Spontaneous breakdown of the continuous symmetry is studied in the framework of discretized light-front quantization. We consider linear sigma model in 3+1 dimension and show that the careful treatment of zero modes together with the regularization of the theory by introducing NG boson mass leads to the correct description of Nambu-Goldstone phase on the light-front. Recently the light-front (L...

1550-7998=20 Spontaneous Lorentz violation due to a time-dependent expectation value for a massless scalar has been suggested as a method for dynamically generating dark energy. A natural candidate for the scalar is a Goldstone boson arising from the spontaneous breaking of a U 1 symmetry. We investigate the lowenergy effective action for such a Goldstone boson in a general class of models invo...

Mesonic baryon resonance decays are calclulated from constituent quark models along a Poincaré-invariant generalization of the elementary emission model. Covariant results of pionic decay widths are presented for the Goldstone-boson-exchange constituent quark model.

We apply the point form of relativistic quantum mechanics to develop a Poincaré invariant coupled-channel formalism for two-particle systems interacting via one-particle exchange. This approach takes the exchange particle explicitly into account and leads to a generalized eigenvalue equation for the Bakamjian-Thomas type mass operator of the system. The coupling of the exchange particle is deri...

We investigate fluctuation effects of a gap parameter in color-superconductors. The fluctuation modes in the super phase are described by two scalar fields of diquarks. One of them is a Nambu-Goldstone boson and the other is a diquark boson whose mass is about twice of the gap energy (an extended quasi-supersymmetry). In the normal phase the fluctuation becomes a precursory (soft) mode whose am...

The existence of large-scale magnetic fields in galaxies is well established, but there is no accepted mechanism for generating a primordial field which could grow into what is observed today. We discuss a model which attempts to account for the necessary primordial field by invoking a pseudo-Goldstone boson coupled to electromagnetism. The evolution of this boson during inflation generates a m...

We propose a scenario in which dark energy and dark matter are described in a unified manner. The ultralight pseudo-Nambu-Goldstone (pNG) boson, A, naturally explains the observed magnitude of dark energy, while the bosonic supersymmetry partner of the pNG boson, B, can be a dominant component of dark matter. The decay of B into a pair of electron and positron may explain the 511 keV γ ray from...

The appearance of a light composite $0^+$ scalar resonance in nearly conformal gauge-fermion theories motivates further study the low energy structure these theories. To this end, we present nonperturbative lattice calculation s-wave scattering Goldstone bosons maximal-isospin channel SU(3) gauge theory with $N_f=8$ light, degenerate flavors. phase shift is measured both for different values un...

We show that the Nambu-Goldstone(NG) boson restricted on the lightfront(LF) can only exist if we regularize the theory by introducing the explicit breaking NG-boson mass m . The NG-boson zero mode, when integrated over the LF, must have a singular behavior 1=m in the symmetric limit of m ! 0. In the discretized LF quantization this peculiarity is clari ed in terms of the zero-mode constraints i...