We set up the effective field theories which describe the SO(5)-invariant picture of the high-T c cuprates in various regimes. We use these to get quantitative conclusions concerning the size of SO(5)-breaking effects. We consider two applications in detail: (i) the thermodynamic free energy, which describe the phase diagram and critical behaviour, and (ii) the Lagrangian governing the interact...

We study the stability of the pentaquarks uuddQ, uudsQ and udssQ (Q = c, b, or t) of positive parity in a constituent quark model based on Goldstone boson exchange interaction between quarks. The pentaquark parity is the antiquark parity times that of a quark excited to a p-shell. We show that the Goldstone boson exchange interaction favors these pentaquarks much more than the negative parity o...

In certain mild extensions of the standard model, spin-independent long range forces can arise by exchange of two very light pseudoscalar spin-0 bosons. In particular, we have in mind models in which these bosons do not have direct tree level couplings to ordinary fermions. Using the dispersion theoretical method, we find a 1/r behavior of the potential for the exchange of very light pseudoscal...

Models of strong WW scattering in the s-wave can be represented in a gauge invariant fashion by defining an effective scalar propagator that represents the strong scattering dynamics. The σ(qq → qqWW ) signal may then be computed in U-gauge from the complete set of tree amplitudes, just as in the standard model, without using the effective W approximation (EWA). The U-gauge “transcription” has ...

A complete characterization of all the possible effective interactions up to dimension 5 of the top and bottom quarks with the electroweak gauge bosons have been made within the context of the chiral Lagrangian. We show that the anomalous dimension 5 operators (19 in total) can contribute to the leading energy power (E 3 for fermion pairs with same sign helicities and E 2 for opposite sign heli...

We study the quantum phase transition occurring in an infinite homogeneous system of spin 1/2 fermions in a non-relativistic context. As an example we consider neutrons interacting through a simple spin-spin Heisenberg force. The two critical values of the coupling strength — signaling the onset into the system of a finite magnetization and of the total magnetization, respectively — are found a...

Recently, Spielman et al have found a new type of Goldstone boson in quantum Hall effect in bilayers. The Goldstone boson is accompanied with a phase transition or broken symmetry. In the vacuum state if there is a broken symmetry, then a massless particle is emitted. Spielman et al have discovered such a quasiparticle. However, it remains to be proved that there is a phase transition associate...

Neutrino decay in the minimal seesaw model containing three right handed neutrinos and a complex SU(2)× U(1) singlet Higgs in addition to the standard model fields is considered. A global horizontal symmetry U(1)H is imposed, which on spontaneous breaking gives rise to a Goldstone boson. This symmetry is chosen in a way that makes a) the contribution of heavy (≤ MeV) majorana neutrinos to the n...

The experimental results of the past decade indicate that the chiral Lagrangian describing EWSB works to one loop accuracy and irrelevant operators (such as |Dω|, where ω are the Goldstone bosons eaten by W and Z) are suppressed by a scale Λ ≫ 1 TeV. This strongly indicates perturbative physics at 1 TeV and a physical Higgs boson H = (h + v)ω. However, this linear sigma model is unstable to qua...

The pseudo-Goldstone boson mechanism for the “doublet-triplet splitting” problem of the grand unified theory can be naturally implemented in the scenario with extra dimensions and branes. The two SU(6) global symmetries of the Higgs sector are located on two separate branes while the SU(6) gauge symmetry is in the bulk. After including several vector-like fields in the bulk, and allowing the mo...