Inflationary initial conditions consistent with causality

Berera, Arjun; Gordon, Chris

doi:10.1103/physrevd.63.063505

Cited by 39 publications

(53 citation statements)

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“…2 also can serve to damp kinetic energy contributions before inflation, thus alleviating the initial condition problem of inflation [41]. Warm inflation is also a conducive regime for the creation of large scale cosmic magnetic fields based on the ferromagnetic Savvidy vacuum scenario [42].…”

Section: Resultsmentioning

confidence: 99%

Warm inflation solution to the eta problem

Berera¹

2003

Proceedings of International Workshop on Astroparticle and High Energy Physics — PoS(AHEP2003)

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Warm inflationary dynamics is shown to satisfy both the slow-roll and density perturbation constraints for m φ H or equivalently η 1 and for inflaton field amplitudes much below the Planck scale, φ < m pl . I start by reviewing the two types of inflation dynamics, isentropic or cold inflation and nonisentropic or warm inflation.In the former, inflation occurs without radiation production, whereas in the latter both radiation production and inflation occur concurrently. I then discuss recent, detailed, quantum field theory calculations showing that many generic inflation models, including hybrid inflation, which were believed only to have cold inflation regimes, in fact have regimes of both warm and cold inflation. These results dispel many foregone assumptions generally made up to now about inflation models and bring to the fore various elementary issues that must be addressed to do reliable calculations from inflation models. I also discuss density perturbations and observational consequences of warm inflation, especially related to WMAP. Finally I show that warm inflation has intrinsic features that make the "eta problem" nonexistent, and field amplitudes are below the Planck scale.

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Section: Resultsmentioning

confidence: 99%

Warm inflation solution to the eta problem

Berera¹

2003

Proceedings of International Workshop on Astroparticle and High Energy Physics — PoS(AHEP2003)

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“…A glance at Eqs. (25,26 reveals that these equations form a two dimensional dynamical system where its fixed points can be obtained by equating f and g to zero…”

Section: Stability Analysismentioning

confidence: 99%

Power spectra in warm G inflation and its consistency: Stochastic approach

2017

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Recently, it has been realized that the so-called G-inflation model inspired by supplementing a generalized covariant Galileon-like non-linear derivative self-interacting term to the standard kinetic term should be ruled out from inflationary models. This is due to the fact that it suffers from lack of an oscillatory phase at the end of the inflationary regime which is typically accompanied by the appearance of a negative squared propagation speed of the scalar mode leading to instabilities of small-scale perturbations. In this regard, the warm G-inflation scenario is proposed where for G-inflation to survive, the Galileon scalar field is coupled to the radiation field through a dissipation term which results in removing the reheating period due to the characteristics of warm inflationary scenario. In so doing, a linear stability analysis is first performed to obtain the appropriate slowroll conditions in such a proposal. Cosmological perturbations of the model are then investigated by utilizing fluctuation-dissipation theorem and analytical expressions are derived for observable quantities; the power spectrum, tilt spectral index and tensor-to-scalar ratio in terms of P SR parameters and Galileon flow functions. Finally, the model is solved for chaotic self-interacting potentials, particularly the renormalizable Higgs potential λ 4 φ 4 , and shown to be consistent with observations in the weak dissipation Q 1 + 3and G-dominant 3 δ GX δ X 1 regime despite its large self-coupling, since the energy scale at the horizon crossing is depressed by the synergy of Galileon and thermal effects.

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“…The presence of a friction term in the inflaton's equation of motion has already been shown to have a substantial impact in determining the minimum size of the initial inflationary patch [37]. In Ref.…”

Section: Introductionmentioning

confidence: 96%

The role of fluctuation-dissipation dynamics in setting initial conditions for inflation

Bastero-Gil

Berera

Brandenberger

et al. 2018

J. Cosmol. Astropart. Phys.

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Abstract.We study the problem of initial conditions for slow-roll inflation along a plateau-like scalar potential within the framework of fluctuation-dissipation dynamics. We consider, in particular, that inflation was preceded by a radiation-dominated epoch where the inflaton is coupled to light degrees of freedom and may reach a near-equilibrium state. We show that the homogeneous field component can be sufficiently localized at the origin to trigger a period of slow-roll if the interactions between the inflaton and the thermal degrees of freedom are sufficiently strong and argue that this does not necessarily spoil the flatness of the potential at the quantum level. We further conclude that the inflaton can still be held at the origin after its potential begins to dominate the energy balance, leading to a period of thermal inflation. This then suppresses the effects of nonlinear interactions between the homogeneous and inhomogeneous field modes that could prevent the former from entering a slow-roll regime. Finally, we discuss the possibility of an early period of chaotic inflation, at large field values, followed by a first stage of reheating and subsequently by a second inflationary epoch along the plateau about the origin. This scenario could prevent an early overclosure of the Universe, at the same time yielding a low tensor-to-scalar ratio in agreement with observations.

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Inflationary initial conditions consistent with causality

Cited by 39 publications

References 50 publications

Warm inflation solution to the eta problem

Warm inflation solution to the eta problem

Power spectra in warm G inflation and its consistency: Stochastic approach

The role of fluctuation-dissipation dynamics in setting initial conditions for inflation

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