JENAM 2010 symposium, 6-7 September 2010, Lisbon, Portugal
List of abstracts Title:Astrophysical Probes of Fundamental Physics The dramatic confrontation between new observations and theories of the early and recent universe makes cosmology one of the most rapidly advancing fields in the physical sciences. The universe is a unique laboratory in which to probe fundamental physics, the rationale being to start from fundamental physics inspired models and explore their consequences in sufficient quantitative detail to be able to identify key astrophysical and cosmological tests of the underlying theory (or developing new tests when appropriate). An unprecedented number of such tests will be possible in the coming years, by exploiting the ever improving observational data. In this spirit I will highlight some open issues in cosmology and particle physics and provide some motivation for this symposium. Title:Probing Dark Energy with Varying Fundamental Parameters I plan to present current constraints on the possible coupling between dark energy and electromagnetism. I also plan to forecast, using different methods, to what accuracy such coupling can be determined or constrained with data from future spectrographs (ESPRESSO and CODEX). Title: Varying Speed of Light and Cosmic Structure I review varying speed of light theories resulting from having different metrics for matter and for gravity. In these theories there are 2 light cones at any point and the speed of light with respect to that of gravity changes. In the minimal theory the action maps into a (anti-)DBI action in the Einstein frame, and scale-invariant fluctuations are produced. I explain how this basic prediction comes about and can be modified in non-minimal theories. The predictive value of the theory is then in its non-Gaussian predictions which have a unique form for each tilt. Title:Beyond Bekenstein’s Theory There are several very different motivations for studying the variation of fundamental constants. They may provide a connection between cosmology and particle physics due to the coincidence of large dimensionless numbers arising from the combination of different physical constants. Bekenstein's variable charge model is very attractive because it is based on very general assumptions: covariance, gauge invariance, causality and time-reversal invariance of electromagnetism. The very generality of its assumptions guarantee the applicability of the scheme to other gauge interactions such as the strong forces. Besides, it introduces a useful simplifying assumption; namely, that the gravitational sector is unaffected by the scalar field introduced to vary the coupling constant . That is why it is interesting to explore first this simplified model, before a similar exploration of more general theories. However, the model uses an ensemble of classical particles to represent matter and this is not a good model of matter wherever quantum phe-nomena are important, neither at high energy scales or small distances scales, since fermions have a natural length scale, namely the Compton wavelength of the particle. Title:Varying Fundamental Constants from Big Bang to Atomic Clocks I present a review of works devoted to the variation of the fine structure constant alpha, strong interaction and fundamental masses (Higgs vacuum). There are some hints for the variation in quasar absorption spectra and Big Bang nucleosynthesis data. A very promising method to search for the variation consists in comparison of different atomic clocks. Huge enhancement of the variation effects happens in transitions between very close atomic, nuclear and molecular energy levels. Large enhancement also happens in nuclear, atomic and molecular collisions near resonances. How changing physical constants may occur? Light scalar fields very naturally appear in modern cosmological models, affecting parameters of the Standard Model (e.g. alpha). Cosmological variations of these scalar fields should occur because of drastic changes of matter composition in Universe: the latest such event is rather recent (about 5 billion years ago), from matter to dark energy domination. Massive bodies can also affect physical constants. Title:Experiments with Optical Clocks Based on Trapped Ions The comparison of different optical transition frequencies over time can be used in a laboratory search for a possible time dependence of the fine structure constant. Optical clocks with laser-cooled trapped ions offer excellent control of systematic frequency shifts and allow to perform highly precise measurements of frequencies and frequency ratios. We investigate two reference transitions with very low natural linewidths that are promising candidates for precise clocks and also offer high sensitivity to variations of alpha: the electric octupole transition at 467 nm in 171Yb+ and the optical nuclear transition at about 7.6 eV in 229Th3+. Title: Testing the stability of fundamental constants using LNE-SYRTE clock ensemble SYRTE is developing an ensemble of high performance atomic clocks and precision oscillators. This unique ensemble comprises three atomic fountain clocks, three optical lattice clocks as well as ultra stable microwave and optical oscillators. This clock ensemble is connected to worldwide remote locations through satellite time and frequency transfer systems. Such an ensemble provides a large number of possibilities for testing fundamental physical laws, relying on the high accuracy and high stability of these devices. We will report on recent progress in the level of performance and on several fundamental tests using LNE-SYRTE clocks. This includes new and improved comparisons between Rb and Cs fountains. This also includes absolute frequency measurements of several optical frequencies using atomic fountains, including the SYRTE transportable fountain FOM. We will also report on the application of these measurements to test the stability of fundamental constants with time and gravitation potential. Improved tests of Lorentz and position invariance using a cryogenic oscillator will also be described. We will also report on the latest developments of Sr and Hg optical lattice clocks. In the future, improved fundamental tests will be done using the possibilities offered by the PHARAO cold atom space clock. We will give an overview of the status of the PHARAO/ACES project. Title:White Dwarf Constraints on Varying Constants In this talk we review the several constraints that can be placed on a varying gravitational constant using white dwarfs. In particular, the cooling of white dwarfs and more specifically the white dwarf luminosity function allows to place constraints on the rate of variation of G. We foresee that future space missions, like Gaia an SIM, will provide tight constraints on such a variation. We also discuss the limits that can be obtained using pulsating white dwarfs, of which G117-B15A, the most stable optical clock know so far, is a representative example. Finally, we summarize the limits on a varying G that can be obtained using the Hubble diagram of Type Ia (thermonuclear) supernovae. Title:Constraining Newton's Gravitational Constant with CMB Temperature and Polarization Anisotropies We present new constraints on cosmic variations of Newton's gravitational constant by making use of the latest CMB data from WMAP, BOOMERANG, CBI and ACBAR experiments and independent constraints coming from Big Bang Nucleosynthesis. We found that current CMB data provide constraints at the 10% level, that can be improved to 3% by including BBN data. We show that future data expected from the Planck satellite could constrain G at the 1.5% level while an ultimate, cosmic variance limited, CMB experiment could reach a precision of about 0.4%, competitive with current laboratory measurements. Title:The Variation of G in a Negatively Curved Space-time Scalar-tensor (ST) gravity theories provide an appropriate theoretical framework for the variation of Newton's fundamental constant, conveyed by the dynamics of a scalar-field non-minimally coupled to the space-time geometry. The experimental scrutiny of scalar-tensor gravity theories has led to a detailed analysis of their post-newtonian features, and is encapsulated into the so-called parametrised post-newtonian formalism (PPN). Of course this approach can only be applied whenever there is a newtonian limit, and the latter is related to the GR solution that is generalized by a given ST solution under consideration. This procedure thus assumes two hypothesis: On the one hand, that there should be a weak field limit of the GR solution; On the other hand that the latter corresponds to the limit case of given ST solution. In the present work we consider a ST solution with negative spatial curvature. It generalizes a general relativistic solution known as being of a degenerate class (A) for its unusual properties. In particular, the GR solution does not exhibit the usual weak field limit in the region where the gravitational field is static. The absence of a weak field limit for the hyperbolic GR solution means that such limit is also absent for comparison with the ST solution, and thus one cannot barely apply the PPN formalism. We therefore analyse the properties of the hyperbolic ST solution, and discuss the question o defining a generalised newtonian limit both for the GR solution and for the purpose of contrasting it with the ST solution. This contributes a basic framework to build up a parametrised pseudo-newtonian formalism adequate to test ST negatively curved space-times. Title:String Theory, Dark Energy and Varying Couplings Semi-realistic compactifications of the extra space dimensions predicted by string theory generically lead to a large number of scalar fields (the moduli fields) in the resulting effective 4D field theory. I review the difficulties of some recent attempts to find stabilized string theory vacua with positive cosmological constant at tree level and comment on various issues related to the discussion of varying fundamental couplings in the context of string compactifications. Title:New Analysis of a Large Sample of VLT Quasar Spectra for Varying Fine structure Constant Previous observations of quasar spectra from the Keck telescope suggested a time variation of the fine structure constant. We have now completed a new study using a large sample of quasar spectra from the VLT. When the new VLT data are combined with the previous Keck sample, a consistency emerges within the data itself, concordant with the earlier Keck result, and in addition revealing a statistically significant signal for a dipole-type spatial dependence. Title:The Value of the Fine-structure Constant over Cosmological Times The optical spectra of objects classified as QSOs in the SDSS catalogues are analyzed with the aim of determining the value of the fine structure constant in the past and then check for possible changes in such constant over cosmological timescales. The analysis is done by measuring the position of the fine structure lines of the [OIII] doublet in QSO nebular emission. A value of Delta alpha / alpha= (+2.4+-2.5) x 10^{-5} (up to redshift z=0.8) was determined. The use of a larger number of spectra allows a factor ~5 improvement on previous constraints based on the same method. On the whole, we find no evidence of changes in alpha on such cosmological timescales. The mean variation compatible with our results is 1/ Delta alpha / alpha=(+0.7+-0.7)x10^{-14} yr^{-1}. Title:Current State of μ Measurements Versus Cosmic Time One of the fundamental constants of the universe is the ratio of the proton to electron mass often designated as mu. The value of this constant has been measured as a function of cosmic time in both terrestrial laboratories and in astronomical objects. This talk examines the results of these measurements with a main focus on the astronomical measurements that produce mu values at early times in the universe. All of the astronomical measurements involve molecular spectroscopy since the rotational and vibrational energies of molecules are sensitive to the value of mu. Radio methods have measured rotational energies in the relatively local universe while optical studies of the electronic-vibrational-rotational transitions in Damped Lyman Alpha clouds have probed the early universe. To date no convincing measurement of a change in the value of mu have been made. The talk will discuss the methods, accuracy, and limitations of each measurement. Title:Robust Limit on a Varying Proton-to-electron Mass Ratio from a Single H2 System The variation of the dimensionless fundamental physical constant mu can be checked through observations of Lyman and Werner lines of molecular hydrogen observed in the spectra of distant QSOs. Only few systems have been used for the purpose providing different results between the different authors. Our intention is to asses the accuracy of the investigation concerning a possible variation of the fundamental physical constant mu=m_p/m_e and to provide more robust results. The goal in mind is to resolve the current controversy on variation and devise explanations for the different findings. We achieve this not by another single result but by providing alternative approaches to the problem. Current analyses tend to underestimate the impact of systematic errors. This work presents alternative approaches to handle systematics and introduces few methods required for precision analysis of QSO spectra available in the near future. Furthermore we present first results of recent state-of-the-art UVES observations. Title:On the Variation of the Proton-to-electron Mass Ratio The dimensionless proton-electron mass ratio is one of the central targets for an experimental search of a varying coupling constant. On a cosmological time scale the hydrogen molecule, being the most abundant molecular species in the universe, is a good test ground. Although many quasar and damped-Lyman systems have been identified only very few of those bear the signatures of a high quality absorption spectrum of molecular hydrogen. We will report on analysis of a high signal-to-noise ratio VLT-spectrum of J2123, which we compare to a spectrum of the same system observed at Keck. A constraint on a varying mass ratio will be derived. Further we will illustrate the analysis of a lower quality spectrum from the Q2348-011 system. Title:Sensitivity of Molecular Microwave Spectra to Varying Fundamental Constants Microwave spectra of molecules are increasingly used in astrophysics to study possible variations of the fine-structure constant alpha and the electron-to-proton mass ratio mu. Typically, microwave transitions are at least 100 times more sensitive to variation of fundamental constants, than optical transitions. Moreover, microwave transitions of different nature are sensitive to different combinations of fundamental constants. We will discuss several examples of transitions, which can be used in astrophysical studies of variation of fundamental constants. Title:Searching for Chameleon-like Scalar Fields Chameleon-like scalar field models predict a strong dependence of masses and coupling constants on the ambient matter density. Since baryonic matter densities in terrestrial and interstellar environments differ by approximately 15 orders of magnitude, one can test this prediction experimentally through the measurements of relative frequencies in molecular transitions which are most sensitive to changes in dimensionless physical parameters such as, e.g., the electron-to-proton mass ratio. We present our recent measurements obtained with three radio telescopes: 32-m Medicina, 45-m Nobeyama, and 100-m Effelsberg. Title:Cosmological Birefringence The possibility that the plane of polarization of light traveling large distances through the universe might rotate arises in a number of fundamental physical contexts, such as the Einstein Equivalence Principle violation and the presence of a dark matter or dark energy pseudo-scalar field. We have devised a test of such cosmological birefringence, using the UV polarization of distant radio galaxies and report on a recent update of this test. Title:Detection of 21cm, H2 and D Absorption at z>3 Along the Line of Sight of J1337+3152 We report the detection of 21-cm and molecular hydrogen absorption lines in the same damped Lyman α± system (DLA; with log N(HI) = 21.36 +/- 0.10) at zabs = 3.17447 towards SDSSJ133724.69+315254.55 (zem ~ 3.174). We constrain the variation of the combination of fundamental constants x = alpha^2 gp/mu, Delta x/x = - (1.7 +/- 1.7)x10-6. This system is unique as we can at the same time have an independent constraint on μ using H2 lines. However, as the H2 column density is low, only Werner band absorption lines are seen and, unfortunately, the range of sensitivity coefficients is too narrow to provide a stringent constraint Delta mu/mu <= 4.0x10-4. Title: Probing Fundamental Constant Evolution with Radio Spectroscopy Astrophysical studies of redshifted spectral lines provide a powerful probe of changes in low-energy fundamental constants over a large lookback time. In this talk, I will focus on radio studies of changes in the fundamental constants, using different molecular and atomic spectral transitions that allow us to test for changes in the fine structure constant, the proton-electron mass ratio and the proton gyromagnetic ratio. I will also discuss the likely improvements to such studies with the planned advent of new telescopes over the next decade. Title:Future Facilities for Probing Fundamental Constants I will review the future roles of the VLT and European Extremely Large Telescope (E-ELT) in probing possible variations of fundamental constants. List of posters Title: [O III] as a probe of variations of the fine-structure constant from z=0 to z=3 We use the separation of the [O III]4959,5007 doublet in spectra of galaxies from z=0 to 0.7 from the SDSS to constrain variations in the fine-structure constant over that redshift range in an extension of an earlier study by Bahcall et al (2004). Combined with observations of [O III]4959,5007 in high redshift quasars with the VLT we use this to constrain the variation of alpha out to z~2.5. Title: Non-Gaussianity in WMAP Data Due to the Correlation of CMB Lensing Potential with Secondary Anisotropies We measure the skewness power spectrum of the Cosmic Microwave Background (CMB) anisotropies optimized for a detection of the secondary bispectrum generated by the correlation of the CMB lensing potential with integrated Sachs-Wolfe effect and the Sunyaev-Zel'dovich effect. The covariance of our measurements is generated by Monte-Carlo simulations of Gaussian CMB fields with noise properties consistent with Wilkinson Microwave Anisotropy Probe (WMAP) 5-year data. When interpreting multi-frequency measurements we also take into account the confusion resulting from unresolved radio point sources. We analyze Q, V and W-band WMAP 5-year raw and foreground-cleaned maps using the KQ75 mask out to lmax = 600. We find no significant evidence for a non-zero non-Gaussian signal from the lensing-secondary correlation in all three bands and we constrain the overall amplitude of the cross power spectrum between CMB lensing potential and the sum of SZ and ISW fluctuations to be 0.42 +- 0.86 and 1.19 +- 0.86 in combined V and W-band raw and foreground-cleaned maps provided by the WMAP team, respectively. The point source amplitude at the bispectrum level measured with this skewness power spectrum is higher than previous measurements of point source non-Gaussianity. We also consider an analysis where we also account for the primordial non-Gaussianity in addition to lensing-secondary bispectrum and point sources. The focus of this paper is on secondary anisotropies. Consequently the estimator is not optimised for primordial non-Gaussianity and the limit we find on local non-Gaussianity from the foreground-cleaned V+W maps is fNL = -13 +- 62, when marginalized over point sources and lensing-ISW/SZ constributions to the total bispectrum. Title: Dark energy and quantum gravitation, from neutrino oscillations We argue that the present classical formalism of neutrino oscillations is just approximate, thus still requiring various second-order corrections. Title: High resolution molecular observations of dense dark cores We present the results from the observation of two dense dark cores, L183 and L1512, carried out at the Medicina radiotelescope. The aim of the work is to probe a positive velocity offset of ~25m/s between the HC3N (J=2-1) 18.2 GHz and the NH3 (J,K)=(1,1) 23.7 in such molecular clouds. The offset in Vr suggests a relative change of the electron-to-proton mass ratio (delta mu/mu = (22 +- 4 stat +- 3 sys) x10^-9, with mu=me/mp) possibly connected with the two extremely different environments terrestrial and interstellar (Levshakov et al. 2008,2009, Molaro et al. 2009). Title: Spectrograph Calibration with Asteroid's Sunlight Astronomical search for a variation of fundamental constants is dealing with accurate radial velocity measurements and need reliable astronomical standards to calibrate the spectrographs to assess possible systematic. Stellar radial velocity standards offer a reference at the level of few hundreds of m/s and are clearly not adequate. We use solar light reflected by the asteroid Ceres observed with HARPS to measure solar lines' wavelengths and we show that sunlight reflected by asteroids could be used can be used to improve the uncertainties of solar line positions and therefore to be used as a radial velocity standard. The new measurements are consistent with the atlas obtained on FTS solar spectra but with higher precision by a factor greater than 3. The new atlas provides a new way to check radial velocity accuracy down to about 50 m/s locally and few m/s globally. The asteroid-based technique could provide a new way to track radial velocity shifts and It could also be used to study radial velocity deviations in spectrographs such as those recently detected in HIRES and UVES which are crucial for the search of the fundamental constants' variability. |
