Generalised tensor fluctuations and inflation

Abstract

Using an effective field theory approach to inflation, we examine novel properties of the spectrum of inflationary tensor fluctuations, that arise when breaking some of the symmetries or requirements usually imposed on the dynamics of perturbations. During single-clock inflation, time-reparameterization invariance is broken by a time-dependent cosmological background. In order to explore more general scenarios, we consider the possibility that spatial diffeomorphism invariance is also broken by effective mass terms or by derivative operators for the metric fluctuations in the Lagrangian. We investigate the cosmological consequences of the breaking of spatial diffeomorphisms, focussing on operators that affect the power spectrum of fluctuations. We identify the operators for tensor fluctuations that can provide a blue spectrum without violating the null energy condition, and operators for scalar fluctuations that lead to non-conservation of the comoving curvature perturbation on superhorizon scales even in single-clock inflation. In the last part of our work, we also examine the consequences of operators containing more than two spatial derivatives, discussing how they affect the sound speed of tensor fluctuations, and showing that they can mimic some of the interesting effects of symmetry breaking operators, even in scenarios that preserve spatial diffeomorphism invariance.

20 pages. V3: typos corrected and references added. Matches version published in JCAP

References in corpus (12)

• The Effective Field Theory of Inflation
• Effective Field Theory for Inflation
• G-inflation: inflation driven by the Galileon field
• Horava-Lifshitz Cosmology: A Review
• Infrared-modified gravities and massive gravitons
• Resilience of the standard predictions for primordial tensor modes
• Blue Tensor Spectrum from Particle Production during Inflation
• Lorentz Breaking Massive Gravity in Curved Space
• The effective field theory of inflation/dark energy and the Horndeski theory
• How much can we learn about the physics of inflation?
• Inflationary Tensor Perturbations After BICEP
• Blue running of the primordial tensor spectrum

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• Science with the space-based interferometer LISA. IV: Probing inflation with gravitational waves
• Parity breaking signatures from a Chern-Simons coupling during inflation: the case of non-Gaussian gravitational waves
• Inflationary gravitational waves in the effective field theory of modified gravity