Heterotic black holes in duality-invariant formalism

A bstract We consider the effective theory of heterotic strings in two spacetime dimensions, in a double field theory-inspired formalism, manifestly consistent with T -duality in string theory. Restricting the gauge group to a single U(1), we study the charged black hole solution and perform a precise analysis of the properties of the dual geometry with the O(1, 2; ℝ )-valued generalized metric. We comment on some aspects related to singularities and gauge dependence. We show that the classification program for higher-derivative corrections can also be applied to the heterotic case. We further elucidate how a previously proposed solution to the equations of motion, parametrized in a manner fully non-perturbative in α ′ , can be extended to the scenario with r abelian fields and the corresponding O(1, 1 + r ; ℝ ) symmetry. We discuss some novel features of the solution for charged black holes.