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Inflation after wmap3: Confronting the slowroll and exact power spectra with cmb data
, 2006
"... ... year data for inflation are investigated using both the slowroll approximation and an exact numerical integration of the inflationary power spectra including a phenomenological modelling of the reheating era. At slowroll leading order, the constraints ǫ1 < 0.022 and −0.07 < ǫ2 < 0.07 ..."
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... year data for inflation are investigated using both the slowroll approximation and an exact numerical integration of the inflationary power spectra including a phenomenological modelling of the reheating era. At slowroll leading order, the constraints ǫ1 < 0.022 and −0.07 < ǫ2 < 0.07 are obtained at 95 % CL (Confidence Level) implying a tensortoscalar ratio r10 < 0.21 and a Hubble parameter during inflation H/mPl < 1.3 × 10−5. At nexttoleading order, a tendency for ǫ3> 0 is observed. With regards to the exact numerical integration, large field models, V (φ) ∝ φp, with p> 3.1 are now excluded at 95 % CL. Small field models, V (φ) ∝ 1 − (φ/µ) p, are still compatible with the data for all values of p. However, if µ/mPl < 10 is assumed, then the case p = 2 is slightly disfavoured. In addition, mild constraints on the reheating temperature for an extreme equation of state wreh � −1/3 are found, namely Treh> 2 TeV at 95 % CL. Hybrid models are disfavoured by the data, the best fit model having ∆χ2 ≃ +5 with two extra parameters in comparison with large field models. Running mass models remain compatible, but no prior independent constraints can be obtained. Finally, superimposed oscillations of transPlanckian origin are studied. The vanilla slowroll model is still the most probable one. However, the overall statistical weight in favour of superimposed oscillations has increased in comparison with the WMAP first year data, the amplitude of the oscillations satisfying 2xσ0 < 0.76 at 95 % CL. The best fit model leads to an improvement of ∆χ2 ≃ −12 for 3 extra parameters. Moreover, compared to other oscillatory patterns, the logarithmic shape is favoured.
Supergravity analysis of hybrid inflation model from D3D7 system,” Phys. Rev. D 69 (2004) 106001 [Erratumibid. D 70 (2004) 81 [arXiv:hepth/0311191
 Shandera, “Slow roll in brane inflation,” JCAP 0504 (2005) 011 [arXiv:hepth/0412077
"... Abstract The slowroll inflation is a beautiful paradigm, yet the inflaton potential can hardly be sufficiently flat when unknown gravitational effects are taken into account. However, the hybrid inflation models constructed in D = 4 N = 1 supergravity can be consistent with N = 2 supersymmetry, an ..."
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Abstract The slowroll inflation is a beautiful paradigm, yet the inflaton potential can hardly be sufficiently flat when unknown gravitational effects are taken into account. However, the hybrid inflation models constructed in D = 4 N = 1 supergravity can be consistent with N = 2 supersymmetry, and can be naturally embedded into string theory. This article discusses the gravitational effects carefully in the string model, using D = 4 supergravity description. We adopt the D3D7 system of Type IIB string theory compactified on K3 × T 2 /Z 2 orientifold for definiteness. It turns out that the slowroll parameter can be sufficiently small despite the nonminimal Kähler potential of the model. The conditions for this to happen are given in terms of string vacua. We also find that the geometry obtained by blowing up singularity, which is necessary for the positive vacuum energy, is stabilized by introducing certain 3form fluxes.
Stable de Sitter Vacua in 4 Dimensional Supergravity Originating from 5 Dimensions
, 809
"... The five dimensional stable de Sitter ground states in N = 2 supergravity obtained by gauging SO(1,1) symmetry of the real symmetric scalar manifold (in particular a generic Jordan family manifold of the vector multiplets) simultaneously with a subgroup Rs of the Rsymmetry group descend to four dim ..."
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The five dimensional stable de Sitter ground states in N = 2 supergravity obtained by gauging SO(1,1) symmetry of the real symmetric scalar manifold (in particular a generic Jordan family manifold of the vector multiplets) simultaneously with a subgroup Rs of the Rsymmetry group descend to four dimensional de Sitter ground states under certain conditions. First, the holomorphic section in four dimensions has to be chosen carefully by using the symplectic freedom in four dimensions; and second, a group contraction is necessary to bring the potential into a desired form. Under these conditions, stable de Sitter vacua can be obtained in dimensionally reduced theories (from 5D to 4D) if the semidirect product of SO(1,1) with R (1,1) together with a simultaneous Rs is gauged. We review the stable de Sitter vacua in four dimensions found in earlier literature for N = 2 YangMills Einstein supergravity with SO(2,1) ×Rs gauge group in a symplectic basis that comes naturally after dimensional reduction. Although this particular gauge group does not descend directly from five dimensions, we show that, its contraction does. Hence, two different theories overlap in certain limits. Examples of stable de Sitter vacua are given for
Eternal Inflation, past and future
"... Cosmological inflation, if it occurred, radically alters the picture of the ‘big bang’, which would merely point to reheating at the end of inflation. Moreover, this reheating may be only local so that inflation continues elsewhere and forever, continually spawning bigbanglike regions. This chapte ..."
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Cosmological inflation, if it occurred, radically alters the picture of the ‘big bang’, which would merely point to reheating at the end of inflation. Moreover, this reheating may be only local so that inflation continues elsewhere and forever, continually spawning bigbanglike regions. This chapter reviews this idea of ‘eternal inflation’, then focuses on what this may mean for the ultimate beginning of the universe. In particular, I will argue that given eternal inflation, the universe may be free of a cosmological initial singularity, might be eternal (and eternally inflating) to the past, and might obey an interesting sort of cosmological timesymmetry. 1 The inflationary Genie Cosmological inflation, as discussed at length in Chapter 2, was developed as a means of explaining the very simple yet specific ‘initial ’ conditions that define the hot bigbang cosmological model. But while inflation grants the wish of providing a very large, uniform, hot, monopolefree region with appropriate density fluctuations, it is also, like the proverbial Genie let out of
Emergence of symmetries
 Phys. Lett. B 718
, 2012
"... Abstract The mechanism of gauge symmetry formation is discussed in the framework of multidimensional gravity. It is shown that this process is strictly connected to the entropy decrease of compact space. The existence of gauge symmetries is not postulated from the beginning. They could be absent du ..."
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Abstract The mechanism of gauge symmetry formation is discussed in the framework of multidimensional gravity. It is shown that this process is strictly connected to the entropy decrease of compact space. The existence of gauge symmetries is not postulated from the beginning. They could be absent during the inflationary stage. The conditions of this effect are discussed.
O(d,d)invariance in inhomogeneous string cosmologies with perfect fluid
, 1999
"... In the first part of the present paper, we show that O(d,d)invariance usually known in a homogeneous cosmological background written in terms of proper time can be extended to backgrounds depending on one or several coordinates (which may be any spacelike or timelike coordinate(s)). In all cases, ..."
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In the first part of the present paper, we show that O(d,d)invariance usually known in a homogeneous cosmological background written in terms of proper time can be extended to backgrounds depending on one or several coordinates (which may be any spacelike or timelike coordinate(s)). In all cases, the presence of a perfect fluid is taken into account and the equivalent duality transformation in Einstein frame is explicitly given. In the second part, we present several concrete applications to some fourdimensional metrics, including inhomogeneous ones, which illustrate the different duality transformations discussed in the first part. Note that most of the dual solutions given here do not seem to be known in the literature.
Gravitational waves from an early matter era
, 2009
"... We investigate the generation of gravitational waves due to the gravitational instability of primordial density perturbations in an early matterdominated era which could be detectable by experiments such as LIGO and LISA. We use relativistic perturbation theory to give analytic estimates of the ten ..."
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We investigate the generation of gravitational waves due to the gravitational instability of primordial density perturbations in an early matterdominated era which could be detectable by experiments such as LIGO and LISA. We use relativistic perturbation theory to give analytic estimates of the tensor perturbations generated at second order by linear density perturbations. We find that large enhancement factors with respect to the naive secondorder estimate are possible due to the growth of density perturbations on subHubble scales. However very large enhancement factors coincide with a breakdown of linear theory for density perturbations on small scales. To produce a primordial gravitational wave background that would be detectable with LIGO or LISA from density perturbations in the linear regime requires primordial comoving curvature perturbations on small scales of order 0.02 for Advanced LIGO or 0.005 for LISA, otherwise numerical calculations of the nonlinear evolution on subHubble scales are required. 1