15,198 research outputs found
Almost-Commutative Geometries Beyond the Standard Model III: Vector Doublets
We will present a new extension of the standard model of particle physics in
its almostcommutative formulation. This extension has as its basis the algebra
of the standard model with four summands [11], and enlarges only the particle
content by an arbitrary number of generations of left-right symmetric doublets
which couple vectorially to the U(1)_YxSU(2)_w subgroup of the standard model.
As in the model presented in [8], which introduced particles with a new colour,
grand unification is no longer required by the spectral action. The new model
may also possess a candidate for dark matter in the hundred TeV mass range with
neutrino-like cross section
The Inverse Seesaw Mechanism in Noncommutative Geometry
In this publication we will implement the inverse Seesaw mechanism into the
noncommutative framework on the basis of the AC-extension of the Standard
Model. The main difference to the classical AC model is the chiral nature of
the AC fermions with respect to a U(1) extension of the Standard Model gauge
group. It is this extension which allows us to couple the right-handed
neutrinos via a gauge invariant mass term to left-handed A-particles. The
natural scale of these gauge invariant masses is of the order of 10^17 GeV
while the Dirac masses of the neutrino and the AC-particles are generated
dynamically and are therefore much smaller (ca. 1 GeV to 10^6 GeV). From this
configuration a working inverse Seesaw mechanism for the neutrinos is obtained
Almost-Commutative Geometries Beyond the Standard Model II: New Colours
We will present an extension of the standard model of particle physics in its
almost-commutative formulation. This extension is guided by the minimal
approach to almost-commutative geometries employed in [13], although the model
presented here is not minimal itself.
The corresponding almost-commutative geometry leads to a Yang-Mills-Higgs
model which consists of the standard model and two new fermions of opposite
electro-magnetic charge which may possess a new colour like gauge group. As a
new phenomenon, grand unification is no longer required by the spectral action.Comment: Revised version for publication in J.Phys.A with corrected Higgs
masse
Almost-Commutative Geometries Beyond the Standard Model
In [7-9] and [10] the conjecture is presented that almost-commutative
geometries, with respect to sensible physical constraints, allow only the
standard model of particle physics and electro-strong models as
Yang-Mills-Higgs theories. In this publication a counter example will be given.
The corresponding almost-commutative geometry leads to a Yang-Mills-Higgs
model which consists of the standard model of particle physics and two new
fermions of opposite electro-magnetic charge. This is the second
Yang-Mills-Higgs model within noncommutative geometry, after the standard
model, which could be compatible with experiments. Combined to a hydrogen-like
composite particle these new particles provide a novel dark matter candidate
Bose-Einstein condensate coupled to a nanomechanical resonator on an atom chip
We theoretically study the coupling of Bose-Einstein condensed atoms to the
mechanical oscillations of a nanoscale cantilever with a magnetic tip. This is
an experimentally viable hybrid quantum system which allows one to explore the
interface of quantum optics and condensed matter physics. We propose an
experiment where easily detectable atomic spin-flips are induced by the
cantilever motion. This can be used to probe thermal oscillations of the
cantilever with the atoms. At low cantilever temperatures, as realized in
recent experiments, the backaction of the atoms onto the cantilever is
significant and the system represents a mechanical analog of cavity quantum
electrodynamics. With high but realistic cantilever quality factors, the strong
coupling regime can be reached, either with single atoms or collectively with
Bose-Einstein condensates. We discuss an implementation on an atom chip.Comment: published version (5 pages, 3 figures
Mixing and condensation in a wet granular medium
We have studied the effect of small amounts of added liquid on the dynamic
behavior of a granular system consisting of a mixture of glass beads of two
different sizes. Segregation of the large beads to the top of the sample is
found to depend in a nontrivial way on the liquid content. A transition to
viscoplastic behavior occurs at a critical liquid content, which depends upon
the bead size. We show that this transition can be interpreted as a
condensation due to the hysteretic liquid bridge forces connecting the beads,
and provide the corresponding phase diagram.Comment: submitted to PR
Finite-size effects lead to supercritical bifurcations in turbulent rotating Rayleigh-B\'enard convection
In turbulent thermal convection in cylindrical samples of aspect ratio \Gamma
= D/L (D is the diameter and L the height) the Nusselt number Nu is enhanced
when the sample is rotated about its vertical axis, because of the formation of
Ekman vortices that extract additional fluid out of thermal boundary layers at
the top and bottom. We show from experiments and direct numerical simulations
that the enhancement occurs only above a bifurcation point at a critical
inverse Rossby number 1/\Ro_c, with 1/\Ro_c \propto 1/\Gamma. We present a
Ginzburg-Landau like model that explains the existence of a bifurcation at
finite 1/\Ro_c as a finite-size effect. The model yields the proportionality
between 1/\Ro_c and and is consistent with several other measured
or computed system properties.Comment: 4 pages, 4 figure
Polarization observables in the semiexclusive photoinduced three-body breakup of 3He
The photon and 3He analyzing powers as well as spin correlation coefficients
in the semiexclusive three-body photodisintegration of 3He are investigated for
incoming photon laboratory energies E=12, 40 and 120 MeV. The nuclear states
are obtained by solving three-body Faddeev equations with the AV18
nucleon-nucleon potential alone or supplemented with the UrbanaIX three-nucleon
force. Explicit pi- and rho-meson exchange currents are taken into account, but
we also compare to other models of the electromagnetic current. In some
kinematical conditions we have found strong effects of the three-nucleon force
for the 3He analyzing power and spin correlation coefficients, as well strong
sensitivities to the choice of the currents. This set of predictions should be
a useful guidance for the planning of measurements. In addition, we compare our
results for two-body 3He breakup induced by polarized photons with a few
existing data.Comment: 23 pages, 16 figure
A survey of users of earth resources remote sensing data
The results of a NASA supported Battelle survey to obtain user views on the nature and value of LANDSAT data use, on current LANDSAT capabilities, and on ways to improve data use were summarized. Questionnaire and interview responses from over 1000 private and public sector users were analyzed and discussed
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