41586733
Combining universal and odd RR axions for aligned natural inflation
We successfully embed the Kim-Nilles-Peloso (KNP) alignment mechanism for enhancing the axion decay constant in the context of large volume type IIB orientifolds. The flat direction is generated in the plane of (C-0-C-2) axions corresponding to the involutively even universal axion C-0 and odd axion C-2, respectively. The moduli stabilization with large volume scheme has been established as well.
54215476
Dimensional oxidation and modular completion of non-geometric type IIB action
A bstractUtilizing a setup of type IIB superstring theory compactified on an orientifold of T6/ℤ2×ℤ2$$ {\mathbb{T}}^6/\left({\mathbb{Z}}_2\times {\mathbb{Z}}_2\right) $$, we propose a modular invariant dimensional oxidation of the four- dimensional scalar potential. In the oxidized ten-dimensional supergravity action, the standard NS-NS and RR three form fluxes (H-, F -) as well as the non-geometric fluxes (Q-, P -) are found to nicely rearrange themselves to form generalized flux-combinations. As an application towards moduli stabilization, using the same S-duality invariant scalar potential, we examine the recently proposed No-Go theorem [1] about creating a mass-hierarchy between universal-axion and the dilaton relevant for axionic-inflation. Considering a two-field dynamics of universal axion and dilator while assuming the other moduli/axions being stabilized, we find a part of the No-Go arguments to be quite robust even with the inclusion of non-geometric (Q-, P -) fluxes.
119114774
On non-Gaussianities in two-field poly-instanton inflation
A bstractIn the context of Type IIB LARGE volume orientifold setup equipped with poly-instanton corrections, the standard single-field poly-instanton inflation driven by a ‘Wilson’ divisor volume modulus is generalized by the inclusion of respective axion modulus. This two-field dynamics results in a “Roulette” type inflation with the presence of several inflationary trajectories which could produce 50 (or more) e-foldings. The evolution of various trajectories along with physical observables are studied. The possibility of generating primordial non-Gaussianities in the slow-roll as well as in the beyond slow-roll region is investigated. We find that although the non-linearity parameters are quite small during the slow-roll regime, the same are significantly enhanced in the beyond slow-roll regime investigated up to the end of inflation.
59027051
Competition between the s-wave and p-wave superconductivity phases in a holographic model
A bstractWe build a holographic superconductor model with a scalar triplet charged under an SU(2) gauge field in the bulk. In this model, the s-wave and p-wave condensates can be consistently realized. We find that there are totally four phases in this model, namely, the normal phase without any condensate, s-wave phase, p-wave phase and the s + p coexisting phase. By calculating Gibbs free energy, the s + p coexisting phase turns out to be thermodynamically favored once it can appear. The phase diagram with the dimension of the scalar operator and temperature is drawn. The temperature range for the s + p coexisting phase is very narrow, which shows the competition between the s-wave and p-wave orders in the superconductor model.
119246227
Cosmological observables in multi-field inflation with a non-flat field space
Using delta N formalism in the context of a generic multi-field inflation driven on a non-flat field space background, we revisit the analytic expressions of the various cosmological observables such as scalar tensor power spectra, scalar/tensor spectral tilts, non-Gaussianity parameters, tensor-to-scalar ratio, and the various runnings of these observables. In our backward formalism approach, the subsequent expressions of observables automatically include the terms beyond the leading order slow-roll expansion correcting many of the expression at subleading order. To connect our analysis properly with the earlier results, we rederive the (well) known (single field) expressions in the limiting cases of our generic formulae. Further, in the light of PLANCK results, we examine for the compatibility of the consistency relations within the slow-roll regime of a two-field roulette poly-instanton inflation realized in the context, of large volume scenarios.
118438338
A note on poly-instanton effects in type IIB orientifolds on Calabi-Yau threefolds
A bstractThe zero mode structure for the generation of poly-instanton corrections for Euclidian D3-branes wrapping complex surfaces in Type IIB orientifolds with O7- and O3-planes is analyzed. Working examples of such surfaces and explicit embeddings into compact Calabi-Yau threefolds are presented, with special emphasis on geometries capable of realizing the LARGE volume scenario.
15618257
Reheating and Cosmic String Production
Abstract We compute the string production rate at the end of inflation, using the string spectrum obtained in [M. Li, W. Song, Y. Song, Quantizing strings in de Sitter space, JHEP 0704 (2007) 042, hep-th/0701258 ] in a near-de Sitter space. Our result shows that highly excited strings are hardly produced, thus the simple slow-roll inflation alone does not offer a cosmic string production mechanism.
119210037
Oscillatory features in the curvature power spectrum after a sudden turn of the inflationary trajectory
In the context of two-field inflation characterized by a light direction and a heavy direction, we revisit the question of the impact of the massive modes on the power spectrum produced after a turn in the inflationary trajectory. We consider in particular the resonant effect due to the background oscillations following a sharp turn. Working in the mass basis, i.e. in the basis spanned by the eigenvectors of the effective mass matrix for the perturbations, we provide an analytical estimate of the resonant effect, using the in-in formalism. In comparison with earlier estimates, we find the same the spectral dependence but a smaller amplitude. We also compute, again via the in-in formalism, the effect of the direct coupling between the light and heavy modes at the instant of the turn and confirm our previous results obtained via a different method.
118734465
Conserved cosmological perturbation in Galileon models
We prove the existence of a fully nonlinear conserved curvature perturbation on large scales in Galileon-type scalar field models in two approaches. The first approach is based on the conservation of energy-momentum tensor of the Galileon field, which is also the familiar approach in understanding the conservation in k-essence or perfect fluid models. We show that the fluid corresponding to the Galileon field becomes perfect and barotropic on large scales, which is responsible to the conservation. The difference from k-essence model is that, besides the energy-momentum conservation, the Einstein equation must be employed in order to complete the proof of barotropy. In the second approach, we derive the fully non-perturbative action for the curvature perturbation ζ in Galileon models on large scales, and argue that ζ = const is indeed an exact solution on large scales. This conservation of curvature perturbation is important since it relates the later and the primordial universe.
118686297
Can relic superhorizon inhomogeneities be responsible for large-scale CMB anomalies?
We investigate the effects of the presence of relic classical superhorizon inhomogeneities during inflation. This superhorizon inhomogeneity appears as a gradient locally and picks out a preferred direction. Quantum fluctuations on this slightly inhomogeneous background are generally statistical anisotropic. We find a quadrupole modification to the ordinary isotropic spectrum. Moreover, this deviation from statistical isotropy is scale-dependent, with a similar to -1/k(2) factor. This result implies that the statistical anisotropy mainly appears on large scales, while the spectrum on small scales remains highly isotropic. Moreover, due to this -1/k(2) factor, the power on large scales is suppressed. Thus, our model can simultaneously explain the observed anisotropic alignments of the low-l multipoles and their low power. (C) 2011 Elsevier B.V All rights reserved.
749285
Non-supersymmetric attractors in Born-Infeld black holes with a cosmological constant
We investigate the attractor mechanism for spherically symmetric extremal black holes in Einstein-Born-Infeld-dilaton theory of gravity in four-dimensions, in the presence of a cosmological constant. We look for solutions analytic near the horizon by using perturbation method. It is shown that the values of the scalar fields at the horizon are only dependent on the charges carried by the black hole and are irrelevant in their asymptotic values. This analysis supports the validity of non-supersymmetric attractors in the presence of higher derivative interactions in the gauge fields part and in non-asymptotically flat spacetime.