Search arXivSearch

arXiv · 1504.03469

Hyperbolic Inflation in the Light of Planck 2015 data

Abstract

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 inflation, we find that the main slow-roll parameters, like the scalar spectral index, the running of the spectral index and the tensor-to-scalar fluctuation ratio can be computed analytically. Finally, in order to test the viability of this hyperbolic scalar field model at the early stages of the Universe, we compare the predictions of that model against the latest observational data, namely Planck 2015.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Spyros Basilakos, John D. Barrow. 2015-05-21. Hyperbolic Inflation in the Light of Planck 2015 data. https://doi.org/10.1103/physrevd.91.103517

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

The Heavy Tailed Non-Gaussianity of the Supermassive Black Hole Gravitational Wave Background

We study the non-Gaussian features of the gravitational wave (GW) background generated by a population of inspiraling supermassive black hole (SMBH) binaries. We show that the SMBH GW amplitude distribution (GWAD) features a universal heavy power-law tail $\propto A^{-4}$, while the low-amplitude tail depends on the SMBH merger rate and the energy-loss mechanisms of the binaries. The distribution of the induced timing residuals inherits this heavy tail. As a result, the ensemble averaged statistical moments of order three and higher diverge, limiting their usefulness as measures of non-Gaussianity, and the GW background from SMBH binaries exhibits the single loud source principle, according to which the strongest signals are more likely to be caused by a small number of loud sources. We confirm that the variance-averaged Gaussian approximation accurately describes the timing residual statistics. This approximation justifies a factored likelihood structure that combines standard Gaussian-process PTA posteriors with the non-Gaussian population prior, enabling consistent incorporation of non-Gaussian effects into SMBH model inference. We provide a fast and flexible Python implementation to compute the distribution of timing residuals from a given SMBH merger rate or GWAD.

astro-ph.CO

The dynamics of the Anglerfish cluster

Merging galaxy clusters represent the ideal laboratory to test our understanding of the large scale structure formation history and the processes involved. While many merging clusters have been identified, only a limited number have been studied in detail through multi-wavelength analysis and dynamical reconstruction, this type of analysis being crucial to account for projection degeneracies. This work investigates the merger dynamics of the massive and complex cluster MACS0600 using high spatial, $\sim 15$ arcsec, radio and X-ray datasets in combination with ancillary optical data. We analyze the cluster morphology and the thermodynamic properties of the intracluster medium (ICM) through XMM-Newton and Chandra X-ray observations, and explore the non-thermal component via diffuse radio emission observed with Meerkat. We find a disturbed X-ray morphology with multiple substructures and a clear offset between the bulk of the radio emission and the X-ray peak. At the location of the X-ray peak, we detect a compact cool core surrounded by hotter gas and associated with a surface brightness discontinuity consistent with a cold front. The central region exhibits elevated temperatures and hosts most of the diffuse radio emission, suggesting merger-driven turbulence. Optical data further support a relative motion between the cool core and the main cluster along the line of sight. We conclude that MACS0600 is undergoing a merger in which a compact cool core has crossed the main, more massive cluster without being completely disrupted, while significantly perturbing the surrounding ICM.

astro-ph.CO

Environmental dependence of Type Ia supernova standardization on the local luminosity-weighted age

Context. The dependence of Type Ia supernova (SN Ia) standardised luminosity on host galaxy properties is a major source of uncertainty in cosmology. As next-generation surveys like LSST and HLTDS reduce statistical uncertainties, cosmological precision will be limited by astrophysical systematics. However, the empirical mass step, an indirect global proxy, may obscure the physical link to the progenitor environment. Aims. We test whether local luminosity-weighted age (LWA), used as a statistical proxy for the age of the stellar population associated with SN Ia progenitors, is more closely related to the physical driver of standardised-luminosity variations than host galaxy mass. Methods. Using SDSS-MaNGA Pipe3D, we extracted local LWA within a 1 kpc aperture for 56 SNe Ia and performed a joint likelihood analysis of local age and mass effects on Hubble residuals. Results. SNe Ia in younger environments are significantly fainter than those in older ones, with a step amplitude of 0.163 mag (5.2 sigma) after standardisation. Global and local mass steps are initially observed (0.071 mag, 2.0 sigma and 0.087 mag, 2.4 sigma), but both become insignificant when age and mass are fitted simultaneously: the global mass step decreases to 0.028 mag (0.9 sigma), while the age step remains robust at 0.156 mag (4.9 sigma). Similarly, the local mass step becomes insignificant (0.012 mag, 0.3 sigma), whereas the age step persists at 0.157 mag (4.4 sigma). The weighted Hubble residual decreases from 0.1550 to 0.1376 mag after introducing the local LWA step. Conclusions. The mass step is substantially reduced when local LWA is included. The inferred dark energy equation of state parameter (w) could be affected by local LWA, highlighting the importance of environmental effects for next-generation SN Ia cosmology.

astro-ph.CO