Noncommutative waves have infinite propagation speed

We prove the existence of global solutions to the Cauchy problem for noncommutative nonlinear wave equations in arbitrary even spatial dimensions where the noncommutativity is only in the spatial directions. We find that for existence there are no conditions on the degree of the nonlinearity provided the potential is positive. We furthermore prove that nonlinear noncommutative waves have infinite propagation speed, i.e., if the initial conditions at time 0 have a compact support then for any positive time the support of the solution can be arbitrarily large.Comment: 15 pages, references adde

Helioseismology, solar models and neutrino fluxes

We present our results concerning a systematical analysis of helioseismic implications on solar structure and neutrino production. We find Y$_{ph}=0.238-0.259$, $R_b/R_\odot=0.708-0.714$ and $\rho_b=(0.185-0.199)$ gr/cm$^3$. In the interval $0.2<R/R_\odot<0.65$, the quantity $U=P/\rho$ is determined with and accuracy of $\pm 5$\permille~or better. At the solar center still one has remarkable accuracy, $\Delta U/U <4$. We compare the predictions of recent solar models (standard and non-standard) with the helioseismic results. By constructing helioseismically constrained solar models, the central solar temperature is found to be $T=1.58 \times 10^7$K with a conservatively estimated accuracy of 1.4%, so that the major unceratainty on neutrino fluxes is due to nuclear cross section and not to solar inputs.Comment: 14 pages including 9 figures, LaTex file, espcrc2.sty is needed; to appear in Nucl. Phys. B Proc. Suppl., Proceedings of TAUP97 conference, Laboratori Nazionali del Gran Sasso, September 199

Effect of Nuclear Quadrupole Interaction on the Relaxation in Amorphous Solids

Recently it has been experimentally demonstrated that certain glasses display an unexpected magnetic field dependence of the dielectric constant. In particular, the echo technique experiments have shown that the echo amplitude depends on the magnetic field. The analysis of these experiments results in the conclusion that the effect seems to be related to the nuclear degrees of freedom of tunneling systems. The interactions of a nuclear quadrupole electrical moment with the crystal field and of a nuclear magnetic moment with magnetic field transform the two-level tunneling systems inherent in amorphous dielectrics into many-level tunneling systems. The fact that these features show up at temperatures $T<100mK$, where the properties of amorphous materials are governed by the long-range $R^{-3}$ interaction between tunneling systems, suggests that this interaction is responsible for the magnetic field dependent relaxation. We have developed a theory of many-body relaxation in an ensemble of interacting many-level tunneling systems and show that the relaxation rate is controlled by the magnetic field. The results obtained correlate with the available experimental data. Our approach strongly supports the idea that the nuclear quadrupole interaction is just the key for understanding the unusual behavior of glasses in a magnetic field.Comment: 18 pages, 9 figure

Challenges confronting road freight transport and the use of vehicle-pavement interaction analysis in addressing these challenges

Traditional arguments for maintaining riding quality of pavement are expanded in this paper to examine the effects of deteriorating riding quality on vehicle operating costs, freight damage and logistics. The objectives of this paper are to analyse the effects of different levels of riding quality on a truck and its freight, and to discuss potential applications of the analysis in terms of effectiveness of the freight transport system. The paper discusses needs and drivers influencing freight transport costs, vehicle-pavement interaction concepts, and the potential physical effects and costs from roads with deteriorating riding quality. A case study is presented analysing vehicle-pavement interaction for selected roadways in California. It is concluded that investments in pavement and freight transport industry improvements can be investigated by applying vehicle-pavement interaction analysis to evaluate damage to pavement, vehicle and freight that would result from alternative levels of pavement riding quality. The paper recommends that existing concepts, tools and resources such as dedicated truck lanes and vehicle-pavement interaction analysis can help to improve the freight transport system. A framework is proposed to better understand the scale of potential impacts of riding quality from localised effects to larger-scale influences, including costs to customers and global competitiveness.Caltranshttp://www.journals.co.za/ej/ejour_civileng.htm

Fermion Masses, Mixing Angles and Supersymmetric SO(10) Unification

We reanalyse the problem of fermion masses in supersymmetric SO(10) grand unified models. In the minimal model, both low energy Higgs doublets belong to the same {\bf{10}} representation of SO(10) implying the unification not only of the gauge but also of the third generation Yukawa couplings. These models predict large values of $\tan\beta \sim 50$. In this paper we study the effects of departing from the minimal conditions in order to see if we can find models with a reduced value of $\tan\beta$. In order to maintain predictability, however, we try to do this with the addition of only one new parameter. We still assume that the fermion masses arise from interactions of the spinor representations with a single ${\bf 10}$ representation, but this ${\bf 10}$ now only contains a part of the two light Higgs doublets. This enables us to introduce one new parameter $\omega=\lambda_b/\lambda_t$. For values of $\omega \ll 1$ we can in principle reduce the value of $\tan\beta$. In fact, $\omega$ is an overall factor which multiplies the down quark and charged lepton Yukawa matrices. Thus the theory is still highly constrained. We show that the first generation quark masses and the CP-violation parameter $\epsilon_K$ yield strong constraints on the phenomenologically allowed models. In the end, we find that large values of $\tan\beta$ are still preferred.Comment: 15 pages, latex, 6 uuencoded figure

The genera Melanothamnus Bornet & Falkenberg and Vertebrata S.F. Gray constitute well-defined clades of the red algal tribe Polysiphonieae (Rhodomelaceae, Ceramiales).

Polysiphonia is the largest genus of red algae, and several schemes subdividing it into smaller taxa have been proposed since its original description. Most of these proposals were not generally accepted, and currently the tribe Polysiphonieae consists of the large genus Polysiphonia (190 species), the segregate genus Neosiphonia (43 species), and 13 smaller genera (< 10 species each). In this paper, phylogenetic relationships of the tribe Polysiphonieae are analysed, with particular emphasis on the genera Carradoriella, Fernandosiphonia, Melanothamnus, Neosiphonia, Polysiphonia sensu stricto, Streblocladia and Vertebrata. We evaluated the consistency of 14 selected morphological characters in the identified clades. Based on molecular phylogenetic (rbcL and 18S genes) and morphological evidence, two speciose genera are recognized: Vertebrata (including the type species of the genera Ctenosiphonia, Enelittosiphonia, Boergeseniella and Brongniartella) and Melanothamnus (including the type species of the genera Fernandosiphonia and Neosiphonia). Both genera are distinguished from other members of the Polysiphonieae by synapomorphic characters, the emergence of which could have provided evolutionarily selective advantages for these two lineages. In Vertebrata trichoblast cells are multinucleate, possibly associated with the development of extraordinarily long, photoprotective, trichoblasts. Melanothamnus has 3-celled carpogonial branches and plastids lying exclusively on radial walls of the pericentral cells, which similarly may improve resistance to damage caused by excessive light. Other relevant characters that are constant in each genus are also shared with other clades. The evolutionary origin of the genera Melanothamnus and Vertebrata is estimated as 75.7-95.78 and 90.7-138.66 Ma, respectively. Despite arising in the Cretaceous, before the closure of the Tethys Seaway, Melanothamnus is a predominantly Indo-Pacific genus and its near-absence from the northeastern Atlantic is enigmatic. The nomenclatural implications of this work are that 46 species are here transferred to Melanothamnus, six species are transferred to Vertebrata and 13 names are resurrected for Vertebrata

Anthropology in conversation with an Islamic tradition : Emmanuel Levinas and the practice of critique

Funded by the Carnegie Trust for the Universities of Scotland This research was funded by the Carnegie Trust for the Universities of Scotland. I would like to thank Arnar Arnason, Alison Brown, Tim Ingold, Jo Vergunst, and the anonymous JRAI readers for their critical feedback, which greatly improved the quality and coherence of this article.Peer reviewedPostprin