Gaussian estimates for fundamental solutions of higher-order parabolic equations with time-independent coefficients

We study the De Giorgi-Moser-Nash estimates of higher-order parabolic equations in divergence form with complex-valued, measurable, bounded, uniformly elliptic (in the sense of G$\mathring{a}$rding inequality) and time-independent coefficients. We also obtain Gaussian upper bounds and Hölder regularity estimates for the fundamental solutions of this class of parabolic equations.