Z1/Z2 defects in 4H-SiC

First-principles calculations are carried out on models for the Z(1)/Z(2) defects in 4H-SiC which are found in as-grown and irradiated n-type material. We show that an interstitial-nitrogen-interstitial-carbon defect is exceptionally thermally stable, bistable, and has negative-U character with donor and acceptor levels close to those attributed to the defect.     

Flavour-changing Z decays

We compute neutral Higgs and Z⁰-boson couplings to quarks in a model with three quark-lepton families and one mirror family. Mixing between ordinary and mirrorquarks leads to flavour-changing couplings which are negligible for the known quarks. However, t-quark couplings are sizeable and the branching ratio for the decay can be as large as 10⁻⁴.     

Z charmoniumlike mesons

A brief review of the experimental situation concerning the electrically charged charmoniumlike meson candidates, Z^-, is presented.     

The structure of the Z 1 Z 2 → l + l − Z 1 Z 2 amplitude process outside the born approximation framework

Resummation of the perturbative series for the amplitude of lepton pair production in nucleus-nucleus collisions is performed based on the Watson theorem and the hypothesis of infrared stability. An explicit expression for this amplitude is obtained, which is valid to within terms of the ninth order in the fine structure constant.     

High-intensity-laser-driven Z pinches

Experiments were performed in which ultrahigh intensity laser pulses (I>5 x 10(19) W cm(-2)) were used to irradiate thin wire targets. It was observed that such interactions generate a large number of relativistic electrons which escape the target and induce multimega ampere return currents within the wire. MHD instabilities can subsequently be observed in the pinching plasma along with field emission of electrons from nearby objects. Coherent optical transition radiation from adjacent objects was also observed.     

Ternary Z2 × Z3 Graded Algebras and Ternary Dirac Equation

The wave equation generalizing the Dirac operator to the Z₃-graded case is introduced, whose diagonalization leads to a sixth-order equation. It intertwines not only quark and anti-quark state as well as the u and d quarks, but also the three colors, and is therefore invariant under the product group Z₂ × Z₂ × Z₃. The solutions of this equation cannot propagate because their exponents always contain non-oscillating real damping factor. We show how certain cubic products can propagate nevertheless. The model suggests the origin of the color SU(3) symmetry and of the SU(2) × U(1) that arise automatically in this model, leading to the full bosonic gauge sector of the Standard Model.

     

Z n-graded differential calculus

We investigate the properties of differential algebras generated by an operator d satisfying the property d ^N = 0 instead of d ² = 0 as in the usual case. The commutation relations for the generalized differentials ensuring the desired property can be put into the cyclic form a ₁ a ₂ a ₃...a _N = q a _N a ₁ a ₂...a _N–1, where q is a primitive N-th root of unity.Examples of realizations of such differential algebras are given, either in the space of Z _N-graded N × N matrix algebras, or as generalized differential calculus on manifolds. A generalization of gauge theories based on such differential calculus is briefly discussed.     

Sequential W and Z bosons

We present and discuss a class of electroweak gauge models where the low-energy phenomenology is naturally identical to that of the standard model, but which allows for the existence of an arbitrary number of weak gauge bosons which have nontrivial couplings to the known fermions. The lightest W and Z in these models must be lighter than the W and Z of the standard model.     

Configuration of Z2 strings

Vachaspati and Vilenkin's numerical simulation of the configuration of strings produced at a U(1)-breaking phase transition is extended to the Z₂ strings appearing in the breaking of SO(3). The results are similar, but the overall proportion of closed loops is only about a third as large. This may have important implications for the evolution of cosmic strings.     

Charged Bottomonium-Like Structures Z b (10610) and Z b (10650)

The observation of two charged bottomonium-like structures Z _b (10610) and Z _b (10650) has stimulated extensive studies of the properties of Z _b (10610) and Z _b (10650). In this talk, we briefly introduce the research status of Z _b (10610) and Z _b (10650) combined with our theoretical progress.