26 research outputs found

### On the dual flow of slow-roll Inflation

We study the dual 3d Euclidean RG flow of single-field slow-roll Inflation
using the postulates of the dS/CFT correspondence. For that purpose we solve
for the inflationary fluctuation at all times using a matching procedure
between two approximate solutions which are separately valid at different
regions of the space of parameters but together cover all of it. The two modes
of the full solution mix such that each of the modes at late times is a
superposition of the modes in the quasi-de Sitter region. We find that the dual
theory admits two phases of explicit and spontaneous breaking of conformal
symmetry.
We also find that the mixing effect between the two modes in the bulk implies
that slow-roll inflation does not guarantee, but rather generically generates,
a nearly scale invariant power spectrum, except in fine-tuned situations. We
suggest that the mixing effect can have a unique signature on other
cosmological observables such as the bispectrum.Comment: 20 pages. v2: minor changes, references added. v3: version to appear
in JHE

### Duality in Einstein's Gravity

We show that the Einstein equations in the vacuum are invariant under an
$SO(2)$ duality symmetry which rotates the curvature 2-form into its tangent
space Hodge dual. Akin to electric-magnetic duality in gauge theory, the
duality operation maps classical solutions into each other. As an example, we
demonstrate that the Kerr solution is non-linearly mapped by duality into
Kerr-Taub-NUT.Comment: v2: references adde

### Asymptotic Dynamics in Perturbative Quantum Gravity and BMS Supertranslations

Recently it has been shown that infrared divergences in the conventional
S-matrix elements of gauge and gravitational theories arise from a violation of
the conservation laws associated with large gauge symmetries. These infrared
divergences can be cured by using the Faddeev-Kulish (FK) asymptotic states as
the basis for S-matrix elements. Motivated by this connection, we study the
action of BMS supertranslations on the FK asymptotic states of perturbative
quantum gravity. We compute the BMS charge of the FK states and show that it
characterizes the superselection sector to which the state belongs.
Conservation of the BMS charge then implies that there is no transition between
different superselection sectors, hence showing that the FK graviton clouds
implement the necessary vacuum transition induced by the scattering process.Comment: 39 page

### Classical double copy at null infinity

We give two double copy prescriptions which construct asymptotically flat
solutions in gravity from asymptotically flat gauge fields. The first
prescription applies to radiative fields, which are non-linear vacuum solutions
determined by characteristic data at null infinity. For any two such radiative
gauge fields (linear or non-linear), the characteristic data of a radiative
metric, dilaton and axion is constructed by a simple `squaring' procedure,
giving a classical double copy at the level of radiation fields. We demonstrate
the procedure with several examples where the characteristic data can be
explicitly integrated; for linear fields this also sheds light on the
twistorial description of Weyl double copy. Our second prescription applies to
all asymptotically flat fields at the level of their asymptotic equations of
motion: we give a map between any solution of the asymptotic Maxwell equations
and any solution of the asymptotic Einstein equations at null infinity. This
also extends to the asymptotic charges and their duals, preserves the soft and
hard sectors between gauge theory and gravity, and is related to the usual
notion of double copy in scattering amplitudes.Comment: 44 pages, 2 figures. v2: additions to references and discussio

### Duality in Gauge Theory, Gravity and String Theory

Einstein's theory in the vacuum was recently shown to possess an $SO(2)$
duality invariance, which is broken by coupling to matter. Duality invariance
can be restored by enlarging the phase space of the theory to allow for
violations of the algebraic Bianchi identity. We show that in cases where the
matter content can be understood as a component of the torsion tensor duality
can be restored and we compute the corresponding duality current. We consider
the case of NS-NS gravity as an example and find that the duality current is
given by the divergence of the axion. In the linearized approximation of the
low energy heterotic string theory these results imply that duality of the
generalized Riemann curvature tensor implements Riemannian, axion-dilaton and
electro-magnetic dualities simultaneously

### The Radial Action from Probe Amplitudes to All Orders

We extract the relativistic classical radial action from scattering
amplitudes, to all orders in perturbation theory, in the probe limit. Our
sources include point charges and monopoles, as well as the Schwarzschild and
pure-NUT gravitational backgrounds. A characteristic relativistic effect, that
scattering trajectories may wind around these sources any number of times, can
be recovered when all-order amplitudes are available. We show that the
amplitude for scattering a probe off a pure NUT is given by the solution of a
transcendental equation involving continued fractions, and explain how to solve
this equation to any desired loop order