Fritzsch-Stech model in SO(10)

Abstract

The combined Fritzsch-Stech model for quarks is consistent with our present knowledge of quark masses and mixing angles. A possible way to extend it to leptons-by using an SOilO) framework-has been suggested by Bottino, Kim, Nishiura, and Sze. We investigate this model further and find some new features. It is first noted that the allowed quark masses are somewhat sensitive to the experimental uncertainties in the input parameters. This is carefully analyzed and we find that the original Stech Ansatz for the hadron sector is consistent. However, if the top-quark mass is greater than about 45 GeV, this Ansatz must be slightly modified. It is found that in a model of the present type the seesaw mechanism for neutrino masses may be drastically modified. This occurs because in SO(10) it is likely that the matrix of heavy "right-handed" neutrinos is close to a singular matrix. This feature is analyzed both analytically and numerically. Various patterns involving two extremely light neutrinos and one intermediate-mass (order of several MeV) neutrino which may arise are compared with experiment. More orthodox and perhaps more probable patterns for neutrino masses are also discussed. The lepton-mixing matrices are predicted and the results support recent explanations of the solar-neutrino paradox. -FRITZSCH-STECH MODEL IN SO( 10) 283

Elementary excitations in dimerized and frustrated Heisenberg chains

“…Finally we discuss the case of (V O) 2 P 2 O 7 -a spin chain compound whose magnetic properties have given rise to controversial interpretations. This compound has been initially considered as an ideal realization of a twoleg antiferromagnetic Heisenberg spin ladder [43]. Subsequently, however, it has been shown that the susceptibility data on polycristalline material could be well fitted by either a ladder or an alternating chain model [44].…”

Coexistence of double alternating antiferromagnetic chains in(VO)2P2Kikuchi1, Motoya2, Yamauchi3 et al. 1999Phys. Rev. B

“…Vanadyl pyrophosphate (VO) 2 P 2 O 7 is a gapped antiferromagnet with spin 1/2 and had long been known as a good model compound of a two-leg antiferromagnetic Heisenberg spin ladder. [1][2][3] Recently, dispersion of the magnetic excitations was measured using the inelastic neutron-scattering technique and is found to be inconsistent with a simple ladder model. 4 Although an alternating Heisenberg antiferromagnetic chain is proposed as an alternative magnetic model of (VO) 2 P 2 O 7 , the suggested direction of the chain is not readily known from the crystal structure and the excitation spectrum is not fully compatible with a simple alternating spin chain.…”

Phase diagram of magnetic ladders constructed from a composite-spin model

“…The recent discovery of several families of new materials, [1][2][3] such as (VO) 2 P 2 O 7 , Sr n−1 Cu n O 2n−1 (n = 2, 3, . .…”