English

Birefringent Gravitational Waves and the Consistency Check of Inflation

High Energy Physics - Theory 2009-11-10 v1 Astrophysics General Relativity and Quantum Cosmology High Energy Physics - Phenomenology

Abstract

In this work we show that the gravitational Chern-Simons term, aside from being a key ingredient in inflationary baryogenesis, modifies super-horizon gravitational waves produced during inflation. We compute the super-Hubble gravitational power spectrum in the slow-roll approximation and show that its overall amplitude is modified while its spectral index remains unchanged (at leading order in the slow-roll parameters). Then, we calculate the correction to the tensor to scalar ratio, T/S. We find a correction of T/S which is dependent on N\cal{N} (more precisely quadratic in N{\cal N}), the parameter characterizing the amplitude of the Chern-Simons terms. In a stringy embedding of the leptogenesis mechanism, N\cal{N} is the ratio between the Planck scale and the fundamental string scale. Thus, in principle, we provide a direct probe of leptogenesis due to stringy dynamics in the Cosmic Microwave Background (CMB). However, we demonstrate that the corresponding correction of T/S is in fact very small and not observable in the regime where our calculations are valid. To obtain a sizable effect, we argue that a non-linear calculation is necessary.

Keywords

Cite

@article{arxiv.hep-th/0410230,
  title  = {Birefringent Gravitational Waves and the Consistency Check of Inflation},
  author = {Stephon Alexander and Jerome Martin},
  journal= {arXiv preprint arXiv:hep-th/0410230},
  year   = {2009}
}

Comments

9 pages, 1 figure, RevTex