Study of the Change from Walking to Non-Walking Behavior in a Vectorial Gauge Theory as a Function of N_f

Based on recent works [1,2], we present the results of calculations for several physical quantities (meson masses, the S parameter, etc.) in a vectorial gauge theory, as a function of the number of fermions, N_f. Solutions of the Schwinger-Dyson and the Bethe-Salpeter equations with the improved ladder approximation are used for the calculations. We focus on how the values of physical quantities change as one moves from the QCD-like (non-walking) to walking regimes.Comment: 7 pages, 4 figures, to appear in the proceedings of The 2006 International Workshop ``Origin of Mass and Strong Coupling Gauge Theories'' (SCGT 06), Nagoya, Japan, November 21 - 24, 200

More on Electroweak-Skyrmion

We discuss the properties of the topological soliton, or the Electroweak-Skyrmion, in the system of the Standard Model Higgs Lagrangian with addition of general O(p^4) terms. We show that the upper bound on the mass of the Electroweak-Skyrmion is about 10 TeV, which is obtained from currently available experimental constraints on coefficients of O(p^4) terms. The impact on the properties of the Electroweak-Skyrmion due to further modification of the Lagrangian is also discussed, and comments on possible mechanisms for the generation of the Electroweak-Skyrmion in the early Universe as a dark matter are given.Comment: 13 pages, 6 figurew

Non-Abelian strings and domain walls in two Higgs doublet models

Contrary to the standard model that does not admit topologically nontrivial solitons, two Higgs doublet models admit topologically stable vortex strings and domain walls. We numerically confirm the existence of a topological $Z$-string confining fractional $Z$-flux inside. We show that topological strings at $\sin\theta_W = 0$ limit reduce to non-Abelian strings which possess non-Abelian moduli $S^2$ associated with spontaneous breakdown of the $SU(2)$ custodial symmetry. We numerically solve the equations of motion for various parameter choices. It is found that a gauging $U(1)_Y$ always lowers the tension of the $Z$-string while it keeps that of the $W$-string. On the other hand, a deformation of the Higgs potential is either raising or lowering the tensions of the $Z$-string and $W$-string. We numerically obtain an effective potential for the non-Abelian moduli $S^2$ for various parameter deformations under the restriction $\tan\beta=1$. It is the first time to show that there exists a certain parameter region where the topological $W$-string can be the most stable topological excitation, contrary to conventional wisdom of electroweak theories. We also obtain numerical solutions of composites of the string and domain walls in a certain condition.Comment: 37 pages, 15 figures. v2: minor corrections, new references adde