Atomic calculations and search for variation of the fine structure constant in quasar absorption spectra

A brief review of the search for variation of the fine structure constant in quasar absorption spectra is presented. Special consideration is given to the role of atomic calculations in the analysis of the observed data. A range of methods which allow to perform calculations for atoms or ions with different electron structure and which cover practically all periodic table of elements is discussed. Critical compilation of the results of the calculations as well as a review of the most recent results of the analysis are presented.Comment: 9 pages, 2 figures. Based on the talk at the Symposium on Atomic Physics: A Tribute to Walter Johnson, Notre Dame, 5 April 2008. Reference 26 is correcte

STIM1/Orai1-mediated store-operated Ca2+ entry: the tip of the iceberg

Highly efficient mechanisms regulate intracellular calcium (Ca2+) levels. The recent discovery of new components linking intracellular Ca2+ stores to plasma membrane Ca2+ entry channels has brought new insight into the understanding of Ca2+ homeostasis. Stromal interaction molecule 1 (STIM1) was identified as a Ca2+ sensor essential for Ca2+ store depletion-triggered Ca2+ influx. Orai1 was recognized as being an essential component for the Ca2+ release-activated Ca2+ (CRAC) channel. Together, these proteins participate in store-operated Ca2+ channel function. Defective regulation of intracellular Ca2+ is a hallmark of several diseases. In this review, we focus on Ca2+ regulation by the STIM1/Orai1 pathway and review evidence that implicates STIM1/Orai1 in several pathological conditions including cardiovascular and pulmonary diseases, among others

Fundamental Physical Constants: Looking from Different Angles

We consider fundamental physical constants which are among a few of the most important pieces of information we have learned about Nature after its intensive centuries-long studies. We discuss their multifunctional role in modern physics including problems related to the art of measurement, natural and practical units, origin of the constants, their possible calculability and variability etc

Isotope shift calculations for atoms with one valence electron

This work presents a method for the ab initio calculation of isotope shift in atoms and ions with one valence electron above closed shells. As a zero approximation we use relativistic Hartree-Fock and then calculate correlation corrections. The main motivation for developing the method comes from the need to analyse whether different isotope abundances in early universe can contribute to the observed anomalies in quasar absorption spectra. The current best explanation for these anomalies is the assumption that the fine structure constant, alpha, was smaller at early epoch. We test the isotope shift method by comparing the calculated and experimental isotope shift for the alkali and alkali-like atoms Na, MgII, K, CaII and BaII. The agreement is found to be good. We then calculate the isotope shift for some astronomically relevant transitions in SiII and SiIV, MgII, ZnII and GeII.Comment: 11 page

Constraining fundamental constants of physics with quasar absorption line systems

We summarize the attempts by our group and others to derive constraints on variations of fundamental constants over cosmic time using quasar absorption lines. Most upper limits reside in the range 0.5-1.5x10-5 at the 3sigma level over a redshift range of approximately 0.5-2.5 for the fine-structure constant, alpha, the proton-to-electron mass ratio, mu, and a combination of the proton gyromagnetic factor and the two previous constants, gp(alpha^2/mu)^nu, for only one claimed variation of alpha. It is therefore very important to perform new measurements to improve the sensitivity of the numerous methods to at least <0.1x10-5 which should be possible in the next few years. Future instrumentations on ELTs in the optical and/or ALMA, EVLA and SKA pathfinders in the radio will undoutedly boost this field by allowing to reach much better signal-to-noise ratios at higher spectral resolution and to perform measurements on molecules in the ISM of high redshift galaxies.Comment: 11 pages, 3 figure

Black holes in the varying speed of light theory

We consider the effect of the \emph{Varying Speed of Light} theory on non-rotating black holes. We show that in any varying-$c$ theory, the Schwarzschild solution is neither static nor stationary. For a no-charged black hole, the singularity in the Schwarzschild horizon cannot be removed by coordinate transformation. Hence, no matter can enter the horizon, and the interior part of the black hole is separated from the rest of the Universe. If $\dot{c}<0$, then the size of the Schwarzschild radius increases with time. The higher value of the speed of light in the very early Universe may have caused a large reduction in the probability of the creation of the primordial black holes and their population.The same analogy is also considered for the charged black holes.Comment: 5 page

Time Variations in the Scale of Grand Unification

We study the consequences of time variations in the scale of grand unification, $M_U$, when the Planck scale and the value of the unified coupling at the Planck scale are held fixed. We show that the relation between the variations of the low energy gauge couplings is highly model dependent. It is even possible, in principle, that the electromagnetic coupling $\alpha$ varies, but the strong coupling $\alpha_3$ does not (to leading approximation). We investigate whether the interpretation of recent observations of quasar absorption lines in terms of time variation in $\alpha$ can be accounted for by time variation in $M_U$. Our formalism can be applied to any scenario where a time variation in an intermediate scale induces, through threshold corrections, time variations in the effective low scale couplings.Comment: 14 pages, revtex4; Updated observational results and improved statistical analysis (section IV); added reference

Constraints on the Variation of the Fine Structure Constant from Big Bang Nucleosynthesis

We put bounds on the variation of the value of the fine structure constant $\alpha$, at the time of Big Bang nucleosynthesis. We study carefully all light elements up to $^7$Li. We correct a previous upper limit on $|\Delta \alpha / \alpha|$ estimated from $^4$He primordial abundance and we find interesting new potential limits (depending on the value of the baryon-to-photon ratio) from $^7$Li, whose production is governed to a large extent by Coulomb barriers. The presently unclear observational situation concerning the primordial abundances preclude a better limit than |\Delta \alpha/\alpha| \lsim 2\cdot 10^{-2}, two orders of magnitude less restrictive than previous bounds. In fact, each of the (mutually exclusive) scenarios of standard Big Bang nucleosynthesis proposed, one based on a high value of the measured deuterium primordial abundance and one based on a low value, may describe some aspects of data better if a change in $\alpha$ of this magnitude is assumed.Comment: 21 pages, eps figures embedded using epsfig macr

Search for varying constants of nature from astronomical observation of molecules

The status of searches for possible variation in the constants of nature from astronomical observation of molecules is reviewed, focusing on the dimensionless constant representing the proton-electron mass ratio $\mu=m_p/m_e$. The optical detection of H$_2$ and CO molecules with large ground-based telescopes (as the ESO-VLT and the Keck telescopes), as well as the detection of H$_2$ with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope is discussed in the context of varying constants, and in connection to different theoretical scenarios. Radio astronomy provides an alternative search strategy bearing the advantage that molecules as NH$_3$ (ammonia) and CH$_3$OH (methanol) can be used, which are much more sensitive to a varying $\mu$ than diatomic molecules. Current constraints are $|\Delta\mu/\mu| < 5 \times 10^{-6}$ for redshift $z=2.0-4.2$, corresponding to look-back times of 10-12.5 Gyrs, and $|\Delta\mu/\mu| < 1.5 \times 10^{-7}$ for $z=0.88$, corresponding to half the age of the Universe (both at 3$\sigma$ statistical significance). Existing bottlenecks and prospects for future improvement with novel instrumentation are discussed.Comment: Contribution to Workshop "High Performance Clocks in Space" at the International Space Science Institute, Bern 201

Constraints on the Variations of the Fundamental Couplings

We reconsider several current bounds on the variation of the fine-structure constant in models where all gauge and Yukawa couplings vary in an interdependent manner, as would be expected in unified theories. In particular, we re-examine the bounds established by the Oklo reactor from the resonant neutron capture cross-section of 149Sm. By imposing variations in \Lambda_{QCD} and the quark masses, as dictated by unified theories, the corresponding bound on the variation of the fine-structure constant can be improved by about 2 orders of magnitude in such theories. In addition, we consider possible bounds on variations due to their effect on long lived \alpha- and \beta-decay isotopes, particularly 147Sm and 187Re. We obtain a strong constraint on \Delta \alpha / \alpha, comparable to that of Oklo but extending to a higher redshift corresponding to the age of the solar system, from the radioactive life-time of 187Re derived from meteoritic studies. We also analyze the astrophysical consequences of perturbing the decay Q values on bound state \beta-decays operating in the s-process.Comment: 25 pages, latex, 5 eps figure