### Conveners

#### 04 - Dark energy

- Martin Kunz (Universite de Geneve (CH))

#### 04 - Dark energy

- Martin Kunz (Universite de Geneve (CH))

#### 04 - Dark energy

- Martin Kunz (Universite de Geneve (CH))

Dr
Timothée Delubac
(Ecole Polytechnique Fédérale de Lausanne)

14/12/2015, 14:00

Talk

The first detection of Baryon Acoustic Oscillations (BAO) in the correlation function of the galaxy density field by Eisenstein et al. (2005) and Cole et al. (2005) set a milestone in the era of precision cosmology, providing a new, independent method for the measurement of cosmological distances. The Baryon Oscillation Spectroscopic Survey (BOSS), one of the experiment of the third generation...

Justyna Średzińska
(Nicolaus Copernicus Astronomical Center PAS)

14/12/2015, 14:27

Talk

The discovery of the accelerated expansion of the Universe lead to the concept of dark energy. This is one of the most interesting topic in modern relativistic astrophysics. Precise measurement of this effect is a key to understand the nature of this medium, and we need good probes to do that. Quasars appears as an ideal candidate for this purpose as these objects are highly luminous and...

Lorenzo Amati
(INAF - IASF Bologna)

14/12/2015, 14:53

Talk

Given their huge isotropic-equivalent radiated energies, up to more than 10$^{54}$ erg released in a few tens of seconds,
and their redshift distribution extending up to more than z = 9, Gamma-Ray Bursts (GRB) are in principle a powerful tool for
measuring the geometry and expansion rate of the Universe. In the recent years, several attempts have been made to
exploit the correlation between...

Mr
Phillip Helbig
(*)

14/12/2015, 15:19

Talk

The magnitude-distance relation for type Ia supernovae is one of the key pieces of evidence supporting the cosmological "concordance model". The resulting constraints on the cosmological parameters are often derived under the idealized assumption that the universe is perfectly homogeneous (at least as far as light propagation is concerned). However, we know that the universe is not...

Clare Burrage
(University of Nottingham)

14/12/2015, 16:15

Talk

I will discuss the prospect that the first evidence for dark energy may be found through meter scale, laboratory based, atom interferometry experiments. I will discuss how, in order to be compatible with fifth force constraints, dark energy scalar fields must have a screening mechanism which hides their effects from us within the solar system. Focusing in particular on one such screening...

Ignacy Leonard Sawicki
(University of Geneva)

14/12/2015, 16:40

Talk

I will discuss how considerations of causality put constraints on modifications of gravity where the perturbations in new degrees of freedom propagate on an acoustic metric different from the space time metric. More to come.

Massimiliano Rinaldi
(University of Trento)

14/12/2015, 17:05

Talk

We study the Einstein Yang-Mills Higgs equations in the SO(3) representation on a isotropic and homogeneous flat Universe, in the presence of radiation and matter fluids. We map the equations of motion into an autonomous dynamical system of first-order differential equations and we find the equilibrium points. We show that there is only one stable fixed point that corresponds to an accelerated...

Yves Dirian
(University of Geneva)

14/12/2015, 17:29

Talk

We study the cosmological predictions of two recently proposed non-local modifications of General Relativity. Both models have the same number of parameters as $\Lambda$CDM, with a mass parameter $m$ replacing the cosmological constant. We implement the cosmological perturbations of the non-local models into a modification of the CLASS Boltzmann code, and we make a full comparison to CMB,...

Mr
Erick Jonathan Almaraz Aviña
(Instituto de Física / UNAM)

14/12/2015, 17:53

Poster

The physical explanation of the dark energy as the responsible agent of the currently accelerated expansion of the Universe remains as one of the most challenging questions of the modern physcis. Besides the standard scenario (in which it is caused by a cosmological constant) there are other proposals which range from the introduction of new more or less exotic components, to modifications to...

Ms
Mariana Jaber
(Universidad Nacional Autónoma de México)

14/12/2015, 17:56

Poster

For this work a parametrization for the Dark Energy (DE) equation of state is proposed and tested.
We derive constraints on our state equation parameters from the baryon acoustic oscillation (BAO) measurements. In particular we take advantage of high precision BAO measurements from galaxy clustering and the Lymann-$\alpha$ forest in the SDSS-III Baryon Oscillation Spectroscopic Survey...

attaallah almasi
(vu university of amsterdam)

14/12/2015, 17:59

Poster

The search for non-Newtonian forces has been pursued following many different paths. Recently it was suggested that hypothetical chameleon interactions, which might explain the mechanisms behind dark energy, could be detected in a high-precision force measurement. In such an experiment, interactions between parallel plates kept at constant separation could be measured as a function of the...

Jacob Moldenhauer
(University of Dallas)

14/12/2015, 18:02

Poster

It is not only important to constrain the parameters of cosmological models with the most recent and precise observations, but it is also crucial to understand the physical consequences of those parameters for the different, but complimentary observations involved. CosmoEJS is an interactive Java package of simulations that allow the user to explore the ramifications of choosing various...

Mr
Hanwool Koo
(Seoul National University)

14/12/2015, 18:05

Poster

By analyzing the spin alignment of isolated galaxy pairs from SDSS DR10 and in N-body simulation data for the coupled dark energy (cDE) model, we constrain the strength of dark sector interaction of cDE model. We perform Kolmogorov-Smirnov 2-sample tests to 6 different cases, one is the spin alignments from SDSS DR10 and in N-body simulation data for LCDM model, others are the spin alignments...

Dragan Hajdukovic
(Institute of Physics, Astrophysics and Cosmology (ME))

14/12/2015, 18:08

Poster

Our study is based on the working hypothesis that by their nature quantum vacuum fluctuations are virtual gravitational dipoles. This hypothesis is the simplest solution to the cosmological constant problem and opens the possibility to consider the known Standard Model matter (i.e. matter made from quarks and leptons interacting through the exchange of gauge bosons) as the only content of the...

Anna Paula Bacalhau
(Centro Brasileiro de Pesquisas Físicas)

14/12/2015, 18:12

Poster

In this work we investigate the features of the primordial power spectrum when it arises from a contracting phase in the context of a bouncing Universe.
We consider a toy model in which the Universe is dominated by a scalar field with an exponential potential, further on referred as the quintessence component. This choice is motivated by known results in the literature showing that such...

Alicia Simon-Petit
(Applied Mathematics Laboratory, ENSTA ParisTech, Université Paris-Saclay)

14/12/2015, 18:15

Poster

How effective barotropic matter can emerge from the interaction of cosmological fluids in an isotropic and homogeneous cosmological model ?
The dynamics of homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker universes is a natural special case of generalized Lotka-Volterra systems where each of the universe's fluid components can be seen as a competitive species in a predator-prey...

Matteo Martinelli
(ITP, Heidelberg)

15/12/2015, 14:00

Talk

The latest cosmic microwave background data obtained by ESA Planck satellite allow us to test the evolution and content of the Universe in great detail. I will review the analysis done by the Planck collaboration and presented in the "Planck 2015 results. XIV. Dark energy and modified gravity" paper, which considered two broad cases: a DE which affects the background evolution and DE or MG...

Jason Dossett
(INAF - Osservatorio Astronomico di Brera)

15/12/2015, 14:26

Talk

There has been quite a bit of recent discussion about tension between CMB and weak lensing data sets, especially in the context of testing general relativity using modified growth parameters. We use a combination of cosmological data sets, including the CMB temperature anisotropy data from Planck, weak lensing tomography from CFHTLenS, and the WiggleZ galaxy power spectrum to place...

Mario Ballardini
(University of Bologna)

15/12/2015, 14:53

Talk

We study the predictions for structure formation in an induced gravity
dark energy model
with a quartic potential. By developing a dedicated Einstein-Boltzmann
code, we study
self-consistently the dynamics of homogeneous cosmology and of linear
perturbations
without using any parametrization,
accurately recovering the quasi-static analytic approximation in the
matter dominated era.
We...

Caroline Heneka
(Dark Cosmology Centre, Copenhagen)

15/12/2015, 15:19

Talk

Cold (or clustering) dark energy models present an interesting phenomonology in comparison to standard homogeneous dark energy.
We investigate the impact of cold dark energy on the background evolution, on the linear level, as well as at the nonlinear level on structure formation. For an accurate description at the nonlinear level, the halo mass function is carefully recalibrated to include...