17,181 research outputs found
Quantum Double Models coupled with matter: an algebraic dualisation approach
In this paper, we constructed a new generalization of a class of discrete
bidimensional models, the so called Quantum Double Models, by introduce matter
qunits to the faces of the lattice that supports these models. This new
generalization can be interpreted as the algebraic dual of a first, where we
introduce matter qunits to the vertices of this same lattice. By evaluating the
algebraic and topological orders of these new models, we prove that, as in the
first generalization, a new phenomenon of quasiparticle confinement may appear
again: this happens when the co-action homomorphism between matter and gauge
groups is non-trivial. Consequently, this homomorphism not only classifies the
different models that belong to this new class, but also suggests that they can
be interpreted as a 2-dimensional restriction of the 2-lattice gauge theories.Comment: 18 pages, 8 figures; submitted to publicatio
Ejection mechanisms in the sublayer of a turbulent channel
A possible model for the inception of vorticity ejections in the viscous sublayer of a turbulent rectangular channel is presented. It was shown that this part of the flow is dominated by protruding strong shear layers of z-vorticity, and it was proposed as a mechanism for their maintenance and reproduction which is essentially equivalent to that responsible for the instability of 2-D Tollmien-Schlichting waves. The efforts to isolate computationally a single structure for its study have failed up to now, since it appears that single structures decay in the absence of external forcing, but a convenient computation model was identified in the form of a long and narrow periodic computational box containing at each moment only a few structures. Further work in the identification of better reduced systems is in progress
The Uniqueness of the Pentaquark
The existence of the pentaquark requires a peculiar mechanism to
explain its stability. Looking at quark clusters, notably diquark and triquark
configurations, such a mechanism may be found in the color-magnetic interaction
between quarks. It is possible to understand why the is unique.
Chiral dynamics, in particular the ease of pion emission, will render other
members of the same flavor antidecuplet, such as the very unstable.Comment: 6 pages, 5 figures, 19th European Few Body Conferenc
Gas Kinematics and Excitation in the Filamentary IRDC G035.39-00.33
Some theories of dense molecular cloud formation involve dynamical
environments driven by converging atomic flows or collisions between
preexisting molecular clouds. The determination of the dynamics and physical
conditions of the gas in clouds at the early stages of their evolution is
essential to establish the dynamical imprints of such collisions, and to infer
the processes involved in their formation. We present multi-transition 13CO and
C18O maps toward the IRDC G035.39-00.33, believed to be at the earliest stages
of evolution. The 13CO and C18O gas is distributed in three filaments
(Filaments 1, 2 and 3), where the most massive cores are preferentially found
at the intersecting regions between them. The filaments have a similar
kinematic structure with smooth velocity gradients of ~0.4-0.8 km s-1 pc-1.
Several scenarios are proposed to explain these gradients, including cloud
rotation, gas accretion along the filaments, global gravitational collapse, and
unresolved sub-filament structures. These results are complemented by HCO+,
HNC, H13CO+ and HN13C single-pointing data to search for gas infall signatures.
The 13CO and C18O gas motions are supersonic across G035.39-00.33, with the
emission showing broader linewidths toward the edges of the IRDC. This could be
due to energy dissipation at the densest regions in the cloud. The average H2
densities are ~5000-7000 cm-3, with Filaments 2 and 3 being denser and more
massive than Filament 1. The C18O data unveils three regions with high CO
depletion factors (f_D~5-12), similar to those found in massive starless cores.Comment: 20 pages, 14 figures, 6 tables, accepted for publication in MNRA
Dynamical NNLO parton distributions
Utilizing recent DIS measurements (\sigma_r, F_{2,3,L}) and data on hadronic
dilepton production we determine at NNLO (3-loop) of QCD the dynamical parton
distributions of the nucleon generated radiatively from valencelike positive
input distributions at an optimally chosen low resolution scale (Q_0^2 < 1
GeV^2). These are compared with `standard' NNLO distributions generated from
positive input distributions at some fixed and higher resolution scale (Q_0^2 >
1 GeV^2). Although the NNLO corrections imply in both approaches an improved
value of \chi^2, typically \chi^2_{NNLO} \simeq 0.9 \chi^2_{NLO}, present DIS
data are still not sufficiently accurate to distinguish between NLO results and
the minute NNLO effects of a few percent, despite of the fact that the
dynamical NNLO uncertainties are somewhat smaller than the NLO ones and both
are, as expected, smaller than those of their `standard' counterparts. The
dynamical predictions for F_L(x,Q^2) become perturbatively stable already at
Q^2 = 2-3 GeV^2 where precision measurements could even delineate NNLO effects
in the very small-x region. This is in contrast to the common `standard'
approach but NNLO/NLO differences are here less distinguishable due to the much
larger 1\sigma uncertainty bands. Within the dynamical approach we obtain
\alpha_s(M_Z^2)=0.1124 \pm 0.0020, whereas the somewhat less constrained
`standard' fit gives \alpha_s(M_Z^2)=0.1158 \pm 0.0035.Comment: 44 pages, 15 figures; minor changes, footnote adde
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