Ultra slow-turn inflation

Journal of Cosmology and Astroparticle Physics, vol. 2026, pp. 059

Abstract

Abstract In standard multi-field models, tachyonic isocurvature perturbations generally indicate the presence of an instability. We revisit the stability of some known counterexamples and show that, in a certain class of models that we call ultra slow-turn , an exponentially decreasing turn rate can shut off this potential instability. We argue that the stability of a given model can be correctly inferred by the total entropy perturbation, even if the effective mass squared of the isocurvature perturbation is negative. Several recent supergravity- or string-inspired models such as fibre inflation, SL(2,ℤ) attractors and modular inflation fall into the ultra slow-turn class.

Authors 4

1. Ana Achúcarro Aachen Instituut-Lorentz of Theoretical Physics

   Leiden University

   Affiliation as printed

   Instituut-Lorentz of Theoretical Physics, Universiteit Leiden, 2333 CA Leiden,

2. Perseas Christodoulidis

   Ewha Womans University

   Affiliation as printed

   Department of Science Education, Ewha Womans University, Seoul 03760,

3. Jinn-Ouk Gong

   Ewha Womans University · Asia Pacific Center for Theoretical Physics

   Affiliation as printed

   Asia Pacific Center for Theoretical Physics, Pohang 37673,

   Department of Science Education, Ewha Womans University, Seoul 03760,

4. Oksana Iarygina Aachen Instituut-Lorentz of Theoretical Physics

   Leiden University · Stockholm University · KTH Royal Institute of Technology

   Affiliation as printed

   Instituut-Lorentz of Theoretical Physics, Universiteit Leiden, 2333 CA Leiden,

   Nordita, KTH Royal Institute of Technology and Stockholm University, 10691 Stockholm,

   The Oskar Klein Centre, Stockholm University, 10691 Stockholm,