Decay Rates of Fixed Planes and Closed-string Tachyons on Unstable Orbifolds

We consider closed-string tachyon condensation in the twisted sectors on the C/Z_{2n+1} \times R^{7,1} orbifold. We calculate the localized energy density in the fixed plane on the orbifold at the one-loop level, and we obtain the decay rate per unit volume of the fixed plane to leading order. We show that the decay rate increases monotonically as a function of n.Comment: 19 pages, 2 figures, LaTeX. v2: typos corrected. v3: section 5 is modified, main results unchanged. v4: published version in Prog. Theor. Phy

The ~U(12)-Classification Scheme, Static U(4)-Spin Symmetry for Light-Quarks and "Exotic" Hadrons

Several years ago we have proposed a manifestly covariant $\tilde{U}(12)_{SF}$-classification scheme of hadrons, which maintains the successful $SU(6)_{SF}\otimes O(3)_{L}$ framework in Non-Relativistic Quark Model and is also reconcilable with the mechanism of Spontaneously-Broken Chiral Symmetry in Relativistic Field Theoretical Models. The essential point here is to notice the overlooked freedom of the $SU(2)_{\rho}$-spin for (confined) light quarks, which leads to existence of new type of ``exotic'' hadrons, called ``chiralons'' and to a selection rule, $\rho_{3}$-line rule, on the spectator quark line. A series of puzzling new hadrons recently observed such as X(3872)-meson family and $\Theta (1540)$ and so on are possibly classified mostly as chiralons.Comment: Nov 2005. 5pp. To appear in the proceedings of the 11th International Conference on Hadron Spectroscopy (Hadron05), Rio de Janeiro, Brazil, 21-26 Aug 200

Application of a coordinate space method for the evaluation of lattice Feynman diagrams in two dimensions

We apply a new coordinate space method for the evaluation of lattice Feynman diagrams suggested by L\"uscher and Weisz to field theories in two dimensions. Our work is to be presented for the theories with massless propagators. The main idea is to deal with the integrals in position space by making use of the recursion relation for the free propagator $G(x)$ which allows to compute the propagator recursively by its values around origin. It turns out that the method is very efficient and gives very precise results. We illustrate the technique by evaluating a number of two- and three-loop diagrams explicitly.Comment: 25 pages, Latex, 2 figures, revised by discussing some points in more detail and correcting a few typo

Dirichlet Boundary Conditions in Generalized Liouville Theory toward a QCD String

We consider bosonic noncritical strings as QCD strings and we present a basic strategy to construct them in the context of Liouville theory. We show that Dirichlet boundary conditions play important roles in generalized Liouville theory. Specifically, they are used to stabilize the classical configuration of strings and also utilized to treat tachyon condensation in our model. We point out that Dirichlet boundary conditions for the Liouville mode maintains Weyl invariance, if an appropriate condition is satisfied, in the background with a (non-linear) dilaton.Comment: 21 pages, Latex. Typos corrected. The final version for Prog.Theor.Phy