Blow-up estimates and a priori bounds for the positive solutions of a class of superlinear indefinite elliptic problems

In this paper we find out some new blow-up estimates for the positive explosive solutions of a paradigmatic class of elliptic boundary value problems of superlinear indefinite type. These estimates are obtained by combining the scaling technique of Guidas-Spruck together with a generalized De Giorgi-Moser weak Harnack inequality found, very recently, by Sirakov. In a further step, based on a comparison result of Amann and L\'opez-G\'omez, we will show how these bounds provide us with some sharp a priori estimates for the classical positive solutions of a wide variety of superlinear indefinite problems. It turns out that this is the first general result where the decay rates of the potential in front of the nonlinearity $a(x)$ do not play any role for getting a priori bounds for the positive solutions when $N\geq 3$.