2,995 research outputs found
Neutrino Anomalies in an Extended Zee Model
We discuss an extended model which naturally leads to mass
scales and mixing angles relevant for understanding both the solar and
atmospheric neutrino anomalies. No right-handed neutrinos are introduced in the
model.The model uses a softly broken symmetry. Neutrino
masses arise only at the loop level. The one-loop neutrino masses which arise
as in the Zee model solve the atmospheric neutrino anomaly while breaking of
generates at two-loop order a mass splitting needed for
the vacuum solution of the solar neutrino problem. A somewhat different model
is possible which accommodates the large-angle MSW resolution of the solar
neutrino problem.Comment: 11 pages including 2 figures; a reference added and text changed
accordingl
Fluctuations in the Site Disordered Traveling Salesman Problem
We extend a previous statistical mechanical treatment of the traveling
salesman problem by defining a discrete "site disordered'' problem in which
fluctuations about saddle points can be computed. The results clarify the basis
of our original treatment, and illuminate but do not resolve the difficulties
of taking the zero temperature limit to obtain minimal path lengths.Comment: 17 pages, 3 eps figures, revte
Charge and current oscillations in Fractional quantum Hall systems with edges
Stationary solutions of the Chern-Simons effective field theory for the
fractional quantum Hall systems with edges are presented for Hall bar, disk and
annulus. In the infinitely long Hall bar geometry (non compact case), the
charge density is shown to be monotonic inside the sample. In sharp contrast,
spatial oscillatory modes of charge density are found for the two circular
geometries, which indicate that in systems with compact geometry, charge and
current exist also far from the edges.Comment: 16 pages, 6 figures Revte
Mach's Principle and Model for a Broken Symmetric Theory of Gravity
We investigate spontaneous symmetry breaking in a conformally invariant
gravitational model. In particular, we use a conformally invariant scalar
tensor theory as the vacuum sector of a gravitational model to examine the idea
that gravitational coupling may be the result of a spontaneous symmetry
breaking. In this model matter is taken to be coupled with a metric which is
different but conformally related to the metric appearing explicitly in the
vacuum sector. We show that after the spontaneous symmetry breaking the
resulting theory is consistent with Mach's principle in the sense that inertial
masses of particles have variable configurations in a cosmological context.
Moreover, our analysis allows to construct a mechanism in which the resulting
large vacuum energy density relaxes during evolution of the universe.Comment: 9 pages, no figure
Neutrino-Lepton Masses, Zee Scalars and Muon g-2
Evidence for neutrino oscillations is pointing to the existence of tiny but
finite neutrino masses. Such masses may be naturally generated via radiative
corrections in models such as the Zee model where a singlet Zee-scalar plays a
key role. We minimally extend the Zee model by including a right-handed singlet
neutrino \nu_R. The radiative Zee-mechanism can be protected by a simple U(1)_X
symmetry involving only the \nu_R and a Zee-scalar. We further construct a
class of models with a single horizontal U(1)_FN (a la Frogatt-Nielsen) such
that the mass patterns of the neutrinos and leptons are naturally explained. We
then analyze the muon anomalous magnetic moment (g-2) and the flavor changing
\mu --> e\gamma decay. The \nu_R interaction in our minimal extension is found
to induce the BNL g-2 anomaly, with a light charged Zee-scalar of mass 100-300
GeV.Comment: Version for Phys. Rev. Lett. (typos corrected, minor refinements
Charged Scalar Particles and Leptonic Decay
Charged scalar particles introduced in some extensions of the standard model
can induce leptonic decay at tree level. We find that with some charged
SU(2)-singlet scalar particles, like ones introduced in Zee-type models,
leptonic decay width is always smaller than what is predicted by the standard
model, therefore they may offer a natural solution to decay puzzle. To
be more specific, we examine some Zee-type models in detail to see if at the
same time they are acceptable in particle physics, cosmology and astrophysics.
It is shown that decay data do put some constrains on these models.Comment: ICTP Report No. IC/93/31, 12 pages, Latex, one figure is not
included, it is available upon deman
The Hamburg/SAO survey for low metallicity blue compact/HII-galaxies (HSS-LM). I. The first list of 46 strong-lined galaxies
We present the description and the first results of a new project devoted to
the search for extremely metal-deficient blue compact/HII-galaxies (BCGs) and
to the creation of a well selected large BCG sample with strong emission lines.
Such galaxies should be suitable for reliable determination of their oxygen
abundance through the measurement of the faint [OIII]4363A line. The goals of
the project are two-fold: a) to discover a significant number of new extremely
metal-poor galaxies (Z <= 1/20 Zo), and b) to study the metallicity
distribution of local BCGs. Selection of candidates for follow-up slit
spectroscopy is performed on the database of objective prism spectra of the
Hamburg Quasar Survey. The sky region is limited by delta >= 0 deg. and b^ii <=
-30 deg. In this paper we present the results of the follow-up spectroscopy
conducted with the Russian 6m telescope. The list of observed candidates
contained 52 objects, of which 46 were confirmed as strong-lined BCGs
(EW([OIII]5007) >= 100 A). The remaining five lower excitation ELGs include
three BCGs, and two galaxies classified as SBN (Starburst Nucleus) and DANS
(Dwarf Amorphous Nucleus Starburst). One object is identified as a quasar with
a strong Ly_alpha emission line near 5000 A (z~3). We provide a list with
coordinates, measured radial velocities, B-magnitudes, equivalent widths
EW([OIII]5007) and EW(H_beta) and for the 46 strong-lined BCGs the derived
oxygen abundances 12+log(O/H). The abundances range between 7.42 and 8.4
(corresponding to metallicities between 1/30 and 1/3 Zo). The sample contains
four galaxies with Z < 1/20 Zo, of which three are new discoveries.Comment: 19 pages, 13 figures, accepted for publication in A&A, corrected
typos, reference
Neutrino masses from operator mixing
We show that in theories that reduce, at the Fermi scale, to an extension of
the standard model with two doublets, there can be additional dimension five
operators giving rise to neutrino masses. In particular there exists a singlet
operator which can not generate neutrino masses at tree level but generates
them through operator mixing. Under the assumption that only this operator
appears at tree level we calculate the neutrino mass matrix. It has the Zee
mass matrix structure and leads naturally to bimaximal mixing. However, the
maximal mixing prediction for solar neutrinos is very sharp even when higher
order corrections are considered. To allow for deviations from maximal mixing a
fine tuning is needed in the neutrino mass matrix parameters. However, this
fine tuning relates the departure from maximal mixing in solar neutrino
oscillations with the neutrinoless double beta decay rate.Comment: 11 pages, 1 figure, revte
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