69 research outputs found

### Impact and Implication of Bi-Large Neutrino Mixings on GUTs

Under the assumptions that 1) the quark/lepton mass matrices take
Froggatt-Nielsen's factorized power form \lambda^{\psi_i+\psi_j} with anomalous
U(1) charges \psi_i, and 2) the U(1) charges \psi_i respect the SU(5) GUT
structure, we show that the quark mass data necessarily implies the large 2-3
mixing in the MNS mixing matrix U_{MNS}. If we further add the data of the mass
squared difference ratio of solar and atmospheric neutrinos, then, it implies
that the 1-2 mixing in U_{MNS} is also large, so explaining the bi-large
mixing. This analysis also gives a prediction that U_{e3}\equiv(U_{\rm
MNS})_{13} should be of order \lambda \sim (0.1 - 0.5).Comment: 8 pages, uses ws-procs9x6.cls, talk at NOON03 (Kanazawa, Feb. 2003

### Unoriented Open-Closed String Field Theory

The string field theory for unoriented open-closed string mixed system is
constructed up to quadratic order based on the joining-splitting type vertices.
The gauge invariance with closed string transformation parameter is proved. The
infinity cancellation mechanism between disk and projective plane amplitudes
plays an essential role for the gauge invariance of the theory.Comment: 40 pages, LaTeX with PTPTeX.sty, 19 eps figure

### Dynamical Symmetry Breaking in an E_6 GUT Model

Dynamical symmetry breaking is studied in an E_6 GUT model of a single
generation of fermions with strong 4-fermi interactions. The effective
potential is analyzed analytically by the help of Michel's conjecture and the
result is confirmed numerically. We find that the E_6 symmetry is spontaneously
broken either to F_4 or to Sp(8) or G_2 or SU(3), depending on which of the
4-fermi coupling constants G_27 and G_351 in the 27/351 channels is stronger.
The possibilities for obtaining other type of breaking patterns are also
discussed.Comment: 29 pages (no figures), phyzzx and tables.tex KUNS-125

### Neutrino Masses in E_6 Unification

We show that the neutrino masses with large mixing between \nu_\mu and
\nu_\tau are naturally reproduced in a supersymmetric E_6 grand unification
model with an anomalous U(1)_X symmetry. We propose a simple scenario which
incorporates a novel mechanism called `E-twisting' by which all the
characteristic features of the fermion mass matrices, not only the
quark/lepton's Dirac masses but also the neutrino's Majorana masses, can be
well reproduced despite all the members in 27 of each generation are assigned a
common U(1)_X charge.Comment: 21 pages, 2 eps figures, v2 (almost published version

### Covariant Approach to the No-ghost Theorem in Massive Gravity

We discuss the no-ghost theorem in the massive gravity in a covariant manner.
Using the BRST formalism and St\"{u}ckelberg fields, we first clarify how the
Boulware-Deser ghost decouples in the massive gravity theory with Fierz-Pauli
mass term. Here we find that the crucial point in the proof is that there is no
higher (time) derivative for the St\"{u}ckelberg `scalar' field. We then
analyze the nonlinear massive gravity proposed by de Rham, Gabadadze and
Tolley, and show that there is no ghost for general admissible backgrounds. In
this process, we find a very nontrivial decoupling limit for general
backgrounds. We end the paper by demonstrating the general results explicitly
in a nontrivial example where there apparently appear higher time derivatives
for St\"{u}ckelberg scalar field, but show that this does not introduce the
ghost into the theory.Comment: 24 page

### Defining the Nambu--Jona-Lasinio Model by Higher Derivative Kinetic Term

Usual treatment of the Nambu--Jona-Lasinio (NJL) model using loop momentum
cutoff suffers from ambiguities in choosing the loop momenta to be cut off and
violation of (external) gauge invariance. We define the NJL model from the
starting Lagrangian level by using a higher derivative fermion kinetic term
with a cutoff parameter $\Lambda$. This definition is free from such
ambiguities and manifestly keeps the chiral symmetry as well as the gauge
invariance. Quantization of this higher derivative system, current operators
and calculational method are discussed in some detail. Calculating the pion
decay constant and $\pi^0\rightarrow 2\gamma$ decay amplitude, we explicitly
demonstrate that the low energy theorem holds. It is observed that the NJL mass
relation $m_\sigma = 2 m_0$ between the $\sigma$ meson and fermion masses no
longer holds in this model. We also present a simplified calculational method
which is valid when the cutoff parameter $\Lambda$ is much larger than the
energy scale of physics.Comment: 31 pages, phyzzx, 3 uuencoded epsf figures, KUNS-126

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