The challenge for single field inflation with BICEP2 result

• DOI: 10.1016/j.physletb.2014.05.018
• Publication Date: 2014-05-16T00:01:19Z
• Authors: Qing Gao; Yungui Gong
• Keywords: High Energy Physics - Theory; Nuclear and High Energy Physics; Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th); 0103 physical sciences; FOS: Physical sciences; General Relativity and Quantum Cosmology (gr-qc); 01 natural sciences; General Relativity and Quantum Cosmology; Astrophysics - Cosmology and Nongalactic Astrophysics

The detection of B-mode power spectrum by the BICEP2 collaboration constrains the tensor-to-scalar ratio $r=0.20^{+0.07}_{-0.05}$ for the lensed-$��$CDM model. The consistency of this big value with the {\em Planck} results requires a large running of the spectral index. The large values of the tensor-to-scalar ratio and the running of the spectral index put a challenge to single field inflation. For the chaotic inflation, the larger the value of the tensor-to-scalar ratio is, the smaller the value of the running of the spectral index is. For the natural inflation, the absolute value of the running of the spectral index has an upper limit.<br/>4 figures, 3 pages, some references added, PLB in press<br/>