This paper is devoted to recent progress made towards the understanding of closed bosonic
and fermionic string perturbation theory, formulated in a Lorentz-covariant way on Euclidean …

We give a comprehensive review of recent developments on using the pure spinor
formalism to compute massless superstring scattering amplitudes at tree level. The main …

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 …

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 give a brief overview of the string landscape and techniques used to construct string
compactifications. We then explain how this motivates the notion of the swampland and …

We derive a formula which expresses any closed string tree amplitude in terms of a sum of
the products of appropriate open string tree amplitudes. This formula is applicable to the …

A general framework for analyzing string propagation on the quotient of a manifold by a
discrete group is presented. The conditions necessary for modular invariance and absence …

We calculate the complete low-energy effective action to quartic order in the bosonic fields
for the heterotic string. We find that, in addition to the term involving Ξ (3) found previously …

A new theory of closed orientable superstrings is constructed as a chiral combination of the
closed D= 26 bosonic and D= 10 fermionic strings. The resulting ten-dimensional theory is …

The zero modes of closed strings on a torus—the torus coordinates plus dual coordinates
conjugate to winding number—parameterize a doubled torus. In closed string field theory …