arXiv subjects

S. J. Landau

Publications and source records attributed to S. J. Landau.

6 recordsLinked to original sources

arXiv2022

Constraining a possible time-variation of the speed of light along with the fine-structure constant using strong gravitational lensing and Type Ia supernovae observations

The possible time variation of the fundamental constants of nature has been an active subject of research since the large-number hypothesis was proposed by Dirac. In this paper, we propose a new method to investigate a possible time variation of the speed of light ($c$) along with the fine-structure constant ($α$) using Strong Gravitational Lensing (SGL) and Type Ia Supernovae (SNe Ia) observations. We assume a general approach to describe the mass distribution of lens-type galaxies, the one in favor of the power-law index model (PLAW). We also consider the runaway dilaton model to describe a possible time-variation of $α$. In order to explore the results deeply, we split the SGL sample into five sub-samples according to the lens stellar velocity dispersion and three sub-samples according to lens redshift. The results suggest that it is reasonable to treat the systems separately, but no strong indication of varying $c$ was found.

astro-ph.CO↗

arXiv2016

Galaxy clusters, type Ia supernovae and the fine structure constant

As is well known, measurements of the Sunyaev-Zeldovich effect can be combined with observations of the X-ray surface brightness of galaxy clusters to estimate the angular diameter distance to these structures. In this paper, we show that this technique depends on the fine structure constant, $α$. Therefore, if $α$ is a time-dependent quantity, e.g., $α=α_0 ϕ(z)$, where $ϕ$ is a function of redshift, we argue that current data do not provide the real angular diameter distance, $D_{\rm{A}}(z)$, to the cluster but instead $D_A^{data}(z) = ϕ(z)^2 D_{\rm{A}}(z)$. We use this result to derive constraints on a possible variation of $α$ for a class of dilaton runaway models considering a sample of 25 measurements of $D_A^{data}(z)$ in redshift range $0.023 < z < 0.784$ and estimates of $D_{\rm{A}}(z)$ from current type Ia supernovae observations. We find no significant indication of variation of $α$ with the present data.

astro-ph.CO↗

arXiv2016

Constraints on a possible variation of the fine structure constant from galaxy cluster data

We propose a new method to probe a possible time evolution of the fine structure constant $α$ from X-ray and Sunyaev-Zeldovich measurements of the gas mass fraction ($f_{gas}$) in galaxy clusters. Taking into account a direct relation between variations of $α$ and violations of the distance-duality relation, we discuss constraints on $α$ for a class of dilaton runaway models. Although not yet competitive with bounds from high-$z$ quasar absorption systems, our constraints, considering a sample of 29 measurements of $f_{gas}$, in the redshift interval $0.14 < z < 0.89$, provide an independent estimate of $α$ variation at low and intermediate redshifts. Furthermore, current and planned surveys will provide a larger amount of data and thus allow to improve the limits on $α$ variation obtained in the present analysis.

astro-ph.CO↗

arXiv2006

On Inflation and Variation of the Strong Coupling Constant

Variation of constants in the very early universe can generate inflation. We consider a scenario where the strong coupling constant was changing in time and where the gluon condensate underwent a phase transition ending the inflation.

astro-ph↗

arXiv2004

A Time Varying Strong Coupling Constant as a Model of Inflationary Universe

We consider a scenario where the strong coupling constant was changing in the early universe. We attribute this change to a variation in the colour charge within a Bekenstein-like model. Treating the vacuum gluon condensate $ $ as a free paramete r, we could generate inflation with the required properties to solve the fluctuation and other standard cosmology problems. A possible approach to end the inflation is suggested.

astro-ph↗

arXiv2001

Bekenstein model and the time variation of the strong coupling constant

We propose to generalize Bekenstein model for the time variation of the fine structure "constant" $α_{em}$ to QCD strong coupling constant $α_S$. We find that, except for a ``fine tuned'' choice of the free parameters, the extension can not be performed trivially without being in conflict with experimental constraints and this rules out $α_S$ variability. This is due largely to the huge numerical value of the QCD vacuum gluon condensate when compared to the matter density of the universe.

astro-ph↗