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In a recent paper we proposed a mechanism for a continuous transition betweena contracting Ekpyrotic phase and the Standard Big Bang phase of expansion: thebounce is generated by an S-brane which represents the effects of higher massstring states in the low energy effective field theory. We showed thatgravitational waves on cosmological scales obtain a nearly scale-invariantspectrum. Here, we study the cosmological fluctuations in this setup, assumingthat the S-brane has zero shear. We find a nearly scale-invariant spectrum ofcosmological perturbations with a slight red tilt. The scenario yields twoconsistency relations for cosmological observations, the first one relating thetensor to scalar ratio with the scalar spectral tilt, the second relating thetensor tilt to the scalar tilt. The predicted tensor to scalar ratio is withinthe reach of upcoming CMB observations. The tensor tilt is blue.

Ekpyrotic Cosmology with a Zero-Shear S-Brane