Universal upper bound on the inflationary energy scale from the trans-Planckian censorship conjecture
Abstract
We study the constraint on the inflationary energy scale from the recently proposed trans-Planckian censorship conjecture (TCC). We find a universal upper bound on the inflationary Hubble expansion rate Hinf which is solely determined by the reheating temperature Trh: Hinf/MPl≲T0/Trh, where T0 is the photon temperature today. The upper limit can be saturated by a postinflationary oscillatory stage with the critical equation-of-state parameter w ≈-1 /3 , or by an inflation model with multiple stages. In the lowest reheating temperature required for big bang nucleosynthesis, the upper bound on the tensor-to-scalar ratio r at the CMB scales is r ≲10-8, which can be realized in many string-inspired inflation models.
- Publication:
-
Physical Review D
- Pub Date:
- July 2020
- DOI:
- 10.1103/PhysRevD.102.021301
- arXiv:
- arXiv:1910.02979
- Bibcode:
- 2020PhRvD.102b1301M
- Keywords:
-
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- General Relativity and Quantum Cosmology;
- High Energy Physics - Theory
- E-Print:
- 7 pages, 4 figures