7,949 research outputs found
A point mass in an isotropic universe: III. The region
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 . 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
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
All Maximally Entangled Four Qubits States
We find an operational interpretation for the 4-tangle as a type of residual
entanglement, somewhat similar to the interpretation of the 3-tangle. Using
this remarkable interpretation, we are able to find the class of maximally
entangled four-qubits states which is characterized by four real parameters.
The states in the class are maximally entangled in the sense that their average
bipartite entanglement with respect to all possible bi-partite cuts is maximal.
We show that while all the states in the class maximize the average tangle,
there are only few states in the class that maximize the average Tsillas or
Renyi -entropy of entanglement. Quite remarkably, we find that up to
local unitaries, there exists two unique states, one maximizing the average
-Tsallis entropy of entanglement for all , while the
other maximizing it for all (including the von-Neumann case of
). Furthermore, among the maximally entangled four qubits states,
there are only 3 maximally entangled states that have the property that for 2,
out of the 3 bipartite cuts consisting of 2-qubits verses 2-qubits, the
entanglement is 2 ebits and for the remaining bipartite cut the entanglement
between the two groups of two qubits is 1ebit. The unique 3 maximally entangled
states are the 3 cluster states that are related by a swap operator. We also
show that the cluster states are the only states (up to local unitaries) that
maximize the average -Renyi entropy of entanglement for all .Comment: 15 pages, 2 figures, Revised Version: many references added, an
appendix added with a statement of the Kempf-Ness theore
The Great Recession, Austerity and Inequality: Evidence from Ireland. ESRI WP499. April 2015
The advent of the Great Recession and the widespread adoption of fiscal austerity policies have heightened concern about inequality and its effects. We examine how the distribution of income in Ireland has evolved over the years 2008 to 2013, using data from the CSO’s Survey on
Income and Living Conditions. Snapshots of the income distribution show that the greatest falls in income were for the bottom decile (poorest 10 per cent). Longitudinal analysis shows that these sharp falls were not due to decreasing income for those remaining in the bottom decile, but to falling income among those with somewhat higher incomes. Most of those falling into the bottom decile came from the bottom one third of the income distribution
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
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Macular Pigment and Visual Function in Patients With Glaucoma: The San Diego Macular Pigment Study.
PurposeAlthough recent studies have shown that macular pigment (MP) is significantly lower in glaucoma patients, this relationship merits further investigation.MethodsThis cross-sectional study included 85 glaucoma patients and 22 controls. All subjects had standard automated perimetry (SAP) and retinal nerve fiber layer (RNFL) thickness measurements. Intake of lutein (L) and zeaxanthin (Z) was estimated using a novel dietary screener. The Heidelberg Spectralis dual-wavelength autofluorescence (AF) technology was employed to study the relationship between MP and glaucoma. The association between MP volume and glaucoma was investigated using linear regression models accounting for potential confounding factors.ResultsGlaucoma patients had significantly worse SAP mean deviation (MD) and lower RNFL thickness in the study eye compared to control subjects (P < 0.001 for both). MP (volume) was comparable between groups (P = 0.436). In the univariable model, diagnosis of glaucoma was not associated with MP volume (R2 = 1.22%; P = 0.257). Dietary intake of L and Z was positively and significantly related to MP in the univariable (P = 0.022) and multivariable (P = 0.020) models.ConclusionsThese results challenge previous studies that reported that glaucoma is associated with low MP. Dietary habits were found to be the main predictor of MP in this sample. Further research is merited to better understand the relationship between glaucoma, MP, and visual performance in these patients
Colorado solar radiation data with supplemental climatic data
Includes bibliographical references (page 99).August, 1982
A Characterisation of Strong Wave Tails in Curved Space-Times
A characterisation of when wave tails are strong is proposed. The existence
of a curvature induced tail (i.e. a Green's function term whose support
includes the interior of the light-cone) is commonly understood to cause
backscattering of the field governed by the relevant wave equation. Strong
tails are characterised as those for which the purely radiative part of the
field is backscattered. With this definition, it is shown that electromagnetic
waves in asymptotically flat space-times and fields governed by tail-free
propagation have weak tails, but minimally coupled scalar fields in a
cosmological scenario have strong tails.Comment: 17 pages, Revtex, to appear in Classical and Quantum Gravit
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