Galaxy clusters have been used as a cosmic laboratory to verify a possible time variation of fundamental constants. Particularly, it has been shown that the ratio YSZD 2 A /CXZSYX, which is expected to be constant with redshift, can be used to probe a variation of the fine structure constant, α. In this ratio, YSZD 2 A is the integrated comptonization parameter of a galaxy cluster obtained via Sunyaev-Zel'dovich (SZ) effect observations multiplied by its angular diameter distance, DA, YX is the X-ray counterpart and CXSZ is an arbitrary constant. Using a combination of SZ and X-ray data, a recent analysis found YSZD 2 A /CXZSYX = Cα(z) 3.5 , where C is a constant. In this paper, following previous results that suggest that a variation of α necessarily leads to a violation of the cosmic distance duality relation, DL/DA(1 + z) 2 = 1, where DL is the luminosity distance of a given source, we derive a new expression, YSZD 2 A /CXSZYX = Cα 3.5 η −1 (z), where η(z) = DL/DA(1 + z) 2 . In particular, considering the direct relation η(z) ∝ α(z) 1/2 , derived from a class of dilaton runaway models, and 61 measurements of the ratio YSZD 2 A /CXSZYX provided by the Planck collaboration, we discuss bounds on a possible variation of α. We also estimate the value of the constant C, which is compatible with the unity at 2σ level, indicating that the assumption of isothermality for the temperature profile of the galaxy clusters used in the analysis holds. 95.36.+x, 98.80.Es

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 = α0φ(z), where φ is a function of redshift, we argue that current data do not provide the real angular diameter distance, DA(z), to the cluster, but instead D data A (z) = φ(z) 2 DA(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 data A (z) in redshift range 0.023 < z < 0.784 and estimates of DA(z) from current type Ia supernovae observations. We find no significant indication of variation of α with the present data.

In this paper, new bounds on possible variations of the fine structure constant, α, for a class of runaway dilaton models are performed. By considering a possible evolution with redshift, z, such as ∆α α = −γ ln(1 + z), where in γ are the physical properties of the model, we constrain this parameter by using a deformed cosmic distance duality relation jointly with gas mass fraction (GMF) measurements of galaxy clusters and luminosity distances of type Ia supernovae. The GMF's used in our analyses are from cluster mass data from 82 galaxy clusters in the redshift range 0.12 < z < 1.36, detected via the Sunyaev-Zeldovich effect at 148 GHz by the Atacama Cosmology Telescope. The type Ia supernovae are from the Union2.1 compilation. We also explore the dependence of the results from four models used to describe the galaxy clusters. As a result no evidence of variation was obtained. 95.36.+x, 98.80.Es

In this paper, we propose a new test to the cosmic distance duality relation (CDDR), DL=DA(1+z)2, where DL and DA are the luminosity and angular diameter distances, respectively. The data used correspond to 61 Type Ia Supernova luminosity distances and YSZE−YX measurements of 61 galaxy clusters obtained by the Planck mission and the deep XMM-Newton X-ray data, where YSZE is the integrated comptonization parameter obtained via Sunyaev-Zel'dovich effect observations and YX is the X-ray counterpart. More precisely, we use the YSZEDA2/CXSZEYX scaling-relation and a deformed CDDR, such as DL/DA(1+z)2=η(z), to verify if η(z) is compatible with the unity. Two η(z) functions are used, namely, η(z)=1+η0 z and η(z)=1+η0 z /(1+z). We obtain that the CDDR validity (η0=0) is verified within ≈ 1.5σ c.l. for both η(z) functions.

In order to probe a possible time variation of the fine-structure constant ($$\alpha $$ α ), we propose a new method based on Strong Gravitational Lensing and Type Ia Supernovae observations. By considering a class of runaway dilaton models, where $$\frac{\Delta \alpha }{\alpha }= - \gamma \ln {(1+z)}$$ Δ α α = - γ ln ( 1 + z ) , we obtain constraints on $$\frac{\Delta \alpha }{\alpha }$$ Δ α α at the level $$\gamma \sim 10^{-2}$$ γ ∼ 10 - 2 ($$\gamma $$ γ captures the physical properties of the model). Since the data set covers the redshift range $$0.075 \le z \le 2.2649$$ 0.075 ≤ z ≤ 2.2649 , the constraints derived here provide independent bounds on a possible time variation of $$\alpha $$ α at low, intermediate and high redshifts.