422 research outputs found
Scalar fields in the de Sitter spacetime
We examine long-wavelength correlation functions of massive scalar fields in de Sitter spacetime. For the theory with a quartic self-interaction, the two-point function is calculated up to two loops. Comparing our results with the Hartree-Fock approximation and with the stochastic approach shows that the former resums only the cactus type diagrams, whereas the latter contains the sunset diagram as well and produces the correct result. We compare our results with the preceding results obtained for the massless scalar field
Higgs Starobinsky inflation
In this paper we point out that Starobinky inflation could be induced by quantum effects due to a large non-minimal coupling of the Higgs boson to the Ricci scalar. The Higgs Starobinsky mechanism provides a solution to issues attached to large Higgs field values in the early universe which in a metastable universe would not be a viable option. We verify explicitly that these large quantum corrections do not destabilize Starobinsky's potential
Cosmological attractor models and higher curvature supergravity
We study cosmological \u3b1-attractors in superconformal/supergravity models, where \u3b1 is related to the geometry of the moduli space. For \u3b1 = 1 attractors [1] we present a generalization of the previously known manifestly superconformal higher curvature supergravity model [2]. The relevant standard 2-derivative supergravity with a minimum of two chiral multiplets is shown to be dual to a 4-derivative higher curvature supergravity, where in general one of the chiral superfields is traded for a curvature superfield. There is a degenerate case when both matter superfields become non-dynamical and there is only a chiral curvature superfield, pure higher derivative supergravity. Generic \u3b1-models [3] interpolate between the attractor point at \u3b1 = 0 and generic chaotic inflation models at large \u3b1, in the limit when the inflaton moduli space becomes flat. They have higher derivative duals with the same number of matter fields as the original theory or less, but at least one matter multiplet remains. In the context of these models, the detection of primordial gravity waves will provide information on the curvature of the inflaton submanifold of the K\ue4hler manifold, and we will learn if the inflaton is a fundamental matter multiplet, or can be replaced by a higher derivative curvature excitation. \ua9 2014 The Author(s)
Lectures on Linear Stability of Rotating Black Holes
These lecture notes are concerned with linear stability of the non-extreme
Kerr geometry under perturbations of general spin. After a brief review of the
Kerr black hole and its symmetries, we describe these symmetries by Killing
fields and work out the connection to conservation laws. The Penrose process
and superradiance effects are discussed. Decay results on the long-time
behavior of Dirac waves are outlined. It is explained schematically how the
Maxwell equations and the equations for linearized gravitational waves can be
decoupled to obtain the Teukolsky equation. It is shown how the Teukolsky
equation can be fully separated to a system of coupled ordinary differential
equations. Linear stability of the non-extreme Kerr black hole is stated as a
pointwise decay result for solutions of the Cauchy problem for the Teukolsky
equation. The stability proof is outlined, with an emphasis on the underlying
ideas and methods.Comment: 25 pages, LaTeX, 3 figures, lectures given at first DOMOSCHOOL in
July 2018, minor improvements (published version
Black Holes: Scatterers, Absorbers and Emitters of Particles
Accurate and powerful analytic and computational methods developped by the
author allow to obtain the highly non trivial total absorption spectrum of the
Black Hole, as well as phase shifts and cross sections (elastic and inelastic),
the angular distribution of absorbed and scattered waves, and the Hawking
emission rates. The exact total absorption spectrum of waves by the Black Hole
presents as a function of frequency a remarkable oscillatory behaviour
characteristic of a diffraction pattern. It oscillates around its optical
geometric limit (27/4) pi (r_s)^2 with decreasing amplitude and almost constant
period. This is an unique distinctive feature of the black hole absorption, and
due to its r=0 singularity. Ordinary absorptive bodies and optical models do
not present these features. The Hamiltonian describing the wave-black hole
interaction is non hermitian (despite being real) due to its singularity at the
origin (r=0). The unitarity optical theorem of scattering theory is generalized
to the black hole case explicitely showing that absorption takes place only at
the origin (r = 0). All these results allow to understand and reproduce the
Black Hole absorption spectrum in terms of Fresnel-Kirchoff diffraction theory.
These fundamental features will be present for generic higher dimensional Black
Hole backgrounds, and whatever the low energy effective theory they arise from.
In recent and increasing litterature on absorption cross sections (`grey body
factors') of black holes (whatever ordinary, stringy, D-braned), the
fundamental remarkable features of the Black Hole Absorption spectrum are
overlooked.Comment: LaTex, 19 pages, Lectures delivered at the Chalonge School, Nato ASI:
Phase Transitions in the Early Universe: Theory and Observations. To appear
in the Proceedings, Editors H. J. de Vega, I. Khalatnikov, N. Sanchez.
(Kluwer Pub
The Cosmic Microwave Background and Particle Physics
In forthcoming years, connections between cosmology and particle physics will
be made increasingly important with the advent of a new generation of cosmic
microwave background (CMB) experiments. Here, we review a number of these
links. Our primary focus is on new CMB tests of inflation. We explain how the
inflationary predictions for the geometry of the Universe and primordial
density perturbations will be tested by CMB temperature fluctuations, and how
the gravitational waves predicted by inflation can be pursued with the CMB
polarization. The CMB signatures of topological defects and primordial magnetic
fields from cosmological phase transitions are also discussed. Furthermore, we
review current and future CMB constraints on various types of dark matter (e.g.
massive neutrinos, weakly interacting massive particles, axions, vacuum
energy), decaying particles, the baryon asymmetry of the Universe,
ultra-high-energy cosmic rays, exotic cosmological topologies, and other new
physics.Comment: 43 pages. To appear in Annual Reviews of Nuclear and Particle Scienc
Starobinsky-like inflation in no-scale supergravity Wess-Zumino model with Polonyi term
We propose a simple modification of the no-scale supergravity Wess-Zumino
model of Starobinsky-like inflation to include a Polonyi term in the
superpotential. The purpose of this term is to provide an explicit mechanism
for supersymmetry breaking at the end of inflation. We show how successful
inflation can be achieved for a gravitino mass satisfying the strict upper
bound TeV, with favoured values
TeV. The model suggests that SUSY may be discovered in collider physics
experiments such as the LHC or the FCC.Comment: 13 pages, 4 figure
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