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Cosmological constraints on string scale and coupling arising from tachyonic instability

Kari Enqvist·Asko Jokinen·Anupam Mazumdar·Tuomas Multamaki·Antti Vaihkonen
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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 $g_{s}<0.1$, hence improving the existing bounds. If tachyon fluctuations during inflation are not negligible, we find the stringent constraint $g_s\sim 10^{-9}$ for $M_{S}/M_{P}<10^{-3}$. This case may soon be ruled out by the forthcoming CMB non-Gaussinianity bounds.

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Kari Enqvist, Asko Jokinen, Anupam Mazumdar, Tuomas Multamaki, Antti Vaihkonen. 2005-03-18. Cosmological constraints on string scale and coupling arising from tachyonic instability. https://doi.org/10.1088/1126-6708%2F2005%2F08%2F084

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