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 momentum-dependent effective sound speed and multi-field inflation

For any physical system satisfying the Einstein's equations the comoving curvature perturbations satisfy an equation involving the momentum-dependent effective sound speed (MESS), valid for any system with a well defined energy-stress tensor (EST), including multi-fields models of inflation. While the power spectrum of adiabatic perturbations may generically receive contributions from many independent quantum degrees of freedom present in these models, there is often a single mode that dominates adiabatic perturbations of a given wavelength and evolves independently of other modes, with evolution entirely described by MESS. We study a number of two-field models with a kinetic coupling between the fields, identifying this single effective mode and showing that MESS fully accounts for the predictions for the power spectrum of adiabatic perturbations. Our results show that MESS is a conventient scheme for describing all inflationary models that admit a single-field effective theory, including the effects of entropy pertubations present in multi-fields systems, which are not included in the effective theory of inflation.Comment: 16 pages, fig.

The Caldera. No. 20

En las páginas de ésta edición encontrarán, en gran parte de los textos elaborados por nuestros educandos, un sencillo pero sentido homenaje a un ser humano que creyó, luchó y dio su vida, por causa de la libertad, de la igualdad, de la paz, por la defensa de sus profundas creencias y de una vida consagrada a su amada patria.PROYECTOS DE INVESTIGACIÓN.- PERFILES CALDISTAS.- LECTURA EN EL CALDAS Experiencias Significativas.- GRAN FINAL III Concurso Intercolegiado de Oratoria.-DEPORTES EN EL CALDAS.- BICENTENARIO FRANCISCO JOSÉ DE CALDAS.- ADIVINANZAS.- EXPRESIONES CALDISTAS.- GALERÍA DE IMÁGENES.-In the pages of this edition you will find, in a large part of the texts prepared by our students, a simple but a heartfelt tribute to a human being who believed, fought and gave his life, for the sake of freedom, equality, peace, for the defense of his deep beliefs and a life consecrated to his beloved homeland.Modalidad Presencia

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Coordinate independent approach to the calculation of the effects of local structure on the luminosity distance

Local structure can have important effects on luminosity distance observations, which could for example affect the local estimation of the Hubble constant based on low red-shift type Ia supernovae. Using a spherically symmetric exact solution of the Eistein's equations and a more accurate expansion of the solution of the geodesic equations, we improve the low red-shift expansion of the monopole of the luminosity distance in terms of the curvature function. Based on this we derive the coordinate independent low red-shift expansion of the monopole of the luminosity distance in terms of the monopole of the density contrast. The advantage of this approach is that it relates the luminosity distance directly to density observations, without any dependency on the radial coordinate choice. We compare our formulae to numerical calculations, and find that the formula in terms of the density contrast is in good agreement with the numerical calculations, in the non linear regime is more accurate than the results obtained using linear perturbation theory, especially in the regime of large Laplacian of the perturbations, and is also more accurate than the formula in terms of the curvature function.Local structure can have important effects on luminosity distance observations, which could for example affect the local estimation of the Hubble constant based on low red-shift type Ia supernovae. Using a spherically symmetric exact solution of the Eistein's equations and a more accurate expansion of the solution of the geodesic equations, we improve the low red-shift expansion of the monopole of the luminosity distance in terms of the curvature function. Based on this we derive the coordinate independent low red-shift expansion of the monopole of the luminosity distance in terms of the monopole of the density contrast. The advantage of this approach is that it relates the luminosity distance directly to density observations, without any dependency on the radial coordinate choice. We compute the effects of different inhomogeneities on the luminosity distance, and find that the formulae in terms of the density contrast are in good agreement with numerical calculations, in the non linear regime are more accurate than the results obtained using linear perturbation theory, and are also more accurate than the formulae in terms of the curvature function

Effects of the modification of gravity on the production of primordial black holes

The enhancement of the spectrum of primordial comoving curvature perturbation R can induce the production of primordial black holes (PBH) which could account for part of present day dark matter. As an example of the effects of the modification of gravity on the production of PBHs, we investigate the effects on the spectrum of R produced by the modification of gravity in the case of G-inflation, deriving the relation between the unitary gauge curvature perturbation ζ and the comoving curvature perturbation R , and identifying a background dependent enhancement function E which can induce large differences between the two gauge invariant variables. We use this relation to derive an equation for R , showing for the presence of a momentum dependent effective sound speed (MESS), associated to the intrinsic entropy which can arise in modified gravity theories, in agreement with the model independent MESS approach to cosmological perturbations.When ζ is not constant in time it is different from R , for example on sub-horizon scales, or in models exhibiting an anomalous super-horizon growth of ζ , but since this growth cannot last indefinitely, eventually they will coincide. We derive the general condition for super-horizon growth of ζ , showing that slow-roll violation is not necessary. Since the abundance of PBHs depends on the statistics of the peaks of the comoving density contrast, which is related to the spectrum of R , it is important to take into account these effects on the PBHs abundance in modified gravity theories.The enhancement of the spectrum of primordial comoving curvature perturbation $\R$ can induce the production of primordial black holes (PBH) which could account for part of present day dark matter. As an example of the effects of the modification of gravity on the production of PBHs, we investigate the effects on the spectrum of $\R$ produced by the modification of gravity in the case of G-inflation, deriving the relation between the unitary gauge curvature perturbation $\zeta$ and the comoving curvature perturbation $\R$, and identifying a background dependent enhancement function \E which can induce large differences between the two gauge invariant variables. We use this relation to derive an equation for $\R$, showing for the presence of a momentum dependent effective sound speed (MESS), associated to the intrinsic entropy which can arise in modified gravity theories, in agreement with the model independent MESS approach to cosmological perturbations. When $\zeta$ is not constant in time it is different from $\R$, for example on sub-horizon scales, or in models exhibiting an anomalous super-horizon growth of $\zeta$, but since this growth cannot last indefinitely, eventually they will coincide. We derive the general condition for super-horizon growth of $\zeta$, showing that slow-roll violation is not necessary. Since the abundance of PBHs depends on the statistics of the peaks of the comoving density contrast, which is related to the spectrum of $\R$, it is important to take into account these effects on the PBHs abundance in modified gravity theories

The momentum-dependent effective sound speed and multi-field inflation

For any physical system satisfying the Einstein's equations the comoving curvature perturbations satisfy an equation involving the momentum-dependent effective sound speed (MESS), valid for any system with a well defined energy-stress tensor (EST), including multi-fields models of inflation. While the power spectrum of adiabatic perturbations may generically receive contributions from many independent quantum degrees of freedom present in these models, there is often a single mode that dominates adiabatic perturbations of a given wavelength and evolves independently of other modes, with evolution entirely described by MESS. We study a number of two-field models with a kinetic coupling between the fields, identifying this single effective mode and showing that MESS fully accounts for the predictions for the power spectrum of adiabatic perturbations. Our results show that MESS is a conventient scheme for describing all inflationary models that admit a single-field effective theory, including the effects of entropy pertubations present in multi-fields systems, which are not included in the effective theory of inflation

The Hitchhiker's guide to the galaxy catalog approach for gravitational wave cosmology

We outline the ``dark siren'' galaxy catalog method for cosmological inference using gravitational wave (GW) standard sirens, clarifying some common misconceptions in the implementation of this method. When a confident transient electromagnetic counterpart to a GW event is unavailable, the identification of a unique host galaxy is in general challenging. Instead, as originally proposed by Schutz (1986), one can consult a galaxy catalog and implement a dark siren statistical approach incorporating all potential host galaxies within the localization volume. Trott & Hunterer 2021 recently claimed that this approach results in a biased estimate of the Hubble constant, $H_0$, when implemented on mock data, even if optimistic assumptions are made. We demonstrate explicitly that, as previously shown by multiple independent groups, the dark siren statistical method leads to an unbiased posterior when the method is applied to the data correctly. We highlight common sources of error possible to make in the generation of mock data and implementation of the statistical framework, including the mismodeling of selection effects and inconsistent implementations of the Bayesian framework, which can lead to a spurious bias

The Hitchhiker's guide to the galaxy catalog approach for gravitational wave cosmology

We outline the ``dark siren'' galaxy catalog method for cosmological inference using gravitational wave (GW) standard sirens, clarifying some common misconceptions in the implementation of this method. When a confident transient electromagnetic counterpart to a GW event is unavailable, the identification of a unique host galaxy is in general challenging. Instead, as originally proposed by Schutz (1986), one can consult a galaxy catalog and implement a dark siren statistical approach incorporating all potential host galaxies within the localization volume. Trott & Hunterer 2021 recently claimed that this approach results in a biased estimate of the Hubble constant, $H_0$, when implemented on mock data, even if optimistic assumptions are made. We demonstrate explicitly that, as previously shown by multiple independent groups, the dark siren statistical method leads to an unbiased posterior when the method is applied to the data correctly. We highlight common sources of error possible to make in the generation of mock data and implementation of the statistical framework, including the mismodeling of selection effects and inconsistent implementations of the Bayesian framework, which can lead to a spurious bias