Math teachers have stymied students for hundreds of years by sticking goats in strangely shaped fields. Learn why one grazing goat problem has stumped mathematicians for more than a century. If you’ve ...

In this paper we establish a uniform Harnack inequality for a class of degenerate equations whose prototype is Kolmogorov's equations in $R^3: D_{yy} u - yD_zu - D_tu ...