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Register a new userPrimordial statistical anisotropy generated at the end of inflation
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We present a new mechanism for generating primordial statistical anisotropy of curvature perturbations. We introduce a vector field which has a non-minimal kinetic term and couples with a waterfall field in hybrid inflation model. In such a system, the vector field gives fluctuations of the end of inflation and hence induces a subcomponent of curvature perturbations. Since the vector has a preferred direction, the statistical anisotropy could appear in the fluctuations. We present the explicit formula for the statistical anisotropy in the primordial power spectrum and the bispectrum of curvature perturbations. Interestingly, there is the possibility that the statistical anisotropy does not appear in the power spectrum but does appear in the bispectrum. We also find that the statistical anisotropy provides the shape dependence to the bispectrum.
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Cosmological inflation remains to be a unique mechanism of generation of plausible initial conditions in the early universe. In particular, it generates the primordial quasiclassical perturbations with power spectrum determined by the fundamental principles of quantum field theory. In this work, we pay attention to the fact that the quasiclassical perturbations permanently generated at early stages of inflation break homogeneity and isotropy of the cosmological background. The evolution of the small-scale quantum vacuum modes on this inhomogeneous background results in statistical anisotropy of the primordial power spectrum, which can manifest itself in the observable large-scale structure and cosmic microwave background. The effect is predicted to have almost scale-invariant form dominated by a quadrupole and may serve as a non-trivial test of the inflationary scenario. Theoretical expectation of the magnitude of this statistical anisotropy depends on the assumptions about the physics in the trans-Planckian region of wavenumbers.
We study primordial non-gaussianity in supersolid inflation. The dynamics of supersolid is formulated in terms of an effective field theory based on four scalar fields with a shift symmetric action minimally coupled with gravity. In the scalar sector, there are two phonon-like excitations with a kinetic mixing stemming from the completely spontaneous breaking of diffeomorphism. In a squeezed configuration, $f_{text{NL}}$ of scalar perturbations is angle dependent and not proportional to slow-roll parameters showing a blunt violation of the Maldacena consistency relation. Contrary to solid inflation, the violation persists even after an angular average and generically the amount of non-gaussianity is significant. During inflation, non-gaussianity in the TSS and TTS sector is enhanced in the same region of the parameters space where the secondary production of gravitational waves is sizeable enough to enter in the sensitivity region of LISA, while the scalar $f_{text{NL}}$ is still within the current experimental limits.
B-Pol is a medium-class space mission aimed at detecting the primordial gravitational waves generated during inflation through high accuracy measurements of the Cosmic Microwave Background (CMB) polarization. We discuss the scientific background, feasibility of the experiment, and implementation developed in response to the ESA Cosmic Vision 2015-2025 Call for Proposals.
We re-examine approximations in the analytical calculation of the primordial spectrum of cosmological perturbation produced during inflation. Taking two inflation models (chaotic inflation and natural inflation) as examples, we numerically verify the accuracy of these approximations.
We consider magnetic monopoles and strings that appear in non-supersymmetric $SO(10)$ and $E_6$ grand unified models paying attention to gauge coupling unification and proton decay in a variety of symmetry breaking schemes. The dimensionless string tension parameter $Gmu$ spans the range $10^{-6}-10^{-30}$, where $G$ is Newtons constant and $mu$ is the string tension. We show how intermediate scale monopoles with mass $sim 10^{13}-10^{14}$ GeV and flux $lesssim 2.8times 10^{-16}$ ${mathrm{cm}^{-2}mathrm{s}^{-1}mathrm{sr}^{-1}}$, and cosmic strings with $Gmu sim 10^{-11}-10^{-10}$ survive inflation and are present in the universe at an observable level. We estimate the gravity wave spectrum emitted from cosmic strings taking into account inflation driven by a Coleman-Weinberg potential. The tensor-to-scalar ratio $r$ lies between $0.06$ and $0.003$ depending on the details of the inflationary scenario.
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