  A variable speed of light (VSL) cosmology is described in which the causal
mechanism of generating primordial perturbations is achieved by varying the
speed of light in a primordial epoch. This yields an alternative to inflation
for explaining the formation of the cosmic microwave background (CMB) and the
large scale structure (LSS) of the universe. The initial value horizon and
flatness problems in cosmology are solved. The model predicts primordial scalar
and tensor fluctuation spectral indices $n_s=0.96$ and $n_t=- 0.04$,
respectively. We make use of the $\delta{\cal N}$ formalism to identify
signatures of primordial nonlinear fluctuations, and this allows the VSL model
to be distinguished from inflationary models. In particular, we find that the
parameter $f_{\rm NL}=5$ in the variable speed of light cosmology. The value of
the parameter $g_{\rm NL}$ evolves during the primordial era and shows a
running behavior.
