Testing multifield inflation with halo bias

Multifield models of inflation predict an inequality between the amplitude tau(NL) of the collapsed limit of the four-point correlator of the primordial curvature perturbation and the amplitude f(NL) of the squeezed limit of its three-point correlator. While a convincing detection of non-Gaussianity through the squeezed limit of the three-point correlator would rule out all single-field models, a robust confirmation or disproval of the inequality between tau(NL) and f(NL) would provide crucial information about the validity of multifield models of inflation. In this paper, we discuss to which extent future measurements of the scale dependence of halo bias can test multifield inflationary scenarios. The strong degeneracy between the effect of a non-vanishing f(NL) and tau(NL) on halo bias can be broken by considering multiple tracer populations of the same surveyed volume. If haloes down to 10(13) M(circle dot)h(-1) are resolved in a survey of volume 25 (Gpc(3) h(-3)), then testing multifield models of inflation at the 3 sigma level would require, for instance, a detection of tau(NL) at the level of tau(NL) similar to 10(5) given a measurement of a local bispectrum with amplitude f(NL) similar to 10. However, we find that disproving multifield models of inflation with measurements of the non-Gaussian bias only will be very challenging, unless vertical bar f(NL)vertical bar greater than or similar to 80 and one can achieve a halo mass resolution of similar to 10(10) M-circle dot h(-1).