3,946 research outputs found
Correlated random fields in dielectric and spin glasses
Both orientational glasses and dipolar glasses possess an intrinsic random
field, coming from the volume difference between impurity and host ions. We
show this suppresses the glass transition, causing instead a crossover to the
low phase. Moreover the random field is correlated with the inter-impurity
interactions, and has a broad distribution. This leads to a peculiar variant of
the Imry-Ma mechanism, with 'domains' of impurities oriented by a few frozen
pairs. These domains are small: predictions of domain size are given for
specific systems, and their possible experimental verification is outlined. In
magnetic glasses in zero field the glass transition survives, because the
random fields are disallowed by time-reversal symmetry; applying a magnetic
field then generates random fields, and suppresses the spin glass transition.Comment: minor modifications, final versio
Supersymmetric Higgs Triplets and Bilinear R-Parity Nonconservation
The supersymmetric standard model of particle interactions is extended to
include two Higgs triplet superfields at the TeV scale, carrying two units of
lepton number. Realistic tree-level Majorana neutrino masses are obtained in
the presence of soft, i.e. bilinear, R-parity nonconservation.Comment: 5 pages, no figur
Toy model for two chiral nonets
Motivated by the possibility that nonets of scalar mesons might be described
as mixtures of "two quark" and "four quark" components, we further study a toy
model in which corresponding chiral nonets (containing also the pseudoscalar
partners) interact with each other. Although the "two quark" and "four quark"
chiral fields transform identically under SU(3) SU(3)
transformations they transform differently under the U(1) transformation
which essentially counts total (quark + antiquark) content of the mesons. To
implement this we formulate an effective Lagrangian which mocks up the U(1)
behavior of the underlying QCD. We derive generating equations which yield Ward
identity type relations based only on the assumed symmetry structure. This is
applied to the mass spectrum of the low lying pseudoscalars and scalars. as
well as their "excitations". Assuming isotopic spin invariance, it is possible
to disentangle the amount of"two quark" vs."four quark" content in the
pseudoscalar type states and in the scalar type states.
It is found that a small "four quark" content in the lightest pseudoscalars is
consistent with a large "four quark" content in the lightest of the scalar
mesons. The present toy model also allows one to easily estimate the
strength of a "four quark" vacuum condensate. There seems to be a rich and
interesting structure.Comment: Numerical results updated, typos corrected, references update
Is Weak Pseudo-Hermiticity Weaker than Pseudo-Hermiticity?
For a weakly pseudo-Hermitian linear operator, we give a spectral condition
that ensures its pseudo-Hermiticity. This condition is always satisfied
whenever the operator acts in a finite-dimensional Hilbert space. Hence weak
pseudo-Hermiticity and pseudo-Hermiticity are equivalent in finite-dimensions.
This equivalence extends to a much larger class of operators. Quantum systems
whose Hamiltonian is selected from among these operators correspond to
pseudo-Hermitian quantum systems possessing certain symmetries.Comment: published version, 10 page
Double Threefold Degeneracies for Active and Sterile Neutrinos
We explore the possibility that the 3 active (doublet) neutrinos have nearly
degenerate masses which are split only by the usual seesaw mechanism from 3
sterile (singlet) neutrinos in the presence of a softly broken symmetry.
We take the unconventional view that the sterile neutrinos may be light, i.e.
less than 1 keV, and discuss some very interesting and novel phenomenology,
including a connection between the LSND neutrino data and solar neutrino
oscillations.Comment: 8 pages, no figur
Charged Lepton Electric Dipole Moments from TeV Scale Right-handed Neutrinos
We study the connection between charged lepton electric dipole moments,
, and seesaw neutrino mass generation in a simple two Higgs
doublet extension of the Standard Model plus three right-handed neutrinos (RHN)
, . For RHN with hierarchical masses and at least one with mass
in the 10 TeV range we obtain the upper bounds of
e-cm and e-cm. Our scenario favors the normal
mass hierarchy for the light neutrinos. We also calculated the cross section
for e^-e^- \ra W^- W^- in a high luminosity collider with constraints from
neutrinoless double beta decay of nuclei included. Among the rare muon decay
experiments we find that \mu\ra e\gamma is most sensitive and the upper limit
is .Comment: references added, typos correcte
A Supersymmetric Solution to the Solar and Atmospheric Neutrino Problems
The simplest unified extension of the Minimal Supersymmetric Standard Model
with bi-linear R--Parity violation provides a predictive scheme for neutrino
masses which can account for the observed atmospheric and solar neutrino
anomalies in terms of bi-maximal neutrino mixing. The maximality of the
atmospheric mixing angle arises dynamically, by minimizing the scalar
potential, while the solar neutrino problem can be accounted for either by
large or by small mixing oscillations. One neutrino picks up mass by mixing
with neutralinos, while the degeneracy and masslessness of the other two is
lifted only by loop corrections. Despite the smallness of neutrino masses
R-parity violation is observable at present and future high-energy colliders,
providing an unambiguous cross-check of the model.Comment: 5 pages, final version published in Phys. Rev. D61, 2000, 071703(R
Comment on ``Confirmation of the Sigma Meson''
We comment on the recent paper by N.A. Tornqvist and M. Roos published in
Phys. Rev. Lett. 76, 1575 (1996).Comment: 3 pages (LaTeX), 1 PostScript Figur
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