Special Physics Seminar

String Theory and the Weak Gravity Conjecture

Ben Heidenreich

Harvard University

String theory is the only known candidate for a consistent theory of quantum gravity, yet it is notorious for making no testable predictions. I explain why such predictions are difficult to obtain, and describe in detail a recent approach to this problem known as the “Weak Gravity Conjecture.” This conjecture posits that all black holes are quantum mechanically unstable and decay via Hawking radiation. It has important and potentially observable consequences for the spectrum of charged particles in our universe, as well as implications for cosmic inflation, disfavoring scenarios where observable primordial gravitational waves are generated. A stronger form of this conjecture appears to hold in many string theory examples, and may be a universal feature of quantum gravity.