Extending the Coyote emulator to dark energy models with standard w0w_0-waw_a parametrization of the equation of state

We discuss an extension of the Coyote emulator to predict non-linear matter power spectra of dark energy (DE) models with a scale factor dependent equation of state of the form w = w_0 + ( 1 - a )w_a . The extension is based on the mapping rule between non-linear spectra of DE models with constant equation of state and those with time varying one originally introduced in ref. [40]. Using a series of N-body simulations we show that the spectral equivalence is accurate to sub-percent level across the same range of modes and redshift covered by the Coyote suite. Thus, the extended emulator provides a very efficient and accurate tool to predict non-linear power spectra for DE models with w_0 - w_a parametrization. According to the same criteria we have developed a numerical code, and we have implemented in a dedicated module for the CAMB code, that can be used in combination with the Coyote Emulator in likelihood analyses of non-linear matter power spectrum measurements. All codes can be found at https://github.com/luciano-casarini/PKequalComment: All codes can be found at https://github.com/luciano-casarini/PKequa

Null test for interactions in the dark sector

Since there is no known symmetry in Nature that prevents a non-minimal coupling between the dark energy (DE) and cold dark matter (CDM) components, such a possibility constitutes an alternative to standard cosmology, with its theoretical and observational consequences being of great interest. In this paper we propose a new null test on the standard evolution of the dark sector based on the time dependence of the ratio between the CDM and DE energy densities which, in the standard $\Lambda$CDM scenario, scales necessarily as $a^{-3}$. We use the latest measurements of type Ia supernovae, cosmic chronometers and angular baryonic acoustic oscillations to reconstruct the expansion history using model-independent Machine Learning techniques, namely, the Linear Model formalism and Gaussian Processes. We find that while the standard evolution is consistent with the data at $3\sigma$ level, some deviations from the $\Lambda$CDM model are found at low redshifts, which may be associated with the current tension between local and global determinations of $H_0$.Comment: 15 pages, 12 figure

High precision spectra at large redshift for dynamical DE cosmologies

The next generation mass probes will investigate DE nature by measuring non-linear power spectra at various z, and comparing them with high precision simulations. Producing a complete set of them, taking into account baryon physics and for any DE state equation w(z), would really be numerically expensive. Regularities reducing such duty are essential. This paper presents further n-body tests of a relation we found, linking models with DE state parameter w(z) to const.-w models, and also tests the relation in hydro simulations.Comment: PASCOS 2010, the 16th International Symposium on Particles, Strings and Cosmology, Valencia (Spain), July 19th - 23rd, 201

Conformational Assignement, Absolute Configuration and Chiral Separation of all the Stereoisomers Created by the Combined Presence of Stereogenic Centers and Stereogenic Conformational Axes in a Highly Hindered 1,5-Naphthyl Sulfoxide.

The presence of two stereogenic centers and of two stereogenic conformational axes in 2,6-dimethyl-1,5-bis(2-methyl-2-propylsulfinyl)naphthalene (1) entails the existence of 10 stereoisomers. In particular, both the meso form (1a) and the racemic form (1b) are constituted by three atropisomers; in the case of the latter (1b) each of them entails a pair of enantiomers (total of six species), whereas owing to the symmetry only one of the three atropisomers of the meso form (1a) yields a pair of enantiomers (a total of four species). Despite the low conformational interconversion barrier (18.5 kcal/mol) all of them have been separated by low temperature (-45°C) chiral HPLC. Their configurational and conformational assignment has been achieved by a combined use of NMR (both in solution and solid state) and on-line CD-detected chiral HPLC. The single crystal X-ray diffraction yielded the absolute configuration of one of the stereoisomers ((ZR,ER)-1b) from which all the others could be obtained by CD relationship