20 research outputs found
Schiff Theorem Revisited
We carefully rederive the Schiff theorem and prove that the usual expression
of the Schiff moment operator is correct and should be applied for calculations
of atomic electric dipole moments. The recently discussed corrections to the
definition of the Schiff moment are absent.Comment: 6 page
Schiff moment of the Mercury nucleus and the proton dipole moment
We calculated the contribution of internal nucleon electric dipole moments to
the Schiff moment of Hg. The contribution of the proton electric dipole
moment was obtained via core polarization effects that were treated in the
framework of random phase approximation with effective residual forces. We
derived a new upper bound cm of the proton
electric dipole moment.Comment: 4 pages, 2 figures, RevTex
Black hole uniqueness theorems and new thermodynamic identities in eleven dimensional supergravity
We consider stationary, non-extremal black holes in 11-dimensional
supergravity having isometry group . We prove that
such a black hole is uniquely specified by its angular momenta, its electric
charges associated with the various 7-cycles in the manifold, together with
certain moduli and vector valued winding numbers characterizing the topological
nature of the spacetime and group action. We furthermore establish interesting,
non-trivial, relations between the thermodynamic quantities associated with the
black hole. These relations are shown to be a consequence of the hidden
symmetry in this sector of the solution space, and are distinct
from the usual "Smarr-type" formulas that can be derived from the first law of
black hole mechanics. We also derive the "physical process" version of this
first law applicable to a general stationary black hole spacetime without any
symmetry assumptions other than stationarity, allowing in particular arbitrary
horizon topologies. The work terms in the first law exhibit the topology of the
horizon via the intersection numbers between cycles of various dimensions.Comment: 50pp, 3 figures, v2: references added, correction in appendix B,
conclusions added, v3: reference section edited, typos removed, minor changes
in appendix
Black hole instabilities and local Penrose inequalities
Various higher-dimensional black holes have been shown to be unstable by
studying linearized gravitational perturbations. A simpler method for
demonstrating instability is to find initial data that describes a small
perturbation of the black hole and violates a Penrose inequality. An easy way
to construct initial data is by conformal rescaling of the unperturbed black
hole initial data. For a compactified black string, we construct initial data
which violates the inequality almost exactly where the Gregory-Laflamme
instability appears. We then use the method to confirm the existence of the
"ultraspinning" instability of Myers-Perry black holes. Finally we study black
rings. We show that "fat" black rings are unstable. We find no evidence of any
rotationally symmetric instability of "thin" black rings.Comment: 35 pages, 12 figures. v2: typos corrected, matches published versio