Do Maternal Investments in Human Capital Affect Childrens' Academic Achievement?

Children of educated mothers fare better on a variety of educational outcomes. However, little research has been done on the effects of human capital investments undertaken by mothers with children at home. Such investments have a theoretically ambiguous effect on child outcomes, since human capital investment reduces time spent with children but may have positive spillover effects on child investment. Using childand sibling-fixed effects models to deal with unobserved heterogeneity, we find that cumulative maternal schooling undertaken during a child's lifetime has significant positive effects on child outcomes, and that negative time allocation effects are minimal.

Making History Visible: Ireland’s National Famine Way Told Through Models and Interactive Digital Narratives

The National Famine Way is a trail along Ireland’s Royal Canal that traces the remarkable trek of the 1,490 tenants who were evicted by their landlord, Denis Mahon, from his estate in Strokestown, County Roscommon, in the Republic of Ireland, during ‘Black ’47,’ the worst year of the Great Irish Famine (Irish: An Gorta Mór, the Great Hunger of 1847). The evictees were ‘escorted’ from their homes to vessels that awaited them in Dublin. They were then taken to Liverpool, where they were placed on four so-called ‘coffin ships’ bound for Canada. The path along the Royal Canal is 165 kilometres, or approximately one hundred miles. Today it is shared by hikers, bikers, ‘boat people,’ site-seekers, commemorators, and self-identified famine ‘pilgrims.’ For some of the latter, the signposts of children’s shoes erected along the path have acquired an iconic or even mythic significance. This article begins by applying a model that approaches the Way as a five-pronged cultural heritage complex. The article expands the model by considering how the National Famine Way’s cultural heritage is being approached from the lenses of transmedia

‘at the altar of memory’: Great Irish Famine Memorials in Words and Images

After discussing some of the most important facts and figures pertaining to An Gorta Mór (the Great Irish Famine of 1845-1852), this article turns to some of the images of monuments, crosses, stones and sculptures erected in commemoration of those who succumbed during the period. Alongside the images are travelers\u27 statements, many of which were captured by the author while journeying to \u27dark pilgrimage\u27 sites in Ireland, Canada and the United States

Novel Families of Fractional Quantum Hall States: Pairing of Composite Fermions

Fractional quantum Hall (FQH) states have recently been observed at unexpected values of the filling factor nu. Here we interpret these states as a novel family of FQH states involving pairing correlations rather than Laughlin correlations among the quasiparticles (QP's). The correlations depend upon the behavior of the QP-QP pseudopotential V_QP(L'), the interaction energy of a pair as a function of the pair angular momentum L'. This behavior, known from numerical studies of small systems, is used to demonstrate that pairing correlations give rise to FQH states at the experimentally observed values of nu.Comment: to appear in Physics Letters

Dark Matter Halos within Clusters

We examine the properties of dark matter halos within a rich galaxy cluster using a high resolution simulation that captures the cosmological context of a cold dark matter universe. The mass and force resolution permit the resolution of 150 halos with circular velocities larger than 80 kms within the cluster's virial radius of 2 Mpc. This enables an unprecedented study of the statistical properties of a large sample of dark matter halos evolving in a dense environment. The cumulative fraction of mass attached to these halos varies from 0% at 200 kpc, to 13% at the virial radius. Even at this resolution the overmerging problem persists; halos that pass within 200 kpc of the cluster center are tidally disrupted. Additional substructure is lost at earlier epochs within the massive progenitor halos. The median ratio of apocentric to pericentric radii is 6:1; the orbital distribution is close to isotropic, circular orbits are rare, radial orbits are common. The orbits of halos are unbiased with respect to both position within the cluster and with the orbits of the smooth dark matter background and no velocity bias is detected. The tidal radii of surviving halos are generally well-fit using the simple analytic prediction applied to their orbital pericenters. Halos within clusters have higher concentrations than those in the field. Within the cluster, halo density profiles can be modified by tidal forces and individual encounters with other halos that cause significant mass loss - ``galaxy harassment''. Mergers between halos do not occur inside the clusters virial radius.Comment: LaTeX MN style, 20 pages, 30 figures included + 1 colour plo

Resolving the Structure of Cold Dark Matter Halos

We examine the effects of mass resolution and force softening on the density profiles of cold dark matter halos that form within cosmological N-body simulations. As we increase the mass and force resolution, we resolve progenitor halos that collapse at higher redshifts and have very high densities. At our highest resolution we have nearly 3 million particles within the virial radius, several orders of magnitude more than previously used and we can resolve more than one thousand surviving dark matter halos within this single virialised system. The halo profiles become steeper in the central regions and we may not have achieved convergence to a unique slope within the inner 10% of the virialised region. Results from two very high resolution halo simulations yield steep inner density profiles, $\rho(r)\sim r^{-1.4}$. The abundance and properties of arcs formed within this potential will be different from calculations based on lower resolution simulations. The kinematics of disks within such a steep potential may prove problematic for the CDM model when compared with the observed properties of halos on galactic scales.Comment: Final version, to be published in the ApJLetter

Fractional quantum Hall effect and electron correlations in partially filled first excited Landau level

We present a quantitative study of most prominent incompressible quantum Hall states in the partially filled first excited Landau level (LL1) which have been recently studied experimentally by Choi et al. The pseudopotential describing the electron - electron interaction in LL1 is harmonic at short range. It produces a series of incompressible states which is different from its LL0 counterpart. The numerical data indicate that the most prominent states $\nu={5/2}$, 7/3, and 8/3 are not produced by Laughlin correlated electrons, but result from a tendency of electrons to form pairs or larger clusters which eventually become Laughlin correlated. States with smaller gaps at filling factors 14/5, 16/7, 11/5, 19/7 are Laughlin correlated electron or hole states and fit Jain's sequence of filled $\rm{CF}^4$ levels.Comment: 4 pages, 7 figure

Cold collapse and the core catastrophe

We show that a universe dominated by cold dark matter fails to reproduce the rotation curves of dark matter dominated galaxies, one of the key problems that it was designed to resolve. We perform numerical simulations of the formation of dark matter halos, each containing \gsim 10^6 particles and resolved to 0.003 times the virial radius, allowing an accurate comparison with rotation curve data. A good fit to both galactic and cluster sized halos can be achieved using the density profile rho(r) \propto [(r/r_s)^1.5(1+(r/r_s)^1.5)]^-1, where r_s is a scale radius. This profile has a steeper asymptotic slope, rho(r) \propto r^-1.5, and a sharper turnover than found by lower resolution studies. The central structure of relaxed halos that form within a hierarchical universe has a remarkably small scatter (unrelaxed halos would not host disks). We compare the results with a sample of dark matter dominated, low surface brightness (LSB) galaxies with circular velocities in the range 100-300 km/s. The rotation curves of disks within cold dark matter halos rise too steeply to match these data which require a constant mass density in the central regions. The same conclusion is reached if we compare the scale free shape of observed rotation curves with the simulation data. It is important to confirm these results using stellar rather than HI rotation curves for LSB galaxies. We test the effects of introducing a cut-off in the power spectrum that may occur in a universe dominated by warm dark matter. In this case halos form by a monolithic collapse but the final density profile hardly changes, demonstrating that the merger history does not play a role in determining the halo structure.Comment: Latex 13 pages, 4 figures. Submitted to MNRAS. High resolution colour version of figure 4 and other N-body images here: http://star-www.dur.ac.uk:80/~moore/images