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Inflationary scenarios from branes at angles
 JHEP 0207 (2002) 051 [arXiv:hepth/0203163
"... Abstract: We describe a simple mechanism that can lead to inflation within stringbased braneworld scenarios. The idea is to start from a supersymmetric configuration with two parallel static Dpbranes, and slightly break the supersymmetry conditions to produce a very flat potential for the field t ..."
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Cited by 48 (2 self)
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Abstract: We describe a simple mechanism that can lead to inflation within stringbased braneworld scenarios. The idea is to start from a supersymmetric configuration with two parallel static Dpbranes, and slightly break the supersymmetry conditions to produce a very flat potential for the field that parametrises the distance between the branes, i.e. the inflaton field. This breaking can be achieved in various ways: by slight relative rotations of the branes with small angles, by considering small relative velocities between the branes, etc. If the breaking parameter is sufficiently small, a large number of efolds can be produced within the Dbrane, for small changes of the configuration in the compactified directions. Such a process is local, i.e. it does not depend very strongly on the compactification space nor on the initial conditions. Moreover, the breaking induces a very small velocity and acceleration, which ensures very small slowroll parameters and thus an almost scale invariant spectrum of metric fluctuations, responsible for the observed temperature anisotropies in the microwave background. Inflation ends as in hybrid inflation, triggered by the negative curvature of the string tachyon potential. In this paper we elaborate on one of the simplest examples: two almost parallel D4branes in a flat compactified space. JHEP01(2002)036
Bouncing universes in stringinspired gravity
 JCAP 0603
"... Preprint typeset in JHEP style HYPER VERSION hepth/0508194 ..."
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Cited by 47 (7 self)
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Preprint typeset in JHEP style HYPER VERSION hepth/0508194
Signatures of short distance physics in the cosmic microwave background,” Phys
 Rev. D
"... We systematically investigate the effect of short distance physics on the spectrum of temperature anistropies in the Cosmic Microwave Background produced during inflation. We present a general argument–assuming only low energy locality–that the size of such effects are of order H 2 /M 2, where H is ..."
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Cited by 46 (2 self)
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We systematically investigate the effect of short distance physics on the spectrum of temperature anistropies in the Cosmic Microwave Background produced during inflation. We present a general argument–assuming only low energy locality–that the size of such effects are of order H 2 /M 2, where H is the Hubble parameter during inflation, and M is the scale of the high energy physics. We evaluate the strength of such effects in a number of specific string and M theory models. In weakly coupled field theory and string theory models, the effects are far too small to be observed. In phenomenologically attractive HoˇravaWitten compactifications, the effects are much larger but still unobservable. In certain M theory models, for which the fundamental Planck scale is several orders of magnitude below the conventional scale of grand unification, the effects may be on the threshold of detectability. However, observations of both the scalar and tensor fluctuation contributions to the Cosmic Microwave Background power spectrum–with a precision near the cosmic variance limit–are necessary in order to unambiguously demonstrate the existence of these signatures of high energy physics. This is a formidable experimental challenge. January
The selfreproducing inflationary universe
 Scientific American
, 1994
"... According to the inflationary universe scenario the universe in the very early stages of its evolution was exponentially expanding in the unstable vacuumlike state. At the end of the exponential expansion (inflation) the energy of the unstable vacuum (of a classical scalar field) transforms into th ..."
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Cited by 43 (1 self)
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According to the inflationary universe scenario the universe in the very early stages of its evolution was exponentially expanding in the unstable vacuumlike state. At the end of the exponential expansion (inflation) the energy of the unstable vacuum (of a classical scalar field) transforms into the energy ofhQt dense matter, and the subsequent evolution of the universe is described by the usual hot universe theory. Recently it was realised that the exponential expansion during the very early stages of evolution of the universe naturally occurs in a wide class of realistic theories of elementary particles. The inflationary universe scenario makes it possible to obtain a simple solution to many longstanding cosmological problems and leads to a crucial modification of the standard point of view of the largescale structure of the universe. This review was received in February 1984. 00344885/84/080925 +62$09.00 @ 1984 The Institute of Physics 925 The inflationary universe 981 energy cancellation between the 'up ' and 'down ' vacua seems so simple and natural
Origin and Propagation of Extremely High Energy Cosmic Rays
 Phys. Rept
, 2000
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Inflationary cosmology: progress and problems
 Proceedings International School on Cosmology, Kish Island, Iran (Kluwer, Dordrecht) 2000) ePrint Archive: hepph/9910410
"... Abstract. These lecture notes 1 intend to form a short pedagogical introduction to inflationary cosmology, highlighting selected areas of recent progress such as reheating and the theory of cosmological perturbations. Problems of principle for inflationary cosmology are pointed out, and some new att ..."
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Cited by 41 (12 self)
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Abstract. These lecture notes 1 intend to form a short pedagogical introduction to inflationary cosmology, highlighting selected areas of recent progress such as reheating and the theory of cosmological perturbations. Problems of principle for inflationary cosmology are pointed out, and some new attempts at solving them are indicated, including a nonsingular Universe construction by means of higher derivative terms in the gravitational action, and the study of backreaction of cosmological perturbations. 1.
Analyticity properties and thermal effects for general quantum field theory on de Sitter spacetime
, 1998
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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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Cited by 34 (10 self)
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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.
Twopoint functions and quantum fields in de Sitter universe
 Rev. Math. Phys
, 1996
"... We present a theory of general twopoint functions and of generalized free fields in ddimensional de Sitter spacetime which closely parallels the corresponding minkowskian theory. The usual spectral condition is now replaced by a certain geodesic spectral condition, equivalent to a precise thermal ..."
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Cited by 30 (7 self)
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We present a theory of general twopoint functions and of generalized free fields in ddimensional de Sitter spacetime which closely parallels the corresponding minkowskian theory. The usual spectral condition is now replaced by a certain geodesic spectral condition, equivalent to a precise thermal characterization of the corresponding “vacuum”states. Our method is based on the geometry of the complex de Sitter spacetime and on the introduction of a class of holomorphic functions on this manifold, called perikernels, which reproduce mutatis mutandis the structural properties of the twopoint correlation functions of the minkowskian quantum field theory. The theory contains as basic elementary case the linear massive field models in their “preferred ” representation. The latter are described by the introduction of de Sitter plane waves in their tube domains which lead to a new integral representation of the twopoint functions and to a FourierLaplace type transformation on the hyperboloid. The Hilbert space structure of these theories is then analysed by using this transformation. In particular we show the ReehSchlieder property. For general twopoint functions, a substitute to the Wick rotation is defined both in complex spacetime and in the complex mass variable, and substantial results concerning the derivation