Statistical Inconsistencies in the KiDS-450 Dataset

The Kilo-Degree Survey (KiDS) has been used in several recent papers to infer constraints on the amplitude of the matter power spectrum and matter density at low redshift. Some of these analyses have claimed tension with the Planck $\Lambda \mathrm{CDM}$ cosmology at the $\sim 2-3\sigma$ level, perhaps indicative of new physics. However, Planck is consistent with other low redshift probes of the matter power spectrum such as redshift space distortions and the combined galaxy-mass and galaxy-galaxy power spectra. Here we perform consistency tests of the KiDS data, finding internal tensions for various cuts of the data at $\sim 2.2 - 3.5\sigma$ significance. Until these internal tensions are understood, we argue that it is premature to claim evidence for new physics from KiDS. We review the consistency between KiDS and other weak lensing measurements of $S_8$, highlighting the importance of intrinsic alignments for precision cosmology.Comment: Comments: 8 pages, 5 figures. Accepted for publication in MNRA

Co-orbital resonance with a migrating proto-giant planet

In this work we pose the possibility that, at an early stage, the migration of a proto--giant planet caused by the presence of a gaseous circumstellar disk could explain the continuous feeding of small bodies into its orbit. Particularly, we study the probability of capture and permanence in co--orbital resonance of these small bodies, as planets of diverse masses migrate by interaction with the gaseous disk, and the drag induced by this disk dissipates energy from these small objects, making capture more likely. Also, we study the relevance of the circumplanetary disk, a structure formed closely around the planet where the gas density is enhanced, in the process of capture. It is of great interest for us to study the capture of small bodies in 1:1 resonance because it could account for the origin of the Trojan population, which has been proposed \citep{2011Icar..215..669K} as a mechanism of quasi-satellites and irregular satellites capture.Comment: This is a pre-copyedited, author-produced PDF of an article accepted for publication in PSS following peer review; 9 pages, 9 figure

Quantifying dimensionality: Bayesian cosmological model complexities

We demonstrate a measure for the effective number of parameters constrained by a posterior distribution in the context of cosmology. In the same way that the mean of the Shannon information (i.e. the Kullback-Leibler divergence) provides a measure of the strength of constraint between prior and posterior, we show that the variance of the Shannon information gives a measure of dimensionality of constraint. We examine this quantity in a cosmological context, applying it to likelihoods derived from Cosmic Microwave Background, large scale structure and supernovae data. We show that this measure of Bayesian model dimensionality compares favourably both analytically and numerically in a cosmological context with the existing measure of model complexity used in the literature.Comment: 14 pages, 9 figures. v2: updates post peer-review. v3: typographical correction to equation 3

Quantifying tensions in cosmological parameters: Interpreting the DES evidence ratio

We provide a new interpretation for the Bayes factor combination used in the Dark Energy Survey (DES) first year analysis to quantify the tension between the DES and Planck datasets. The ratio quantifies a Bayesian confidence in our ability to combine the datasets. This interpretation is prior-dependent, with wider prior widths boosting the confidence. We therefore propose that if there are any reasonable priors which reduce the confidence to below unity, then we cannot assert that the datasets are compatible. Computing the evidence ratios for the DES first year analysis and Planck, given that narrower priors drop the confidence to below unity, we conclude that DES and Planck are, in a Bayesian sense, incompatible under LCDM. Additionally we compute ratios which confirm the consensus that measurements of the acoustic scale by the Baryon Oscillation Spectroscopic Survey (SDSS) are compatible with Planck, whilst direct measurements of the acceleration rate of the Universe by the SHOES collaboration are not. We propose a modification to the Bayes ratio which removes the prior dependency using Kullback-Leibler divergences, and using this statistical test find Planck in strong tension with SHOES, in moderate tension with DES, and in no tension with SDSS. We propose this statistic as the optimal way to compare datasets, ahead of the next DES data releases, as well as future surveys. Finally, as an element of these calculations, we introduce in a cosmological setting the Bayesian model dimensionality, which is a parameterisation-independent measure of the number of parameters that a given dataset constrains.Comment: 16 pages, 9 figures. v2 & v3: updates post peer-review. v4: typographical correction to the reported errors in the log S column of Table II. v5: typographical correction to equation 2

The Impact of Peculiar Velocities on the Estimation of the Hubble Constant from Gravitational Wave Standard Sirens

In this work we investigate the systematic uncertainties that arise from the calculation of the peculiar velocity when estimating the Hubble constant ($H_0$) from gravitational wave standard sirens. We study the GW170817 event and the estimation of the peculiar velocity of its host galaxy, NGC 4993, when using Gaussian smoothing over nearby galaxies. NGC 4993 being a relatively nearby galaxy, at $\sim 40 \ {\rm Mpc}$ away, is subject to a significant effect of peculiar velocities. We demonstrate a direct dependence of the estimated peculiar velocity value on the choice of smoothing scale. We show that when not accounting for this systematic, a bias of $\sim 200 \ {\rm km \ s ^{-1}}$ in the peculiar velocity incurs a bias of $\sim 4 \ {\rm km \ s ^{-1} \ Mpc^{-1}}$on the Hubble constant. We formulate a Bayesian model that accounts for the dependence of the peculiar velocity on the smoothing scale and by marginalising over this parameter we remove the need for a choice of smoothing scale. The proposed model yields$H_0 = 68.6 ^{+14.0}_{-8.5}~{\rm km\ s^{-1}\ Mpc^{-1}}$. We demonstrate that under this model a more robust unbiased estimate of the Hubble constant from nearby GW sources is obtained.Comment: 9 pages, 5 figure

The Cosmic Microwave Background and H0H_0

The cosmic microwave background (CMB) offers a unique window into the early universe, providing insights into cosmological parameters like the Hubble constant. Recent precise measurements of the CMB by experiments like Planck seem to point to a lower value for the Hubble constant compared to some other measurements like those from Type Ia supernovae. This discrepancy, known as the Hubble tension, currently lacks a definitive explanation. In this chapter, we provide an overview of how the Hubble constant is determined from detailed measurements of the CMB power spectrum. We explain the physics underlying key features of the CMB spectrum and their connection to cosmological parameters. We then examine the consistency of Planck's Hubble constant determination, both internally within the data itself and externally with other astrophysical probes. While largely consistent, some anomalies like the lensing amplitude parameter $A_L$ remain unresolved. We also explore various theoretical extensions to the standard ${\Lambda}$CDM cosmological model and assess their potential to resolve the Hubble tension. No clear resolution emerges, indicating significant tensions remain between early and late universe probes within simple extensions to ${\Lambda}$CDM. Upcoming CMB experiments promise improved precision and should provide further insights into this cosmic conundrum. A coherent picture bridging measurements across cosmic time remains an open challenge at the forefront of modern cosmology.Comment: Invited chapter for the edited book "Hubble Constant Tension" (Eds. E. Di Valentino and D. Brout, Springer Singapore, expected in 2024

Motores del empleo en los países nórdicos : el caso de Islandia y Noruega

Fil: Salvador, Pablo F.. Universidad Nacional de Cuyo. Facultad de Ciencias EconómicasFil: Lemos, Lorena. Universidad Nacional de Cuyo. Facultad de Ciencias Económica

Motores del empleo en los países Nórdicos: : el caso de Islandia y Noruega

Este trabajo se centra en el estudio del mercado de trabajo de dos países Nórdicos: Islandia y Noruega. En particular, se analiza la demanda de trabajo de estos dos países. Para ello, el enfoque se apoya en la teoría de la reacción en cadena que subraya la importancia de utilizar conjuntamente variables estacionarias (instituciones del mercado de trabajo) y variables no estacionarias (variables con tendencia) para analizar el comportamiento del mercado de trabajo o de alguno de sus componentes, como en este caso la demanda de empleo. Del resultado se desprende el rol preponderante que ejerce el stock de capital en el mercado de trabajo de estos dos países a través de la creación o destrucción de empleo.Fil: Salvador, Pablo F..Fil: Lemos, Lorena

Weak-lensing magnification of Type Ia supernovae from the Pantheon sample

Using data from the Pantheon Type Ia supernovae (SN Ia) compilation and the Sloan Digital Sky Survey, we propose an estimator for weak-lensing convergence incorporating positional and photometric data of foreground galaxies. The correlation between this and the Hubble diagram residuals of the supernovae has 3.6σ significance, and is consistent with weak-lensing magnification due to dark matter haloes centred on galaxies. We additionally constrain the properties of the galactic haloes, such as the mass-to-light ratio Γ and radial profile of the halo matter density ρ(r). We derive a new relationship for the additional rms scatter in magnitudes caused by lensing, finding σlens = (0.06 ± 0.017)(dC(z)/dC(z = 1))3/2, where dC(z) is the comoving distance to redshift z. Hence, the scatter in apparent magnitudes due lensing will be of the same size as the intrinsic scatter of SN Ia by z ∼ 1.2. We propose a modification of the distance modulus estimator for SN Ia to incorporate lensing, which can be easily calculated from observational data. We anticipate this will improve the accuracy of cosmological parameter estimation for high-redshift SN Ia data

Contribución de la universidad al desarrollo innovativo de las PyMES

Este trabajo es producto de una investigación actualmente en curso que define como tema de interés el vínculo entre universidad – sector productivo centrándose particularmente en la relación de la Universidad Nacional de Lanús respecto a su inserción en el territorio con la pequeña y mediana empresa por el papel que ésta juega en el desarrollo local y regional a través de la generación de producción y empleo y por la potencialidad que, en materia innovativa, puede llegar a desarrollar. La relación universidad- sector productivo cobra particular importancia a partir de la década de los ’80 en consonancia con la denominada “tercera misión de la universidad": el papel que la misma debe jugar en el desarrollo económico- social comprendiendo la prestación de servicios de capacitación, empleabilidad, asistencia técnica y/o innovación tecnológica, a través de programas de formación técnico/ profesional, de inserción y reinserción laboral, observatorios de demandas laborales y de actividad empresarial, programas de desarrollo local y regional que pueden incluir la constitución de incubadoras universitarias de empresas o de parques tecnológicos. Este vínculo aparece ligado a una confluencia de factores que operan como desencadenantes de esta situación. La globalización de la economía incide sobre el proceso productivo de cada sociedad en el sentido de que ésta se torne más competitiva, ya que los elementos “clásicos" que jugaron un importante papel en el pasado (ventajas comparativas estáticas) han sido reemplazados por la incorporación de conocimiento e innovación como valor agregado a la producción (Sutz, J 1996). La crisis del petróleo en el ’73 conduce en los países industrializados a un proceso de reconversión de su aparato productivo con el surgimiento de nuevas tecnologías, desarrollándose el campo de la economía de la innovación y el diseño de políticas de estímulo a la misma, dando lugar a un cambio de perspectiva centrado, no ya en la “oferta", sino en la “demanda". Paralelo a ello en el ámbito de la ciencia conceptos novedosos como el de “investigación estratégica" tienden a conciliar la libertad de la investigación básica con las necesidades del proceso económico y productivo (Albornoz, M. 1990).Fil: Giangiacomo, Graciela. Universidad Nacional de Lanús (Buenos Aires, Argentina)Fil: Arscone Gasser, Lihuen. Universidad Nacional de Lanús (Buenos Aires, Argentina)Fil: Lemos, Pablo . Universidad Nacional de Lanús (Buenos Aires, Argentina)Fil: Sfrégola, Carmen . Universidad Nacional de Lanús (Buenos Aires, Argentina