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Title: Can a nonsingular bounce reproduce all observed primordial spectra?
Plain: 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: 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.
Settled by: An explicit stable model with computed spectra, or a no-go theorem covering scalar-tensor bounces.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: open
Status note: (empty)
Posed since: (empty)