104 research outputs found
Cosmological -Attractors and de Sitter Landscape
We provide a unified description of cosmological -attractors and
late-time acceleration, in excellent agreement with the latest Planck data. Our
construction involves two superfields playing distinctive roles: one is the
dynamical field and its evolution determines inflation and dark energy, the
other is nilpotent and responsible for a landscape of vacua and supersymmetry
breaking. We prove that the attractor nature of the theory is enhanced when
combining the two sectors: cosmological attractors are very stable with respect
to any possible value of the cosmological constant and, interestingly, to any
generic coupling of the inflationary sector with the field responsible for
uplifting. Finally, as related result, we show how specific couplings generate
an arbitrary inflaton potential in a supergravity framework with varying Kahler
curvature.Comment: 14 pages, 3 figures. v3: minor clarifications and refs added. JHEP
versio
Cosmological Attractors from -Scale Supergravity
The Planck value of the spectral index can be interpreted as
in terms of the number of e-foldings . An appealing explanation for this
phenomenological observation is provided by -attractors: the
inflationary predictions of these supergravity models are fully determined by
the curvature of the Kahler manifold. We provide a novel formulation of
-attractors which only involves a single chiral superfield. Our
construction involves a natural deformation of no-scale models, and employs
these to construct a De Sitter plateau with an exponential fall-off. Finally,
we show how analogous structures with a flat Kahler geometry arise as a
singular limit of such -scale models.Comment: 6 pages, 3 figures. v3: minor clarifications and refs added. PRD
versio
Moduli Backreaction on Inflationary Attractors
We investigate the interplay between moduli dynamics and inflation, focusing
on the KKLT-scenario and cosmological -attractors. General couplings
between these sectors can induce a significant backreaction and potentially
destroy the inflationary regime; however, we demonstrate that this generically
does not happen for -attractors. Depending on the details of the
superpotential, the volume modulus can either be stable during the entire
inflationary trajectory, or become tachyonic at some point and act as a
waterfall field, resulting in a sudden end of inflation. In the latter case
there is a universal supersymmetric minimum where the scalars end up,
preventing the decompactification scenario. The gravitino mass is independent
from the inflationary scale with no fine-tuning of the parameters. The
observational predictions conform to the universal value of attractors, fully
compatible with the Planck data, with possibly a capped number of e-folds due
to the interplay with moduli.Comment: 23 pages, 13 figures. v2: minor clarifications and refs added. PRD
versio
Quantum mechanics in fractional and other anomalous spacetimes
We formulate quantum mechanics in spacetimes with real-order fractional
geometry and more general factorizable measures. In spacetimes where
coordinates and momenta span the whole real line, Heisenberg's principle is
proven and the wave-functions minimizing the uncertainty are found. In spite of
the fact that ordinary time and spatial translations are broken and the
dynamics is not unitary, the theory is in one-to-one correspondence with a
unitary one, thus allowing us to employ standard tools of analysis. These
features are illustrated in the examples of the free particle and the harmonic
oscillator. While fractional (and the more general anomalous-spacetime) free
models are formally indistinguishable from ordinary ones at the classical
level, at the quantum level they differ both in the Hilbert space and for a
topological term fixing the classical action in the path integral formulation.
Thus, all non-unitarity in fractional quantum dynamics is encoded in a
contribution depending only on the initial and final state.Comment: 22 pages, 1 figure. v2: typos correcte
Inflation, Universality and Attractors
In this PhD thesis, we investigate generic features of inflation which are
strictly related to fundamental aspects of UV-physics scenarios, such as string
theory or supergravity. After a short introduction to standard and inflationary
cosmology, we present our research findings. On the one hand, we show that
focusing on universality properties of inflation can yield surprisingly
stringent bounds on its dynamics. This approach allows us to identify the
regime where the inflationary field range is uniquely determined by both the
tensor-to-scalar ratio and the spectral index. Then, we derive a novel
field-range bound, which is two orders of magnitude stronger than the original
one derived by Lyth. On the other hand, we discuss the embedding of inflation
in supergravity and prove that non-trivial hyperbolic K\"ahler geometries
induce an attractor for the inflationary observables: the spectral tilt tends
automatically to the center of the Planck dome whereas the amount of primordial
gravitational waves is directly controlled by curvature of the internal
manifold. We identify the origin of this attractor mechanism in the so-called
-scale supergravity model. Finally, we show how the inclusion of a
nilpotent sector, allowing for a unified description of inflation and dark
energy, implies an enhancement of the attractor nature of the theory. The main
results of this thesis have been already published elsewhere. However, here we
pay special attention to present them in a comprehensive way and provide the
reader with the necessary background.Comment: 174 pages, 52 figures. PhD thesis defended at the University of
Groningen on June 13, 2016. It contains results and material already
published in arXiv:1307.4343, arXiv:1405.7399, arXiv:1408.6839,
arXiv:1411.5671, arXiv:1412.2790, arXiv:1503.07909, arXiv:1506.0136
Can CMB data constrain the inflationary field range?
We study to what extent the spectral index and the tensor-to-scalar
ratio determine the field excursion during inflation. We
analyse the possible degeneracy of by comparing three broad
classes of inflationary models, with different dependence on the number of
e-foldings , to benchmark models of chaotic inflation with monomial
potentials. The classes discussed cover a large set of inflationary single
field models. We find that the field range is not uniquely determined for any
value of ; one can have the same predictions as chaotic inflation and
a very different . Intriguingly, we find that the field range
cannot exceed an upper bound that appears in different classes of models.
Finally, can even become sub-Planckian, but this requires to go
beyond the single-field slow-roll paradigm.Comment: 15 pages, 7 figures. v2: minor typos corrected, refs added, JCAP
versio
The Lyth Bound of Inflation with a Tilt
We provide strong evidence for universality of the inflationary field range:
given an accurate measurement of , one can infer in a
model-independent way in the sub-Planckian regime for a range of universality
classes of inflationary models. Both the tensor-to-scalar ratio as well as the
spectral tilt are essential for the field range. Given the Planck constraints
on , the Lyth bound is strengthened by two orders of magnitude: whereas
the original bound gives a sub-Planckian field range for , we find that brings this down to .Comment: 5 pages, 3 figures. v2: refs added, PRD versio
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