241 research outputs found
Inflatino-less Cosmology
We construct inflationary models in the context of supergravity with
orthogonal nilpotent superfields [1]. When local supersymmetry is gauge-fixed
in the unitary gauge, these models describe theories with only a single real
scalar (the inflaton), a graviton and a gravitino. Critically, there is no
inflatino, no sgoldstino, and no sinflaton in these models. This dramatically
simplifies cosmological models which can simultaneously describe inflation,
dark energy and SUSY breaking.Comment: 4 page
Abelian Z-theory: NLSM amplitudes and alpha'-corrections from the open string
In this paper we derive the tree-level S-matrix of the effective theory of
Goldstone bosons known as the non-linear sigma model (NLSM) from string theory.
This novel connection relies on a recent realization of tree-level
open-superstring S-matrix predictions as a double copy of super-Yang-Mills
theory with Z-theory --- the collection of putative scalar effective field
theories encoding all the alpha'-dependence of the open superstring. Here we
identify the color-ordered amplitudes of the NLSM as the low-energy limit of
abelian Z-theory. This realization also provides natural higher-derivative
corrections to the NLSM amplitudes arising from higher powers of alpha' in the
abelian Z-theory amplitudes, and through double copy also to Born-Infeld and
Volkov-Akulov theories. The Kleiss-Kuijf and Bern-Carrasco-Johansson relations
obeyed by Z-theory amplitudes thereby apply to all alpha'-corrections of the
NLSM. As such we naturally obtain a cubic-graph parameterization for the
abelian Z-theory predictions whose kinematic numerators obey the duality
between color and kinematics to all orders in alpha'.Comment: 37 pages; v2: references, explanations and arguments for
factorization added; published versio
Gauge and Gravity Amplitude Relations
In these lectures I talk about simplifications and universalities found in
scattering amplitudes for gauge and gravity theories. In contrast to Ward
identities, which are understood to arise from familiar symmetries of the
classical action, these structures are currently only understood in terms of
graphical organizational principles, such as the gauge-theoretic
color-kinematics duality and the gravitational double-copy structure, for local
representations of multi-loop S-matrix elements. These graphical principles
make manifest new relationships in and between gauge and gravity scattering
amplitudes. My lectures will focus on arriving at such graphical organizations
for generic theories with examples presented from maximal supersymmetry, and
their use in unitarity-based multi-loop integrand construction.Comment: Presented at the Theoretical Advanced Study Institute (TASI 2014),
Boulder, CO, June 2-27, 201
The Hyperbolic Geometry of Cosmological Attractors
Cosmological alpha-attractors give a natural explanation for the spectral
index n_s of inflation as measured by Planck while predicting a range for the
tensor-to-scalar ratio r, consistent with all observations, to be measured more
precisely in future detection of gravity waves. Their embedding into
supergravity exploits the hyperbolic geometry of the Poincare disk or
half-plane. These geometries are isometric under Mobius transformations, which
include the shift symmetry of the inflaton field. We introduce a new Kahler
potential frame that explicitly preserves this symmetry, enabling the inflaton
to be light. Moreover, we include higher-order curvature deformations, which
can stabilize a direction orthogonal to the inflationary trajectory. We
illustrate this new framework by stabilizing the single superfield
alpha-attractors
One-loop four-point amplitudes in pure and matter-coupled N <= 4 supergravity
We construct all supergravity theories that can be obtained through
factorized orbifold projections of N=8 supergravity, exposing their double-copy
structure, and calculate their one-loop four-point scattering amplitudes. We
observe a unified structure in both matter and gravity amplitudes, and
demonstrate that the four-graviton amplitudes are insensitive to the precise
nature of the matter couplings. We show that these amplitudes are identical for
the two different realizations of N=4 supergravity with two vector multiplets,
and argue that this feature extends to all multiplicities and loop orders as
well as to higher dimensions. We also construct a selected set of
supergravities obtained through a non-factorized orbifold action. Furthermore
we calculate one-loop four-point amplitudes for all pure super-Yang-Mills
theories with less-than-maximal supersymmetry using the duality between color
and kinematics, finding here a unified expression that holds for all four gluon
amplitudes in the theories. We recover the related amplitudes of factorized
N<=4 supergravities employing the double-copy construction. We observe a
requirement that the four-point loop-level amplitudes have non-local integrand
representations, exhibiting a mild non-locality in the form of inverse powers
of the three external Mandelstam invariants. These are the first loop-level
color-kinematic-satisfying representations in reduced supersymmetry theories.Comment: 41 pages, 3 figures, PDFLaTeX, section 3.2 expanded, version accepted
for publication in JHE
UV Massive Resonance from IR Double Copy Consistency
From the perspective of effective field theory (EFT), Wilson coefficients of
the low energy theory are determined by integrating out modes of the full
ultraviolet (UV) theory. The spectrum can be in principle resummed if one has
access to all available infrared (IR) coefficients at low energies. In this
work we show that there exists a general class of consistent massive resonance
double-copy (CMRDC) models where UV massive residues are reconstructed through
double-copy consistency conditions between the IR Wilson coefficients of the
full EFT expansion. Through a color-dual bootstrap, we find surprisingly that
double-copy consistency alone introduces the kinematic factors of CMRDC models
that soften high energy behavior by exponentiating color-dual contacts. This
bootstrap suggests that our massive resonance paradigm is an inevitable
consequence of the duality between color and kinematics, thereby providing a
path towards emergent UV structure directly from the IR. We then demonstrate
how CMRDC models can capture a spectrum of massive modes compatible with
general multiplicity, and use Pad\'{e} extrapolation to solve the inverse
problem of identifying massive UV resonance from a small number of IR Wilson
coefficients.Comment: 48 pages, 2 figure
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