arXiv subjects
Publications and source records attributed to HoSeong La.
It is proposed that the energy-momentum expectation values of flavor states should be identified with the missing energy-momentum of neutrino processes so that the conservation of energy-momentum can be strictly imposed. It is also observed that there is a plausible condition to express neutrino mixing angles in terms of neutrino masses without invoking symmetries.
Cyclic symmetry $C_N$ is gauged in such a way that the local parametrization is provided by a Lie group: matter fields are in irreducible representations of $C_N$ while gauge fields are in the adjoint representation of a Lie group, hence "hybrid". Allowed simple Lie groups are only SO(2) for $N=2$, SU(3) for $N=3$, and SU(2) for all $N$. The implication of the local discrete symmetry $C_N$ is evident as the ratio of the coupling constant to the usual gauge theory one of the parametrization Lie group is given by that of the length between any two vertices of a regular N-polygon to the radius of the circumcircle: $2\sin(nπ/N),\ n\in {\mathbb Z}_N$.
We estimate the PMNS (Pontecorvo-Maki-Nakagawa-Sakata) matrix in terms of neutrino and charged lepton mixing given as $U_{\rm PMNS}=V_{\rm lep}^\dagger(\tildeθ_{13}) U_ν(\tildeθ_{23}, \tildeθ_{12})$, based on a new (emergent) global lepton flavor symmetry. The neutrino and charged lepton mass matrices have simple textures. The resulting $U_{\rm PMNS}$ gives excellent agreement with experimental data (including $|U_{e3}|\simeq 0.16$).
The lepton mixing angles of the PMNS matrix are predicted based on the lepton flavor symmetry of a finite group $C_2\times D_3$, where the cyclic group $C_2$ acts on the charged lepton mass terms and the dihedral group $D_3$ on the neutrino ones. All three mixing angles of the PMNS matrix are given in terms of just one parameter, the charged lepton mixing angle, and fit extremely well to the observed values. In particular, the smallness of $θ_{13}$ is explained in terms of the smallness of the muon-to-tau mass ratio.
The Standard Model is extended minimally with a new flavor-violating family symmetry ${\rm U(1)}_λ$, which acts only on leptons including the right-handed neutrinos. The model is anomaly free with family-dependent ${\rm U(1)}_λ$ charges, and consistent with the observed neutrino mixing angles. It predicts charged lepton flavor-violating processes mediated by a new gauge boson. Under certain conditions, the smallness of $θ_{13}$ of neutrino mixing can be justified in terms of the muon-to-tau mass ratio, at the same time explaining the electron-to-tau large mass hierarchy.
It is shown that perturbative reheating can reach a sufficiently high temperature with small or negligible inflaton decay rate provided that the inflaton potential becomes negative after inflation. In our model, inflaton and dark energy field are two independent scalar fields, and, depending on the mass of the inflaton and its coupling to matter fields, there is a possibility that the remaining inflaton after reheating can become a dark matter candidate.
A new gauge force that acts exclusively on neutrinos is proposed. This new force violates neutrino flavors while masses are diagonal, potentially opening a door for a new field theoretical treatment of the neutrino oscillation. The basic idea and a framework are presented.
Chiral Color is extended by incorporating Technicolor, which induces dynamical breaking of the Electroweak symmetry as well as Chiral Color to Quantum Chromodynamics. Gauge anomalies are cancelled by introducing two generations of technifermions, and the fourth generation of quarks and leptons is required. Each technifermion generation is coupled to only two Standard Model generations by the Yukawa interaction. Various phenomenological implications are explained.
From the point of view of tunneling, the physical meaning of the Davies critical point of a second order phase transition in the black hole thermodynamics is clarified. At the critical point, the nonthermal contribution vanishes so that the black hole radiation is entirely thermal. It separates two phases: one with radiation enhanced by the nonthermal contribution, the other suppressed by the nonthermal contribution. We show this in both charged and rotating black holes. The phase transition is also analyzed in the cases in which emissions of charges and angular momenta are incorporated.
The spontaneous symmetry breaking of a local chiral symmetry to its diagonal vector symmetry naturally realizes a complete geometrical structure more general than that of Yang-Mills (YM) theory, rather similar to that of gravity. A good example is the Quantum Chromodynamics (QCD) with respect to the Chiral Color model. Also, a new anomaly-free particle content for a Chiral Color model is introduced: the Chiral Color can be realized without introducing whole new generations of quarks and leptons, but by simply enlarging each generation with new exotic fermions.
Generalizing the geometry of the gauge covariant variables in Yang-Mills theory proposed by Johnson and Haagensen, the 4-d geometry associated with a monopole is defined for SU(2). There are three relevant geometries: AdS$_2\times S^2$, $R^2\times S^2$ and $H_+\times S^2$, depending on the asymptotic behavior of the torsion. Using this geometry, the Wilson loop average is computed {\it à la} Nambu-Goto action. In case of AdS$_2\times S^2$, it satisfies the area law.
We propose a systematic way of introducing the (nongravitational) low energy dilaton and a scheme for spontaneous breaking of scale symmetry (SBSS) is explained.
The supersymmetric generalization of dilatations in the presence of the dilaton is defined. This is done by defining the supersymmetric dilaton geometry which is motivated by the supersymmetric volume preserving diffeomorphisms. The resulting model is classical superconformal field theory with an additional dilaton-axion supermultiplet coupled to the supersymmetric gauge theory, where the dilaton-axion couplings are nonrenormalizable. The possibility of spontaneous scale symmetry breaking is investigated in this context. There are three different types of vacua with broken scale symmetry depending on the details of the dilaton sector: unbroken supersymmetry, spontaneously broken supersymmetry and softly broken supersymmetry. If the scale symmetry is broken in the bosonic vacuum, then the Poincaré supersymmetry must be broken at the same time. If the scale symmetry is broken in the fermionic vacuum but the bosonic vacuum remains invariant, then the Poincaré supersymmetry can be preserved as long as the R-symmetry breaking is specifically related to the scale symmetry breaking.
Dilatation, i.e. scale, symmetry in the presence of the dilaton in Minkowski space is derived from diffeomorphism symmetry in curved spacetime, incorporating the volume-preserving diffeomorphisms. The conditions for scale invariance are derived and their relation to conformal invariance is examined. In the presence of the dilaton scale invariance automatically guarantees conformal invariance due to diffeomorphism symmetry. Low energy scale-invariant phenomenological Lagrangians are derived in terms of dilaton-dressed fields, which are identified as the fields satisfying the usual scaling properties. The notion of spontaneous scale symmetry breaking is defined in the presence of the dilaton. In this context, possible phenomenological implications are advocated and by computing the dilaton mass the idea of PCDC (partially conserved dilatation current) is further explored.
Considering the linearized gravity with matter fields, the effective potential of the ``conformal dilaton'' in the string frame is generated semiclassically by one-loop contribution of heavy matter fields. This in turn generates a nontrivial potential for the physical dilaton in the Einstein frame with the trace of the graviton in the Einstein frame gauged away. The remaining manifest local spacetime symmetry is only the volume preserving diffeomorphism symmetry. The consistency of this procedure is examined and the possibility of spontaneous diffeomorphism symmetry breaking is suggested.
Area preserving diffeomorphisms of a 2-d compact Riemannian manifold with or without boundary are studied. We find two classes of decompositions of a Riemannian metric, namely, h- and g-decomposition, that help to formulate a gravitational theory which is area preserving diffeomorphism (SDiff$M$-) invariant but not necessarily diffeomorphism invariant. The general covariance of equations of motion of such a theory can be achieved by incorporating proper Weyl rescaling. The h-decomposition makes the conformal factor of a metric SDiff$M$-invariant and the rest of the metric invariant under conformal diffeomorphisms, whilst the g-decomposition makes the conformal factor a SDiff$M$ scalar and the rest a SDiff$M$ tensor. Using these, we reformulate Liouville gravity in SDiff$M$ invariant way. In this context we also further clarify the dual formulation of Liouville gravity introduced by the author before, in which the affine spin connection is dual to the Liouville field.
A model in which the massive dilaton is introduced by minimally extending the two dimensional topological gravity is studied semi-classically. The theory is no longer topological because of the explicit Weyl scale symmetry breaking. Due to the dilaton the semiclassical stress-energy tensor gets renormalized and it is shown how the gravitational background coupled to the the dilaton depends on the dilaton mass as well as the renormalization mass scale, but not on the Newton's constant.
In the standard model with two Higgs doublets it is shown that the existence of the electroweak Z-string in general requires the same characteristic length for the two Higgs fields as well as a specific ratio of the two Higgs vacuum expectation values, i.e. $\tanβ$. This ratio can be determined in terms of the couplings in the Higgs potential. Some remarks on the supersymmetric case are given. \noindent (Talk presented at SUSY '93, March 29-April 1st, Northeastern University, Boston, MA 02115, USA.)