Search Publications
Hyperbolic inflation in the light of Planck 2015 data
Basilakos, Spyros; Barrow, John D.
Rubano and Barrow have discussed the emergence of a dark energy, with late-time cosmic acceleration arising from a self-interacting homogeneous scalar field with a potential of hyperbolic power type. Here, we study the evolution of this scalar-field potential back in the inflationary era. Using the hyperbolic power potential in the framework of in…
Post-Planck dark energy constraints
Hazra, Dhiraj Kumar; Pal, Supratik; Sen, Anjan A. +2 more
We constrain plausible dark energy models using the recently published cosmic microwave background (CMB) temperature anisotropy data from Planck together with WMAP9 low-ℓ polarization data and the data from low redshift surveys. To circumvent the limitations of any particular equation of state toward describing all existing dark energy models, we …
Searching for features of a string-inspired inflationary model with cosmological observations
Hu, Bin; Cai, Yi-Fu; Ferreira, Elisa G. M. +1 more
The latest Planck results show a power deficit in the temperature anisotropies near ℓ≈20 in the cosmic microwave background (CMB). This observation can hardly be explained within the standard inflationary Λ -cold-dark-matter (Λ CDM ) scenario. In this paper we consider a string theory inspired inflationary model (axion monodromy inflation) with a …
Robustness of cosmological axion mass limits
Di Valentino, Eleonora; Mena, Olga; Gariazzo, Stefano +1 more
We present the cosmological bounds on the thermal axion mass in an extended cosmological scenario in which the primordial power spectrum of scalar perturbations differs from the usual power-law shape predicted by the simplest inflationary models. The power spectrum is instead modeled by means of a "piecewise cubic Hermite interpolating polynomial"…
Searching for primordial localized features with CMB and LSS spectra
Hu, Bin; Torrado, Jesús
Inspired by the study of mild transient reductions in the speed of sound of the adiabatic mode during inflation, we search for a primordial localized feature imprinted in cosmic microwave background and large-scale structure formation observables. We find some common oscillatory patterns both in the Planck CMB temperature-temperature power spectru…
CMB power spectrum of Nambu-Goto cosmic strings
Shellard, E. P. S.; Landriau, Martin; Lazanu, Andrei
We improve predictions of the cosmic microwave background (CMB) power spectrum induced by cosmic strings by using source terms obtained from Nambu-Goto network simulations in an expanding universe. We use three high-resolution cosmic string simulations that cover the entire period from recombination until late-time Λ domination to calculate unequa…
Constraints on the early and late integrated Sachs-Wolfe effects from the Planck 2015 cosmic microwave background anisotropies in the angular power spectra
Melchiorri, Alessandro; Cabass, Giovanni; Gerbino, Martina +3 more
The integrated Sachs-Wolfe (ISW) effect predicts additional anisotropies in the cosmic microwave background (CMB) due to time variation of the gravitational potential when the expansion of the Universe is not matter dominated. The ISW effect is therefore expected in the early Universe, due to the presence of relativistic particles at recombination…
Sound speed of scalar field dark energy: Weak effects and large uncertainties
Sergijenko, Olga; Novosyadlyj, Bohdan
The possibility of a reconstruction of the Lagrangian for the scalar field dark energy with constant effective sound speed cs is analyzed. It is found that such a reconstruction can be made with accuracy up to an arbitrary constant. The value of cs is estimated together with other dark energy parameters (Ωd e , w
Cosmological tests of modified gravity: Constraints on F (R ) theories from the galaxy clustering ratio
Brax, Philippe; Marinoni, Christian; Bel, Julien +1 more
The clustering ratio η , a large-scale structure observable originally designed to constrain the shape of the power spectrum of matter density fluctuations, is shown to provide a sensitive probe of the nature of gravity in the cosmological regime. We apply this analysis to F (R ) theories of gravity using the luminous red galaxy sample extracted f…
Constraints on the exponential f (R ) model from latest Hubble parameter measurements
Geng, Chao-Qiang; Lee, Chung-Chi; Chen, Yun +2 more
We investigate the viable exponential f (R ) gravity in the metric formalism with f (R )=-β Rs(1 -e-R /Rs). The latest sample of the Hubble parameter measurements with 23 data points is used to place bounds on this f (R ) model. A joint analysis is also performed with the luminosity distances of type Ia supernovae …