at is large for growing c models and is strongly suppressed for diminishing c models. As for G varying, the probability of tunneling is large for G diminishing, while it is small for G increasing. In general, both varying c and G change the probability of tunneling in comparison to the standard matter content (cosmological term, dust, radiation) universe models.

Observational constraint on the varying speed of light theory

The varying speed of light (VSL) theory is controversial. It succeeds in explaining some cosmological problems, but on the other hand it is excluded by mainstream physics because it will shake the foundation of physics. In the present paper, we devote ourselves to test whether the speed of light is varying from the observational data of the type Ia Supernova, Baryon Acoustic Oscillation, Observational $H(z)$ data and Cosmic Microwave Background (CMB). We select the common form $c(t)=c_0a^n(t)$ with the contribution of dark energy and matter, where $c_0$ is the current value of speed of light, $n$ is a constant, and consequently construct a varying speed of light dark energy model (VSLDE). The combined observational data show a much trivial constraint $n=-0.0033 \pm 0.0045$ at 68.3\% confidence level, which indicates that the speed of light may be a constant with high significance. By reconstructing the time-variable $c(t)$, we find that the speed of light almost has no variation for redshift $z < 10^{-1}$. For high-$z$ observations, they are more sensitive to the VSLDE model, but the variation of speed of light is only in order of $10^{-2}$. We also introduce the geometrical diagnostic $Om (z)$ to show the difference between the VSLDE and $\Lambda$CDM model. The result shows that the current data are difficult to differentiate them. All the results show that the observational data favor the constant speed of light.

SNe data analysis in variable speed of light cosmologies without cosmological constant

In this work, we aim to show the possibilities of the variable speed of light (VSL) theory in explaining the type Ia supernovae (SNe) observations without introducing dark energy. The speed of light is assumed to be scale factor-dependent, which is the most popular assumption in VSL theory. We show the modified calculation of the distance modulus and the validity of the redshift-scale factor relation in VSL theory. Three different models of VSL are tested SNe data-sets with proper constraints on the model parameters. The comparison of the three models and flat ΛCDM in distance modulus is showed. Some basic problems and the difficulties of the confirmation of the VSL theory are also discussed.

A statefinder luminosity distance formula in varying speed of light cosmology

We derive a luminosity distance formula for the varying speed of light (VSL) theory which involves higher order characteristics of expansion such as jerk, snap and lerk which can test the impact of varying c onto the evolution of the universe. We show that the effect of varying c is possible to be isolated due to the relations connecting observational parameters already by measuring the second-order term in redshift z unless there is a redundancy between the curvature and an exotic fluid of cosmic strings scaling the same way as the curvature.

Is Time Inhomogeneous?

In this article, we discuss probability of inhomogeneous time in high or low energy scale of physics. Consequently, the possibility was investigated of using theories such as varying speed of light (VSL) and fractal mathematics to build a framework within which answers can be found to some of standard cosmological problems and physics theories on the basis of time non-homogeneity.

Is Time Inhomogeneous?

In this article, we discuss probability of inhomogeneous time in high or low energy scale of physics. Consequently, the possibility was investigated of using theories such as varying speed of light (VSL) and fractal mathematics to build a framework within which answers can be found to some of standard cosmological problems and physics theories on the basis of time non-homogeneity.

Calculating the Exact Experimental Density of the Dark Energy in the Cosmos Assuming a Fractal Speed of Light

Fractal speed of light theory is a variation of Magueijo-Smolin varying speed of light (VSL) theoretical modification of Einstein’s energy mass relation. We use this theory to derive an exact value for the missing dark energy which is found to be in astonishing agreement with the latest result of the WMAP measurement and the independent supernova analysis. Thus while Einstein’s formula predicts 95.5% more energy than found in highly precise astrophysical measurement, our VSL- based calculation indicates an exact theoretical value of only 4.508497% real energy. Consequently, the exact conjectured missing dark energy must be 95.491502%. By any standards, this is an astounding confirmation for both the cosmological measurement and the VSL theory.

Redshift drift in varying speed of light cosmology

We derive a redshift drift formula within the framework of varying speed of light (VSL) theory using the specific ansatz for the variability of c(t)=c0an(t). We show that negative values of the parameter n, which correspond to diminishing value of the speed of light during the evolution of the universe, effectively rescale dust matter to become little negative pressure matter, and the cosmological constant to became phantom. Positive values of n (growing c(t)) make VSL model to become more like Cold Dark Matter (CDM) model. Observationally, there is a distinction between the VSL model and the ΛCDM model for the admissible values of the parameter n∼−10−5, though it will be rather difficult to detect by planned extremely large telescopes (EELT, TMT, GMT) within their accuracy.

Bianchi Type-II Cosmological Model with a Linear Equation of State in Vsl Theory

We study Bianchi type-II model with time varying constant under the self similarity approach. In first part of the paper we have studied the model by considering time variable G and Λ and obtain the solutions of the field equations by using linear equation of state (EOS) of the form ρ = np+ρo where n and ρo are constants. It is observed that G must be time growing function while nature of Λ depends on the nature of γ. In the second part of paper we have studied the model by considering variable speed of light (VSL) and obtain the similar types of solutions as in the first model and all the physical parameters which depends on ∫ cdt. Arriving to the conclusion that c must be growing time function and Λ depends on value γ.

Particle creation in cosmology with varying speed of light

This paper investigates the behaviour of the particle creation in Einstein’s field equations with a variable speed of light and variable energy density in the context of open thermodynamical systems where the particle creation gives rise to a supplementary negative creation pressure in addition to the thermodynamic pressure. The dynamical behaviour of the cosmological models has been investigated.

Why the Speed of Light Is Not a Constant

A variable Speed of Light is supported by the fact that all direct measurements of that speed are basically flawed, because the “meter per second” is proportional to the Speed of Light. Since it is impossible to measure the Speed of Light directly, any variations of it can only be obtained in an indirect way. It will be shown that the recent Supernovae data are in very good agreement with a universe that is slowly expanding exponentially with a Speed of Light that falls over time, inversely proportionally to the expansion of the universe. It will be shown that the definition of the angular and standard impulse momentum has to be modified to get a consistent expansion of the universe. And that all clocks run inversely proportionally to the red-shift z + 1. General Relativity remains valid even with a varying Speed of Light and also Quantum Mechanics is unaffected.

General relativity with variable speed of light and Pioneers anomaly

We consider a General Relativistic RW’s metric, with variable speed of light, and find a field of Universal acceleration, numerically coincident with the value of the Pioneers anomalous one. This deceleration may decrease with time, as we calculated. This is relevant to understand the Physics that may be involved in the Cosmological approach to the Pioneers anomaly.

VARIABLE SPEED OF LIGHT THEORIES: A THERMODYNAMIC ANALYSIS OF PLANETARY AND WHITE DWARF PHENOMENA

The thermodynamics of a scalar field interacting with a perfect fluid is studied, and observable consequences of the covariant variable speed of light (VSL) theory proposed by J. Magueijo are obtained. The first law of thermodyamics is modified as the scalar field becomes an additional thermodynamical variable. A recipe to obtain the modified equations of state is also obtained. After discussing the Newtonian limit and the non-relativistic hydrostatic equilibrium equation for the theory, the time-variation of the radius of Mercury induced by the variability of the speed of light (c), and the scalar contribution to the luminosity of white dwarfs are found. Using a bound for the change of that radius and combining it with an upper limit for the variation of the fine-structure constant, a bound on the time-variation of c is set. An independent bound is obtained from luminosity estimates for Stein 2015B.

Are Vortices in Rotating Superfluids Breaking the Weak Equivalence Principle?

Due to the breaking of gauge symmetry in rotating superfluid Helium, the inertial mass of a vortex diverges logarithmically with the vortex size. The vortex inertial mass is thus much higher than the classical inertial mass of the vortex core. An equal increase of the vortex gravitational mass is questioned. The possibility that the vortices in a rotating superfluid could break the weak equivalence principle in relation with a variable speed of light in the superfluid vacuum is debated. Experiments to test this possibility are investigated on the basis that superfluid helium vortices would not fall, under the single influence of a uniform gravitational field, at the same rate as the rest of the superfluid helium mass.

The speed of light in extended gravity theories

We shall investigate the possibility of formulation of varying speed of light (VSL) in the framework of Palatini nonlinear Ricci scalar and Ricci squared theories. Different speeds of light including the causal structure constant, electromagnetic and gravitational wave speeds are discussed. We shall see that two local frames are distinguishable and discuss the velocity of light in these two frames. We shall investigate which one of these local frames is inertial.

Bianchi II with time varying constants. Self-similar approach

We study a perfect fluid Bianchi II models with time varying constants under the self-similarity approach. In the first of the studied model, we consider that only vary $G$ and $\Lambda.$ The obtained solution is more general that the obtained one for the classical solution since it is valid for an equation of state $\omega\in(-1,\infty) $ while in the classical solution $\omega\in(-1/3,1) .$ Taking into account the current observations, we conclude that $G$ must be a growing time function while $\Lambda$ is a positive decreasing function. In the second of the studied models we consider a variable speed of light (VSL). We obtain a similar solution as in the first model arriving to the conclusions that $c$ must be a growing time function if $\Lambda$ is a positive decreasing function.