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17
New string vacua from twistor spaces
 PHYS REV. D
, 2008
"... We find a new family of AdS4 vacua in IIA string theory. The internal space is topologically either the complex projective space CP3 or the “flag manifold” SU(3)/(U(1)×U(1)), but the metric is in general neither Einstein nor Kähler. All known moduli are stabilized by fluxes, without using quantum ef ..."
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Cited by 55 (1 self)
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We find a new family of AdS4 vacua in IIA string theory. The internal space is topologically either the complex projective space CP3 or the “flag manifold” SU(3)/(U(1)×U(1)), but the metric is in general neither Einstein nor Kähler. All known moduli are stabilized by fluxes, without using quantum effects or orientifold planes. The analysis is completely
Micromanaging de Sitter holography
, 2010
"... We develop tools to engineer de Sitter vacua with semiholographic duals, using elliptic fibrations and orientifolds to uplift FreundRubin compactifications with CFT duals. The dual brane construction is compact and constitutes a microscopic realization of the dS/dS correspondence, realizing ddime ..."
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Cited by 24 (7 self)
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We develop tools to engineer de Sitter vacua with semiholographic duals, using elliptic fibrations and orientifolds to uplift FreundRubin compactifications with CFT duals. The dual brane construction is compact and constitutes a microscopic realization of the dS/dS correspondence, realizing ddimensional de Sitter space as a warped compactification down to (d − 1)dimensional de Sitter gravity coupled to a pair of largeN matter sectors. This provides a parametric microscopic interpretation of the GibbonsHawking entropy. We illustrate these ideas with an explicit class of
Monodromy in the CMB: Gravity waves and string inflation,” arXiv:0803.3085 [hepth]; – 71
 J. High Energy Phys
"... We present a simple mechanism for obtaining largefield inflation, and hence a gravitational wave signature, from string theory compactified on twisted tori. For Nil manifolds, we obtain a leading inflationary potential proportional to φ 2/3 in terms of the canonically normalized field φ, yielding p ..."
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Cited by 20 (1 self)
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We present a simple mechanism for obtaining largefield inflation, and hence a gravitational wave signature, from string theory compactified on twisted tori. For Nil manifolds, we obtain a leading inflationary potential proportional to φ 2/3 in terms of the canonically normalized field φ, yielding predictions for the tilt of the power spectrum and the tensortoscalar ratio, ns ≈ 0.98 and r ≈ 0.04 with 60 efoldings of inflation; we note also the possibility of a variant with a candidate inflaton potential proportional to φ 2/5. The basic mechanism involved in extending the field range – monodromy in Dbranes as they move in circles on the manifold – arises in a more general class of compactifications, though our methods for controlling the
Simple de Sitter Solutions
"... We present a framework for de Sitter model building in type IIA string theory, illustrated with specific examples. We find metastable dS minima of the potential for moduli obtained from a compactification on a product of two Nil threemanifolds (which have negative scalar curvature) combined with or ..."
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Cited by 18 (1 self)
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We present a framework for de Sitter model building in type IIA string theory, illustrated with specific examples. We find metastable dS minima of the potential for moduli obtained from a compactification on a product of two Nil threemanifolds (which have negative scalar curvature) combined with orientifolds, branes, fractional ChernSimons forms, and fluxes. As a discrete quantum number is taken large, the curvature, field strengths, inverse volume, and four dimensional string coupling become parametrically small, and the de Sitter Hubble scale can be tuned parametrically smaller than the scales of the moduli, KK, and winding mode masses. A subtle point in the construction is that although the curvature remains consistently weak, the circle fibers of the nilmanifolds become very small in this limit (though this is avoided in illustrative solutions at modest values of the parameters). In the simplest version of the construction, the heaviest moduli masses are parametrically of the same order as the lightest KK and winding masses. However, we provide a method for separating these marginally overlapping scales, and more generally the underlying supersymmetry of the model protects against large corrections to the lowenergy moduli potential. December
Simple exercises to flatten your potential
, 2011
"... We show how backreaction of the inflaton potential energy on heavy scalar fields can flatten the inflationary potential, as the heavy fields adjust to their most energetically favorable configuration. This mechanism operates in previous UVcomplete examples of axion monodromy inflation – flattening ..."
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Cited by 9 (2 self)
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We show how backreaction of the inflaton potential energy on heavy scalar fields can flatten the inflationary potential, as the heavy fields adjust to their most energetically favorable configuration. This mechanism operates in previous UVcomplete examples of axion monodromy inflation – flattening a wouldbe quadratic potential to one linear in the inflaton field – but occurs more generally, and we illustrate the effect with several examples. Special choices of compactification minimizing backreaction may realize chaotic inflation with a quadratic potential, but we argue that a flatter potential such as powerlaw inflation V (φ) ∝ φ p with p < 2 is a more generic option at sufficiently large values of φ.
Towards Classical de Sitter Solutions in String Theory
, 907
"... We investigate the type II string effective potential at treelevel and derive necessary ingredients for having de Sitter solutions in orientifold models with fluxes. Furthermore, we examine some explicit O6 compactifications in IIA theory on manifolds with SU(3)structure in the limit where the ori ..."
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Cited by 8 (2 self)
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We investigate the type II string effective potential at treelevel and derive necessary ingredients for having de Sitter solutions in orientifold models with fluxes. Furthermore, we examine some explicit O6 compactifications in IIA theory on manifolds with SU(3)structure in the limit where the orientifold sources are smeared. In particular, we use a simple tendimensional Ansatz for fourdimensional de Sitter solutions and find the explicit criteria in terms of the torsion classes such that these de Sitter solutions solve the equations of motion. We have verified these torsion conditions for the cosets and the Iwasawa manifold and it turns out that the conditions cannot be fulfilled for these spaces. However this investigation allows us to find new nonsupersymmetric AdS solutions for some cosets. It remains an open question whether there exist SU(3)structure manifolds that satisfy the conditions on the torsion classes for the simple de Sitter solutions to exist. Contents
Les Houches lectures on inflationary observables and string theory,’’ arXiv:1311.2312 [hepth
"... These lectures cover the theoretical structure and phenomenology of some basic mechanisms for inflation. A full treatment of the problem requires ‘ultraviolet completion ’ because of the sensitivity of inflation to quantum gravity effects, while the observables are elegantly parameterized using low ..."
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Cited by 6 (0 self)
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These lectures cover the theoretical structure and phenomenology of some basic mechanisms for inflation. A full treatment of the problem requires ‘ultraviolet completion ’ because of the sensitivity of inflation to quantum gravity effects, while the observables are elegantly parameterized using low energy field theory. String theory provides novel mechanisms for inflation, some subject to significant observational tests, with highly UVsensitive tensor mode measurements being a prime example. Although the ultraviolet completion is not directly accessible experimentally, some of these mechanisms have helped stimulate a more systematic analysis of the space of low energy theories and signatures relevant for data analysis, including searches for nonGaussianity and additional structure in the power spectrum. We include a pedagogical overview of string compactifications, with a focus on candidate inflatons and their symmetry structure. In the last lecture we attack the problem of thoughtexperimental observables in inflation, developing a generalization of gaugegravity duality that relies on the structure of the scalar potential in string theory. ar X iv
New solutions with accelerated expansion in string theory
"... We present concrete solutions with accelerated expansion in string theory, requiring a small, tractable list of stress energy sources. We explain how this construction (and others in progress) evades previous no go theorems for simple accelerating solutions. Our solutions respect an approximate sca ..."
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Cited by 5 (2 self)
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We present concrete solutions with accelerated expansion in string theory, requiring a small, tractable list of stress energy sources. We explain how this construction (and others in progress) evades previous no go theorems for simple accelerating solutions. Our solutions respect an approximate scaling symmetry and realize discrete sequences of values for the equation of state, including one with an accumulation point at w = −1 and another accumulating near w = −1/3 from below. In another class of models, a density of defects generates scaling solutions with accelerated expansion. We briefly discuss potential applications to dark energy phenomenology, and to holography for cosmology. Published in arXiv:1310.5297 and NSF.