Constraints on Single-Field Inflation from the BOSS Galaxy Survey
  Non-local primordial non-Gaussianity (NLPNG) is a smoking gun of interactions
in single-field inflationary models, and can be written as a combination of the
equilateral and orthogonal templates. We present the first constraints on these
from the redshift-space galaxy power spectra and bispectra of the Baryon
Oscillation Spectroscopic Survey (BOSS) data. These are the first such
measurements independent of the cosmic microwave background fluctuations. We
perform a consistent analysis that includes all necessary nonlinear corrections
generated by NLPNG, and vary all relevant cosmological and nuisance parameters
in a global fit to the data. Our conservative analysis yields joint limits on
the amplitudes of the equilateral and orthogonal shapes, $f_{\rm NL}^{\rm
equil}=940\pm 600$, $f_{\rm NL}^{\rm ortho}= -170\pm 170$ (both at 68\% CL).
These can be used to derive constraints on coefficients of the effective
single-field inflationary Lagrangian; in particular, we find that the sound
speed of inflaton fluctuations has the bound $c_s\geq 0.013$ at 95\% CL. Fixing
the quadratic galaxy bias and cosmological parameters, the constraints can be
tightened to $f_{\rm NL}^{\rm equil}=260\pm 300$, $f_{\rm NL}^{\rm ortho}=
-23\pm 120$ (68\% CL).
