Metric preheating and radiative decay in single-field inflation (original) (raw)

Primordial black holes from the preheating instability in single-field inflation

Journal of Cosmology and Astroparticle Physics, 2020

After the end of inflation, the inflaton field oscillates around a local minimum of its potential and decays into ordinary matter. These oscillations trigger a resonant instability for cosmological perturbations with wavelengths that exit the Hubble radius close to the end of inflation. In this paper, we study the formation of Primordial Black Holes (PBHs) at these enhanced scales. We find that the production mechanism can be so efficient that PBHs subsequently dominate the content of the universe and reheating proceeds from their evaporation. Observational constraints on the PBH abundance also restrict the duration of the resonant instability phase, leading to tight limits on the reheating temperature that we derive. We conclude that the production of PBHs during reheating is a generic and inevitable property of the simplest inflationary single-field models, and does not require any fine tuning of the inflationary potential.

Primordial black holes from the preheating instability

Inflationary preheating and primordial black holes

Physical Review D, 2001

Preheating after inflation may over-produce primordial black holes (PBH's) in many regions of parameter space. As an example we study two-field models with a massless self-interacting inflaton, taking into account second order field and metric backreaction effects as spatial averages. We find that a complex quilt of parameter regions above the Gaussian PBH over-production threshold emerges due to the enhancement of curvature perturbations on all scales. It should be possible to constrain realistic models of inflation through PBH over-production although many issues, such as rescattering and non-Gaussianity, remain unsolved or unexplored. pacs: 98.80.Cq

Inflation and reheating in spontaneously generated gravity

Physical Review D, 2010

Inflation is studied in the context of induced gravity (IG) gammasigma2R\gamma \sigma^2 Rgammasigma2R, where RRR is the Ricci scalar, sigma\sigmasigma a scalar field and gamma\gammagamma a dimensionless constant, and diverse symmetry-breaking potentials V(sigma)V(\sigma)V(sigma) are considered. In particular we compared the predictions for Landau-Ginzburg (LG) and Coleman-Weinberg (CW) type potentials and their possible generalizations with the most recent data. We find that large field inflation generally leads to fewer constraints on the parameters and the shape of the potential whereas small field inflation is more problematic and, if viable, implies more constraints, in particular on the parameter gamma\gammagamma. We also examined the reheating phase and obtained an accurate analytical solution for the dynamics of inflaton and the Hubble parameter by using a multiple scale analysis (MSA). The solutions were then used to study the average expansion of the Universe, the average equation of state for the scalar field and both the perturbative and resonant decays of the inflaton field.

The exponential tail of inflationary fluctuations: consequences for primordial black holes

Journal of Cosmology and Astroparticle Physics, 2020

The curvature perturbations produced during an early era of inflation are known to have quasi-Gaussian distribution functions close to their maximum, where they are well constrained by measurements of the cosmic microwave background anisotropies and of the large-scale structures. In contrast, the tails of these distributions are poorly known, although this part is the relevant one for rare, extreme objects such as primordial black holes. We show that these tails are highly non-Gaussian, and cannot be described with standard non-Gaussian expansions, that are designed to approximate the distributions close to their maximum only. Using the stochastic-δN formalism, we develop a generic framework to compute the tails, which are found to have an exponential, rather than Gaussian, decay. These exponential tails are inevitable, and do not require any non-minimal feature as they simply result from the quantum diffusion of the inflaton field along its potential. We apply our formalism to a few relevant single-field, slow-roll inflationary potentials, where our analytical treatment is confirmed by comparison with numerical results. We discuss the implications for the expected abundance of primordial black holes in these models, and highlight that it can differ from standard results by several orders of magnitude. In particular, we find that potentials with an inflection point overproduce primordial black holes, unless slow roll is violated.

Quantum inflaton, primordial perturbations, and CMB fluctuations

Physical Review D, 2004

We compute the primordial scalar, vector and tensor metric perturbations arising from quantum field inflation. Quantum field inflation takes into account the nonperturbative quantum dynamics of the inflaton consistently coupled to the dynamics of the (classical) cosmological metric. For chaotic inflation, the quantum treatment avoids the unnatural requirements of an initial state with all the energy in the zero mode. For new inflation it allows a consistent treatment of the explosive particle production due to spinodal instabilities. Quantum field inflation (under conditions that are the quantum analog of slow-roll) leads, upon evolution, to the formation of a condensate starting a regime of effective classical inflation. We compute the primordial perturbations taking the dominant quantum effects into account. The results for the scalar, vector and tensor primordial perturbations are expressed in terms of the classical inflation results. For a N-component field in a ON symmetric model, adiabatic fluctuations dominate while isocurvature or entropy fluctuations are negligible. The results agree with the current Wilkinson Microwave Anisotropy Probe observations and predict corrections to the power spectrum in classical inflation. Such corrections are estimated to be of the order of m 2 NH 2 , where m is the inflaton mass and H the Hubble constant at the moment of horizon crossing. An upper estimate turns to be about 4% for the cosmologically relevant scales. This quantum field treatment of inflation provides the foundations to the classical inflation and permits to compute quantum corrections to it.

Inflation and reheating in induced gravity

Physics Letters B, 2009

Inflation is studied in the context of induced gravity (IG) γσ 2 R, where R is the Ricci scalar, σ a scalar field and γ a dimensionless constant. We study in detail cosmological perturbations in IG and examine both a Landau-Ginzburg (LG) and a Coleman-Weinberg (CW) potential toy models for small field and large field (chaotic) inflation and find that small field inflationary models in IG are constrained to γ 3 × 10 −3 by WMAP 5 yrs data. Finally we describe the regime of coherent oscillations in induced gravity by an analytic approximation, showing how the homogeneous inflaton can decay in its short-scale fluctuations when it oscillates around a non-zero value σ0.

Resonant particle production with nonminimally coupled scalar fields in preheating after inflation

Physical Review D, 1999

We investigate a resonant particle production of a scalar field χ coupled non-minimally to a spacetime curvature R (ξRχ 2 ) as well as to an inflaton field φ (g 2 φ 2 χ 2 ). In the case of g < ∼ 3 × 10 −4 , ξ effect assists g-resonance in certain parameter regimes. However, for g > ∼ 3 × 10 −4 , g-resonance is not enhanced by ξ effect because of ξ suppression effect as well as a back reaction effect. If ξ ≈ −4, the maximal fluctuation of produced χ-particle is χ 2 max ≈ 2 × 10 17 GeV for g < ∼ 1 × 10 −5 , which is larger than the minimally coupled case with g ≈ 1 × 10 −3 . 98.80.Cq, 05.70.Fh, 11.15.Kc * electronic address:shinji@gravity.phys.waseda.ac.jp † electronic address:maeda@gravity.phys.waseda.ac.jp ‡ electronic address:torii@th.phys.titech.ac.jp ticles [ . This initial evolutionary phase, which is called preheating stage, provides an explosive particle production and must be discussed separately from the perturbative decay of inflaton. There are many works about the preheating stage based on analytical investigations as well as on numerical studies . The important feature with the existence of preheating stage is that the maximal value of produced fluctuation can be so large that it would result in a non-thermal phase transition and make baryogenesis at the GUT scale possible , although the baryogenesis might be important in much lower energy scale, i.e. the electro-weak scale .

Primordial black holes from single field models of inflation

Physics of the Dark Universe, 2017

Primordial black holes (PBH) have been shown to arise from high peaks in the matter power spectra of multi-field models of inflation. Here we show, with a simple toy model, that it is also possible to generate a peak in the curvature power spectrum of single-field inflation. We assume that the effective dynamics of the inflaton field presents a near-inflection point which slows down the field right before the end of inflation and gives rise to a prominent spike in the fluctuation power spectrum at scales much smaller than those probed by Cosmic Microwave Background (CMB) and Large Scale Structure (LSS) observations. This peak will give rise, upon reentry during the radiation era, to PBH via gravitational collapse. The mass and abundance of these PBH is such that they could constitute the totality of the Dark Matter today. We satisfy all CMB and LSS constraints and predict a very broad range of PBH masses. Some of these PBH are light enough that they will evaporate before structure formation, leaving behind a large curvature fluctuation on small scales. This broad mass distribution of PBH as Dark Matter will be tested in the future by AdvLIGO and LISA interferometers.

Metric preheating and radiative decay in single-field inflation (original) (raw)

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