Nonequilibrium brittle fracture propagation: Steady state, oscillations and intermittency

A minimal model is constructed for two-dimensional fracture propagation. The heterogeneous process zone is presumed to suppress stress relaxation rate, leading to non-quasistatic behavior. Using the Yoffe solution, I construct and solve a dynamical equation for the tip stress. I discuss a generic tip velocity response to local stress and find that noise-free propagation is either at steady state or oscillatory, depending only on one material parameter. Noise gives rise to intermittency and quasi-periodicity. The theory explains the velocity oscillations and the complicated behavior seen in polymeric and amorphous brittle materials. I suggest experimental verifications and new connections between velocity measurements and material properties.Comment: To appear in Phys. Rev. Lett., 6 pages, self-contained TeX file, 3 postscript figures upon request from author at [email protected] or [email protected], http://cnls-www.lanl.gov/homepages/rafi/rafindex.htm

Effects of Symmetry Breaking on the Strong and Electroweak Interactions of the Vector Nonet

Starting from a chiral invariant and quark line rule conserving Lagrangian of pseudoscalar and vector nonets we introduce first and second order symmetry breaking as well as quark line rule violating terms and fit the parameters, at tree level, to many strong and electroweak processes. A number of predictions are made. The electroweak interactions are included in a manifestly gauge invariant manner. The resulting symmetry breaking pattern is discussed in detail. Specifically, for the ``strong'' interactions, we study all the vector meson masses and V -> \phi \phi decays, including isotopic spin violations. In the electroweak sector we study the { rho^0 , omega , phi } -> e^+e^- decays, { pi^+ , K^+ , K^0 } ``charge radii'', K_{l3} ``slope factor'' and the overall e^+e^- -> pi^+ pi^- process. It is hoped that the resulting model may be useful as a reasonable description of low energy physics in the range up to about 1 GeV.Comment: 43 pages (LaTeX), 5 PostScript figures are included as uuencoded-compressed-tar file at the en

Tau mesonic decays and strong anomaly of PCAC

Strong anomaly of the PCAC is found in $\tau\rightarrow\omega \pi\pi\nu$ and $\omega\rho\nu$ in the chiral limit. It originates in WZW anomaly. Theoretical result of $\tau\rightarrow\omega\pi\pi\nu$ agrees with data well and the measurement of $\tau\rightarrow\omega\rho\nu$ will confirm the strong anomaly of PCAC. The strong anomaly of PCAC is studied.Comment: 27 page

Pion and Kaon Vector Form Factors

We develop a unitarity approach to consider the final state interaction corrections to the tree level graphs calculated from Chiral Perturbation Theory ($\chi PT$) allowing the inclusion of explicit resonance fields. The method is discussed considering the coupled channel pion and kaon vector form factors. These form factors are then matched with the one loop $\chi PT$ results. A very good description of experimental data is accomplished for the vector form factors and for the $\pi\pi$ P-wave phase shifts up to $\sqrt{s}\lesssim 1.2$ GeV, beyond which multiparticle states play a non negligible role. In particular the low and resonance energy regions are discussed in detail and for the former a comparison with one and two loop $\chi PT$ is made showing a remarkable coincidence with the two loop $\chi PT$ results.Comment: 20 pages, 7 figs, to appear in Phys. Rev.

Electromagnetic Meson Form Factors in the Salpeter Model

We present a covariant scheme to calculate mesonic transitions in the framework of the Salpeter equation for $q\bar{q}$-states. The full Bethe Salpeter amplitudes are reconstructed from equal time amplitudes which were obtained in a previous paper\cite{Mue} by solving the Salpeter equation for a confining plus an instanton induced interaction. This method is applied to calculate electromagnetic form factors and decay widths of low lying pseudoscalar and vector mesons including predictions for CEBAF experiments. We also describe the momentum transfer dependence for the processes $\pi^0,\eta,\eta'\rightarrow\gamma\gamma^*$.Comment: 22 pages including 10 figure

The M-Machine Multicomputer

The M-Machine is an experimental multicomputer being developed to test architectural concepts motivated by the constraints of modern semiconductor technology and the demands of programming systems. The M- Machine computing nodes are connected with a 3-D mesh network; each node is a multithreaded processor incorporating 12 function units, on-chip cache, and local memory. The multiple function units are used to exploit both instruction-level and thread-level parallelism. A user accessible message passing system yields fast communication and synchronization between nodes. Rapid access to remote memory is provided transparently to the user with a combination of hardware and software mechanisms. This paper presents the architecture of the M-Machine and describes how its mechanisms maximize both single thread performance and overall system throughput

Wheat Flour Fortification With that of Defatted Seed of Citrulluslanatus (Cucurbitaceae): Effects on Organs Biometry

This study used to determine the effects of wheat flour fortification with that of defatted seed of Citrulluslanatus(Cucurbitaceae)on organ biometry.Thirty rats (30) team up into five per group were fed during 14 days with the six diets prepared: Diet made with casein (RTC); diet containing classic bread (RPC) and diets based on bread in which the wheat flour has been substituted by defatted seed flour of Citrulluslanatus(RPFd) at different proportions 5 % (RPFd5); 10% (RPFd10); 15 % (RPFd15); 20% (RPFd20).After the end of the experimental period, animals were sacrificed and kidney, liver, stomach, ileum and spleen were removed and weighted.Result showed that relative kidney weight of rats fed with RTC (0.84±0.08) and RPC (0.90±0.05) were significantly higher (p ≤ 0.05) than that of rats fed with RPFd (0.69±0.04 to 0.75±0.02). Relative weight of the other organs of rats fed with RPFd (0.24±0.11to 0.28±0.06) do not show a significant difference(p ≥ 0.05) when compared to that of rats fed with RTC and RPC. This study suggested that except for kidney, the wheat flour fortification with that of defatted seed of Citrullus lanatushave not effects on the biometry of others organs

Pion and Kaon Electromagnetic Form Factors

We study the electromagnetic form factor of the pion and kaons at low-energies with the use of Chiral Perturbation Theory. The analysis is performed within the three flavour framework and at next-to-next-to-leading order. We explain carefully all the relevant consistency checks on the expressions, present full analytical results for the pion form factor and describe all the assumptions in the analysis. From the phenomenological point of view we make use of our expression and the available data to obtain the charge radius of the pion obtaining $_V^\pi=(0.452+-0.013) fm^2$, as well as the low-energy constant $L_9^r(m_\rho)= (5.93+-0.43)10^{-3}$. We also obtain experimental values for 3 combinations of order $p^6$ constants.Comment: 50 page

Quark-meson coupling model with the cloudy bag

Using the volume coupling version of the cloudy bag model, the quark-meson coupling model is extended to study the role of pion field and the properties of nuclear matter. The extended model includes the effect of gluon exchange as well as the pion-cloud effect, and provides a good description of the nuclear matter properties. The relationship between the extended model and the EFT approach to nuclear matter is also discussed.Comment: 13 pages, 3 figure

Hard Constituent Quarks and Electroweak Properties of Pseudoscalar Mesons

The high momentum components generated in the wave function of pseudoscalar mes* by the one-gluon-exchange interaction are investigated within a relativistic constituent quark model. Adopting the light-cone formalism, the sensitivity of the weak decay constant and the charge form factor to hard constituent quarks is illustrated.Comment: 11 pages and 5 figs. (to be requested), LaTeX, INFN-ISS 94/3. To appear in Physics Lett.