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Abstract The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological applications of gravitational-wave observations extends well beyond these two objectives. This publication presents a summary of the state of the art in LISA cosmology, theory and methods, and identifies new opportunities to use gravitational-wave observations by LISA to probe the universe.

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, one can consult a galaxy catalog and implement a dark siren statistical approach incorporating all potential host galaxies within the localization volume. Trott & Huterer 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.

Resumen Frente a la emergencia de lo urbano como condición planetaria y a múltiples crisis en las ciudades, en la última década surgieron iniciativas en Banco Mundial (BM), la Organización para la Cooperación y el Desarrollo Económico (OCDE), ONU-Hábitat, Banco Interamericano de Desarrollo (BID), New York University (NYU), Rockefeller Foundation y el Departamento Nacional de Planeación (DNP) de Colombia para hacer sostenibles, prósperas y modernas a las ciudades. ¿Por qué tanto interés en la gobernanza urbana por parte de organizaciones tan heterogéneas? Un discurso global señalaba que en 2008 cruzamos el “punto de inflexión” en que 50% de los humanos pasamos a vivir en áreas urbanas, centros de prosperidad y dispositivos para la resolución de múltiples crisis. Nuestro estudio cuestiona los riesgos y limitaciones de concebir lo urbano desde esta perspectiva, comparando nueve marcos operativos de iniciativas globales, regionales y nacionales para gestionar sistemas urbanos y las ciudades. Abstract Given the surge of urban life as a planetary condition and the multiple crises in cities, in the last decade we saw the flourishing of several initiatives in the World Bank, the Organisation for Economic Co-operation and Development, UN-Habitat, the Inter- American Development Bank, New York University, Rockefeller Foundation and Colombia’s National Department of Planning, to make cities sustainable, prosperous, and modern. Why the interest in urban governance among so diverse organizations? A global discourse stated that, in 2008, 50% of humanity was already living in urban areas, centers of prosperity and means to solve multiple crises. Our study questions the risk of this perspective on cities, by comparing nine operational frameworks from global, regional and national initiatives to manage urban systems and cities.

Several features in the mass spectrum of merging binary black holes (BBHs) have been identified using data from the Third Gravitational Wave Transient Catalog (GWTC-3). These features are of particular interest as they may encode the uncertain mechanism of BBH formation. We assess if the features are statistically significant or the result of Poisson noise due to the finite number of observed events. We simulate catalogs of BBHs whose underlying distribution does not have the features of interest, apply the analysis previously performed on GWTC-3, and determine how often such features are spuriously found. We find that one of the features found in GWTC-3, the peak at ∼35 M _☉ , cannot be explained by Poisson noise alone: peaks as significant occur in 1.7% of catalogs generated from a featureless population. This peak is therefore likely to be of astrophysical origin. The data is suggestive of an additional significant peak at ∼10 M _☉ , though the exact location of this feature is not resolvable with current observations. Additional structure beyond a power law, such as the purported dip at ∼14 M _☉ , can be explained by Poisson noise. We also provide a publicly available package, GWMockCat , that creates simulated catalogs of BBH events with correlated measurement uncertainty and selection effects according to user-specified underlying distributions and detector sensitivities.

Gravitational-wave (GW) catalogs are rapidly increasing in number, allowing for statistical analyses of the population of compact binaries. Nonetheless, GW inference of cosmology has typically relied on additional electromagnetic counterparts or galaxy catalogs. I present a new probe of cosmological modifications of general relativity with GW data only. I focus on deviations of the GW luminosity distance constrained with the astrophysical population of binary black holes (BBHs). The three key observables are 1) the number of events as a function of luminosity distance, 2) the stochastic GW background of unresolved binaries and 3) the location of any feature in the source mass distribution, such as the pair instability supernova (PISN) gap. Modifications of the GW luminosity distance are a priori degenerate with the unknown evolution of the merger rate and source masses. However, a large damping of the GW amplitude predicts a reduction of the events and lowering of the edges of the PISN gap with redshift that is against standard astrophysical expectations. Applying a hierarchical Bayesian analysis to the current LIGO–Virgo catalog (GWTC-2), the strongest constraints to date are placed on deviations from the GW luminosity distance, finding cM=−3.2−2.0+3.4 at 68% C.L., which is ∼10 times better than multi-messenger GW170817 bounds. These modifications also affect the determination of the BBH masses, which is crucial to accommodate the high-mass binary GW190521 away from the PISN gap. In this analysis it is found that the maximum mass of 99% of the population shifts to lower masses with increased uncertainty, m99%=46.2−9.1+11.4M⊙ at 68% C.L. Testing gravity at large scales with the population of BBHs will become increasingly relevant with future catalogs, providing an independent and self-contained test of the standard cosmological model.

Primordial Black Holes (PBH) arise naturally from high peaks in the curvature power spectrum of near-inflection-point single-field inflation, and could constitute today the dominant component of the dark matter in the universe. In this letter we explore the possibility that a broad spectrum of PBH is formed in models of Critical Higgs Inflation (CHI), where the near-inflection point is related to the critical value of the RGE running of both the Higgs self-coupling λ(μ) and its non-minimal coupling to gravity ξ(μ). We show that, for a wide range of model parameters, a half-domed-shaped peak in the matter spectrum arises at sufficiently small scales that it passes all the constraints from large scale structure observations. The predicted cosmic microwave background spectrum at large scales is in agreement with Planck 2015 data, and has a relatively large tensor-to-scalar ratio that may soon be detected by B-mode polarization experiments. Moreover, the wide peak in the power spectrum gives an approximately lognormal PBH distribution in the range of masses 0.01–100M⊙, which could explain the LIGO merger events, while passing all present PBH observational constraints. The stochastic background of gravitational waves coming from the unresolved black-hole-binary mergers could also be detected by LISA or PTA. Furthermore, the parameters of the CHI model are consistent, within 2σ, with the measured Higgs parameters at the LHC and their running. Future measurements of the PBH mass spectrum could allow us to obtain complementary information about the Higgs couplings at energies well above the EW scale, and thus constrain new physics beyond the Standard Model.

Gravitational waves (GWs) provide a new tool to probe the nature of dark energy (DE) and the fundamental properties of gravity. We review the different ways in which GWs can be used to test gravity and models for late-time cosmic acceleration. Lagrangian-based gravitational theories beyond general relativity (GR) are classified into those breaking fundamental assumptions, containing additional fields and massive graviton(s). In addition to Lagrangian based theories we present the effective theory of DE and the μ-Σ parametrization as general descriptions of cosmological gravity. Multi-messenger GW detections can be used to measure the cosmological expansion (standard sirens), providing an independent test of the DE equation of state and measuring the Hubble parameter. Several key tests of gravity involve the cosmological propagation of GWs, including anomalous GW speed, massive graviton excitations, Lorentz violating dispersion relation, modified GW luminosity distance and additional polarizations, which may also induce GW oscillations. We summarize present constraints and their impact on DE models, including those arising from the binary neutron star merger GW170817. Upgrades of LIGO-Virgo detectors to design sensitivity and the next generation facilities such as LISA or Einstein Telescope will significantly improve these constraints in the next two decades.

La ampliación del principal eje de una ciudad capital y la conversión y recuperación de suelos urbanos industriales da lugar a parques y áreas densamente ocupadas. El objetivo es intensificar el uso de las áreas centrales al tiempo que replantear estrategias de accesibilidad y movilidad urbana.