Instanton Theory of Burgers Shocks and Intermittency

A lagrangian approach to Burgers turbulence is carried out along the lines of the field theoretical Martin-Siggia-Rose formalism of stochastic hydrodynamics. We derive, from an analysis based on the hypothesis of unbroken galilean invariance, the asymptotic form of the probability distribution function of negative velocity-differences. The origin of Burgers intermittency is found to rely on the dynamical coupling between shocks, identified to instantons, and non-coherent background fluctuations, which, then, cannot be discarded in a consistent statistical description of the flow.Comment: 7 pages; LaTe

Special Theory of Relativity through the Doppler Effect

We present the special theory of relativity taking the Doppler effect as the starting point, and derive several of its main effects, such as time dilation, length contraction, addition of velocities, and the mass-energy relation, and assuming energy and momentum conservation, we discuss how to introduce the 4-momentum in a natural way. We also use the Doppler effect to explain the "twin paradox", and its version on a cylinder. As a by-product we discuss Bell's spaceship paradox, and the Lorentz transformation for arbitrary velocities in one dimension.Comment: 20 pages, 1 figur

Log-Poisson Cascade Description of Turbulent Velocity Gradient Statistics

The Log-Poisson phenomenological description of the turbulent energy cascade is evoked to discuss high-order statistics of velocity derivatives and the mapping between their probability distribution functions at different Reynolds numbers. The striking confirmation of theoretical predictions suggests that numerical solutions of the flow, obtained at low/moderate Reynolds numbers can play an important quantitative role in the analysis of experimental high Reynolds number phenomena, where small scales fluctuations are in general inaccessible from direct numerical simulations

Effective action for QED in 2+1 dimensions at finite temperature

We calculate the effective action for a constant magnetic field and a time-dependent time-component of the gauge field in 2+1 dimensions at finite temperature. We also discuss the behaviour of the charge density and the fermion condensate as order parameters of symmetry breaking.Comment: Latex, 10 pages, no figure

Classification of reflection matrices related to (super) Yangians and application to open spin chain models

We present a classification of diagonal, antidiagonal and mixed reflection matrices related to Yangian and super-Yangian R matrices associated to the infinite series so(m), sp(n) and osp(m|n). We formulate the analytical Bethe Ansatz resolution for the so(m) and sp(n) open spin chains with boundary conditions described by the diagonal solutions.Comment: 36 pages ; references added ; typos corrected, precisions adde

Noncommutative Burgers Equation

We present a noncommutative version of the Burgers equation which possesses the Lax representation and discuss the integrability in detail. We find a noncommutative version of the Cole-Hopf transformation and succeed in the linearization of it. The linearized equation is the (noncommutative) diffusion equation and exactly solved. We also discuss the properties of some exact solutions. The result shows that the noncommutative Burgers equation is completely integrable even though it contains infinite number of time derivatives. Furthermore, we derive the noncommutative Burgers equation from the noncommutative (anti-)self-dual Yang-Mills equation by reduction, which is an evidence for the noncommutative Ward conjecture. Finally, we present a noncommutative version of the Burgers hierarchy by both the Lax-pair generating technique and the Sato's approach.Comment: 24 pages, LaTeX, 1 figure; v2: discussions on Ward conjecture, Sato theory and the integrability added, references added, version to appear in J. Phys.

Desempenho agronômico de genótipos de girassol em cultivo de safra, no município de Espírito Santo do Pinhal-SP.

Resumo: O trabalho teve como objetivo avaliar o desempenho agronômico de genótipos de girassol em cultivo de safra, no município de Espírito Santo do Pinhal-SP, microregião de São João da Boa Vista. Foram testados sete cultivares pré-comerciais de girassol (BRS G34, BRS G35, SYN 3840, SYN 4065, Multissol, V90013 e V90631) e três cultivares comerciais como testemunhas (EMBRAPA 122 (T), HELIO 358 (T), M734(T)) na safra 2012/13; sob delineamento experimental de blocos ao acaso, em quatro repetições. Utilizaram-se parcelas de quatro linhas de 6,00 m, espaçadas 0,75 m entre si e 0,3 m entre plantas, avaliando-se apenas 8,1 m de área útil. As variáveis avaliadas foram: a) altura de plantas (cm); b) início do florescimento (dias); c) estande (número de capítulos m 2); d) diâmetro de capítulo (cm) e e) produtividade (kg ha 2), todas submetidas à análise de variâncias e teste Tukey de comparação de médias. Houve diferenças significativas entre os genótipos para as variáveis: altura de plantas, início do florescimento e produtividade. Os genótipos V90631 e V90013 foram os mais altos de todos estudados. As maiores produtividades foram observadas nos genótipos de ciclo médio (BRSG34, V90013, V90631 e M734). Assim, conclui-se que os genótipos de girassol de ciclo médio apresentam elevado desempenho agronômico durante o período da safra, com produtividades significativamente superiores à média nacional, sendo os mais recomendados para inserção nos sistemas de produção vigentes no município de Espírito Santo do Pinhal-SP. Abstract: The objective of this study was evaluate sunflower genotypes productive performance in Espírito Santo do Pinhal/SP. Therewere tested seven new (BRS G34, BRS G35, SYN 3840, SYN 4065, Multissol, V90013 and V90631) and three commercial (EMBRAPA 122 (T), HELIO 358 (T), M734 (T)) genotypes of sunflower in a randomized block design, with four replications. Each plot consisted of four rows 6.0 m long, spaced from 0.75 m and 0.3 m each plant, which was evaluated just 8,1 m as useful. There was evaluated: a) plant height (cm), b) flowering date (days); c) final plant stand (nº m 2); d) diameter of heads (cm) ; e) production (kg ha ), which was analyzed by variance test and Scott-Knott mean test (P < 0.05). The V90631 and V90013 genotype was the highest than all. Genotypes with medium maturity (BRSG34, V90013, V90631 e M734) were the most productive than early and late maturity genotypes tested. It concludes that sunflower genotypes? with medium maturity have better productive performance than others in the water season and is recommended to be used in Espírito Santo do Pinhal-SP

Correlations between VIMS and RADAR data over the surface of Titan: Implications for Titan's surface properties

We apply a multivariate statistical method to Titan data acquired by different instruments onboard the Cassini spacecraft. We have searched through Cassini/VIMS hyperspectral cubes, selecting those data with convenient viewing geometry and that overlap with Cassini/RADAR scatterometry footprints with a comparable spatial resolution. We look for correlations between the infrared and microwave ranges the two instruments cover. Where found, the normalized backscatter cross-section obtained from the scatterometer measurement, corrected for incidence angle, and the calibrated antenna temperature measured along with the scatterometry echoes, are combined with the infrared reflectances, with estimated errors, to produce an aggregate data set, that we process using a multivariate classification method to identify homogeneous taxonomic units in the multivariate space of the samples.In medium resolution data (from 20 to 100. km/pixel), sampling relatively large portions of the satellite's surface, we find regional geophysical units matching both the major dark and bright features seen in the optical mosaic. Given the VIMS cubes and RADAR scatterometer passes considered in this work, the largest homogeneous type is associated with the dark equatorial basins, showing similar characteristics as each other on the basis of all the considered parameters.On the other hand, the major bright features seen in these data generally do not show the same characteristics as each other. Xanadu, the largest continental feature, is as bright as the other equatorial bright features, while showing the highest backscattering coefficient of the entire satellite. Tsegihi is very bright at 5 μm but it shows a low backscattering coefficient, so it could have a low roughness on a regional scale and/or a different composition. Another well-defined region, located southwest of Xanadu beyond the Tui Regio, seems to be detached from the surrounding terrains, being bright at 2.69, 2.78 and 5 μm but having a low radar brightness. In this way, other units can be found that show correlations or anti-correlations between the scatterometric response and the spectrophotometric behavior, not evident from the optical remote sensing data. © 2010 Elsevier Inc

Gauge invariant derivative expansion of the effective action at finite temperature and density and the scalar field in 2+1 dimensions

A method is presented for the computation of the one-loop effective action at finite temperature and density. The method is based on an expansion in the number of spatial covariant derivatives. It applies to general background field configurations with arbitrary internal symmetry group and space-time dependence. Full invariance under small and large gauge transformations is preserved without assuming stationary or Abelian fields nor fixing the gauge. The method is applied to the computation of the effective action of spin zero particles in 2+1 dimensions at finite temperature and density and in presence of background gauge fields. The calculation is carried out through second order in the number of spatial covariant derivatives. Some limiting cases are worked out.Comment: 34 pages, REVTEX, no figures. Further comments adde