Open universe from inflation

1982

We present a natural scenario for obtaining an open universe (Ω0 < 1) through inflation. In this scenario, there are two epochs of inflationary expansion—an epoch of ‘old inflation, ’ during which the inflaton field is stuck in a false vacuum, followed by an epoch of ‘new inflation, ’ during which the inflaton field slowly rolls toward its true minimum. During the first epoch, inflation solves the smoothness and horizon problems. Then an open universe (with negative spatial curvature) is created by the nucleation of a single bubble. In effect Ω is instantaneously ‘reset ’ to zero. During the subsequent ‘new ’ inflation Ω rises toward unity. The value of Ω today is calculable in terms of the parameters of the potential, and we show that obtaining values significantly different from zero or unity (though within the range 0 < Ω < 1) does not require significant fine tuning. We compute the spectrum of density perturbations by evolving the Bunch-Davies vacuum modes across the bu...

Physical Review D, 1995

We calculate the power spectrum of adiabatic density perturbations in an open inflationary model in which inflation occurs in two stages. First an epoch of old inflation creates a large, smooth universe, solving the horizon and homogeneity problems. Then an open universe emerges through the nucleation of a single bubble, with constant density hypersurfaces inside the bubble having constant negative spatial curvature. An epoch of 'slow roll' inflation, shortened to give Ω 0 < 1 today, occurs within the bubble, which contains our entire observable universe. In this paper we compute the resulting density perturbations in the same 'new thin wall' approximation used in a previous paper, but for an arbitrary positive mass of the inflaton field in the false vacuum.

1995

We calculate the power spectrum of adiabatic density perturbations in an open inflationary model in which inflation occurs in two stages. First an epoch of old inflation creates a large, smooth universe, solving the horizon and homogeneity problems. Then an open universe emerges through the nucleation of a single bubble, with constant density hypersurfaces inside the bubble having constant negative spatial curvature. An epoch of `slow roll' inflation, shortened to give $\Omega _0<1$ today, occurs within the bubble, which contains our entire observable universe. In this paper we compute the resulting density perturbations in the same `new thin wall' approximation used in a previous paper, but for an arbitrary positive mass of the inflaton field in the false vacuum.

1995

We calculate the power spectrum of adiabatic density perturbations in an open inflationary model in which inflation occurs in two stages. First an epoch of old inflation creates a large, smooth universe, solving the horizon and homogeneity problems. Then an open universe emerges through the nucleation of a single bubble, with constant density hypersurfaces inside the bubble having constant negative spatial curvature. An epoch of ‘slow roll ’ inflation, shortened to give Ω0 &lt; 1 today, occurs within the bubble, which contains our entire observable universe. In this paper we compute the resulting density perturbations in the same ‘new thin wall ’ approximation used in a previous paper, but for an arbitrary positive mass of the inflaton field in the false vacuum. January

2013

The inflationary phase of the Universe is explored by proposing a toy model related to the scalar field, termed as {\it inflaton}. The potential part of the energy density in the said era is assumed to have a constant vacuum energy density part and a variable part containing the inflaton. The prime idea of the proposed model constructed in the framework of the closed Universe is based on a fact that the inflaton is the root cause of the orientation of the space. According to this model the expansion of the Universe in the inflationary epoch is not approximately rather exactly exponential in nature and thus it can solve some of the fundamental puzzles, viz. flatness as well as horizon problems. It is also predicted that the constant energy density part in the potential may be associated to the dark energy, which is eventually different from the vacuum energy, at least in the inflationary phase of the Universe. However, the model keeps room for the end of inflationary era.

Nuclear Physics B, 1998

Nuclear Physics B - Proceedings Supplements, 1996

Open Inflation has recently been suggested as a possible way out of the age crisis caused by observations of a large rate of expansion of the universe, in conflict with the existence of very old globular clusters. It proposes that our local patch of the universe originated in a quantum tunneling event, with the formation of a single bubble within which our universe inflated to almost flatness. I review the different models proposed together with their predictions for the amplitude of temperature anisotropies in the cosmic microwave background.

Nuclear Physics B, 1999

The spectrum of cosmological perturbations in the context of the one-bubble open inflation model is discussed, taking into account fluctuations of the metric. We find that, quite generically,thin wall single field models have no supercurvature modes. However, single field models with supercurvature modes do exist. In these models the density parameter Ω becomes a random variable taking a range of values inside of each bubble. We also show that the model dependence of the continuous spectrum for both scalar and tensor-type perturbations is small as long as the kinetic energy density of the background field does not dominate the total energy density. We conclude that the spectrum of the density perturbation predicted in the single-field model of the one-bubble open inflation is rather robust. We also consider the spectrum of scalar and tensor perturbations in a model of the Hawking-Turok type, without a false vacuum.

1995

We show that particle production during the expansion of bubbles of true vacuum in the sea of false vacuum is possible and calculate the resulting rate. As a result the nucleated bubbles cannot expand due to the transfer of false vacuum energy to the created particles inside the bubbles. Therefore all the inflationary models dealing with the nucleation and expansion

Journal of Cosmology and Astroparticle Physics, 2003

In the presence of a short-distance cutoff, the choice of a vacuum state in an inflating, non-de Sitter universe is unavoidably ambiguous. The ambiguity is related to the time at which initial conditions for the mode functions are specified and to the way the expansion of the universe affects those initial conditions. In this paper we study the imprint of these uncertainties on the predictions of inflation. We parametrize the most general set of possible vacuum initial conditions by two phenomenological variables. We find that the generated power spectrum receives oscillatory corrections whose amplitude is proportional to the Hubble parameter over the cutoff scale. In order to further constrain the phenomenological parameters that characterize the vacuum definition, we study gravitational particle production during different cosmological epochs.