Q-complements on log surfaces

In this paper the log surfaces without \QQ-complement are classified. In particular, they are non-rational always. This result takes off the restriction in the theory of complements and allows one to apply it in the most wide class of log surfaces.Comment: Latex2e, 3 page

Three-body DDˉπD\bar{D}\pi dynamics for the X(3872)

We investigate the role played by the three-body $D\bar{D}\pi$ dynamics on the near-threshold resonance X(3872) charmonium state, which is assumed to be formed by nonperturbative $D\bar D^*$ dynamics. It is demonstrated that, as compared to the naive static-pions approximation, the imaginary parts that originate from the inclusion of dynamical pions reduce substantially the width from the $D\bar{D}\pi$ intermediate state. In particular, for a resonance peaked at 0.5 MeV below the $D^0\bar D^{*0}$ threshold, this contribution to the width is reduced by about a factor of 2, and the effect of the pion dynamics on the width grows as long as the resonance is shifted towards the $D^0\bar{D^0}\pi^0$ threshold. Although the physical width of the $X$ is dominated by inelastic channels, our finding should still be of importance for the $X$ line shapes in the $D\bar{D}\pi$ channel below $D{\bar D}^*$ threshold. For example, in the scattering length approximation, the imaginary part of the scattering length includes effects of all the pion dynamics and does not only stem from the $D^*$ width. Meanwhile, we find that another important quantity for the $X$ phenomenology, the residue at the $X$ pole, is weakly sensitive to dynamical pions. In particular, we find that the binding energy dependence of this quantity from the full calculation is close to that found from a model with pointlike $D\bar D^*$ interactions only, consistent with earlier claims. Coupled-channel effects (inclusion of the charged $D\bar{D}^*$ channel) turn out to have a moderate impact on the results.Comment: 34 pages, 6 figures, version to appear in Phys.Rev.

A remark on collisions of domain walls in a supersymmetric model

The process of collision of two parallel domain walls in a supersymmetric model is studied both in effective Lagrangian approximation and by numerical solving of the exact classical field problem. For small initial velocities we find that the walls interaction looks like elastic reflection with some delay. It is also shown that in such approximation internal parameter of the wall may be considered as a time-dependent dynamical variable.Comment: 6 pages, LaTeX, 3 figures (eps), fig. 2 correcte

Investigation of a0-f0 mixing

We investigate the isospin-violating mixing of the light scalar mesons a0(980) and f0(980) within the unitarized chiral approach. Isospin-violating effects are considered to leading order in the quark mass differences and electromagnetism. In this approach both mesons are generated through meson-meson dynamics. Our results provide a description of the mixing phenomenon within a framework consistent with chiral symmetry and unitarity, where these resonances are not predominantly q q-bar states. Amongst the possible experimental signals, we discuss observable consequences for the reaction J/Psi -> phi pi0 eta in detail. In particular we demonstrate that the effect of a0-f0 mixing is by far the most important isospin-breaking effect in the resonance region and can indeed be extracted from experiment.Comment: 15 pages, 9 figures; discussion extended, title changed, version published in Phys. Rev.