5,391 research outputs found
Scalar mesons above and below 1 GeV
We show that two nonets and a glueball provide a consistent description of
data on scalar mesons below 1.7 GeV. Above 1 GeV the states form a conventional
(q bar q) nonet mixed with the glueball of lattice QCD. Below 1 GeV the states
also form a nonet, as implied by the attractive forces of QCD, but of more
complicated nature. Near the center they are 4 quark states of the Jaffe type
in S-wave, with some (q bar q) in P-wave, but further out they rearrange in
colour to two colourless (q bar q) pairs and finally as meson-meson states. A
simple effective chiral model for such a system with two scalar nonets can be
made involving two coupled linear sigma models. One of these could be looked
upon as the Higgs sector of nonpertubative QCD.Comment: 34 pages in Latex, minor improvements in sec
Modeling radiation in particle clouds: On the importance of inter-particle radiation for pulverized solid fuel combustion
The importance of inter-particle radiation for clusters of gray and diffuse
particles is investigated. The radiative cooling of each individual particle is
found to vary strongly with its position in the cluster, and a mean radiative
particle cooling term is proposed for single particle simulations of particle
clusters or for high detail simulation, like Direct Numerical Simulations of
small sub-volumes of large clusters of particles. Radiative cooling is shown to
be important both for furnaces for coal gasification and coal combustion.
Broadening the particle size distribution is found to have just a minor effect
on the radiative particle cooling. This is particularly the case for large and
dense particle clusters where there is essentially no effect of size
distribution broadening at all. For smaller and more dilute particle clusters,
the effect of distribution broadening is clear but still not dominant
Descent via (3,3)-isogeny on Jacobians of genus 2 curves
We give parametrisation of curves C of genus 2 with a maximal isotropic
(ZZ/3)^2 in J[3], where J is the Jacobian variety of C, and develop the theory
required to perform descent via (3,3)-isogeny. We apply this to several
examples, where it can shown that non-reducible Jacobians have nontrivial
3-part of the Tate-Shafarevich group.Comment: 17 page
On finiteness conjectures for endomorphism algebras of abelian surfaces
It is conjectured that there exist finitely many isomorphism classes of
simple endomorphism algebras of abelian varieties of GL_2-type over \Q of
bounded dimension. We explore this conjecture when particularized to quaternion
endomorphism algebras of abelian surfaces by giving a moduli interpretation
which translates the question into the diophantine arithmetic of Shimura curves
embedded in Hilbert surfaces. We address the resulting problems on these curves
by local and global methods, including Chabauty techniques on explicit
equations of Shimura curves.Comment: We have reorganized the article, correcting some misprints, improving
some results and giving more detailed explanations and reference
Multifunctionality: Concepts and Applications to the WTO Negotiations on Agriculture
The ongoing negotiations in the WTO will most certainly lead to a further liberalization of the global agricultural trade. Related to this, many national governments, including Norway, Switzerland and Japan have placed substantial emphasis on the so-called non-trade concerns. In addition to the production of food and fiber, agriculture also provides or may provide national food security, environmental benefits, and viable rural areas. The term "Multifunctional Agriculture" has been applied to describe these additional functions. In this paper, we will show how the economic concepts of "positive and negative externalities" and "public goods" can be used to analyse non-trade concerns and multifunctionality, especially with reference to agriculture's impact on the environment. We conclude the paper with suggestions for international trade rules that can allow countries to meet domestic environmental policy objectives in a minimally trade-distorting manner.Non-trade concerns, multifunctionality, externalities, public goods, cultural landscape, optimum subsidy, WTO, International Relations/Trade,
Alien Registration- Persson, Nils E. (Readfield, Kennebec County)
https://digitalmaine.com/alien_docs/17239/thumbnail.jp
CNO abundances in the Galactic bulge
The carbon, nitrogen, and oxygen abundances and trends in the bulge are
discussed in the context of our recent analysis of these elements in an
on-going project based on near-IR spectra (Ryde et al. 2009). We obtained these
using the CRIRES spectrometer on the VLT. The formation and evolution of the
Milky Way bulge can be constrained by studying elemental abundances of bulge
stars. Due to the large and variable visual extinction in the line-of-sight
towards the bulge, an analysis in the near-IR is preferred.Comment: Contributed talk at Chemical Abundances in the Universe, Connecting
First Stars to Planets, Proceedings of the International Astronomical Union,
IAU Symposium, Volume 265, K. Cunha, M. Spite and B. Barbuy, eds, Cambridge
University Press, in pres
- …