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 were discovered by Dai, Leigh and Polchinski , and independently by Hořava in 1989. In 1995, Polchinski identified D-branes with black p-brane solutions of supergravity , a discovery that triggered the Second Superstring Revolution and led to both holographic and M-theory dualities.
The W bosons are named after the w eak force. The physicist Steven Weinberg named the additional particle the "Z particle",  and later gave the explanation that it was the last additional particle needed by the model. The W bosons had already been named, and the Z bosons have z ero electric charge.