Cosmological constraints on string scale and coupling arising from tachyonic instability

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 $M_S/M_P\le 10^{-4}$ 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.

12 pages, 2 figures, typo corrected, discussion and references added

References in corpus (3)

• Non-Gaussianity from Preheating
• Non-Gaussianity from Instant and Tachyonic Preheating
• Non-Gaussianity in braneworld and tachyon inflation

Cited by in corpus (8)

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• Primordial Non-Gaussianities of General Multiple Field Inflation
• Large Nongaussianity from Nonlocal Inflation
• Predictions for Nongaussianity from Nonlocal Inflation
• Reheating in supersymmetric high scale inflation
• On the evolution of tachyonic perturbations at super-Hubble scales
• Exciting gauge field and gravitons in a brane-anti-brane annihilation
• Revisiting non-Gaussianity of multiple-field inflation from the field equation