Study of open bosonic strings in presence of D-branes

Abstract

The purpose of this memorandum is the study of the open bosonic string theories in the presence of D-branes. Essential results are obtained: - The mass operator is modified leading to a theory with no tachyon. - Coherence between the development of the partition function and the degeneration of states for each mass level. - Apart from the ordinary case that we find and which confirms that the presence of parallel D-branes of the same dimensionality does notmodify the positive anomaly in the central term of the Virasoro algebra. Keywords: D-branes, spectrum, partition fonction, Virasoroalgebra.