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48
D3/D7 inflationary model and Mtheory
 Phys. Rev. D
"... A proposal is made for a cosmological D3/D7 model with a constant magnetic flux along the D7 worldvolume. It describes an N = 2 gauge model with FayetIliopoulos terms and the potential of the hybrid Pterm inflation. The motion of the D3brane towards D7 in a phase with spontaneously broken supers ..."
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A proposal is made for a cosmological D3/D7 model with a constant magnetic flux along the D7 worldvolume. It describes an N = 2 gauge model with FayetIliopoulos terms and the potential of the hybrid Pterm inflation. The motion of the D3brane towards D7 in a phase with spontaneously broken supersymmetry provides a period of slowroll inflation in the de Sitter valley, the role of the inflaton being played by the distance between D3 and D7branes. After tachyon condensation a supersymmetric ground state is formed: a D3/D7 bound state corresponding to an Abelian nonlinear (noncommutative) instanton. In this model the existence of a nonvanishing cosmological constant is associated with the resolution of the instanton singularity. We discuss a possible embedding of this model into a compactified Mtheory setup. 1
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.
String Theory and Hybrid Inflation/Acceleration,” JHEP 0112 (2001) 027, hepth/0110271
 D3/D7 Inflationary Model and Mtheory,” Phys. Rev. D65 (2002) 126002, hepth/0203019
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Moduli corrections to Dterm inflation
 JCAP 0701 (2007) 026 [hepth/0610195
"... Abstract. We present a Dterm hybrid inflation model, embedded in supergravity with moduli stabilisation. Its novel features allow us to overcome the serious challenges of combining Dterm inflation and moduli fields within the same stringmotivated theory. One salient point of the model is the posi ..."
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Abstract. We present a Dterm hybrid inflation model, embedded in supergravity with moduli stabilisation. Its novel features allow us to overcome the serious challenges of combining Dterm inflation and moduli fields within the same stringmotivated theory. One salient point of the model is the positive definite uplifting Dterm arising from the moduli stabilisation sector. By coupling this Dterm to the inflationary sector, we generate an effective FayetIliopoulos term. Moduli corrections to the inflationary dynamics are also obtained. Successful inflation is achieved for a range of parameter values with spectral index compatible with the WMAP3 data. Cosmic Dterm strings are also formed at the end of inflation; these are no longer BPS objects. The properties of the strings are studied. Keywords: inflation, string theory and cosmologyModuli Corrections to Dterm Inflation 2 1.
Seeing through the String Landscape  a String Hunter’s Companion
 in Particle Physics and Cosmology,” JHEP 0903, 149 (2009) arXiv:0904.4601 [hepth
"... Abstract: In this article we will overview several aspects of the string landscape, namely intersecting Dbrane models and their statistics, possible model independent LHC signatures of intersecting brane models, flux compactification, moduli stabilization in type II compactifications, domain wall s ..."
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Abstract: In this article we will overview several aspects of the string landscape, namely intersecting Dbrane models and their statistics, possible model independent LHC signatures of intersecting brane models, flux compactification, moduli stabilization in type II compactifications, domain wall solutions and brane inflation.
Dterm inflation and leptogenesis by righthanded sneutrino,” Phys. Rev. D73
, 2006
"... We discuss a Dterm inflation scenario where a righthanded sneutrino can be an inflaton field leading to a viable inflation and leptogenesis, with a minimal form of Kähler potential. The decay of an inflaton sneutrino can nonthermally create large enough lepton asymmetry. Its entropy production is ..."
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We discuss a Dterm inflation scenario where a righthanded sneutrino can be an inflaton field leading to a viable inflation and leptogenesis, with a minimal form of Kähler potential. The decay of an inflaton sneutrino can nonthermally create large enough lepton asymmetry. Its entropy production is also big enough to ameliorate the gravitino problem caused by too high a reheating temperature from the decay of a symmetry breaking field. PACS: 98.80.Cq 1
Inflation with racetrack superpotential and matter field
"... Several models of inflation with the racetrack superpotential for the volume modulus coupled to a matter field are investigated. In particular, it is shown that two classes of racetrack inflation models, saddle point and inflection point ones, can be constructed in a fully supersymmetric framework w ..."
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Several models of inflation with the racetrack superpotential for the volume modulus coupled to a matter field are investigated. In particular, it is shown that two classes of racetrack inflation models, saddle point and inflection point ones, can be constructed in a fully supersymmetric framework with the matter field Fterm as a source of supersymmetry breaking and uplifting. Two models of Fterm supersymmetry breaking are considered: the Polonyi model and the quantum corrected O’Raifeartaigh model. In the former case, both classes of racetrack inflation models differ significantly from the corresponding models with nonsupersymmetric uplifting. The main difference is a quite strong dominance of the inflaton by the matter field. In addition, finetuning of the parameters is relaxed as compared to the original racetrack models. In the case of the racetrack inflation models coupled to the O’Raifeartaigh model, the matter field is approximately decoupled from the inflationary dynamics. In all of the above models the gravitino mass is larger than the Hubble scale during inflation. The possibility of having the gravitino much lighter than the Hubble scale is also investigated. It is very hard to construct models with light gravitino in which the volume modulus dominates inflation. On the other hand, models in which the inflationary dynamics is dominated by the matter field are relatively simple and seem to be more natural.
Anomaly mediation and cosmology
, 2011
"... Abstract: We consider an extension of the MSSM wherein anomaly mediation is the source of supersymmetrybreaking, and the tachyonic slepton problem is solved by a gauged U(1) symmetry, which is broken at high energies in a manner preserving supersymmetry, thereby also facilitating the seesaw mechan ..."
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Abstract: We consider an extension of the MSSM wherein anomaly mediation is the source of supersymmetrybreaking, and the tachyonic slepton problem is solved by a gauged U(1) symmetry, which is broken at high energies in a manner preserving supersymmetry, thereby also facilitating the seesaw mechanism for neutrino masses and a natural source for the Higgs µterm. We show that these favourable outcomes can occur both in the presence and the absence of a large FayetIliopoulos (FI) Dterm associated with the new U(1). We explore the cosmological consequences of the model, showing that it naturally produces a period of hybrid inflation, terminating in the production of cosmic strings. In spite of the presence of a U(1) (even with an FI term), inflation is effected by the Fterm, with a Dflat tree potential (the FI term, if present, being cancelled by nonzero squark and slepton fields). Calculating the 1loop corrections to the inflaton potential, we estimate the constraints on the parameters of the model from Cosmic Microwave Background data. We will see that a consequence of these constraints is that the Higgs µterm necessarily small. We briefly discuss the mechanisms for baryogenesis via conventional leptogenesis, the outofequilibrium production of neutrinos from the cosmic strings, or the AffleckDine mechanism. Cosmic string decays also boost the relic density of dark matter above the low value normally obtained in AMSB scenarios.