Ngee-Pong Chang

KINEMATICS AT INFINITE MOMENTUM.

Abstract In this paper we perform a contraction on the Poincare group which leads to a group isomorphic to the Poincare group. By “contracting” the canonical representation of the Poincare generators, we show that this iso-Poincare group describes the kinematics of a system of particles all with νz = 1. We give explicitly the behavior of the pz infinite states under finite iso-Poincare transformations. We also give the corresponding transformation laws under parity and time reversal. As an application, we study a scattering process as viewed by an observer moving with νz = −1. This leads to a very natural justification of the impact parameter representation of S-matrix element. In conclusion, we give some indications on the covariant generalization of the iso-Poincare group.

B-L nonconservation and neutron oscillation

Abstract We present a general discussion of B-L violation in an SU(5) invariant theory, for a single generation of light fermions. We realize the simplest of such mechanism through the 15 Higgs. Its consequences for neutron oscillation are discussed.

Proton stability in an asymptotically free SU(5) theory

Abstract In this note we point out a complication with the study of the mass-dependent low energy renormalization group equation for spontaneously broken gauge theories. We derive a new renormalization group theorem which avoids this complication. This theorem allows for a complete determination of an SU(5) grand unified theory that is asymptotically free. We report on the proton lifetime calculation including mass renormalization effects.

Oscillations of faster than light Majorana neutrinos: A Causal field theory

In this paper, we carry out the canonical quantization of the field theory of an interacting tachyonic Majorana neutrino. We show how micro-causality is preserved in the physical scattering matrix elements between the in and out vacua. The phenomenology of this radical proposal is nevertheless compatible with normal timelike oscillations.

Models of non-abelian orbifolds☆

Abstract Several models of non-abelian orbifolds have been constructed. There are models with three or four families of quarks and leptons, and gauge symmetry SU(3) × SU(2) × SU(2) × U(1) 2 × SU(3)′ × SO(10)′ × U(1)′ or SU(3) × SU(2) × U(1) 3 × SU(4)′ × SO(8)′ × U(1)′.

THE ELUSIVE ν MASS SINCE 1933

We review briefly the history of the νe mass since 1933, and point out how the KATRIN experiment can resolve the mystery of the tachyonic mass indicated by the Mainz-Trotsky experiments.

Endowing the Standard Model with a new r-symmetry

In the Standard Model, there is the single Higgs field, ϕ, which gives rise to constituent quark and lepton masses. The Yukawa coupling is a highly complex set of 3 × 3 matrices, resulting in many textures of quark and lepton masses. In this talk, we propose to transfer the complexity of the Yukawa coupling matrices to a family of Higgs fields, so that the Yukawa coupling itself becomes a simple interaction. In the context of an Enriched Standard Model, we introduce a new r-symmetry in the extended SU(2)L × U(1)Y × U(1)R model and show how a particularly simple scenario results in a near degeneracy of masses in the 126 GeV region, with a hierarchy of heavier masses suggested by the quark and lepton texture mass matrices.

Spacetime quantization of the Braaten-Pisarski-Frenkel-Taylor-Wong action: Spacelike plasmon cut and new phase of the thermal vacuum.

The properties of quark propagation through a hot medium are summarized by the Braaten-Pisarski-Frenkel-Taylor-Wong effective action. The fermion thermal propagator shows a pseudo-Lorentz-invariant particle pole as well as a spacelike cut. In an earlier paper, we performed the explicit quantization of the action in momentum space, and showed how a canonical Dirac field of mass [ital T][prime] arises. In this paper, we perform the quantization in coordinate space. In the process, we relate the spacelike plasmon cut in the propagator to the homogeneous solutions of the local equaton of motion for auxiliary fields. Our quantization shows how the spacelike cut produces a 90[degree] phase factor in the thermal vacuum at high [ital T]. This phase factor is responsible for the vanishing of [l angle][bar [psi]][psi][r angle] at high [ital T].

Instantons with fractional topological charge

Abstract We introduce and discuss the properties of multivalent gauges for Yang-Mills fields, and demonstrate the existence of instantons with fractional topological charges in such gauges.

Impact parametrisation and daughter trajectories

Abstract Using the impact-parameter representation suggested by a study of kinematics at infinite momentum, we discuss the analytic properties of the direct s -channel partial-wave amplitude and have found that a simple b =0 behaviour of the impact-parameter amplitude leads to an infinite number of poles in l -plane.