Relieving string tension by making baby universes in a dynamical string tension braneworld model

Abstract

String tension fundamentally determines the properties of strings; yet its value is often assigned arbitrarily, creating a fine-tuning problem. We describe a mechanism for dynamically generating string tension in a flat or almost flat spacetime, using the ‘modified measures formalism’, which in turn naturally generates a new type of stringy braneworld scenario. Such a scenario allows strings to achieve near infinite tension confining the strings to two very close expanding surfaces, but the infinite tensions also threaten to distort the near-flat embedding spacetime through large back reactions. We argue that this danger can be neutralized via the creation of a baby universe — a growing region of embedding spacetime that divorces from the ambient embedding spacetime, while our universe is still a brane separating two nearly flat spacetimes. The avoidance of a minimum length and a maximum Hagedorn temperature in the context of dynamical string tension generation is also discussed.