Past Talks @ ICE

Número de entradas: 21

31
Octubre 2017

On the trace anomaly of a Weyl fermion


Inicio: 12:00h
Ponente: Fiorenzo Bastianelli (University of Bologna and INFN, Bologna)
Lugar: Conference Room

We discuss the status of the trace anomaly of a massless chiral fermion in a curved background, which we calculate again using a Pauli-Villars regularization. The motivation of our analysis stems from recent claims that the trace anomaly might contain a term proportional to the topological Pontryagin…
Inicio: 12:00h
Ponente: Fiorenzo Bastianelli (University of Bologna and INFN, Bologna)
Lugar: Conference Room


We discuss the status of the trace anomaly of a massless chiral fermion in a curved background, which we calculate again using a Pauli-Villars regularization. The motivation of our analysis stems from recent claims that the trace anomaly might contain a term proportional to the topological Pontryagin density of the curved background. We do not find such a term in the trace anomaly.
31
Octubre 2017

Cosmological Constant and Renormalization of Gravity


Inicio: 11:00h
Ponente: Shinichi Nojiri (Kobayashi-Maskawa-Institute, Nagoya University, Japan)
Lugar: Conference Room

We propose several covariant models which may solve one of the problems in the cosmological constant.
Inicio: 11:00h
Ponente: Shinichi Nojiri (Kobayashi-Maskawa-Institute, Nagoya University, Japan)
Lugar: Conference Room

We propose several covariant models which may solve one of the problems in the cosmological constant.
19
Octubre 2017

Geometric Foundations of Gravity - An overview of research in Tartu


Inicio: 12:00h
Ponente: Manuel Hohmann (Füüsika Instituut Tartu Ülikool)
Lugar: D2/20

We present a systematic analysis of the dynamics of flat Friedmann-Lema\^{i}tre-Robertson-Walker cosmological models with radiation and dust matter in generalized teleparallel f(T) gravity. We show that the cosmological dynamics of this model is fully described by a function W(H) of the Hubble parameter,…
Inicio: 12:00h
Ponente: Manuel Hohmann (Füüsika Instituut Tartu Ülikool)
Lugar: D2/20

We present a systematic analysis of the dynamics of flat Friedmann-Lema\^{i}tre-Robertson-Walker cosmological models with radiation and dust matter in generalized teleparallel f(T) gravity. We show that the cosmological dynamics of this model is fully described by a function W(H) of the Hubble parameter, which is constructed from the function f(T). I will also give an overview of research in Tartu.
27
Septiembre 2017

MSSM-inspired multifield inflation


Inicio: 12:00h
Ponente: Sergey Vernov ; Ekaterina Pozdeeva
Lugar: Alberto Lobo Conference Room S1-01

We analyze the inflationary scenarios which could be induced by the two-Higgs-doublet potential of the Minimal Supersymmetric Standard Model (MSSM) where five scalar fields have nonminimal couplings to gravity. Observables following from such MSSM-inspired multifield inflation are calculated and a number…
Inicio: 12:00h
Ponente: Sergey Vernov ; Ekaterina Pozdeeva
Lugar: Alberto Lobo Conference Room S1-01

We analyze the inflationary scenarios which could be induced by the two-Higgs-doublet potential of the Minimal Supersymmetric Standard Model (MSSM) where five scalar fields have nonminimal couplings to gravity. Observables following from such MSSM-inspired multifield inflation are calculated and a number of consistent inflationary scenarios are constructed. Cosmological evolution with different initial conditions for the multifield system leads to consequences fully compatible with observational data on the spectral index and the tensor-to-scalar ratio.
01
Marzo 2017

Modeling the distribution of HI in the post-reionization era: Cosmology with SKA


Inicio: 12:30h
Ponente: Francisco Villaescusa-Navarro (Center for Computational Astrophysics (Simons Foundation, New York))
Lugar: Sala Alberto Lobo

I will discuss the possibility of sampling the large-scale structure of the Universe using radio-telescopes through the 21cm intensity mapping technique in the post-reionization era. I will show how to model the spatial distribution of cosmic neutral hydrogen using numerical simulations and the constraints…
Inicio: 12:30h
Ponente: Francisco Villaescusa-Navarro (Center for Computational Astrophysics (Simons Foundation, New York))
Lugar: Sala Alberto Lobo

I will discuss the possibility of sampling the large-scale structure of the Universe using radio-telescopes through the 21cm intensity mapping technique in the post-reionization era. I will show how to model the spatial distribution of cosmic neutral hydrogen using numerical simulations and the constraints that the Square Kilometre Array (SKA) instrument will place on warm dark matter and massive neutrinos. I will also examine how well the SKA1-MID instrument will be able to detect the BAO. Finally, I will discuss the potential problems such as the presence of bright foregrounds and the role of instrument calibration.
16
Febrero 2017

Sufficient Statistics for Cosmology


Inicio: 12:00h
Ponente: Istvan Szapudi (Institute of Astronomy (University of Hawai))
Lugar: Sala Alberto Lobo

Sufficient statistics extract all the cosmological information from a large scale structure survey, thus they sharpen constraints available from traditional statistics, such as power spectrum. The log-power spectrum, the simplest among the approximations studies to date, will double the effective survey…
Inicio: 12:00h
Ponente: Istvan Szapudi (Institute of Astronomy (University of Hawai))
Lugar: Sala Alberto Lobo

Sufficient statistics extract all the cosmological information from a large scale structure survey, thus they sharpen constraints available from traditional statistics, such as power spectrum. The log-power spectrum, the simplest among the approximations studies to date, will double the effective survey volume of future surveys, such as EUCLID and WFIRST. I will review the theory of sufficient statistics, forecasting, and recent results on predicting the log power spectrum.
26
Enero 2017

Redshift-space distortions - Measuring the growth rate of structures from the final VIPERS dataset


Inicio: 12:00h
Ponente: Andrea Pezzotta (Brera Observatory (Milan))
Lugar: Sala Alberto Lobo

Observations of Type Ia Supernovae combined with the anisotropies of the Cosmic Microwave Background have reinforced the conclusion that our Universe is dominated by a repulsive dark energy capable of driving the observed accelerated expansion. Unfortunately this scenario is highly degenerate with the…
Inicio: 12:00h
Ponente: Andrea Pezzotta (Brera Observatory (Milan))
Lugar: Sala Alberto Lobo

Observations of Type Ia Supernovae combined with the anisotropies of the Cosmic Microwave Background have reinforced the conclusion that our Universe is dominated by a repulsive dark energy capable of driving the observed accelerated expansion. Unfortunately this scenario is highly degenerate with the more radical breakdown of General Relativity on cosmological scales, since modified gravity can predict the same expansion history H(z) as in a LCDM (dark energy+ GR). In principle, this degeneracy can be lifted by measuring the growth rate of structure, which depends on the specific theory describing gravity. One of the most reliable probes of the growth of structures is provided by redshift-space distortions (RSD). These arise when measured redshifts, that contain also the contribution of galaxy peculiar velocities, are used as distance proxy, introducing an anisotropy in the measured clustering.  Unfortunately, extracting the linear RSD signal from galaxy redshift surveys is non-trivial, because much of the RSD signal lies on quasi-linear and non-linear scales. This requires a strong effort to properly model non-linear clustering and velocities. Here I present measurements of the growth rate of structure from the new data of the complete VIPERS survey. We implement and improve specific techniques and models, both to correct for any defects inside the measured 2PCF and also to understand the impact of different RSD models on the recovery of the growth rate.   Measurements of the growth rate from VIPERS are in agreement with standard cosmology predictions assuming Einstein gravity in a LCDM background, although they still do not exclude a variety of models in which gravity is modified on cosmic scales
24
Enero 2017

Photometric redshift estimation for precision cosmology


Inicio: 10:30h
Ponente: markus rau (LMU (Munich))
Lugar: Sala Alberto Lobo

Abstract: Photometric redshift uncertainty is one of the dominant sources of systematic error in ongoing and future large area photometric surveys like DES, KiDS, LSST and Euclid. Accurate photometric redshift validation and treatment of redshift uncertainty is therefore a vital requirement…
Inicio: 10:30h
Ponente: markus rau (LMU (Munich))
Lugar: Sala Alberto Lobo

Abstract: Photometric redshift uncertainty is one of the dominant sources of systematic error in ongoing and future large area photometric surveys like DES, KiDS, LSST and Euclid. Accurate photometric redshift validation and treatment of redshift uncertainty is therefore a vital requirement to enter the era of precision cosmology using these surveys. In my talk I will discuss these challenges and present a Machine Learning based photometric redshift methodology, that uses synthetic data from simulations, templates and spectroscopic data to produce highly accurate photometric redshift predictions. In combination with the Smoothed Bootstrap, a specialized resampling technique, it is then possible to incorporate the remaining photometric redshift error into the cosmological parameter constraint.
23
Enero 2017

Addressing systematic effects in the new generation of galaxy surveys


Inicio: 10:30h
Ponente: Jonás Chaves Montero (CEFCA (Teruel))
Lugar: Sala Alberto Lobo

There is a world-wide effort to unravel the nature of gravity and the expansion history of the Universe. The new generation of cosmological surveys such as DES, PAUS, J-PAS, DESI, LSST, Euclid, WFIRST, etc., will provide tons of data that will no longer be dominated by statistical errors but by systematic…
Inicio: 10:30h
Ponente: Jonás Chaves Montero (CEFCA (Teruel))
Lugar: Sala Alberto Lobo

There is a world-wide effort to unravel the nature of gravity and the expansion history of the Universe. The new generation of cosmological surveys such as DES, PAUS, J-PAS, DESI, LSST, Euclid, WFIRST, etc., will provide tons of data that will no longer be dominated by statistical errors but by systematic uncertainties.  I will study the impact of some of these systematic uncertainties on the large-scale structure. I will address baryonic effects using a new implementation of subhalo abundance matching, a model for connecting dark matter haloes with galaxies, that produces the same galaxy clustering as hydrodynamical simulations within statistical errors. Then, I will show the effect of sub-percent redshift uncertainties on the baryonic acoustic oscillations (BAO). I will provide analytical expressions for their effects and I will show how the cosmological information encoded in the BAO is modulated by the interplay of redshift space distortions, redshift errors, bias, and number density of the sample. Finally, I will present ELDAR, a new method for detecting AGN and computing their redshifts in medium- and narrow-band photometric surveys.
19
Enero 2017

Galaxy formation in the Planck Millennium


Inicio: 12:00h
Ponente: Carlton Baugh (Durham)
Lugar: Sala Alberto Lobo

I will give an overview of semi-analytical modelling of galaxy formation, and show how the model predictions are affected by the uncertainty in the modelling of sub-grid physics, as set out in Lacey et al. (2016). I will then show how the model can be used to make predictions for HI intensity…
Inicio: 12:00h
Ponente: Carlton Baugh (Durham)
Lugar: Sala Alberto Lobo

I will give an overview of semi-analytical modelling of galaxy formation, and show how the model predictions are affected by the uncertainty in the modelling of sub-grid physics, as set out in Lacey et al. (2016). I will then show how the model can be used to make predictions for HI intensity mapping experiments.  
123
Institute of Space Sciences (IEEC-CSIC)

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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya