We study the detailed evolution of the fine-structure constant $α$ in the string-inspired runaway dilaton class of models of Damour, Piazza and Veneziano. We provide constraints on this scenario using the most recent $α$ measurements and discuss ways to distinguish it from alternative models for varying $α$. For model parameters which saturate bounds from current observations, the redshift drift signal can differ considerably from that of the canonical $Λ$CDM paradigm at high redshifts. Measurements of this signal by the forthcoming European Extremely Large Telescope (E-ELT), together with more sensitive $α$ measurements, will thus dramatically constrain these scenarios.
One of the clear predictions of string theory is the presence of a dynamical scalar partner of the spin-2 graviton, known as the dilaton. This will violate the Einstein Equivalence Principle, leading to a plethora of possibly observable consequences which is a cosmological context include dynamical dark energy and spacetime variations of nature's fundamental constants. The runaway dilaton scenario of Damour, Piazza and Veneziano is a particularly interesting class of string theory inspired models which can in principle reconcile a massless dilaton with experimental data. Here we use the latest…
In order to probe a possible time variation of the fine-structure constant ($α$), we propose a new method based on Strong Gravitational Lensing and Type Ia Supernovae observations. By considering a class of dilaton runaway models, where $\frac{Δα}α= - γ\ln{(1+z)}$, we obtain constraints on $\frac{Δα}α$ at the level $γ\approx 10^{-2}$ ($γ$ captures the physical properties of the model). Since the data set covers the redshift range $0.075 \leq z \leq 2.2649$, the constraints derived here provide independent bounds on a possible time variation of $α$ at low, intermediate and high redshifts.
Dilatons (and moduli) couple to the masses and coupling constants of ordinary matter, and these quantities are fixed by the local value of the dilaton field. If, in addition, the dilaton with mass $m_ϕ$ contributes to the cosmic dark matter density, then such quantities oscillate in time at the dilaton Compton frequency. We show how these oscillations lead to broadening and shifting of the Voigt profile of the Ly$α$ forest, in a manner that is correlated with the local dark matter density. We further show how tomographic methods allow the effect to be reconstructed by observing the Ly$α$ fores…
We search for a variation of the electromagnetic fine structure constant ($α\equiv e^2/\hbar c$) using a sample of 58 SZ selected clusters in the redshift range ($0.2<z<1.5$) detected by the South Pole Telescope, along with X-ray measurements using the XMM-Newton observatory. We use the ratio of the integrated SZ Compto-ionization to its X-ray counterpart as our observable for this search. We first obtain a model-independent constraint on $α$ of about 0.7%, using the fact that the aforementioned ratio is constant as a function of redshift. We then look for a logarithmic dependence of $α$ as a …
Constraints on a possible variation of the fine structure constant from galaxy cluster data
提出了一种新的方法来探测精细结构常数$α$的可能的时间演化的气体质量分数（$f_{gas}$）在星系团的X射线和Sunyaev-Zeldovich测量。考虑到$α$的变化与距离-对偶关系的破坏之间的直接关系，我们讨论了一类非线性逃逸模型对$α$的约束。虽然还没有竞争力的边界从高$z$类星体吸收系统，我们的限制，考虑样本的29个测量$f_{gas}$，在红移间隔$0.14 < z < 0.89$，提供了一个独立的估计$α$变化在低和中等红移。此外，当前和计划中的调查将提供更大量的数据，从而可以改善本分析中获得的$α$变化的限制。
A new method based on large-scale structure observations is proposed to probe a possible time variation of the fine-structure constant ($α$). Our analyses are based on time-delay of Strong Gravitational Lensing and Type Ia Supernovae observations. By considering a class of runaway dilaton models, where the cosmological evolution of the fine-structure constant is given by $\frac{Δα}α \approx -γ\ln{(1+z)}$, we obtain limits on the physical properties parameter of the model ($γ$) at the level $10^{-2}$ ($1σ$). Although our limits are less restrictive than those obtained by quasar spectroscopy, th…
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 …
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 $Y_{SZ}D_{A}^{2}/C_{XZS}Y_X $, which is expected to be constant with redshift, can be used to probe a variation of the fine structure constant, $α$. In this ratio, $Y_{SZ}D_{A}^{2}$ is the integrated comptonization parameter of a galaxy cluster obtained via Sunyaev-Zel'dovich (SZ) effect observations multiplied by its angular diameter distance, $D_A$, $Y_X$ is the X-ray counterpart and $C_{XSZ}$ is an arbitrary constant. Using a comb…
The background evolution of an accelerated, dark energy dominated universe is aptly described by non-canonical tachyon scalar field models. The accelerated expansion of the universe is determined by the choice of a suitable scalar field potential; in the case of a tachyon field, a 'runaway' potential. In the absence of a fundamental theory, dark energy properties are studied in a phenomenological approach. This includes determining the model parameters using observations and to probe the allowed deviation from the cosmological constant model. In this paper, we present constraints on tachyon sc…
