Workshop
New Horizons for Modern Cosmology
Jan 19, 2009  Mar 13, 2009The success of the standard cosmological model has many puzzling consequences and raises several key questions which are far from being answered. The observation of dark energy demonstrates that our well established theories of particles and gravity are incomplete if not incorrect. What makes up the dark side of the universe? What created the primordial fluctuations? Is gravity purely geometry as envisaged by Einstein, or is there more to it (such as scalar partners and extra dimensions)? An unprecedented experimental effort is currently being devoted to address these grandchallenge questions in cosmology. This is an intrinsically interdisciplinary issue that will inevitably be at the forefront of research in astrophysics and fundamental physics in the coming decades.
Topics
 Dark energy
 Dark matter
 Inflation
 Gravity
Later applications will be also considered until all the positions will be filled.
Organizers
Marc Kamionkowski (Caltech, USA)
Carlos Martins (CAUP, Porto, Portugal)
Alessandro Melchiorri (University of Rome La Sapienza")
Antonello Polosa (INFN, Rome)
Licia Verde (ICE/CSIC Barcelona, Spain)
Related events
Dark Matter (Conference)  Feb 09, 2009
Dark Energy (Conference)  Mar 02, 2009
Talks
Date  Speaker  Title  Type  Useful Links  

Jan 19, 2009  11:30  P. Creminelli  The Effective Theory of Quintessence: the w<1 Side Unveiled  Seminar 
Abstract
The Effective Theory of Quintessence: the w<1 Side Unveiled We study generic singlefield dark energy models, by a parametrization of the most general theory of their perturbations around a given background, including higher derivative terms. In appropriate limits this approach reproduces standard quintessence, kessence and ghost condensation. We find no general pathology associated to an equation of state w_Q < 1 or in crossing the phantom divide w_Q = 1. Stability requires that the w_Q < 1 side of dark energy behaves, on cosmological scales, as a kessence fluid with a virtually zero speed of sound. This implies that one should set the speed of sound to zero when comparing with data models with w_Q < 1 or crossing the phantom divide. We summarize the theoretical and stability constraints on the quintessential plane (1+w_Q) vs. speed of sound squared. 

Jan 20, 2009  11:30  J. Pritchard  Cosmology from high redshift 21 cm observations  Seminar 
Abstract
Cosmology from high redshift 21 cm observations Upcoming 21 cm experiments present the possibility of opening a new observational window into the high redshift Universe. Many challenges and opportunities face this new cosmological probe. In this talk, I'll cover some of the possibilities for measuring the neutrino mass and the tilt and running of the primordial power spectrum. 
Slides  
Jan 20, 2009  16:30  D. Wands  Local nonGaussianity from inflation: beyond f_NL  Seminar 
Abstract
Local nonGaussianity from inflation: beyond f_NL fNL has become widely used to quantify the nonGaussianity of the primordial density perturbation due to inflation, or alternative, models for the origin of structure in the very early universe. fNL is sufficient to describe the primordial bispectrum in some models, notably the curvaton or ekpyrotic models. However other models of local evolution on superHubble scales may produce other types of local nonGaussianity which may have different observational signatures. One can also give more information, which may be testable observationally, including higherorder statistics (such as the trispectrum) or the full probability distribution function. 
Slides  
Jan 21, 2009  11:30  D. Chung  Phenomenological Connections Between Particle Physics and Dark Energy  Seminar 
Abstract
Phenomenological Connections Between Particle Physics and Dark Energy I explore how particle physics experiments in the near future may give us a new handle on dark energy. 
Slides  
Jan 21, 2009  15:30  L. Senatore  Informal discussion on the preprint arXiv:0901.2572  Informal discussion  
Jan 22, 2009  11:30  A Avgoustidis  Slowroll and DBI inflation with Wilson Lines  Seminar 
Abstract
Slowroll and DBI inflation with Wilson Lines I will describe a novel model of inflation in string theory, where the inflaton field is a Wilson line in the worldvolume of a Dbrane. In its simplest realisation, this construction yields a slowroll model with a Coulomblike potential, giving rise to a nearly flat or red tilted spectrum of (Gaussian) scalar perturbations and negligible gravitational waves. In a warped compactification, however, the inflaton acquires noncanonical kinetic terms of the DBI type, thus allowing for potentially observable nonGaussianity. In Wilson line DBI inflation, many of the stringent constraints applicable to ordinary (position field) DBI inflation get relaxed, allowing for example a significant amount of primordial tensor perturbations. 
Slides  
Jan 22, 2009  16:30  F. Vernizzi  Action approach to cosmological perturbations and inflationary trispectrum from graviton exchange  Seminar 
Abstract
Action approach to cosmological perturbations and inflationary trispectrum from graviton exchange I will present the computation of the connected fourpoint correlation function of the primordial curvature perturbation generated during slowroll inflation with standard kinetic terms, where the correlation is established via exchange of a graviton between two pairs of scalar fluctuations. This contribution yields a nonlinearity parameter of order tau_NL ~ r, which is one order of magnitude larger than the one previously calculated on the basis of scalar perturbations interacting at a point. Finally, I will show that it satisfies a simple relation in the limit where the momentum of the graviton which is exchanged becomes much smaller than the external momenta. 
Slides  
Jan 23, 2009  11:30  C. Martins  From alpha (and mu) to omega  Seminar 
Abstract
From alpha (and mu) to omega I will review the motivation for varying fundamental couplings and discuss how these measurements can be used to constrain fundamental physics scenarios that would otherwise be inaccessible to experiment. I will then focus on the relation between varying couplings and dark eenrgy, and explain how varying coupling measurements might be used to probe the nature of dark energy, with important advantages over standard methods. Assuming that the current (controversial) evidence for varying couplings is correct, a severalsigma detection of dynamical dark energy is feasible within a few years, even using current groundbased facilities. With future instruments like CODEX, a highaccuracy reconstruction of the dark energy equation of state may be possible all the way up to redshift 4. 
Slides  
Jan 30, 2009  11:30  G. Mangano  Did you check your model against the BBN constraints?  Seminar 
Abstract
Did you check your model against the BBN constraints? Abstract: I'll review the present status of BBN, experimental data on light nuclei and theoretical expectations. I'll then go through several examples to illustrate how BBN can constrain physics beyond the Standard Model. 

Jan 30, 2009  15:30  A. Avgoustidis  Informal discussion on contraining tau(z) with supernovas and H(z) data  Informal discussion  
Feb 02, 2009  11:30  A. Achucarro  Moduli stabilization and de Sitter vacua in Supergravity/Superstrings  Seminar 
Abstract
Moduli stabilization and de Sitter vacua in Supergravity/Superstrings Supersymmetric theories have scalar and moduli fields that could account for inflation, dark energy and/or varying constants. On the other hand, our world is not supersymmetric, and in string theory and supergravity, the moduli fields that describe the size and shape of the compactied extra dimensions can be destabilized by supersymmetry breaking. I will review some recent supergravity results about the stability of de Sitter vacua, the conditions for slow roll inflation and the consistency or otherwise of low energy effective actions (e.g. KKLTtype models) obtained by fixing some of the compactification moduli at their critical points. The talk assumes NO prior knowledge of supergravity. 

Feb 02, 2009  15:30  C. Martins  Informal discussion on the ESF Exploratory Workshop Final Report  Informal discussion  
Feb 03, 2009  11:30  F. Piazza  Scale invariant spectrum and rapidly varying speed of sound  Seminar 
Abstract
Scale invariant spectrum and rapidly varying speed of sound I want to give account of a work recently made in collaboration with Justin Khoury (arXiv:0811.3633). We show that curvature perturbations acquire a scale invariant spectrum for any constant equation of state, provided the fluid has a suitably timedependent sound speed. In order for modes to exit the physical horizon, and in order to solve the usual problems of standard big bang cosmology, we argue that the only allowed possibilities are inflationary (albeit not necessarily slowroll) expansion or ekpyrotic contraction. NonGaussianities offer many distinguish features. As usual with a small sound speed, nonGaussianity can be relatively large, around current sensitivity levels. For DBIlike lagrangians, the amplitude is negative in the inflationary branch, and positive in the ekpyrotic branch. Unlike the power spectrum, the threepoint amplitude displays strong running, peaking on smallest (largest) scales in the expanding (contracting) case. While the shape is predominantly of the equilateral type in the inflationary branch, as in DBI inflation, it is of the local form in the ekpyrotic branch. The tensor spectrum is also generically far from scale invariant. In the contracting case, for instance, tensors are strongly blue tilted, resulting in an unmeasurably small gravity wave amplitude on cosmic microwave background scales. 

Feb 03, 2009  16:30  R. Durrer  CMB anisotropies from acausal scaling seeds  Seminar 
Abstract
CMB anisotropies from acausal scaling seeds We investigate models where structure formation is initiated by scaling seeds: We consider rapidly expanding relativistic shells of energy and show that they can fit current CMB and large scale structure data if they expand with superluminal velocities. These acausally expanding shells provide a viable alternative to inflation for cosmological structure formation with the same minimal number of parameters to characterize the initial fluctuations. Causally expanding shells alone cannot fit present data. Hybrid models where causal shells and inflation are mixed also provide good fits. 
Slides  
Feb 04, 2009  10:30  J. Hamann  Constraining the physics of (slowroll) inflation  Seminar 
Abstract
Constraining the physics of (slowroll) inflation After briefly reviewing the phenomenological signatures of inflation, I will discuss the present observational status and give an outlook on what future cosmological probes may be able to reveal about the physics of inflation. 
Slides  
Feb 05, 2009  11:30  L. Verde  Primordial nongaussianity from large scale structure  Seminar 
Abstract
Primordial nongaussianity from large scale structure While simple slowroll inflationary models predict initial conditions extremely close to being Gaussian, recently there has been renewed interest in primordial nongaussianity, motivated mainly by Cosmic Microwave Background results. I will discuss several was to constrain primordial non gaussianity from observations of large scale structures, which are independent and highly complementary to Cosmic Microwave Backgroundbased tests . 

Feb 06, 2009  11:30  C. Bambi  Strange stars: a laboratory to investigate the problem of the cosmological constant.  Seminar 
Abstract
Strange stars: a laboratory to investigate the problem of the cosmological constant. The well known problem of the cosmological constant can have basically two kinds of solutions: very special initial conditions of the Universe or quite peculiar properties of vacuum energy density. The two possibilities may be tested by observing very compact objects (quark stars or hybrid stars). 
Slides  
Feb 12, 2009  10:30  B. Wandelt  Current Constraints and possible pitfalls for parameter estimation in dark energy models with timevarying equation of state  Seminar 
Abstract
Current Constraints and possible pitfalls for parameter estimation in dark energy models with timevarying equation of state I will discuss the surprising ways our knowledge of cosmological parameters is affected when generalizing dark energy to a timevarying equation of state and/or using distance priors to summarize the information in CMB or large scale structure data. 

Feb 12, 2009  16:30  S. Galli  Delayed Recombination and Cosmic Parameters  Seminar 
Abstract
Delayed Recombination and Cosmic Parameters Current cosmological constraints from Cosmic Microwave Background (CMB) anisotropies are typically derived assuming a standard recombination scheme, however additional resonance and ionizing radiation sources can delay recombination, altering the cosmic ionization history and the cosmological inferences drawn from CMB data. We show that for recent observations of CMB anisotropy, from the Wilkinson Microwave Anisotropy Probe satellite mission 5year survey (WMAP5) and from the ACBAR experiment, additional resonance radiation is nearly degenerate with variations in the spectral index, n_s, and has a marked effect on uncertainties in constraints on the Hubble constant, age of the universe, curvature and the upper bound on the neutrino mass. 

Feb 13, 2009  11:30  C. Carbone  Lensed CMB from the Millennium Simulation  Seminar 
Abstract
Lensed CMB from the Millennium Simulation I will present allsky CMB temperature and polarization lensed maps based on a highresolution cosmological Nbody simulation, the Millennium Simulation (MS). I have exploited the lensing potential map obtained using a mapmaking procedure which integrates along the lineofsight the MS dark matter distribution by stacking and randomizing the simulation boxes up to z=127, and which semianalytically supplies the largescale power in the angular lensing potential that is not correctly sampled by the Nbody simulation. The lensed sky has been obtained by properly modifying the LensPix code to account for the MS structures. I will also present allsky lensed maps of the socalled E and B potentials, which are directly related to the electric and magnetic types of polarization. The angular power spectra of the simulated lensed temperature and polarization maps agree well with semianalytic estimates up to l~2500, while on smaller scales there is a slight excess of power which we interpret as being due to nonlinear clustering in the MS. I will also show how nonlinear lensing power in the polarised CMB is transferred to large angular scales by suitably misaligned modes in the CMB and the lensing potential. This work is relevant in view of the future CMB probes, as a way to analyse the lensed sky and disentangle the contribution from primordial gravitational waves. 

Feb 13, 2009  15:30  B. Reid  Informal discussion on applying the Halo Model to Large Scale Structure Measurements of the Luminous Red Galaxies  Informal Discussion 
Abstract
Informal discussion on applying the Halo Model to Large Scale Structure Measurements of the Luminous Red Galaxies We present a method to reconstruct the halo density field traced by LRGs. We use a large set of Nbody simulations to calibrate our model P(k) up to k = 0.2 h/Mpc. We use the halo model as a framework to understand the effects of our uncertainties on the galaxydark matter mapping on the recovered cosmological parameters. We present preliminary constraints from the SDSS DR7 LRG P(k) and contrast our method with previous approaches 
Slides  
Feb 17, 2009  11:30  L. Covi  Gravitino Dark Matter  Seminar 
Abstract
Gravitino Dark Matter We will review the scenario of gravitino DM and discuss in detail the two cases of a colored NLSP with Rparity conservation and of a small Rparity violation, which can both help in relaxing some of the Nucleosynthesis constraints. 

Feb 17, 2009  16:30  J. MiraldaEscude  Strong and Weak Gravitational Lensing as Probes of Dark Matter and Dark Energy  Seminar 
Abstract
Strong and Weak Gravitational Lensing as Probes of Dark Matter and Dark Energy Among the observational tests of the halo density profiles predicted by Cold Dark Matter, strong gravitational lensing in cluster cores is one of the most promising. Recent work on the use of gravitational lensing in cluster cores to constrain the density profile of dark matter will be reviewed and discussed. Possibilities to constrain dark energy models with weak gravitational lensing will also be discussed. 
Slides  
Feb 18, 2009  11:30  Y. Wong  Massive neutrinos and the nonlinear power spectrum  Seminar 
Abstract
Massive neutrinos and the nonlinear power spectrum I will present a brief review of the effects of neutrino masses on cosmological observables such as the cosmic microwave background anisotropies and the largescale structure distribution, as well as the current status of and future prospects for cosmological neutrino mass measurements. I will discuss some recent efforts towards modelling nonlinear effects in the largescale matter power spectrum in the presence of massive neutrinos. 

Feb 19, 2009  11:30  C. PenaGaray  BAO: photometry vs spectroscopy  Seminar 
Abstract
BAO: photometry vs spectroscopy We discuss the requirements for a photometric survey using Luminous Red Galaxies (LRG) to competitively measure the radial baryonic acoustic oscillations (BAO) signal. Spectral variability of the LRG substantially worsens the achievable photometric redshift errors. We estimate the etendue times exposure necessary to obtain a high enough density of galaxies to measure radial BAO with sufficient low shot noise up to a given redsift. 

Feb 19, 2009  16:30  A. Amblard  The CMBPol Mission Concept Study  Seminar 
Abstract
The CMBPol Mission Concept Study I will present some of the conclusions of the CMBPol workshops which took place last yearto study the feasibility and the science benefits of a future satellite mission dedicated to the measurement of the polarization of the CMB. I will review the scientific motivations for such a mission, the systematic effects and show some possible instrumental setups developed for the Experimental Probe for Inflationary Cosmology (EPIC) proposal, a candidate for the future satellite. 

Feb 20, 2009  11:30  R. Crittenden  Looking for nonGaussianity: going beyond fNL  Seminar 
Abstract
Looking for nonGaussianity: going beyond fNL I will review the recent evidence for nonGaussianity in the CMB maps and the techniques by which these measurements are made. Then I will briefly discuss some alternative models for sourcing nonGaussianity from the early universe. 

Feb 25, 2009  11:30  V. Pettorino  Clustering in interacting dark energy cosmologies  Seminar 
Abstract
Clustering in interacting dark energy cosmologies I will illustrate the case of coupled dark Energy, that is to say cosmologies in which dark energy interacts with other components in the universe as cold dark matter or neutrinos. After briefly presenting the topic, I will in particular focus on the case of 'growing neutrinos': in these models, neutrinos with a mass increasing with time might be driven to cluster at very large scales, due to a new interaction stronger than gravity and mediated by the dark energy scalar field. 

Feb 26, 2009  11:30  C. Skordis  EddingtonBornInfeld gravity and the dark sector  Seminar  
Feb 26, 2009  16:30  N. Nunes  Superinflation in Loop Quantum Cosmology  Seminar 
Abstract
Superinflation in Loop Quantum Cosmology We will be looking at the cosmological effects of small scale corrections that arise in Loop Quantum Cosmology (LQC). In particular, we will see how the Friedmann equation is modified under inverse volume and quadratic corrections. We will see that a positively curved universe can undergo a period of several expanding and contracting phases during which a scalar field is displaced in its potential and consequently establishing the initial conditions for standard slowroll inflation. We will also compute the power spectrum of the perturbed scalar field generated during a superinflationary phase of the universe and show that it can be scale invariant and that the horizon problem is solved with only a few efolds of superinflationary expansion. Finally we will see that the tensor spectrum is strongly blue, which means that the abundance of gravitational waves, in these models, is strongly suppressd on the large scales. 
Slides  
Feb 27, 2009  11:30  T. Koivisto  Higher inverse derivative gravity  Seminar 
Abstract
Higher inverse derivative gravity We consider gravitational alternatives to dark energy defined by actions of apparently nonlocal forms with (negative) powers of the d'Alembertian acting on curvature invariants. In particular the effects to cosmological expansion and structure formation will be discussed. 
Slides  
Mar 05, 2009  11:30  H. Peiris & D. Huterer  Measuring the galaxymass and galaxydust correlations through magnification and reddening  Informal Discussion 
Abstract
Measuring the galaxymass and galaxydust correlations through magnification and reddening


Mar 06, 2009  11:30  R. Easther  Generating a Gravitational Wave Background After Inflation  Seminar  
Mar 09, 2009  15:00  A. Cooray  Informal Discussion on CMB Weak Lensing  Informal Discussion  
Mar 11, 2009  11:30  J. Weller  Cosmology with Galaxy Clusters  Seminar  
Mar 12, 2009  11:30  A. Melchiorri  New Constraints from CMB Anisotropies  Seminar  
Mar 11, 2010  14:30  Francesca Borzumati  Flavour Physics in SUSY GUTs  Seminar 