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Laser Interferometer Space Antenna (LISA) will be a transformative experiment for gravitational wave astronomy as it will offer unique opportunities to address many key astrophysical questions in a completely novel way. The synergy with ground-based and other space-based instruments in the electromagnetic domain, by enabling multi-messenger observations, will add further to the discovery potential of LISA. The next decade is crucial to prepare the astrophysical community for LISA's first observations. This review outlines the extensive landscape of astrophysical theory, numerical simulations, and astronomical observations that are instrumental for modeling and interpreting the upcoming LISA datastream. To this aim, the current knowledge in three main source classes for LISA is reviewed: ultra-compact stellar-mass binaries, massive black hole binaries, and extreme or intermediate mass ratio inspirals. The relevant astrophysical processes and the established modeling techniques are summarized. Likewise, open issues and gaps in our understanding of these sources are highlighted, along with an indication of how LISA could help make progress in the different areas. New research avenues that LISA itself, or its joint exploitation with studies in the electromagnetic domain, will enable, are also illustrated. Improvements in modeling and analysis approaches, such as the combination of numerical simulations and modern data science techniques, are discussed. This review is intended to be a starting point for using LISA as a new discovery tool for understanding our Universe., Comment: submitted to Living Reviews In Relativity

The Laser Interferometer Space Antenna (LISA) will be a transformative experiment for gravitational wave astronomy, and, as such, it will offer unique opportunities to address many key astrophysical questions in a completely novel way. The synergy with ground-based and space-born instruments in the electromagnetic domain, by enabling multi-messenger observations, will add further to the discovery potential of LISA. The next decade is crucial to prepare the astrophysical community for LISA's first observations. This review outlines the extensive landscape of astrophysical theory, numerical simulations, and astronomical observations that are instrumental for modeling and interpreting the upcoming LISA datastream. To this aim, the current knowledge in three main source classes for LISA is reviewed; ultracompact stellar-mass binaries, massive black hole binaries, and extreme or intermediate mass ratio inspirals. The relevant astrophysical processes and the established modeling techniques are summarized. Likewise, open issues and gaps in our understanding of these sources are highlighted, along with an indication of how LISA could help making progress in the different areas. New research avenues that LISA itself, or its joint exploitation with upcoming studies in the electromagnetic domain, will enable, are also illustrated. Improvements in modeling and analysis approaches, such as the combination of numerical simulations and modern data science techniques, are discussed. This review is intended to be a starting point for using LISA as a new discovery tool for understanding our Universe.

In cities around the world, Covid-19 lockdowns have improved outdoor air quality, in some cases dramatically. Even if only temporary, these improvements could have longer-lasting effects on policy by making chronic air pollution more salient and boosting political pressure for change. To that end, it is important to develop objective estimates of both the air quality improvements associated with Covid-19 lockdowns and the benefits these improvements generate. We use panel data econometric models to estimate the effect of Bogotás lockdown on fine particulate pollution, epidemiological models to simulate the effect of reductions in that pollution on long-term and short-term mortality, and benefit transfer methods to estimate the monetary value of the avoided mortality. We find that in its first year of implementation, on average, Bogotás lockdown cut fine particulate pollution by more than one-fifth. However, the magnitude of that effect varied considerably over the course of the year and across the citys neighborhoods. Equivalent permanent reductions in fine particulate pollution would reduce long-term premature deaths by more than one-quarter each year, a benefit valued at $670 million per year. Finally, we estimate that in 2020-2021, the lockdown reduced short-term deaths by 31 percent, a benefit valued at $180 million.

We use Gamma Ray Bursts (GRBs) data from Y. Wang (2008) to put additional constraints on a set of cosmological dark energy models based on the holographic principle. GRBs are among the most complex and energetic astrophysical events known in the universe offering us the opportunity to obtain information from the history of cosmic expansion up to about redshift of $z\sim 6$. These astrophysical objects provide us a complementary observational test to determine the nature of dark energy by complementing the information of data from Supernovas (e.g. Union 2.1 compilation). We found that the $\Lambda CDM$ model gives the best fit to the observational data, although our statistical analysis ($\Delta AIC$ and $\Delta BIC$) shows that the models studied in this work ("Hubble Radius Scale" and "Ricci Scale Q") have a reasonable agreement with respect to the most successful, except for the "Ricci Scale CPL" and "Future Event Horizon" models, which can be ruled out by the present study. However, these results reflect the importance of GRBs measurements to provide additional observational constraints to alternative cosmological models, which are mandatory to clarify the way in which the paradigm of dark energy or any alternative model is correct., Comment: 11 pages, 6 figures, 7 tables, poster presentation: Congreso Nacional de F\'isica, Manizales, Caldas, Colombia, 2015

In order to explain the current acceleration of the Universe, the fine tuning problem of the cosmological constant $\Lambda$ and the cosmic coincidence problem, different alternative models have been proposed in the literature. We use the most recent observational data from CMB (Planck 2018 final data release) and LSS (SDSS, WiggleZ, VIPERS) to constrain dynamical dark energy (DE) models. The CMB shift parameter, which traditionally has been used to determine the main cosmological parameters of the standard model $\Lambda CDM$ is employed in addition to data from redshift-space distortions through the growth parameter $A(z)=f(z)\sigma_{8}(z)$ to constrain the mass variance $\sigma_{8}$. BAO data is also used to study the history of the cosmological expansion and the main properties of DE. From the evolution of $q(z)$ we found a slowdown of acceleration behaviour at low redshifts, and by using the Akaike and Bayesian Information Criterion (AIC, BIC) we discriminate different models those that are better suited to the observational data, finding that the interactive dark energy (IDE) model is the most favoured by observational data, including information from SNIa and Hz. The analysis shows that the IDE model is followed closely by EDE and $\Lambda CDM$ models, which in some cases fit better the observational data with individual probes., Comment: 31 pages, 10 figures, 12 tables, Matches the version published in IJMPD. arXiv admin note: text overlap with arXiv:1711.09291 by other authors

The anisotropy study cosmic microwave background (CMB) is one of the main observational tools for modern cosmology. However, alongside the study of the thermal fluctuations of the CMB are other equally important information, which is known as the polarization of the CMB. The inflationary model predicts that the CMB is linearly polarized and the physical mechanism of this polarization is studied from the Thompson scattering, the dominant process on the surface of last scattering. There are basically two types of polarization called E and B modes, the first produced by scalar perturbations and the latter by tensor perturbations, such as those due to gravitational waves in the primordial universe. So if we are able to measure these types of polarization will have an entry to the study of the inflationary epoch. This paper presents the main physical mechanisms that support theoretically the polarization of the CMB due to primordial gravitational waves (PGW) and the revision of the main observables, grouped in so-called Stokes parameters (Q, U, I), Which brings us information to achieve the contrast the angular power spectrum produced by the polarization of the CMB, which shows to be in excellent agreement with the $\Lambda$CDM model., Comment: 8 pages, 3 figures, presented in the Second Workshop on Numerical and Observational Astrophysics: From the First Structures to the Universe Today, 2011. Updated version

In order to explain the current acceleration of the Universe, the fine tuning problem of the cosmological constant $\Lambda$ and the cosmic coincidence problem, different alternative models have been proposed in the literature. We use the most recent observational data from CMB (Planck 2018 final data release) and LSS (SDSS, WiggleZ, VIPERS) to constrain dynamical dark energy (DE) models. The CMB shift parameter, which traditionally has been used to determine the main cosmological parameters of the standard model $\Lambda CDM$ is employed in addition to data from redshift-space distortions through the growth parameter $A(z)=f(z)\sigma_{8}(z)$ to constrain the mass variance $\sigma_{8}$. BAO data is also used to study the history of the cosmological expansion and the main properties of DE. From the evolution of $q(z)$ we found a slowdown of acceleration behaviour at low redshifts, and by using the Akaike and Bayesian Information Criterion (AIC, BIC) we discriminate different models those that are better suited to the observational data, finding that the interactive dark energy (IDE) model is the most favoured by observational data, including information from SNIa and Hz. The analysis shows that the IDE model is followed closely by EDE and $\Lambda CDM$ models, which in some cases fit better the observational data with individual probes., Comment: 31 pages, 10 figures, 12 tables, Matches the version published in IJMPD. arXiv admin note: text overlap with arXiv:1711.09291 by other authors

The anisotropy study cosmic microwave background (CMB) is one of the main observational tools for modern cosmology. However, alongside the study of the thermal fluctuations of the CMB are other equally important information, which is known as the polarization of the CMB. The inflationary model predicts that the CMB is linearly polarized and the physical mechanism of this polarization is studied from the Thompson scattering, the dominant process on the surface of last scattering. There are basically two types of polarization called E and B modes, the first produced by scalar perturbations and the latter by tensor perturbations, such as those due to gravitational waves in the primordial universe. So if we are able to measure these types of polarization will have an entry to the study of the inflationary epoch. This paper presents the main physical mechanisms that support theoretically the polarization of the CMB due to primordial gravitational waves (PGW) and the revision of the main observables, grouped in so-called Stokes parameters (Q, U, I), Which brings us information to achieve the contrast the angular power spectrum produced by the polarization of the CMB, which shows to be in excellent agreement with the $\Lambda$CDM model., Comment: 8 pages, 3 figures, presented in the Second Workshop on Numerical and Observational Astrophysics: From the First Structures to the Universe Today, 2011. Updated version

We use Gamma Ray Bursts (GRBs) data from Y. Wang (2008) to put additional constraints on a set of cosmological dark energy models based on the holographic principle. GRBs are among the most complex and energetic astrophysical events known in the universe offering us the opportunity to obtain information from the history of cosmic expansion up to about redshift of $z\sim 6$. These astrophysical objects provide us a complementary observational test to determine the nature of dark energy by complementing the information of data from Supernovas (e.g. Union 2.1 compilation). We found that the $\Lambda CDM$ model gives the best fit to the observational data, although our statistical analysis ($\Delta AIC$ and $\Delta BIC$) shows that the models studied in this work ("Hubble Radius Scale" and "Ricci Scale Q") have a reasonable agreement with respect to the most successful, except for the "Ricci Scale CPL" and "Future Event Horizon" models, which can be ruled out by the present study. However, these results reflect the importance of GRBs measurements to provide additional observational constraints to alternative cosmological models, which are mandatory to clarify the way in which the paradigm of dark energy or any alternative model is correct., Comment: 11 pages, 6 figures, 7 tables, poster presentation: Congreso Nacional de F\'isica, Manizales, Caldas, Colombia, 2015

The paper discusses the magnitude of commitment in the legal and contractual budget that different governments need to stand by during each fiscal year and realize the gaining momentum.