Motivated by conceptual problems in quantum theories of gravity, the gravitational eikonal
approach, inspired by its electromagnetic predecessor, has been successfully applied to the …

A generalization of Einstein's gravitational theory is discussed in which the spin of matter as
well as its mass plays a dynamical role. The spin of matter couples to a non-Riemannian …

Twenty-five years ago, Michael Green, John Schwarz, and Edward Witten wrote two
volumes on string theory. Published during a period of rapid progress in this subject, these …

This review describes the duality between color and kinematics and its applications, with the
aim of gaining a deeper understanding of the perturbative structure of gauge and gravity …

String Theory comprises two volumes which give a comprehensive and pedagogic account
of the subject. Volume 1, first published in 1998, provides a thorough introduction to the …

Black hole solutions to Einstein's equations are examined in asymptotically flat N+ 1
dimensional space-times. First generalizations of Schwarzschild and Reissner-Nordstrøm …

We provide an overview of the string landscape and the Swampland program. Our review of
the string landscape covers the worldsheet and spacetime perspectives, including vacua …

String theory is one of the most exciting and challenging areas of modern theoretical
physics. This book guides the reader from the basics of string theory to recent developments …

We formulate the propagation of strings in background fields, including the effects of metric,
antisymmetric tensor, and dilaton expectation values, as well as gauge field backgrounds in …

The compatibility between the presence of curvature squared terms and the absence of
ghost particles in the low energy limits of string theories is established. The lagrangian ʃ√ …