Low red-shift effects of local structure on the Hubble parameter in presence of a cosmological constant

In order to estimate the effects of local structure on the Hubble parameter we calculate the low-redshift expansion for $H(z)$ and $\frac{\delta H}{H}$ for an observer at the center of a spherically symmetric matter distribution in presence of a cosmological constant. We then test the accuracy of the formulae comparing them with fully relativistic non perturbative numerical calculations for different cases for the density profile. The low red-shift expansion we obtain gives results more precise than perturbation theory since is based on the use of an exact solution of Einstein's field equations. For larger density contrasts the low red-shift formulae accuracy improves respect to the perturbation theory accuracy because the latter is based on the assumption of a small density contrast, while the former does not rely on such assumption. The formulae can be used to take into account the effects on the Hubble expansion parameter due to the monopole component of the local structure. If the $H(z)$ observations will show deviations from the $\Lambda CDM$ prediction compatible with the formulae we have derived, this could be considered an independent evidence of the existence of a local inhomogeneity, and the formulae could be used to determine the characteristics of this local structure.Comment: 14 pages, 4 figure

Reconstructing the metric of the local Universe from number counts observations

Number counts observations available with new surveys such as the Euclid mission will be an important source of information about the metric of the Universe. We compute the low red-shift expansion for the energy density and the density contrast using an exact spherically symmetric solution in presence of a cosmological constant. At low red-shift the expansion is more precise than linear perturbation theory prediction. We then use the local expansion to reconstruct the metric from the monopole of the density contrast. We test the inversion method using numerical calculations and find a good agreement within the regime of validity of the red-shift expansion. The method could be applied to observational data to reconstruct the metric of the local Universe with a level of precision higher than the one achievable using perturbation theory.Comment: 18 pages,5 figure

Are primordial black holes produced by entropy perturbations in single field inflationary models?

We show that in single field inflationary models the super-horizon evolution of curvature perturbations on comoving slices $\mathcal{R}$, which can cause the production of primordial black holes (PBH), is not due to entropy perturbations, but to the background evolution effect on the conversion between entropy and curvature perturbations. We derive a general relation between the time derivative of comoving curvature perturbations and entropy perturbations, in terms of a conversion factor depending on the background evolution. Contrary to previous results derived in the uniform density gauge assuming the gradient term can be neglected on super-horizon scales, the relation is valid on any scale for any minimally coupled single scalar field model, also on sub-horizon scales where gradient terms are large. We apply it to the case of quasi-inflection inflation, showing that while entropy perturbations are decreasing, $\mathcal{R}$ can grow on super-horizon scales, due to a large increase of the conversion factor. This happens in the time interval during which a sufficiently fast decrease of the equation of state $w$ transforms into a growing mode that in slow-roll models would be a decaying mode. The same mechanism also explains the super-horizon evolution of $\mathcal{R}$ in globally adiabatic systems, for which entropy perturbations vanish on any scale, such as ultra slow-roll inflation and its generalizations

The MESS of cosmological perturbations

We introduce two new effective quantities for the study of comoving curvature perturbations $\zeta$: the space dependent effective sound speed (SESS) and the momentum dependent effective sound speed (MESS) . We use the SESS and the MESS to derive a new set of equations which can be applied to any system described by an effective stress-energy-momentum tensor (EST), including multi-fields systems, supergravity and modified gravity theories. We show that this approach is completely equivalent to the standard one and it has the advantage of requiring to solve only one differential equation for $\zeta$ instead of a system, without the need of explicitly computing the evolution of entropy perturbations. The equations are valid for perturbations respect to any arbitrary flat spatially homogeneous background, including any inflationary and bounce model. As an application we derive the equation for $\zeta$ for multi-fields $KGB$ models and show that observed features of the primordial curvature perturbation spectrum are compatible with the effects of an appropriate local variation of the MESS in momentum space. The MESS is the natural quantity to parametrize in a model independent way the effects produced on curvature perturbations by multi-fields systems, particle production and modified gravity theories and could be conveniently used in the analysis of LSS observations, such as the ones from the upcoming EUCLID mission or CMB radiation measurements.Comment: We study the MESS of cosmological perturbations, version accepted in Physics Letters

Directional dependence of the local estimation of H0H_0 and the non perturbative effects of primordial curvature perturbations

Recent measurements of the cosmic microwave background (CMB) radiation have shown an apparent tension with the present value of the Hubble parameter inferred from local observations of supernovae, which look closer, i.e. brighter, than what is expected in a homogeneous model with a value of $H_0$ equal to the one estimated from CMB observations. We examine the possibility that such a discrepancy is the consequence of the presence of a local inhomogeneity seeded by primordial curvature perturbations, finding that a negative peak of the order of less than two standard deviations could allow to fit low red-shift supernovae observations without the need of using a value of the Hubble parameter different from $H_0^{CMB}$. The type of inhomogeneity we consider does not modify the distance to the last scattering, making it compatible with the constraints of the PLANCK mission data. Our calculation is fully relativistic and non perturbative, and for this reason shows important effects which were missed in the previous investigations using relativistic perturbations or Newtonian approximations, because the structures seeded by primordial curvature perturbations can be today highly non linear, and relativist Doppler terms cannot be neglected. Comparison with studies of local structure based on galaxy surveys and luminosity density analysis reveals that the density profile we find could in fact be compatible with the one obtained for the same region of sky where is located most of the Cepheids used to calibrate the luminosity distance of the supernovae employed for the local $H_0$ estimation, suggesting a possible directional dependence and calibration bias which could be partially attributed to the presence of the Sloan Great Wall.Comment: New updated references have been added. Some more information has been included about the region of sky in which the density profile predicted by our model is in agreement with luminosity density and galaxy surveys observations. Our model predicts the consequent overall supernovae luminosity distance calibration bias effect due to the presence in that region of the Cepheid

Revisión del género Hermodice Kinberg, 1857 (Polychaeta: Amphinomidae)

The genus Hermodice Kinberg, 1857 was established with the species Aphrodita carunculata Pallas, 1766, based on the shape and development of the caruncle. Several species were later described within the genus; however, it is currently regarded as monotypical, with H. carunculata as a widespread species. An evaluation of available type and non-type specimens together with observations of living specimens has allowed the diagnostic features to be refined, and two new features have been included: the number of branchial filaments and the anal lobe. Consequently, in this study we have been able to confirm the differences between Hermodice and Pherecardia Horst, 1886. The type species, H. carunculata, has been redescribed, and H. nigrolineata Baird, 1870 has been re-established. Further, H. formosa (Quatrefages, 1866) has been transferred to Pherecardia, together with H. pennata Treadwell, 1906 and H. distincta Hoagland, 1920.El género Hermodice, Kinberg, 1857 se estableció con la especie Aphrodita carunculata Pallas, 1766, debido a la forma y desarrollo de la carúncula. Posteriormente, se describieron varias especies dentro del género. Sin embargo, actualmente se considera que el género es monotípico y que H. carunculata es una especie cosmopolita. La revisión de material tipo y especímenes adicionales, incluyendo ejemplares vivos, nos ha permitido redefinir las características diagnósticas e incorporar dos nuevos atributos: el número de filamentos branquiales y el lóbulo anal. Como consecuencia, ha sido posible confirmar las diferencias entre Hermodice y Pherecardia Horst, 1886. Así mismo, se redescribe la especie tipo H. carunculata y se reestablece H. nigrolineata Baird, 1870. Además, H. formosa (Quatrefages, 1866) se transfiere a Pherecardia, junto H. pennata Treadwell, 1906 y H. distincta Hoagland, 1920

Lineamientos para el aprovechamiento sostenible de las palmas oleaginosas Colombianas Oenocarpus bataua Mart, Acrocomia aculeata (Jacq.) Lodd. ex Mart. y Attalea butyracea (Mutis ex L.f.) Wess. Boer

En la actualidad, muchas plantas de alto valor, no solo económico sino también nutricional, están siendo subutilizadas y marginadas en el país, impidiendo la posibilidad de aprovechar las grandes bondades que estas pueden presentar. Este es el caso de Oenocarpus bataua Mart, Acrocomia aculeata (Jacq.) Lodd. ex Mart. y Attalea butyracea (Mutis ex L.f.) Wess. Boer, tres especies de palmas productoras de aceite nativas de Colombia. Para comprender la situación actual de estas palmas, se realizó una revisión bibliográfica exhaustiva, teniendo en cuenta diferentes aspectos relacionados con tres tipos de conocimiento: conocimiento tradicional, conocimiento científico y conocimiento tecnológico. Luego, esta información se organizó en una base de datos y se sintetizó en el presente documento. Finalmente, toda la información fue analizada, para así identificar las posibles causas de marginación de estas palmas y proponer prioridades específicas de investigación y de acción, que puedan servir para el desarrollo de un eventual plan o programa de aprovechamiento y comercialización de estas palmas. Se encontró como principales razones posibles de marginación: el enfoque errado en la manera de abordar el proceso de aprovechamiento y comercialización, dejando a un lado aspectos fundamentales, como las percepciones y necesidades de los productores y las percepciones del mercado frente al producto, el gran vacío de conocimiento existente en algunos aspectos, especialmente de Acrocomia aculeata y Attalea butyracea y la falta de compromiso y atención por parte de las entidades de investigación y desarrollo y del propio gobierno. Se propuso un proceso de retroalimentación entre las entidades de investigación y desarrollo de los diferentes países involucrados y, también, se recomendaron prioridades de investigación, teniendo en cuenta los aspectos más importantes de los tres tipos de conocimiento mencionados previamente, fundamentales para pretender desarrollar un programa de aprovechamiento sostenible. Además, se propuso una serie de iniciativas y lineamientos para desarrollar un programa de aprovechamiento y comercialización con estas palmas, enfatizando el papel protagónico de la comunidad local y resaltando la importancia del contexto inmediato de la planta.Biólogo (a)Pregrad