4,276 research outputs found
Equivariant formality of corank-one isotropy actions and products of rational spheres
We completely characterize the pairs of connected Lie groups such
that and the left action of on
is equivariantly formal. The analysis requires us to correct and extend
an existing partial classification of homogeneous quotients with the
rational homotopy type of a product of an odd- and an even-dimensional sphere.Comment: 43 pages; updated to match the journal versio
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Durable and ductile double-network material for dust control
Dust generation is a world-wide issue due to its serious deleterious effects on the environment, human health and safety, and the economy. Although various dust suppression methods have been used for decades, some critical drawbacks in state-of-the-art technology still remain unsolved, such as short-lasting, ground water impact, and prone to water. This work reports a soil stabilizer based on non-toxic material and forms a ductile and durable double-network in soil, namely âD3 soil stabilizerâ, which not only improves soil mechanical toughness of surface soil but also suppresses dust generation. A copolymer comprising hydrophilic and hydrophobic components combined with enzyme-induced carbonate precipitation is utilized as an in-situ gelation binder to soil particle. The tunable hydrophobic-to-hydrophilic component ratio minimizes undesirable soil matrix expansion and mechanical strength loss upon experiencing wet-dry processes, while still retains good water affinity. We further demonstrated controllable treatment depth by fine-tuning precursor composition, which is essential to minimize environmental impact. The double-network morphology with carbonate precipitate embedded uniformly in polymer matrix is observed via microscopic imaging. The nature of outstanding ductility, high durability against water, and good long-term stability were supported by systematic unconfined compressive strength (UCS) measurements on treated soil, which show strong inter-particles binding, good retention of peak strength, increased strain at peak strength, and increased toughness after soil samples have experienced wet-dry processes
Noncommutative QCD corrections to the gluonic decays of heavy quarkonia
We compute the Noncommutative QCD (NCQCD) contributions to the three gluon
decay modes of heavy quarkonia. For triplet quarkonia (ortho-quarkonia), the
NCQCD correction to the QCD three gluon decay mode, like the standard model
contribution, is infrared finite. In the case of singlet quarkonia
(para-quarkonia), whose QCD three gluon decay mode has infrared singularities
which are removed using one-loop corrections to the two gluon mode, we find
that NCQCD contribution is also infrared finite. The calculations are performed
in the weak binding limit and do not require the introduction of additional
effective couplings.Comment: Version accepted for publicatio
Measurement of the refractive index of electrically poled soda-lime glass layers using leaky modes
Electrically poled layers have been formed in soda-lime glass using graphite electrodes in air. The refractive index and thickness of the poled glass layers have been measured by the analysis of leaky optical modes. These modes are supported by the poled layer and can be determined by analysis of the optical reflectivity measured with a prism coupler arrangement. A relatively constant refractive index ~ 1.486 in the poled glass region is measured, which is ~0.03 below the substrate index. The reflectivity data shows that the transition between poled and un-poled glass is very sharp and is consistent with ion transport models. The thickness of the poled glass region is consistent with the removal of Na+ and K+ ions from the poled region. The index and depth data is confirmed by interferometric measurements. The tensile stress in the poled glass layer is also estimated from optical birefringence measurements and is estimated to be ~0.3 GN/m2
Non-Commutative GUTs, Standard Model and C,P,T
Noncommutative Yang-Mills theories are sensitive to the choice of the
representation that enters in the gauge kinetic term. We constrain this
ambiguity by considering grand unified theories. We find that at first order in
the noncommutativity parameter \theta, SU(5) is not truly a unified theory,
while SO(10) has a unique noncommutative generalization. In view of these
results we discuss the noncommutative SM theory that is compatible with SO(10)
GUT and find that there are no modifications to the SM gauge kinetic term at
lowest order in \theta.
We study in detail the reality, hermiticity and C,P,T properties of the
Seiberg-Witten map and of the resulting effective actions expanded in ordinary
fields. We find that in models of GUTs (or compatible with GUTs) right-handed
fermions and left-handed ones appear with opposite Seiberg-Witten map.Comment: 28 pages. Added references and comments in the introductio
CP Violation in B Decays from Anomalous tbW Interactions
We calculate the effect of new CP violating interactions parameterized by an
anomalous coupling on CP-odd observables in B decays. We find that
couplings consistent with current bounds induce observable effects in some CP
asymmetries that will be measured in B-factories. The new effects are
sufficiently large that they can actually test specific models that give rise
to these interactions.Comment: We have added a new section showing that the new effects are
sufficiently large that they can be measured at a B-factor
Mixing of Pentaquark and Molecular States
There are experimental evidences for the existence of narrow states
and with the same quantum numbers of and
pentaquarks and also and molecular states.
Their masses deviate from many theoretical estimates of the pure pentaquark and
molecular states. In this work we study the possibility that the observed
and are mixtures of pure pentaquark and molecular states.
The mixing parameters are in general related to non-perturbative QCD which are
not calculable at present. We determine them by fitting data from known states
and then generalize the mechanism to to predict its mass and width.
The mixing mechanism can also naturally explain the narrow width for
and through destructive interferences, even if the pure pentaquark
and molecular states have much larger decay widths. We also briefly discuss the
properties of the partner eigenstates of and and the
possibility of experimentally observe them. Moreover, probable consequences of
multi-state mixing are also addressed.Comment: 23 pages, 4 figures. Published version in EPJ
MesozoicâTertiary exhumation history of the Altai Mountains, northern Xinjiang, China: New constraints from apatite fission track data
This study uses apatite fission track (FT) analysis to constrain the exhumation history of bedrock samples collected from the Altai Mountains in northern Xinjiang, China. Samples were collected as transects across the main structures related to Palaeozoic crustal accretion events. FT results and modeling identify three stages in sample cooling history spanning the Mesozoic and Tertiary. Stage one records rapid cooling to the low temperature part of the fission track partial annealing zone circa 70 ± 10 °C. Stage two, records a period of relative stability with little if any cooling taking place between 75 and 25â20 Ma suggesting the Altai region had been reduced to an area of low relief. Support for this can be found in the adjacent Junngar Basin that received little if any sediment during this interval. Final stage cooling took place in the Miocene at an accelerated rate bringing the sampled rocks to the Earth's surface. This last stage, linked to the far field effects of the Himalayan collision, most likely generated the surface uplift and relief that define the present-day Altai Mountains
Theory of interlayer tunneling in bi-layer quantum Hall ferromagnets
Spielman et al. have recently observed a large zero-bias peak in the tunnel
conductance of a bi-layer system in a quantum Hall ferromagnet state. We argue
that disorder-induced topological defects in the pseudospin order parameter
limit the peak size and destroy the predicted Josephson effect. We predict that
the peak would be split and shifted by an in-plane magnetic field in a way that
maps the dispersion relation of the ferromagnet's Goldstone mode. We also
predict resonant structures in the DC I-V characteristic under bias by an {\em
ac} electric field.Comment: 4 pages, no figures, submitted to Physical Review Letter
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