D-Branes

Self-contained and pedagogical introduction to key string theory ideas and techniques needed to understand D-branes. In string theory, D-branes are a class of extended objects upon which open strings can end with Dirichlet boundary conditions, after which they are named. D-branes are typically classified by their spatial dimension, which is indicated by a number written after the "D." A "D0-brane" is a single point, a "D1-brane" is a line (sometimes called a "D-string"), a "D2-brane" is a plane, and a "D25-brane" fills the highest-dimensional space considered in "Bosonic string theory." There…