Results 1  10
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31
String cosmology
"... Abstract: We derive the corrections to the Friedmann equation of order ρ 2 in the RandallSundrum (RS) model, where two 3branes bound a slice of fivedimensional AntideSitter space. The effects of radion stabilization by the GoldbergerWise mechanism are taken into account. Surprisingly, we find t ..."
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Cited by 48 (2 self)
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Abstract: We derive the corrections to the Friedmann equation of order ρ 2 in the RandallSundrum (RS) model, where two 3branes bound a slice of fivedimensional AntideSitter space. The effects of radion stabilization by the GoldbergerWise mechanism are taken into account. Surprisingly, we find that an inflaton on either brane will experience no order ρ 2 corrections in the Hubble rate H due to its own energy density, although an observer on the opposite brane does see such a correction. Thus there is no enhancement of the slowroll condition unless inflation is simultaneously driven by inflatons on both branes. Similarly, during radiation domination, the ρ 2 correction to H on a given brane vanish unless there is nonvanishing energy density on the opposite brane. During the electroweak phase transition the correction can be large, but is has the wrong sign for causing sphalerons to go out of thermal equilibrium, so it cannot help electroweak baryogenesis. We discuss the differences
On D3brane potentials in compactifications with fluxes and wrapped Dbranes
 JHEP
, 2006
"... We study the potential governing D3brane motion in a warped throat region of a string compactification with internal fluxes and wrapped Dbranes. If the Kähler moduli of the compact space are stabilized by nonperturbative effects, a D3brane experiences a force due to its interaction with Dbranes ..."
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Cited by 41 (4 self)
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We study the potential governing D3brane motion in a warped throat region of a string compactification with internal fluxes and wrapped Dbranes. If the Kähler moduli of the compact space are stabilized by nonperturbative effects, a D3brane experiences a force due to its interaction with Dbranes wrapping certain fourcycles. We compute this interaction, as a correction to the warped fourcycle volume, using explicit throat backgrounds in supergravity. This amounts to a closedstring channel computation of the loop corrections to the nonperturbative superpotential that stabilizes the volume. We demonstrate for warped conical spaces that the superpotential correction is given by the embedding equation specifying the wrapped fourcycle, in agreement with the general form proposed by Ganor. Our approach automatically provides a solution to the problem of defining a holomorphic gauge coupling on wrapped D7branes in a background with D3branes. Finally, our results have applications to cosmological inflation models in which the inflaton is modeled by a D3brane
Inflation from warped space
 JHEP
, 2005
"... A long period of inflation can be triggered when the inflaton is held up on the top of a steep potential by the infrared end of a warped space. We first study the field theory description of such a model. We then embed it in the flux stabilized string compactification. Some special effects in the th ..."
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Cited by 38 (8 self)
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A long period of inflation can be triggered when the inflaton is held up on the top of a steep potential by the infrared end of a warped space. We first study the field theory description of such a model. We then embed it in the flux stabilized string compactification. Some special effects in the throat reheating process by relativistic branes are discussed. We put all these ingredients into a multithroat brane inflationary scenario. The resulting cosmic string tension Inflation [1–3] provides a natural mechanism for creating the homogeneity and flatness of our observable universe. It also gives an elegant way of generating the perturbations [4–10] which seed the structure formation. In order for the inflation to last sufficiently long and then successfully exit to reheat the universe, the inflaton has to be held up on a potential for
The (p,q) String Tension in a Warped Deformed Conifold
, 2006
"... We find the tension spectrum of the bound states of p fundamental strings and q Dstrings at the bottom of a warped deformed conifold. We show that it can be obtained from a D3brane wrapping a 2cycle that is stabilized by both electric and magnetic fluxes. Because the Fstrings are ZMcharged wi ..."
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Cited by 25 (8 self)
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We find the tension spectrum of the bound states of p fundamental strings and q Dstrings at the bottom of a warped deformed conifold. We show that it can be obtained from a D3brane wrapping a 2cycle that is stabilized by both electric and magnetic fluxes. Because the Fstrings are ZMcharged with nonzero binding energy, binding can take place even if (p, q) are not coprime. Implications for cosmic strings are briefly discussed.
Heating in brane inflation and hidden dark matter
, 2006
"... Towards the end of brane inflation, the brane pair annihilation produces massive closed strings. The transfer of this energy to Standard Model (SM) open string modes depends on where the SM branes and the brane annihilation are located: in the bulk, in the same throat or in different throats. We fi ..."
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Cited by 21 (6 self)
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Towards the end of brane inflation, the brane pair annihilation produces massive closed strings. The transfer of this energy to Standard Model (SM) open string modes depends on where the SM branes and the brane annihilation are located: in the bulk, in the same throat or in different throats. We find that, in all cases as long as the brane annihilation and the SM branes are not both in the bulk, the transfer of energy to start the hot big bang epoch can be efficient enough to be compatible with big bang nucleosynthesis. The suppression of the abundance of the graviton and its KaluzaKlein (KK) thermal relics follows from the warped geometry in flux compactification. This works out even in the scenarios where a long period of tunneling is expected. In the multithroat scenario, we find a dynamical mechnism of selecting a long throat as the SM throat. We establish three new dark matter candidates: KK modes with specific angular momentum in the SM throat, those in the brane annihilation throat, and different matters generated by KK modes tunneled to other throats. Since the latter two couple to the visible matter sector only through graviton mediation, they behave as hidden dark matter. Hidden dark matter has novel implications on the dark matter coincidence problem and the high energy cosmic rays.
Brane inflation and the WMAP data: a Bayesian analysis
, 2007
"... The Wilkinson Microwave Anisotropy Probe (WMAP) constraints on string inspired “brane inflation ” are investigated. Here, the inflaton field is interpreted as the distance between two branes placed in a fluxenriched background geometry and has a DiracBornInfeld (DBI) kinetic term. Our method re ..."
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Cited by 16 (5 self)
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The Wilkinson Microwave Anisotropy Probe (WMAP) constraints on string inspired “brane inflation ” are investigated. Here, the inflaton field is interpreted as the distance between two branes placed in a fluxenriched background geometry and has a DiracBornInfeld (DBI) kinetic term. Our method relies on an exact numerical integration of the inflationary power spectra coupled to a MarkovChain MonteCarlo exploration of the parameter space. This analysis is valid for any perturbative value of the string coupling constant and of the string length, and includes a phenomenological modelling of the reheating era to describe the postinflationary evolution. It is found that the data favour a scenario where inflation stops by violation of the slowroll conditions well before brane annihilation, rather than by tachyonic instability. Concerning the background geometry, it is established that log v> −10 at 95 % confidence level (CL), where v is the dimensionless ratio of the fivedimensional submanifold at the base of the sixdimensional warped conifold geometry to the volume of the unit fivesphere. The reheating energy scale remains poorly constrained, Treh> 20 GeV at 95 % CL, for an extreme equation of state (wreh � −1/3) only. Assuming the string length is known, the favoured values of the string coupling and of the RamondRamond total background charge appear to be correlated. Finally, the stochastic regime (without and with volume effects) is studied using a perturbative treatment of the Langevin equation. The validity of such an approximate scheme is discussed and shown to be too limited for a full characterisation of the quantum effects.
Warped tachyonic inflation in type IIB flux compactifications and the openstring completeness conjecture
 JHEP
"... hepth/0505252 ..."
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Effects of ScaleDependent NonGaussianity on Cosmological Structures
, 2008
"... Abstract: The detection of primordial nonGaussianity could provide a powerful means to test various inflationary scenarios. Although scaleinvariant nonGaussianity (often described by the fNL formalism) is currently best constrained by the CMB, singlefield models with changing sound speed can hav ..."
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Cited by 6 (1 self)
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Abstract: The detection of primordial nonGaussianity could provide a powerful means to test various inflationary scenarios. Although scaleinvariant nonGaussianity (often described by the fNL formalism) is currently best constrained by the CMB, singlefield models with changing sound speed can have strongly scaledependent nonGaussianity. Such models could evade the CMB constraints but still have important effects at scales responsible for the formation of cosmological objects such as clusters and galaxies. We compute the effect of scaledependent primordial nonGaussianity on cluster number counts as a function of redshift, using a simple ansatz to model scaledependent features. We forecast constraints on these models achievable with forthcoming data sets. We also examine consequences for the galaxy bispectrum. Our results are relevant for the DiracBornInfeld model of brane inflation, where the scaledependence of the nonGaussianity is directly related to
Running nongaussianities in dbi inflation
"... We study the nonGaussianity in the simplest infrared (IR) model of the DBI inflation. We show that the nonGaussianity in such a model is compatible with the current observational bound, and is within the sensitivity of future experiments. We also discuss the scale dependence of the nonGaussianity ..."
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Cited by 5 (0 self)
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We study the nonGaussianity in the simplest infrared (IR) model of the DBI inflation. We show that the nonGaussianity in such a model is compatible with the current observational bound, and is within the sensitivity of future experiments. We also discuss the scale dependence of the nonGaussianity. In the DBI inflation, such a feature can be used as a probe to the properties Recently the DBI inflation [1–4] is proposed as an alternative to the slowroll inflation. The motivation comes from the nongenericness of flat potentials. In slowroll inflation, the required flatness is described by the slowroll conditions and is necessary to hold the inflaton on the top of the potential for a sufficiently long time, and at the same time producing
2007 Energy radiation by cosmic superstrings in brane inflation. [ePrint: arXiv:arXiv:0710.4609
"... The dominant method of energy loss by a loop of cosmic Dstrings in models of warped brane inflation is studied. It is shown that the energy loss via RamondRamond field radiation can dominate by many orders of magnitude over the energy radiation via gravitational wave emission. The ratio of these t ..."
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Cited by 2 (0 self)
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The dominant method of energy loss by a loop of cosmic Dstrings in models of warped brane inflation is studied. It is shown that the energy loss via RamondRamond field radiation can dominate by many orders of magnitude over the energy radiation via gravitational wave emission. The ratio of these two energy loss mechanisms depends on the energy scale of inflation, the mass scale of string theory and whether it is a singlethroat or a multithroat inflationary scenario. This can have important consequences for the detection of cosmic superstrings in the near future. It is argued that the bounds from CMB anisotropies and BBN are the dominant cosmological sources to constrain the physical parameters of the network of cosmic superstrings, whereas the role of the gravitational wavebased experiments may be secondary.