Lumps and p branes in open string field theory

We describe numerical methods for constructing lump solutions in open strin g field theory. According to Sen, these lumps represent lower dimensional D p branes and numerical evaluation of their energy can be compared with the expected value for the tension. We take particular care of all higher deriv ative terms inherent in Witten's version of open string field theory. The i mportance of these terms for off shell phenomena is argued in the text. Det ailed numerical calculations done for the case of general p brane show very good agreement with Sen's conjectured value. This gives credence to the co njecture itself and establishes further the usefulness of Witten's version of SFT. (C) 2000 Elsevier Science B.V. All rights reserved.