Cosmological constraints on string scale and coupling arising from tachyonic instability

Enqvist, Kari and Jokinen, Asko and Mazumdar, Anupam and Multamaki, Tuomas and Vaihkonen, Antti (2005) Cosmological constraints on string scale and coupling arising from tachyonic instability. Journal of High Energy Physics, 2005 (8): 84. ISSN 1029-8479

Abstract

We demonstrate that string motivated inflation ending via tachyonic instability leaves a detectable imprint on the cosmic microwave background (CMB) radiation by virtue of the excitation of non-Gaussian gravitational fluctuations. The present WMAP bound on non-Gaussianity is shown to constrain the string scale by $M_S/M_P\leq 10^{-4}$ for string coupling $g_{s} M_{P}