Found 76 talks archived in Cosmology

MIGUEL_ZUMALACARREGUI

MARTIN_CROCCE_1
Monday September 18, 2017
Dr. Martín Crocce
Institute for Space Science, Barcelona, Spain

Abstract


DIEGO_BLAS
Monday September 18, 2017
Dr. Diego Blas
CERN, Switzerland

Abstract


YUN_WANG
Monday September 18, 2017
Prof. Yun Wang
California Institute of Technology, USA

Abstract


fulvio_melia_170531s
Wednesday May 31, 2017
Prof. Fulvio Melia
The University of Arizona

Abstract

The standard model of cosmology has been quite successful accounting for a broad range of data - at least until the past few years. But as the quality of cosmological measurements has continued to improve, tension has grown between observations and the predictions of LCDM. In this talk, we will address several "problem" areas, and then focus on the most recent: the emergence of a rather strong non-inflationary signature in the angular correlation function of the microwave background. Inflation is critical to the internal self-consistency of the standard model. Yet after 4 decades, we still lack convincing evidence that it ever happened.


evencio_mediavilla_170502s
Tuesday May 2, 2017
Prof. Evencio Mediavilla Gradolph
IAC

Abstract

The lack of detection of elementary particles that could explain dark matter and the recent detection of gravitational waves by the LIGO experiment have renewed interest in the hypothesis that dark matter can be made of Primordial Massive Black Holes (PMBH). We review very briefly the outcomes and limits of the classical MACHO experiment, used to probe the dark matter in the halo of the Milky Way from galactic microlensing, and introduce the more universal scenario of quasar microlensing. Quasar microlensing is sensitive to any population of compact objects in the lens galaxy, to their abundance and to their mass. Using microlensing data from 24 lensed quasars, we conclude that the fraction of mass in any type of MACHO is negligible outside of the 0.05 MSun<M<0.45 MSun mass range. This excludes any significant population of intermediate mass PBH. We estimate a fraction of halo mass in microlenses of 20%. The range of masses and abundances are in agreement with those expected for the stellar component. Using the mean mass estimate and some limits derived from multiwavelength microlensing observations we speculate about the stellar Present Day Mass Function.


licia_verde_170131s
Tuesday January 31, 2017
Prof. Licia Verde
ICREA & ICCUB

Abstract

The standard cosmological model has been established  and its parameters are now measured with unprecedented precision. However, there is a big difference between modelling and understanding.  The next decade  will see the era of large surveys; a large coordinated effort of the scientific community in the field  is on-going to map the cosmos producing an  exponentially growing amount of data. This will shrink the statistical errors. But precision is not enough: accuracy is also crucial.   Systematic effects may be in the data but may also be in the model used in their interpretation.  I will present a small selection of examples where I explore  approaches to help the  transition from precision to accurate cosmology. This selection is not meant to be exhaustive or representative, it just cover some of the problems I have been working on recently.


raul_angulo_160728s
Thursday July 28, 2016
Dr. Raúl Angulo
CEFCA

Abstract

Numerical simulations have played a crucial role in the development of modern
cosmology and in the establishment of LCDM. In this talk, I will review the main 
results and the fundamental assumptions behind those dark matter simulations. 
I will focus on the internal structure of halos and report on recent results on the 
formation and evolution of the very first halos to form in cold dark matter cosmologies. 
Then, I will discuss on recent attempts to model and study dark matter in the 
continuum limit. I will show how such methods help to overcome known problems 
of N-body simulations, and also how it is possible to get new insights into dark 
matter dynamics.

rafael_barrena_160315s
Tuesday March 15, 2016
Dr. Rafael Barrena
IAC

Abstract

Planck satellite provides for the first time the possibility to detect galaxy clusters using their Sunyaev-Zeldovich (SZ) effect signature covering the full sky (Planck Col XXIX, 2013). Planck SZ catalogs I and II include more than 1900 sources, of which 700 remain unknown. The study of the purity of these samples and the characterization of SZ sources is essential to perform cosmology with cluster counts. With this aim in mind, the IAC-Planck group is performing the optical validation and characterization of these samples through two long-term observing programs at Canary Island observatories, the ITP 13B15A and the large-term 15B-17A. In this talk we will present intermediate results of this validation program. Using photometric and spectroscopic information (mainly multi-object techniques) we estimate redshifts and dynamical masses in order to minimize the errors in the Msz-Mdyn scaling relation and the SZ clusters mass function which allow a better determination of cosmological parameters (mainly Omega_m, sigma_8 and neutrino mass) from Planck SZ survey.


francisco_kitaura_160128s
Thursday January 28, 2016
Dr. Francisco Kitaura
AIP

Abstract

The cosmological large-scale structure encodes a wealth of information about the origin and evolution of our Universe. Galaxy redshift surveys provide a 3-dimensional picture of the luminous sources in the Universe. These are however biased tracers of the underlying dark matter field. I will discuss the different components which are relevant to model galaxy bias, ranging from deterministic nonlinear, over non-local, to stochastic components. These effective bias ingredients permit us to save computational time and memory requirements, to efficiently produce mock galaxy catalogues. These are useful to study systematics of survey, test analysis tools, and compute covariance matrices to perform a robust analysis of the data. Moreover, this description permits us to implement them in inference analysis methods to recover the dark matter field and its peculiar velocity field. I will show some examples based on the largest sample of luminous red galaxies to date based on the final BOSS SDSS-III data release.



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