Brane Interactions And The Related Dynamics

We study two aspects of sring/M theory:brane interactions and the related dy-namics. These have been investigated from both the stringy and the effective theory approaches.·Brane InteractionsWe re-study the interacting D0-D8 system, pointing out that the divergent piece of the interaction potential energy density in either NS-NS sector or R-R sector is not something which can be ignored but reflects the D8-brane nature of non-existence as an independent object. Along with this, we have also addressed a few subtle issues regarding the existing two interpretations for the non-vanishing counter-intuitive R-R potential and improved them each by considering the divergence piece of the potential. Further studies show that the persistence of divergence for the potential in either sector in the presence of a flux on the D8-branes indicates that adding a flux/fluxes on the D8-branes doesn't help to improve its nature of existence as an independent object. Furthermore, we resolve a subtle issue regarding the regularization of fermionic zero-modes in the R-R sector when the D8-branes carry an electric flux so that a meaningful result for the potential can be calculated.We also calculate the long-range interaction between two p-branes placed parallel at a separation in diverse dimensions via an effective field theory approach. In particu-lar, we considered cases when the p-branes are 10-dimensional Dp-branes carrying with them a special world-volume non-abelian flux. The interaction so computed for each of such systems gives not only the known facts about the underlying system but also some new evidences which may help us to understand the system better. For example, in the case of (Do, D8) system, in contrast to the previous study, our computations indicated that the so constructed (D0, D8) system may well be a marginal bound state.·Brane DynamicsWe find a family of supergravity solutions, characterized by a few parameters, in typeⅡstring theories, which represents the intersecting non-supersymmetric Dp-branes and nicely interpolates between the corresponding black Dp-branes and the Kaluza-Klein "bubble of nothing" (KK BON) by continuously changing some of these param-eters from one set of values to another. We proposed that this interpolation implies a possible transition from black Dp-branes to stable static bubbles (under certain condi-tions) via the closed string tachyon condensation.We also find other families of supergravity interpolation solutions, i.e., the inter-secting non-supersymmetric D1/D5 configuration or the intersecting non-supersymmetric F/NS5 configuration. Similar consideration are applied to them.