A point mass in an isotropic universe: III. The region R≤2mR\leq 2m

McVittie's solution of Einstein's field equations, representing a point mass embedded into an isotropic universe, possesses a scalar curvature singularity at proper radius $R=2m$. The singularity is space-like and precedes, in the expanding case, all other events in the space-time. It is shown here that this singularity is gravitationally weak, and the possible structure of the region $R\leq 2m$ is investigated. A characterization of this solution which does not involve asymptotics is given.Comment: Revtex, 11pp. To appear in Class.Quant.Grav. Paper II appeared as Class. Quant. Grav. 16 (1999) 122

Expansion-induced contribution to the precession of binary orbits

We point out the existence of new effects of global spacetime expansion on local binary systems. In addition to a possible change of orbital size, there is a contribution to the precession of elliptic orbits, to be added to the well-known general relativistic effect in static spacetimes, and the eccentricity can change. Our model calculations are done using geodesics in a McVittie metric, representing a localized system in an asymptotically Robertson-Walker spacetime; we give a few numerical estimates for that case, and indicate ways in which the model should be improved.Comment: revtex, 7 pages, no figures; revised for publication in Classical and Quantum Gravity, with minor changes in response to referees' comment

Odd-parity perturbations of self-similar Vaidya spacetime

We carry out an analytic study of odd-parity perturbations of the self-similar Vaidya space-times that admit a naked singularity. It is found that an initially finite perturbation remains finite at the Cauchy horizon. This holds not only for the gauge invariant metric and matter perturbation, but also for all the gauge invariant perturbed Weyl curvature scalars, including the gravitational radiation scalars. In each case, `finiteness' refers to Sobolev norms of scalar quantities on naturally occurring spacelike hypersurfaces, as well as pointwise values of these quantities.Comment: 28 page

CCD photometry of 2060 Chiron, 1991 January

Observations of 2060 Chiron was performed on 7 to 8 Jan. 1991 with the Mt. Palomar 1.52 m telescope in the Gunn-R passband. On-chip field stars were used to perform differential reductions. The repeatability of the 5.9 hour light curve was excellent, both within a night and from night to night. No evidence for short-term secular variations similar to those seen last year by both Luu and Jewitt (1990) and Buratti and Dunbar (1991) is seen in the new light curve. Chiron's rotational light curve appears strikingly similar to that obtained a year earlier by Luu and Jewitt (1990), both in amplitude and shape. Both light curves show strongly correlated changes over a timescale of perhaps 15 minutes. These same features were marginally visible in the 1986 light curve. Such behavior is believed to be evidence that Chiron may be more aspherical than the 4 percent intensity variation might otherwise indicate, and favors a viewing geometry where the subearth latitude is rather low. Chiron was much fainter in 1985, when a partial light curve was obtained by Marcialis. Due to the lower sampling rate of these early data, no conclusions can be made regarding the high-frequency light curve structure back then. All three of these light curves differ significantly from that obtained by Buratti and Dunbar (1991), one week before the observations of Luu and Jewitt. The Chiron field was calibrated using Landolt standards on Ut 15 Mar. 1991. A mean R-magnitude of 15.6 + or - 0.1 was found. Variability of 2060 Chiron was demonstrated over timescales of minutes, hours, and years. An intense campaign was urged to monitor the photometric behavior of Chiron throughout the 1990s

A note on behaviour at an isotropic singularity

The behaviour of Jacobi fields along a time-like geodesic running into an isotropic singularity is studied. It is shown that the Jacobi fields are crushed to zero length at a rate which is the same in every direction orthogonal to the geodesic. We show by means of a counter-example that this crushing effect depends crucially on a technicality of the definition of isotropic singularities, and not just on the uniform degeneracy of the metric at the singularity.Comment: 13 pp. plain latex. To appear in Classical and Quantum Gravit

Johnston City School, Mine Subsidence or Shallow Foundation Problem?

Johnston City, a small community in southern Illinois, lies above the Herrin (Illinois No. 6) coal seam. The community has experienced sporadic episodes of surface subsidence due to the collapse of underground mines since the 1930\u27s. Although the mining company left a large block of coal beneath the town\u27s elementary school to prevent subsidence damage to the structure, large cracks appeared in the school building in December, 1971. After the building was razed, construction of a new school was initiated in 1974. Approximately six months after the start of construction, new evidence of structural distress was observed in \u27the still-uncompleted structure. Construction was suspended indefinitely while site investigations were conducted. These investigations, along with recent air photo studies, indicate that renewed mine collapse and the resulting downward displacement of the surface, were the cause of this second incident of structural distress

On the time dependent Schwarzschild - de Sitter spacetime

An imperfect cosmic fluid with energy flux is analyzed. Even though its energy density $\rho$ is positive, the pressure $p = -\rho$ due to the fact that the metric is asymptotically de Sitter. The kinematical quantities for a nongeodesic congruence are computed. The scalar expansion is time independent but divergent at the singularity $r = 2m$. Far from the central mass $m$ and for a cosmic time $\bar{t} << H^{-1}$, the heat flux $q$ does not depend on Newton's constant $G$.Comment: 8 pages, no figures, Sections 3 and 5 enlarged, one reference adde

Evaluación de la Formación ediacárica de Doushantuo: mejora de la correlación estratigráfica de las pizarras negras de Doushantuo superior a partir del contenido en mercurio

Mercury enrichments in the black shale unit of the Ediacaran Doushantuo Formation are, likely the result of volcanic input or anoxia-driven mercury deposition. If the Hg enrichments are volcanic in origin, or are due to synchronous regional anoxia, then the patterns of Hg enrichment are consistent with the conventional correlation of these units, with the tripartite units equivalent to Member IV black shales. Additionally comparing redox proxy data from the intervals of Hg enrichment could indicate if the enrichments are due to comparable changes in redox conditions, or increased Hg input under differing redox conditions, consistent with volcanic input.Los enriquecimientos de mercurio en la unidad de esquisto negro de la Formación ediacárica de Doushantuo son probablemente el resultado de la influencia volcánica o del depósito de mercurio mediante anoxia. Si los enriquecimientos de Hg son de origen volcánico, o se deben a una anoxia regional contemporánea, entonces los patrones de enriquecimiento de Hg son consistentes con la correlación convencional de estas unidades, con las unidades tripartitas equivalentes a la pizarra negra del Miembro IV. Además, la comparación de los datos redox de los intervalos de enriquecimiento en Hg podría indicar si los enriquecimientos se deben a cambios comparables en las condiciones redox, o a un aumento de la entrada de Hg bajo diferentes condiciones redox, consistente con la influencia volcánica

Crisis, Response and Distributional Impact: The Case of Ireland. ESRI WP456. May 2013

Ireland is one of the countries most severely affected by the Great Recession. National income fell by more than 10 per cent between 2007 and 2012, as a result of the bursting of a remarkable property bubble, an exceptionally severe banking crisis, and deep fiscal adjustment. This paper examines the income distribution consequences of the recession, and identifies the impact of a broad range of austerity policies on the income distribution. The overall fall in income was just under 8 per cent between 2008 and 2011, but the greatest losses were strongly concentrated on the bottom and top deciles. Tax, welfare and public sector pay changes over the 2008 to 2013 period gave rise to slightly lower than average losses for the bottom decile. Thus, the larger than average losses observed overall are not due to these policy changes; instead, the main driving factors are the direct effects of the recession itself. Policy changes do contribute to the larger than average losses at high income levels