The Cobordism Conjecture postulates that the cobordism classes in a consistent theory of quantum gravity should be trivial. Non-vanishing cobordism classes can be made consistent either by breaking or gauging the symmetry, possibly predicting new stringy defects.
In this light, I will discuss the dynamical cobordism induced by the backreaction of a 9-dimensional non-supersymmetric, positive tension domain wall in string theory. Breaking the cobordism symmetry requires a 8-dimensional defect capping off spacetime. I will provide an explicit description of this defect, in terms of a new non-isotropic solution of the dilaton-gravity equations of motion. Regarding gauging, one can use the deep relation between cobordism and K-theory charges to construct tadpole cancellation conditions from bottom-up. I will illustrate how new contributions to such conditions may arise, when considering cobordism and K-theory groups of certain physically relevant backgrounds.
DFA & INFN
