Why General Theory of Relativity Allows the Existence of Only Extremal Black Holes

Abstract

Supersymmetric String theories find occurrences of extremal Black Holes with gravitational mass M=Q where Q is the charge (G=c=1). Thus, for the chargeless cases, they predict M=0. We show that General Theory of Relativity, too, demands a unique BH mass M=0. And we do this by considering the problem from various angles, both mathematically and physically. Our analysis may be understandable even to the readers not having sufficient background in GTR. Physically, this M=0 result means that, continued gravitational collapse indeed continues for infinite proper time as the system hopelessly tries to radiate its entire original mass energy to attain the lowest energy state M=0. Since no event horizon is formed, the problem of loss of information associated with creation of finite mass BHs or their evaporation ceases to exist.