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Agenda
for the parallel workshop sessions in Cosmology.
All links marked with a⇓ can be used to show/hide the abstracts and presentations.
Click here to show/hide all presentations and abstracts and here for a print version.
You may also download the compact program booklet (PDF, 1.9 MB)
and an abstract booklet (PDF, 0.4 MB).
As long as authors provided us with PDF versions of their slides, the corresponding downloads are available on this page.
Monday – Sep 5, 2011
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16:50 – 18:30 |
Cosmology W1
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Parallel Session (Clubraum 3) – Chair:
Yvonne Wong
16:50
(15' + 5')
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Constraints on small-scale cosmological perturbations from gamma-ray searches for dark matter⇓
slides
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Pat Scott (McGill University)
Events like inflation can produce large density perturbations on very small scales in the Early Universe. Probes of small scales are therefore useful for discriminating between inflationary models. The only such constraint presently comes from non-observation of primordial black holes (PBHs), associated with the largest perturbations. Moderate-amplitude perturbations can collapse shortly after equality to form ultracompact minihalos (UCMHs) of dark matter, in far greater abundance than PBHs. If dark matter self-annihilates, UCMHs become excellent targets for indirect detection. I will describe the gamma-ray fluxes expected from UCMHs, the prospect of observing them with gamma-ray telescopes, and limits upon the primordial power spectrum derived from their non-observation by Fermi.
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17:10
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Cosmological constraints on the number of neutrino species⇓
slides
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Jan Hamann (Aarhus University)
The presence of light particles beyond the standard model's three neutrino species can profoundly impact the physics of decoupling and primordial nucleosynthesis. I will review the observational signatures of extra light species, present constraints from recent data, and discuss the implications of possible sterile neutrinos with O(eV)-masses for cosmology.
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17:30
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Constraining the cosmic radiation density due to lepton number with BBN⇓
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Sergio Pastor (IFIC Valencia)
We have determined the BBN constraints on primordial neutrino-antineutrino asymmetries, with a careful treatment of the dynamics of flavor neutrino oscillations, collisions and pair processes. The allowed regions on both the total neutrino asymmetry and the electron neutrino asymmetry at the onset of BBN are obtained taking into account the time evolution of neutrino distributions and the most recent determinations of primordial 4He mass fraction and 2H/H density ratio, which plays a relevant role. These bounds fix the maximum contribution of neutrinos with primordial asymmetries to the radiation content of the universe (to be measured by the Planck satellite) as a function of the mixing parameter θ13, with a global upper bound Neff < 3.4. Analysis published in JCAP 03 (2011) 035
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17:50
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Estimating the tensor-to-scalar ratio and the effect of residual foreground contamination⇓
slides
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Yabebal Fantaye (SISSA)
We consider cosmic microwave background suborbital experiments designed to search for inflationary gravitational waves, and investigate the impact of residual foregrounds that remain in the final estimated maps. We characterize the error covariance due to subtracted foregrounds, and find it to be subdominant compared to instrumental noise and sample variance in our simulated data analysis. We model the unsubtracted residual foreground using a two-parameter power law model and show that marginalization over these parameters is effective in eliminating a bias due to excess foreground power at low $\ell$. We conclude that, at least in the suborbital experimental setups we have simulated, foreground errors are not the main treat for these experiments to reach their target sensitivity.
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18:10
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Foreground fNL⇓
slides
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Alessandro Renzi (SISSA)
We study the astrophysical foreground emissions in the context of the effort for constraining the Cosmic Microwave Background (CMB) anisotropy non-Gaussianity (NG). We parametrize the NG signal by an equivalent fNL evaluated through the Komatsu-Spergel-Wandelt (KSW, astro-ph/0305189) estimator and induced by the known Galactic and extra-Galactic foreground emissions. We conduct our study in the harmonic as well as space domains, by selecting suitable intervals of angular scales and emission intensities. We investigate the effect of spatially varying spectral indeces of the Galactic emissions. Finally, focusing on the diffuse Galactic emissions, we construct masks where the available sky area is characterized by a foreground induced spurious NG signal which is not cosmologically relevant.
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Tuesday – Sep 6, 2011
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16:50 – 18:30 |
Cosmology W2
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Parallel Session (Clubraum 3) – Chair:
Steen Hannestad
16:50
(15' + 5')
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Results from optical followup program of SPT clusters⇓
slides
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Shantanu Desai (Excellence Cluster Universe/LMU München)
The South Pole Telescope (SPT) is a 10m mm wave telescope located at the South Pole and is expected to complete a 3-band survey of 2500 sq. deg by end of 2011. The main goal of this survey is to detect galaxy clusters using Sunyaev-Zeldovich effect and use these clusters for a variety of cosmological studies such as dark energy equation
of state, primordial non-gaussianity and since 2005 we have initiated
an optical and near-IR followup progam to image high significance SPT clusters to measure the photometric redshift and estimate the false contamination rate
of clusters. We will present details of this optical followup campaign and highlight some important implications of these observations for fundamental physics.
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17:10
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Status and perspectives of the CAST experiment⇓
slides
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Biljana Lakic (Rudjer Boskovic Institute)
CERN Axion Solar Telescope (CAST) is currently the most sensitive axion helioscope designed to search for axions produced by the Primakoff process in the solar core. CAST is using a Large Hadron Collider (LHC) test magnet where axions could be converted into X-rays with energies up to 10 keV. During the phase I, the experiment operated with vacuum inside the magnet bores and covered axion masses up to 0.02 eV. In the phase II, the magnet bores are filled with a buffer gas (first 4He and later 3He) at various densities in order to extend the sensitivity to higher axion masses (up to ~1 eV). So far, no evidence of axion signal has been found and CAST set the most restrictive experimental limit on the axion-photon coupling constant over a broad range of axion masses. The latest CAST results with 3He data and future plans will be presented.
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17:30
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Cosmological constraints on thermal relic axions and axion-like particles⇓
slides
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Davide Cadamuro (MPI für Physik)
Cosmological precision data can be used to set very strict constraints on Axions and Axion-like particles produced thermally in the big bang. We briefly review the known bounds and propose two new constraints for Axions and ALPs decaying in the early universe, based upon the concomitant dilution of baryon and neutrino densities, using WMAP7 and other cosmological data.
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17:50
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First second of lepton asymmetries⇓
slides
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Maik Stuke (University of Bielefeld)
We study the influence of lepton asymmetries $l$ on the evolution of the early Universe. $l$ is poorly constrained by observations and might be orders of magnitudes larger than the observed baryon asymmetry.
We find that large lepton asymmetries can influence the dynamics of the QCD phase transition significantly. The cosmic trajectory in the $\mu_B-T$ phase diagram of strongly interacting matter becomes a function of $l$. The latter might trigger the order of the cosmic transition.
Furthermore a large lepton flavour asymmetry changes the number of helicity degrees of freedom of all particles in equilibrium $g_{\ast}$ significantly and thus changes the relic abundance of a given WIMP candidate.
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18:10
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Effect of massive neutrinos in the nonlinear regime⇓
slides
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Daniel Boriero (UNICAMP / RWTH Aachen)
The distribution of matter in small scales, subject to nonlinear effects, will be much better known in the next few years through upcoming surveys. To acomplish the measurent of parameters such as the neutrino mass the theoretical preciseness must evolve accordingly. We present some improvements in theoretical prediction for the matter power spectrum taking in account the effect of massive neutrinos in the nonlinear regime. The method used was a modified version of Halofit calibrated over NBody simulation with massive neutrinos. The results so far differ a great deal from the linear regime and slightly from previous calibration of Halofit.
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Wednesday – Sep 7, 2011
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16:50 – 18:30 |
Cosmology W3
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Parallel Session (Clubraum 3) – Chair:
Jochen Weller
16:50
(15' + 5')
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Dark energy physics expectations at DES⇓
slides
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Marcelle Soares-Santos (Fermi National Accelerator Laboratory)
Giving rise to a new and exciting research field, observations of the last ten years established dark energy as a component of unknown nature responsible for the accelerated expansion of the Universe. A powerful experimental approach to this problem is the study of complementary cosmological probes in large optical galaxy surveys. For such a study, the Sloan Digital Sky Survey (SDSS) is the state of the art data set to be surpassed only by the next generation of experiments such as the upcoming Dark Energy Survey (DES). In this talk we review the four fundamental probes to be explored by DES -- galaxy clusters, weak lensing, large scale structure and supernova -- and report on the status of the experiment which will be commissioned in the Fall of 2011.
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17:10
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Reconstructing the equation of state and density parameter for dark energy from combined analysis of recent SNe Ia, OHD and BAO data⇓
slides
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Debasish Majumdar (Saha Institute of Nuclear Physics, Kolkata)
We adopt a model independent method to reconstruct the dark energy equation of state by analyzing 5 sets of SNe Ia data along with Baryon Acoustic Oscillation (BAO) and Observational Hubble Data (OHD). The SNe Ia data sets include the most recent UNION2 data and other data compilations from the year 2007 to the present. We assume a closed form parametrization of the luminosity distance in terms of redshift and perform a $\chi^2$ analysis of the observational data. The matter density at the present epoch $\Omega_m^0$ is also taken to be a parameter in the analysis and its best-fit values are obtained for each of the data sets. We found a strong dependence of dark energy equation of state on the matter density in the present and earlier epoch. From the analysis, we also predict the lower limit of matter density parameter at an earlier epoch within 1$\sigma$ confidence level for a flat FRW universe. The dark energy equation of state appears to be a slow varying function of $z$. The variation of dark energy density parameter and the matter density parameter are also shown along with their 1$\sigma$ variations.
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17:30
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21 cm cosmology and dark energy⇓
slides
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Reza Ansari (LAL - Univ. Paris Sud)
3D mapping of matter distribution in the universe through the 21 cm radio emission of atomic hydrogen is a complementary approach to optical surveys for the study of the Large Scale Structures, in particular for measuring the BAO (Baryon Acoustic Oscillation) scale up to redshifts z=3 and constrain dark energy.
We propose an instrument to carry such a survey through intensity mapping, without detecting individual galaxies. An R&D effort (electronics, antenna/feeds, software ...), initiated in 2007, is being carried by an international team (France, USA, Canada, China), to design a multi beam (100-1000 beams), large field of view (10-100 sq.deg) and large bandwidth (100 MHz) instrument suited for 21 cm intensity mapping at z=1.
( http://bao.lal.in2p3.fr/21cm/ )
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17:50
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Coupled quintessence through dark energy density⇓
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Laura Lopez Honorez (Université Libre de Bruxelles)
I will present a coupled quintessence model in which the interaction with the dark matter sector depends on some power of the dark energy density. Such a coupling can naturally arise from a field dependent mass term for the dark matter field. I will show in which cases the dynamical analysis of this system possesses a late time accelerated attractor and present the results of a fit to Supernovae Ia, Cosmic Microwave Background and Baryon Acoustic Oscillation data sets. Constraints arising from weak equivalence principle violation arguments will also be discussed.
Reference arXiv:1009.5263
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18:10
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Measuring dark energy parameters and choosing theoretical models⇓
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Sidney Bludman (Universidad de Chile)
All recent supernova, CMB, baryon acoustic oscillation, galaxy clustering and gravitational weak lensing observations of the cosmological expansion are consistent with a
static fine-tuned cosmological constant Lambda, but also may admit a dynamic mechanism, either material Dark Energy or low-curvature modifications of Einstein gravity (Dark Gravity). Trying to interpret the cosmological constant as material vacuum energy leads inevitably to the Cosmological Constant Problem: Why is it so tiny compared with observed material vacuum energy fluctuations? This problem is avoided if, Lambda is interpreted as a classical fine-tuned intrinsic curvature of space-time. Cosmological Coincidence remains: Why do we live at such a late time that material energy density has diluted down to ~Lambda/2?
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