126 research outputs found
Generalised geometry from the ground up
Extending previous work on generalised geometry, we explicitly construct an E7-valued vielbein in eleven dimensions that encompasses the scalar bosonic degrees of freedom of D=11 supergravity, by identifying new "generalised vielbeine" in eleven dimensions associated with the dual 6-form potential and the dual graviton. By maintaining full on-shell equivalence with the original theory at every step, our construction altogether avoids the constraints usually encountered in other approaches to generalised geometry and, as a side product, also furnishes the non-linear ansatz for the dual (magnetic) 7-form flux for any non-trivial compactification of D=11 supergravity, complementing the known non-linear ansaetze for the metric and the 4-form flux. A preliminary analysis of the generalised vielbein postulate for the new vielbein components reveals tantalising hints of new structures beyond D=11 supergravity and ordinary space-time covariance, and also points to the possible D=11 origins of the embedding tensor. We discuss the extension of these results to E8
Tower of subleading dual BMS charges
We supplement the recently found dual gravitational charges with dual charges
for the whole BMS symmetry algebra. Furthermore, we extend the dual charges away from
null infinity, defining subleading dual charges. These subleading dual charges complement
the subleading BMS charges in the literature and together account for all the NewmanPenrose charges
Lorentzian CFT 3-point functions in momentum space
In a conformal field theory, two and three-point functions of scalar operators and conserved currents are completely determined, up to constants, by conformal invariance. The expressions for these correlators in Euclidean signature are long known in position space, and were fully worked out in recent years in momentum space. In Lorentzian signature, the position-space correlators simply follow from the Euclidean ones by means of the i-epsilon prescription. In this paper, we compute the Lorentzian correlators in momentum space and in arbitrary dimensions for three scalar operators by means of a formal Wick rotation. We explain how tensorial three-point correlators can be obtained and, in particular, compute the correlator with two identical scalars and one energy-momentum tensor. As an application, we show that expectation values of the ANEC operator simplify in this approach
Asymptotic Gravitational Charges
We present a method for finding, in principle, all asymptotic gravitational
charges. The basic idea is that one must consider all possible contributions to
the action that do not affect the equations of motion for the theory of
interest; such terms include topological terms. As a result we observe that the
first order formalism is best suited to an analysis of asymptotic charges. In
particular, this method can be used to provide a Hamiltonian derivation of
recently found dual charges.Comment: 5 page
Subleading BMS charges and fake news near null infinity
In this paper we establish a relation between the non-linearly conserved
Newman-Penrose charges and certain subleading terms in a large- expansion of
the BMS charges in an asymptotically-flat spacetime. We define the subleading
BMS charges by considering a -expansion of the Barnich-Brandt prescription
for defining asymptotic charges in an asymptotically-flat spacetime. At the
leading order, i.e. , one obtains the standard BMS charges, which would
be integrable and conserved in the absence of a flux term at null infinity,
corresponding to gravitational radiation, or Bondi news. At subleading orders,
analogous terms in general provide obstructions to the integrability of the
corresponding charges. Since the subleading terms are defined close to null
infinity, but vanish actually at infinity, the analogous obstructions are not
associated with genuine Bondi news. One may instead describe them as
corresponding to "fake news." At order , we find that a set of
integrable charges can be defined and that these are related to the ten
non-linearly conserved Newman-Penrose charges.Comment: 34 pages;few minor typos correcte
Hamiltonian derivation of dual gravitational charges
Abstract
We provide a Hamiltonian derivation of recently discovered dual BMS charges. In order to do so, we work in the first order formalism and add to the usual Palatini action, the Holst term, which does not contribute to the equations of motion. We give a method for finding the leading order integrable dual charges à la Wald-Zoupas and construct the corresponding charge algebra. We argue that in the presence of fermions, the relevant term that leads to dual charges is the topological Nieh-Yan term.</jats:p
Weyl Double Copy for Gravitational Waves
We establish the status of the Weyl double copy relation for radiative solutions of the vacuum Einstein equations. We show that all type
N
vacuum solutions, which describe the radiation region of isolated gravitational systems with appropriate falloff for the matter fields, admit a degenerate Maxwell field that squares to give the Weyl tensor. The converse statement also holds, i.e., if there exists a degenerate Maxwell field on a curved background, then the background is type
N
. This relation defines a scalar that satisfies the wave equation on the background. We show that for nontwisting radiative solutions, the Maxwell field and the scalar also satisfy the Maxwell equation and the wave equation on Minkowski spacetime. Hence, nontwisting solutions have a straightforward double copy interpretation
Spinor classification of the Weyl tensor in five dimensions
We investigate the spinor classification of the Weyl tensor in five
dimensions due to De Smet. We show that a previously overlooked reality
condition reduces the number of possible types in the classification. We
classify all vacuum solutions belonging to the most special algebraic type. The
connection between this spinor and the tensor classification due to Coley,
Milson, Pravda and Pravdov\'a is investigated and the relation between most of
the types in each of the classifications is given. We show that the black ring
is algebraically general in the spinor classification.Comment: 40 page
Type II Einstein spacetimes in higher dimensions
This short note shows that many of the results derived by Pravda et al
(Class. Quant. Grav. 24 4407-4428) for higher-dimensional Type D Einstein
spacetimes can be generalized to all Einstein spacetimes admitting a multiple
WAND; the main new result being the extension to include the Type II case.
Examples of Type D Einstein spacetimes admitting non-geodesic multiple WANDs
are given in all dimensions greater than 4.Comment: 10 pages. v2: Various minor corrections and clarifications. Accepted
by Class. Quantum Gra
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