1,696 research outputs found
Amenable crossed product Banach algebras associated with a class of -dynamical systems
We prove that the crossed product Banach algebra that is
associated with a -dynamical system is amenable
if is a discrete amenable group and is a commutative or finite
dimensional -algebra. Perspectives for further developments
are indicated.Comment: Improved discussion of the relation with the existing literature and
of perspectives for further developments. 8 pages. To appear in Integral
Equations and Operator Theor
Effect of tillage practices on the soil carbon dioxide flux during fall and spring seasons in a Mediterranean Vertisol
In this study, we assessed the effect of conventional tillage (CT), reduced (RT) and no tillage (NT) practices on the soil CO2 flux of a Mediterranean Vertisol in semi-arid Morocco. The measurements focused on the short term (0 to 96 h) soil CO2 fluxes measured directly after tillage during the fall and spring period. Soil temperature, moisture and soil strength were measured congruently to study their effect on the soil CO2 flux magnitude. Immediately after fall tillage, the CT showed the highest CO2 flux (4.9 g m-2 h-1); RT exhibited an intermediate value (2.1 g m-2 h-1) whereas the lowest flux (0.7 g m-2 h-1) was reported under NT. After spring tillage, similar but smaller impacts of the tillage practices on soil CO2 flux were reported with fluxes ranging from 1.8 g CO2 m-2 h-1 (CT) to less than 0.1 g CO2 m-2 h-1 (NT). Soil strength was significantly correlated with soil CO2 emission; whereas surface soil temperature and moisture were low correlated to the soil CO2 flux. The intensity of rainfall events before fall and spring tillage practices could explain the seasonal CO2 flux trends. The findings promote conservation tillage and more specifically no tillage practices to reduce CO2 losses within these Mediterranean agroecosystems. (Résumé d'auteur
High-density Skyrmion matter and Neutron Stars
We examine neutron star properties based on a model of dense matter composed
of B=1 skyrmions immersed in a mesonic mean field background. The model
realizes spontaneous chiral symmetry breaking non-linearly and incorporates
scale-breaking of QCD through a dilaton VEV that also affects the mean fields.
Quartic self-interactions among the vector mesons are introduced on grounds of
naturalness in the corresponding effective field theory. Within a plausible
range of the quartic couplings, the model generates neutron star masses and
radii that are consistent with a preponderance of observational constraints,
including recent ones that point to the existence of relatively massive neutron
stars with mass M 1.7 Msun and radius R (12-14) km. If the existence of neutron
stars with such dimensions is confirmed, matter at supra-nuclear density is
stiffer than extrapolations of most microscopic models suggest.Comment: 27 pages, 5 figures, AASTeX style; to be published in The
Astrophysical Journa
Third generation sfermions decays into Z and W gauge bosons: full one-loop analysis
The complete one-loop radiative corrections to third generation scalar
fermions into gauge bosons Z and W^\pm is considered. We focus on \wt{f}_2 \to
Z \wt{f}_1 and \wt{f}_i \to W^\pm \wt{f'}_j (f,f'=t,b). We include both
SUSY-QCD, QED and full electroweak corrections. It is found that the
electroweak corrections can be of the same order as the SUSY-QCD corrections.
The two sets of corrections interfere destructively in some region of parameter
space. The full one loop correction can reach 10% in some SUGRA scenario, while
in model independent analysis like general MSSM, the one loop correction can
reach 20% for large \tan\beta and large trilinear soft breaking terms A_b.Comment: Latex file, 18 pages, 8 figures, version to appear in PR
h\to \gamma \gamma In Inert Higgs Doublet Model
Motivated by the recent result reported from LHC on the di-photon search for
a Standard Model (SM) Higgs-like boson. We discuss the implications of this
possible signal in the framework of the Inert Higgs Doublet Model (IHDM),
taking into account previous limits from Higgs searches at LEP, the Tevatron
and the LHC as well as constraints from unitarity, vacuum stability and
electroweak precision tests. We show that the charged Higgs contributions can
interfere constructively or destructively with the W gauge bosons loops leading
to enhancement or suppression of the di-photon rate with respect to SM rate. We
show also that the invisible decay of the Higgs, if open, could affect the
total width of the SM Higgs boson and therefore suppress the di-photon rate.Comment: 15 pages, added reference
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