2,403 research outputs found
Electric and magnetic Weyl tensors in higher dimensions
Recent results on purely electric (PE) or magnetic (PM) spacetimes in n
dimensions are summarized. These include: Weyl types; diagonalizability;
conditions under which direct (or warped) products are PE/PM.Comment: 4 pages; short summary of (parts of) arXiv:1203.3563. Proceedings of
"Relativity and Gravitation - 100 Years after Einstein in Prague", Prague,
June 25-29, 2012 (http://ae100prg.mff.cuni.cz/
Pseudo-Riemannian VSI spaces
In this paper we consider pseudo-Riemannian spaces of arbitrary signature for
which all of their polynomial curvature invariants vanish (VSI spaces). We
discuss an algebraic classification of pseudo-Riemannian spaces in terms of the
boost weight decomposition and define the - and -properties, and show that if the curvature tensors of the space possess the
-property then it is a VSI space. We then use this result to construct
a set of metrics that are VSI. All of the VSI spaces constructed possess a
geodesic, expansion-free, shear-free, and twist-free null-congruence. We also
discuss the related Walker metrics.Comment: 14 page
Studies of dynamo field structure and related effects: DE satellite project guest investigator program
The establishment of the latitudinal and longitudinal structure of the low latitude dynamo electric (DE) field was initiated using data primarily from the Unified Abstract (UA) files of the Atmosphere Explorer E (AE-E) satellite. Mass plots of the vertical ion drift values were made for 1977, 1978, and 1979. The average diurnal variation of V sub v within 20 degrees of the dip equator is remarkably similar to that obtained at Jicamarca in the same years. The average meridional ion drift velocity vectors, obtained as a function of latitude by combining the average vertical and horizontal (nearly north-south) ion drift values from the AE-E, showed the expected variations with local time and season based on the well known equatorial fountain effect theory. The average diurnal variation of the vertical drift was found for four different ranges of dip latitude for a northern solstice season. The effect of the transequatorial neutral winds was as evident in this plotting format as in the meridional or fountain effect format. Finally, the average vertical drift velocity V sub v, not the east-west electric field E sub ew, was found to be approximately independent of longitude, as expected from the dynamo theory
SO(n + 1) Symmetric Solutions of the Einstein Equations in Higher Dimensions
A method of solving the Einstein equations with a scalar field is presented.
It is applied to find higher dimensional vacuum metrics invariant under the
group SO(n + 1) acting on n-dimensional spheres.Comment: 11 page
Lorentzian spacetimes with constant curvature invariants in three dimensions
In this paper we study Lorentzian spacetimes for which all polynomial scalar
invariants constructed from the Riemann tensor and its covariant derivatives
are constant (CSI spacetimes) in three dimensions. We determine all such CSI
metrics explicitly, and show that for every CSI with particular constant
invariants there is a locally homogeneous spacetime with precisely the same
constant invariants. We prove that a three-dimensional CSI spacetime is either
(i) locally homogeneous or (ii) it is locally a Kundt spacetime. Moreover, we
show that there exists a null frame in which the Riemann (Ricci) tensor and its
derivatives are of boost order zero with constant boost weight zero components
at each order. Lastly, these spacetimes can be explicitly constructed from
locally homogeneous spacetimes and vanishing scalar invariant spacetimes.Comment: 14 pages; Modified to match published versio
Bianchi identities in higher dimensions
A higher dimensional frame formalism is developed in order to study
implications of the Bianchi identities for the Weyl tensor in vacuum spacetimes
of the algebraic types III and N in arbitrary dimension . It follows that
the principal null congruence is geodesic and expands isotropically in two
dimensions and does not expand in spacelike dimensions or does not expand
at all. It is shown that the existence of such principal geodesic null
congruence in vacuum (together with an additional condition on twist) implies
an algebraically special spacetime. We also use the Myers-Perry metric as an
explicit example of a vacuum type D spacetime to show that principal geodesic
null congruences in vacuum type D spacetimes do not share this property.Comment: 25 pages, v3: Corrections to Appendix B as given in
Erratum-ibid.24:1691,2007 are now incorporated (A factor of 2 was missing in
certain Bianchi equations.
Note on the invariant classification of vacuum type D spacetimes
We illustrate the fact that the class of vacuum type D spacetimes which are
-\emph{non-degenerate} are invariantly classified by their scalar
polynomial curvature invariants
A note on the peeling theorem in higher dimensions
We demonstrate the ``peeling property'' of the Weyl tensor in higher
dimensions in the case of even dimensions (and with some additional
assumptions), thereby providing a first step towards understanding of the
general peeling behaviour of the Weyl tensor, and the asymptotic structure at
null infinity, in higher dimensions.Comment: 5 pages, to appear in Class. Quantum Gra
Metrics With Vanishing Quantum Corrections
We investigate solutions of the classical Einstein or supergravity equations
that solve any set of quantum corrected Einstein equations in which the
Einstein tensor plus a multiple of the metric is equated to a symmetric
conserved tensor constructed from sums of terms the involving
contractions of the metric and powers of arbitrary covariant derivatives of the
curvature tensor. A classical solution, such as an Einstein metric, is called
{\it universal} if, when evaluated on that Einstein metric, is a
multiple of the metric. A Ricci flat classical solution is called {\it strongly
universal} if, when evaluated on that Ricci flat metric,
vanishes. It is well known that pp-waves in four spacetime dimensions are
strongly universal. We focus attention on a natural generalisation; Einstein
metrics with holonomy in which all scalar invariants are zero
or constant. In four dimensions we demonstrate that the generalised
Ghanam-Thompson metric is weakly universal and that the Goldberg-Kerr metric is
strongly universal; indeed, we show that universality extends to all
4-dimensional Einstein metrics. We also discuss generalizations
to higher dimensions.Comment: 23 page
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