Talking about sex and sexual behaviour of young people in Ireland. ESRI Research Series 112 November 2020.

New research from a joint ESRI/HSE Health and Wellbeing research programme analyses how young people receive information on sex and relationships. Using data from the Growing up in Ireland ’98 Cohort at 13 and 17 years of age, the research also examines the role of this information in shaping sexual behaviours among Irish adolescents. The research finds that four in ten 17 year-olds have not spoken to their parents about sex and relationships

Clusters of health behaviours among young adults in Ireland. ESRI Research Series 101 June 2020.

New ESRI research, funded by HSE Health and Wellbeing, examines how 4 key risk factors for disease (smoking, alcohol consumption, physical activity, diet) cluster together among young adults. Using data from the Growing up in Ireland ’98 Cohort at 17 years of age, the research identified 3 distinct health behaviour clusters among young adults in Ireland: a 'healthy' group, an 'unhealthy group' and an 'unhealthy smokers and drinkers group'

Constraints on Primordial Black Holes from NN-body simulations of the Eridanus II Stellar Cluster

The tidal disruption of old, compact stellar structures provides strong constraints on macroscopic dark matter candidates such as primordial black holes. In view of recent, new observational data on the Eridanus II dwarf galaxy and on its central stellar cluster, we employ, for the first time, $N$-body simulations to assess the impact of compact massive dark matter candidates on the gravitational stability of the cluster. We find evidence that such candidates must be lighter than about one solar mass if they constitute the totality of the dark matter. We additionally derive robust constraints on the fraction of the dark matter in macroscopic objects as a function of mass, by suitably modeling the remainder of the dark matter as standard fluid-like cold dark matter.Comment: 17 pages, 6 figure

Kinetic recoupling of dark matter

We study the possibility that dark matter re-enters kinetic equilibrium with a radiation bath after kinetic decoupling, a scenario we dub kinetic recoupling. This naturally occurs, for instance, with certain types of resonantly-enhanced interactions, or as the result of a phase transition. While late kinetic decoupling damps structure on small scales below a cutoff, kinetic recoupling produces more complex changes in the power spectrum that depend on the nature and extent of the recoupling period. We explore the features that kinetic recoupling imprints upon the matter power spectrum, and discuss how such features can be traced to dark matter microphysics with future observations.Comment: 23 pages, 6 figure

Disrupted transitions? Young adults and the covid-19 pandemic.

The COVID-19 pandemic and related public health restrictions have led to severe disruptions in day-to-day lives, including education, employment and social activities. Young adults have experienced the highest rate of job loss during the pandemic (Central Statistics Office, 2020b). This study draws on a specific survey of the Growing Up in Ireland (GUI) Cohort '98 conducted in December 2020, at a time when restrictions were easing (before a further period of closures). The short online survey was completed by 2,277 young adults, 33 per cent of the total sample, most of whom were 22 years of age at the time. The study seeks to fill a gap in knowledge about the extent of disruption to young adults at a crucial time of transition in their lives and the consequences of this disruption for their mental health

Rogue worlds meet the dark side: revealing terrestrial-mass primordial black holes with the Nancy Grace Roman Space Telescope

Gravitational microlensing is one of the strongest observational techniques to observe non-luminous astrophysical bodies. Existing microlensing observations provide tantalizing evidence of a population of low-mass objects whose origin is unknown. These events may be caused by terrestrial-mass free-floating planets or by exotic objects such as primordial black holes. However, the nature of these objects cannot be resolved on an event-by-event basis, as the induced light curve is degenerate for lensing bodies of identical mass. One must instead statistically compare \textit{distributions} of lensing events to determine the nature of the lensing population. While existing surveys lack the statistics required to identify multiple subpopulations of lenses, this will change with the launch of the Nancy Grace Roman Space Telescope. Roman's Galactic Bulge Time Domain Survey is expected to observe hundreds of low-mass microlensing events, enabling a robust statistical characterization of this population. In this paper, we show that by exploiting features in the distribution of lensing event durations, Roman will be sensitive to a subpopulation of primordial black holes hidden amongst a background of free-floating planets. Roman's reach will extend to primordial black hole dark matter fractions as low as $f_\text{PBH} = 10^{-4}$ at peak sensitivity, and will be able to conclusively determine the origin of existing ultrashort-timescale microlensing events. A positive detection would provide evidence that a significant fraction of the cosmological dark matter consists of macroscopic, non-luminous objects.Comment: 11 pages, 6 figure

Dark Black Holes in the Mass Gap

In the standard picture of stellar evolution, pair-instability -- the energy loss in stellar cores due to electron-positron pair production -- is predicted to prevent the collapse of massive stars into black holes with mass in the range between approximately 50 and 130 solar masses -- a range known as the "{\em black hole mass gap}". LIGO detection of black hole binary mergers containing one or both black holes with masses in this {\em mass gap} thus challenges the standard picture, possibly pointing to an unexpected merger history, unanticipated or poorly understood astrophysical mechanisms, or new physics. Here, we entertain the possibility that a "dark sector" exists, consisting of dark electrons, dark protons, and electromagnetic-like interactions, but no nuclear forces. Dark stars would inevitably form given such dark sector constituents, possibly collapsing into black holes with masses within the mass gap. We study in detail the cooling processes necessary for successful stellar collapse in the dark sector and show that for suitable choices of the particle masses, we indeed predict populating the mass gap with dark sector black holes. In particular, we numerically find that the heavier of the two dark sector massive particles cannot be lighter than, approximately, the visible sector proton for the resulting dark sector black holes to have masses within the mass gap. We discuss constraints on this scenario and how to test it with future, larger black hole merger statistics.Comment: 25 pages, 6 figures, Comments Welcome, added citations in v

Updated constraints on asteroid-mass primordial black holes as dark matter

Microlensing of stars places significant constraints on sub-planetary-mass compact objects, including primordial black holes, as dark matter candidates. As the lens' Einstein radius in the source plane becomes comparable to the size of the light source, however, source amplification is strongly suppressed, making it challenging to constrain lenses with a mass at or below $10^{-10}$ solar masses, i.e. asteroid-mass objects. Current constraints, using Subaru HSC observations of M31, assume a fixed source size of one solar radius. Here we point out that the actual stars in M31 bright enough to be used for microlensing are typically much larger. We correct the HSC constraints by constructing a source size distribution based on the M31 PHAT survey and on a synthetic stellar catalogue, and by correspondingly weighing the finite-size source effects. We find that the actual HSC constraints are weaker by up to almost three orders of magnitude in some cases, broadening the range of masses for which primordial black holes can be the totality of the cosmological dark matter by almost one order of magnitude

Fast Parameter Inference on Pulsar Timing Arrays with Normalizing Flows

Pulsar timing arrays (PTAs) perform Bayesian posterior inference with expensive MCMC methods. Given a dataset of ~10-100 pulsars and O(10^3) timing residuals each, producing a posterior distribution for the stochastic gravitational wave background (SGWB) can take days to a week. The computational bottleneck arises because the likelihood evaluation required for MCMC is extremely costly when considering the dimensionality of the search space. Fortunately, generating simulated data is fast, so modern simulation-based inference techniques can be brought to bear on the problem. In this paper, we demonstrate how conditional normalizing flows trained on simulated data can be used for extremely fast and accurate estimation of the SGWB posteriors, reducing the sampling time from weeks to a matter of seconds.Comment: 8 pages, 3 figure