2,520 research outputs found
Asymptotic symmetries of three dimensional gravity and the membrane paradigm
The asymptotic symmetry group of three-dimensional (anti) de Sitter space is
the two dimensional conformal group with central charge . Usually
the asymptotic charge algebra is derived using the symplectic structure of the
bulk Einstein equations. Here, we derive the asymptotic charge algebra by a
different route. First, we formulate the dynamics of the boundary as a
1+1-dimensional dynamical system. Then we realize the boundary equations of
motion as a Hamiltonian system on the dual Lie algebra, , of
the two-dimensional conformal group. Finally, we use the Lie-Poisson bracket on
to compute the asymptotic charge algebra. This streamlines the
derivation of the asymptotic charge algebra because the Lie-Poisson bracket on
the boundary is significantly simpler than the symplectic structure derived
from the bulk Einstein equations. It also clarifies the analogy between the
infinite dimensional symmetries of gravity and fluid dynamics.Comment: 15 page
Radiation of scalar modes and the classical double copy
The double copy procedure relates gauge and gravity theories through
color-kinematics replacements and holds for both scattering amplitudes and in
classical contexts. Moreover, it has been shown that there is a web of theories
whose scattering amplitudes are related through operations that exchange color
and kinematic factors. In this paper, we generalize and extend this procedure
by showing that the classical perturbative double copy of pions corresponds to
special Galileons. We consider point-particles coupled to the relevant scalar
fields, and find the leading and next to leading order radiation amplitudes. By
considering couplings motivated by those that would arise from extracting the
longitudinal modes of the gauge and gravity theories, we are able to map the
non-linear sigma model radiation to that of the special Galileon. We also
construct the single copy by mapping the bi-adjoint scalar radiation to the
non-linear sigma model radiation through generalized color-kinematics
replacements.Comment: 30 pages, 5 figure
The classical double copy in maximally symmetric spacetimes
The classical double copy procedure relates classical asymptotically-flat
gravitational field solutions to Yang-Mills and scalar field solutions living
in Minkowski space. In this paper we extend this correspondence to maximally
symmetric curved spacetimes. We consider asymptotically (A)dS spacetimes in
Kerr-Schild form and construct the corresponding single and zeroth copies. In
order to clarify the interpretation of these copies, we study several examples
including (A)dS-Schwarzschild, (A)dS-Kerr, black strings, black branes, and
waves, paying particular attention to the source terms. We find that the single
and zeroth copies of stationary solutions satisfy different equations than
those of wave solutions. We also consider how to obtain Einstein-Maxwell
solutions using this procedure. Finally, we derive the classical single and
zeroth copy of the BTZ black hole.Comment: matches published versio
Bounds on EFT's in an expanding Universe
We find bounds on the Wilson coefficients of effective field theories (EFTs)
living in a Universe undergoing expansion by requiring that its modes do not
propagate further than a minimally coupled photon by a resolvable amount. To do
so, we compute the spatial shift suffered by the EFT modes at a fixed time
slice within the WKB approximation and the regime of validity of the EFT. We
analyze the bounds arising on shift-symmetric scalars and curved space
generalizations of Galileons.Comment: double-column, 7 pages plus appendices and references, 2 figures; v2
matches the published versio
Testing Hybrid Natural Inflation with BICEP2
We analyse Hybrid Natural Inflation in view of the recent results for the
tensor index reported by BICEP2. We find that it predicts a large running of
the scalar spectrum which is potentially detectable by large scale structure
and observations. The running of the running is also
relatively large becoming close to . Along the way, we find general
consistency relations at which observables are subject if the slow-roll
approximation is imposed. Failure to satisfy these equations by the values
obtained for the observables in surveys would be a failure of the slow-roll
approximation itself.Comment: V3: Published versio
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