Theories of inflation and conformal transformation

Kalara, S.; Kaloper, Nemanja; Olive, Keith A.

doi:10.1016/0550-3213(90)90270-n

Cited by 77 publications

(70 citation statements)

References 39 publications

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“…This "shearing" of the vacuum energy to both pursuits is the cause of a moderate power law inflation instead of an exponential one [40]. In this scenario the Universe begins with a contraction, and therefore the same shearing mechanism, moreover here due to the Higgs field, drives a "friction" process for the contraction, due to the varying of G(χ), making the deflation era always weaker.…”

Section: Initial Conditions and Inflationmentioning

confidence: 99%

Induced gravity inflation in the standard model of particle physics

1995

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We are considering the cosmological consequences of an induced gravity theory coupled to the minimal standard model of particle physics. The non-minimal coupling parameter between gravity and the Higgs field must then be very large, yielding some new cosmological consequences for the early Universe and new constraints on the Higgs mass. As an outcome, new inflation is only possible for very special initial conditions producing first a short contraction era after which an inflationary expansion automatically follows; a chaotic inflationary scenario is successfully achieved. The contrast of density perturbations required to explain the seed of astronomic structures are obtained for very large values of the Higgs mass (M H >> G −1/2 F ), otherwise the perturbations have a small amplitude; in any case, the spectral index of scalar perturbations agrees with the observed one.

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Section: Initial Conditions and Inflationmentioning

confidence: 99%

Induced gravity inflation in the standard model of particle physics

1995

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“…The main ingredient of this mechanism has been observed in string cosmology earlier in [20,21]. In the backgrounds dominated by conformal matter where T µ µ = 0 the source terms arising from the gravitational couplings of the moduli to matter vanish and moduli are quickly kinetically damped [22,23]. Their energy density dilutes as ρ h ∼ 1/a 6 for the homogeneous mode or as ρ i ∼ 1/a 4 for inhomogeneities [24], where a is the cosmological scale factor.…”

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confidence: 99%

“…As the universe evolves undergoing cosmic expansion, the energy density of the black hole gas will change in two ways: i) it will redshift away according to the usual ∼ 1/a 3 law for massive particles, since we are ignoring the black hole interactions (we expect that this is justified for heavy black holes when they are sufficiently separated [37]) and ii) the evolution of the modulus will change the coupling and so the mass of the black holes, as is clear from (4). When the evolution is smooth, a good approximation accounting for these two effects is to represent the energy density as a function of the scale factor and the modulus vev as [22,23] ρ BH =n 0 M P l a 0 a 3 q e g 2 κφ/2 + p e −g 2 κφ/2 ,…”

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confidence: 99%

Moduli entrapment with primordial black holes

Kaloper¹,

Rahmfeld²,

Sorbo³

2005

Physics Letters B

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We argue that primordial black holes in the early universe can provide an efficient resolution of the Brustein-Steinhardt moduli overshoot problem in string cosmology. When the universe is created near the Planck scale, all the available states in the theory are excited by strong interactions and cosmological particle production. The heavy states are described in the low energy theory as a gas of electrically and magnetically charged black holes. This gas of black holes quickly captures the moduli which appear in the relation between black hole masses and charges, and slows them down with their vevs typically close to the Planck scale. From there, the modulus may slowly roll into a valley with a positive vacuum energy, where inflation may begin. The black hole gas will redshift away in the course of cosmic expansion, as inflation evicts the black holes out of the horizon.

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“…This argument opens up new possibilities that one can constrain a broad class of inflation models from the reheating temperature. Reheating in Starobinsky's R 2 inflation has been considered by [16,19].Interactions between φ and matter stem from a mixing between metric and scalar field perturbations through f (φ)R [6]. It is this "gravitational decay channel" from φ to matter that makes the universe reheat after inflation.…”

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confidence: 99%

Reheating of the universe after inflation withf(ϕ)Rgravity

Watanabe

Komatsu

2007

Phys. Rev. D

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We show that reheating of the universe occurs spontaneously in a broad class of inflation models with f (φ)R gravity (φ is inflaton). The model does not require explicit couplings between φ and bosonic or fermionic matter fields. The couplings arise spontaneously when φ settles in the vacuum expectation value (vev) and oscillates, with coupling constants given by derivatives of f (φ) at the vev and the mass of resulting bosonic or fermionic fields. This mechanism allows inflaton quanta to decay into any fields which are not conformally invariant in f (φ)R gravity theories.Inflation is an indispensable building-block of the standard model of cosmology [1,2], and has passed a number of stringent observational tests [3]. Any inflation models must contain a mechanism by which the universe reheats after inflation [4]. The reheating mechanism requires detailed knowledge of interactions (e.g., Yukawa coupling) between inflaton fields and their decay products. Since the physics behind inflation is beyond the standard model of elementary particles, the precise nature of inflaton fields is currently undetermined, and the coupling between inflaton and matter fields is often put in by hand. On the other hand, inflaton and matter fields are coupled through gravity. Of course the gravitational coupling is suppressed by the Planck mass and thus too weak to yield interesting effects [1]; however, we shall show that the reheating occurs spontaneously if inflaton is coupled to gravity non-minimally, i.e., the gravitational action is given not by the Einstein-Hilbert form, R, but by f (φ)R, where φ is an inflaton field. Even if matter fields do not interact with φ directly, they ought to interact via gravitation whose perturbations lead to Yukawatype interactions. A similar idea was put forward by [5], who considered preheating with a non-minimal coupling between matter and gravity. Here, we do not consider preheating, but focus only on the perturbative reheating arising from f (φ)R gravity. Therefore, we can calculate the resulting reheating temperature after inflation.Why study f (φ)R gravity? There are a number of motivations [6,7]. The strongest motivation comes from the fact that almost any candidate theories of fundamental physics which involve compactification of extra dimensions yield f (φ)R with the form of f (φ) depending on models. One illuminating example would be string moduli with f (φ) ∝ e −αφ . Zee's induced gravity theory [8] has f (φ) = ξφ 2 , and renormalization in the curved spacetime yields other more complicated higher derivative terms [9]. Classic scalar-tensor theories, originally motivated by Mach's principle [10], also fall into this category. It has been shown that inflation occurs naturally * Electronic address: yuki@astro.as.utexas.edu in these generalized gravity models [11,12,13,14,15,16], and the spectrum of scalar curvature perturbations [17] as well as of tensor gravity wave perturbations [18] can be affected by the presence of f (φ)R, thereby allowing us to constrain f (φ) from the cosmological d...

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Theories of inflation and conformal transformation

Cited by 77 publications

References 39 publications

Induced gravity inflation in the standard model of particle physics

Induced gravity inflation in the standard model of particle physics

Moduli entrapment with primordial black holes

Reheating of the universe after inflation withf(ϕ)Rgravity

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