Can a nonsingular bounce reproduce all observed primordial spectra?

In plain words

Instead of inflation, the universe might have contracted and then bounced into expansion. Such models must avoid unstable or unphysical fields at the bounce while matching observations.

Precise statement

Construct a geodesically complete bouncing or ekpyrotic cosmology, free of ghost and gradient instabilities and under effective-field-theory control through the bounce, that predicts $n_s = 0.974 \pm 0.003$, $r < 0.036$ and $\mid f_{\mathrm{NL}}^{\mathrm{local}}\mid < 10$. Answer yes with an explicit model, or no with a no-go theorem for a defined class.

What would settle it

An explicit stable model with computed spectra, or a no-go theorem covering scalar-tensor bounces.

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