1,092 research outputs found
Inflation and Conformal Invariance: The Perspective from Radial Quantization
According to the dS/CFT correspondence, correlators of fields generated
during a primordial de Sitter phase are constrained by three-dimensional
conformal invariance. Using the properties of radially quantized conformal
field theories and the operator-state correspondence, we glean information on
some points. The Higuchi bound on the masses of spin-s states in de Sitter is a
direct consequence of reflection positivity in radially quantized CFT and
the fact that scaling dimensions of operators are energies of states. The
partial massless states appearing in de Sitter correspond from the boundary
CFT perspective to boundary states with highest weight for the conformal
group. We discuss inflationary consistency relations and the role of asymptotic
symmetries which transform asymptotic vacua to new physically inequivalent
vacua by generating long perturbation modes. We show that on the CFT side,
asymptotic symmetries have a nice quantum mechanics interpretation. For
instance, acting with the asymptotic dilation symmetry corresponds to evolving
states forward (or backward) in "time" and the charge generating the asymptotic
symmetry transformation is the Hamiltonian itself. Finally, we investigate the
symmetries of anisotropic inflation and show that correlators of
four-dimensional free scalar fields can be reproduced in the dual picture by
considering an isotropic three-dimensional boundary enjoying dilation symmetry,
but with a nonvanishing vacuum expectation value of the boundary stress-energy
momentum tensor.Comment: 41 pages, 4 figure
Right-handed neutrinos as the source of density perturbations
We study the possibility that cosmological density perturbations are
generated by the inhomogeneous decay of right-handed neutrinos. This will occur
if a scalar field whose fluctuations are created during inflation is coupled to
the neutrino sector. Robust predictions of the model are a detectable level of
non-Gaussianity and, if standard leptogenesis is the source of the baryon
asymmetry, a baryon isocurvature perturbations at the level of the present
experimental constraints.Comment: 14 pages, 2 figure
Frequentist analyses of solar neutrino data (updated including KamLAND and SNO data)
The solar neutrino data are analyzed in a frequentist framework, using the
Crow-Gardner and Feldman-Cousins prescriptions for the construction of
confidence regions. Including in the fit only the total rates measured by the
various experiments, both methods give results similar to the commonly used
Delta chi^2-cut approximation. When fitting the full data set, the Delta
chi^2-cut still gives a good approximation of the Feldman-Cousins regions.
However, a careful statistical analysis significantly reduces the
goodness-of-fit of the SMA and LOW solutions.
In the addenda we discuss the implications of the latest KamLAND, SNO and SK
data.Comment: 24 pages, 12 figures. Version 2: addendum about the CC SNO data
(section 6). Version 3: addendum about the NC and day/night SNO data (section
7). Version 4: addendum about the KamLAND data (section 8). Version 5:
addendum about SNO salt data (section 9, pages 22, 23). Version 6: final
addendum about final SNO salt data and KamLAND (section 10, page 24
Galilean Genesis: an alternative to inflation
We propose a novel cosmological scenario, in which standard inflation is
replaced by an expanding phase with a drastic violation of the Null Energy
Condition (NEC): \dot H >> H^2. The model is based on the recently introduced
Galileon theories, that allow NEC violating solutions without instabilities.
The unperturbed solution describes a Universe that is asymptotically Minkowski
in the past, expands with increasing energy density until it exits the regime
of validity of the effective field theory and reheats. This solution is a
dynamical attractor and the Universe is driven to it, even if it is initially
contracting. The study of perturbations of the Galileon field reveals some
subtleties, related to the gross violation of the NEC and it shows that
adiabatic perturbations are cosmologically irrelevant. The model, however,
suggests a new way to produce a scale invariant spectrum of isocurvature
perturbations, which can later be converted to adiabatic: the Galileon is
forced by symmetry to couple to the other fields as a dilaton; the effective
metric it yields on the NEC violating solution is that of de Sitter space, so
that all light scalars will automatically acquire a nearly scale-invariant
spectrum of perturbations.Comment: 25 pages, 1 figure. v2: minor changes, JCAP published versio
Galilean symmetry in the effective theory of inflation: new shapes of non-Gaussianity
We study the consequences of imposing an approximate Galilean symmetry on the
Effective Theory of Inflation, the theory of small perturbations around the
inflationary background. This approach allows us to study the effect of
operators with two derivatives on each field, which can be the leading
interactions due to non-renormalization properties of the Galilean Lagrangian.
In this case cubic non-Gaussianities are given by three independent operators,
containing up to six derivatives, two with a shape close to equilateral and one
peaking on flattened isosceles triangles. The four-point function is larger
than in models with small speed of sound and potentially observable with the
Planck satellite.Comment: 23 pages, 6 figures. v2: minor changes to match JCAP published
versio
Resilience of the standard predictions for primordial tensor modes
We show that the prediction for the primordial tensor power spectrum cannot
be modified at leading order in derivatives. Indeed, one can always set to
unity the speed of propagation of gravitational waves during inflation by a
suitable disformal transformation of the metric, while a conformal one can make
the Planck mass time-independent. Therefore, the tensor amplitude unambiguously
fixes the energy scale of inflation. Using the Effective Field Theory of
Inflation, we check that predictions are independent of the choice of frame, as
expected. The first corrections to the standard prediction come from two parity
violating operators with three derivatives. Also the correlator
is standard and only receives higher derivative
corrections. These results hold also in multifield models of inflation and in
alternatives to inflation and make the connection between a (quasi)
scale-invariant tensor spectrum and inflation completely robust.Comment: 5 pages, reference added, version accepted in PR
Conformal consistency relations for single-field inflation
We generalize the single-field consistency relations to capture not only the
leading term in the squeezed limit---going as 1/q^3, where q is the small
wavevector---but also the subleading one, going as 1/q^2. This term, for an
(n+1)-point function, is fixed in terms of the variation of the n-point
function under a special conformal transformation; this parallels the fact that
the 1/q^3 term is related with the scale dependence of the n-point function.
For the squeezed limit of the 3-point function, this conformal consistency
relation implies that there are no terms going as 1/q^2. We verify that the
squeezed limit of the 4-point function is related to the conformal variation of
the 3-point function both in the case of canonical slow-roll inflation and in
models with reduced speed of sound. In the second case the conformal
consistency conditions capture, at the level of observables, the relation among
operators induced by the non-linear realization of Lorentz invariance in the
Lagrangian. These results mean that, in any single-field model, primordial
correlation functions of \zeta are endowed with an SO(4,1) symmetry, with
dilations and special conformal transformations non-linearly realized by \zeta.
We also verify the conformal consistency relations for any n-point function in
models with a modulation of the inflaton potential, where the scale dependence
is not negligible. Finally, we generalize (some of) the consistency relations
involving tensors and soft internal momenta.Comment: 26 pages, 1 figure. v2. Corrected typos, notably a sign error in eq.
(54). Matches JCAP published versio
The consistency condition for the three-point function in dissipative single-clock inflation
We generalize the consistency condition for the three-point function in
single field inflation to the case of dissipative, multi-field, single-clock
models. We use the recently introduced extension of the effective field theory
of inflation that accounts for dissipative effects, to provide an explicit
proof to leading (non-trivial) order in the generalized slow roll parameters
and mixing with gravity scales. Our results illustrate the conditions necessary
for the validity of the consistency relation in situations with many degrees of
freedom relevant during inflation, namely that there is a preferred clock.
Departures from this condition in forthcoming experiments would rule out not
only single field but also a large class of multi-field models.Comment: 26+11 page
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