International Journal of Modern Physics A

After a very brief review of twentieth century elementary particle physics, prospects for the next century are discussed. First and most important are technological limits of opportunities; next, the future experimental program, and finally the status of the theory, in particular its limitations as well as its opportunities.

We examine duality transformations of supersymmetric and κ-symmetric Dp-brane actions in a general type IIB supergravity background where in particular the dilaton and the axion are not supposed to be zero or a constant but a general superfield. Due to nonconstant dilaton and axion, we can explicitly show that the dilaton and the axion as well as the two two-form gauge potentials transform as doublets under the SL(2,R) transformation from the point of view of the world volume field theory.

Two-body nonleptonic decays of mesons involving heavy to heavy transitions are discussed in detail. All these decay widths are estimated by the use of spectator model dominance. The form factors for various transitions are calculated in BSW model improved to O(1/m_Q) by comparison with the heavy quark effective theory.

The Higgs sector of the minimal 3-3-1 model with three triplets and one sextet is investigated in detail under the most general lepton-number conserving potential. The mass spectra and multiplet decomposition structure are explicitly given in a systematic order and a transparent way allowing them to be easily checked and used in further investigations. A previous problem that arose from the inconsistent signs of f₂ is also automatically solved.

We discuss some basic properties of the open string on the symmetric product which is supposed to describe the open string field theory in discrete light-cone quantization (DLCQ). We first derive the consistent twisted boundary conditions for Annulus/Möbius/Klein Bottle diagrams and give the explicit form of the corresponding amplitude. They have the interpretation as the long open (or closed) string amplitude but the world sheet topology viewed from the short string and from the long string is in general different. Boundary (cross-cap) states of the short string are classified into three categories, the boundary (cross-cap) states of the long string and the "joint" state which connects two strings. The partition function has the typical structure of the string field theory in DLCQ. Tadpole condition is also analyzed and gives a reasonable gauge group SO(2¹³).

We determine the ν_R Majorana mass matrix from the experimental data on neutrino oscillations in the framework of a see-saw SO(10) model, where we impose the condition (M^R)₃₃=0 to avoid too large fine-tunings in the see-saw formula. We find a class of solutions with the two lowest neutrino masses almost degenerate and the scale of the matrix elements of M^R in the range 10¹¹–10¹² GeV in agreement with Pati–Salam intermediate symmetry. We find also solutions with smaller neutrino masses, for which the scale of M_R depends on the solution to the "solar neutrino problem" and on the value of the component of ν_e along the highest mass eigenstate, U_e3.

The supersymmetric sinh–Gordon model on a half-line with integrable boundary conditions is considered perturbatively to verify conjectured exact reflection factors to one loop order. Propagators for the boson and fermion fields restricted to a half-line contain several novel features and are developed as prerequisites for the calculations.