Specific heat amplitude ratios for anisotropic Lifshitz critical behaviors

We determine the specific heat amplitude ratio near a $m$-axial Lifshitz point and show its universal character. Using a recent renormalization group picture along with new field-theoretical $\epsilon_{L}$-expansion techniques, we established this amplitude ratio at one-loop order. We estimate the numerical value of this amplitude ratio for $m=1$ and $d=3$. The result is in very good agreement with its experimental measurement on the magnetic material $MnP$. It is shown that in the limit $m \to 0$ it trivially reduces to the Ising-like amplitude ratio.Comment: 8 pages, RevTex, accepted as a Brief Report in Physical Review

A new picture of the Lifshitz critical behavior

New field theoretic renormalization group methods are developed to describe in a unified fashion the critical exponents of an m-fold Lifshitz point at the two-loop order in the anisotropic (m not equal to d) and isotropic (m=d close to 8) situations. The general theory is illustrated for the N-vector phi^4 model describing a d-dimensional system. A new regularization and renormalization procedure is presented for both types of Lifshitz behavior. The anisotropic cases are formulated with two independent renormalization group transformations. The description of the isotropic behavior requires only one type of renormalization group transformation. We point out the conceptual advantages implicit in this picture and show how this framework is related to other previous renormalization group treatments for the Lifshitz problem. The Feynman diagrams of arbitrary loop-order can be performed analytically provided these integrals are considered to be homogeneous functions of the external momenta scales. The anisotropic universality class (N,d,m) reduces easily to the Ising-like (N,d) when m=0. We show that the isotropic universality class (N,m) when m is close to 8 cannot be obtained from the anisotropic one in the limit d --> m near 8. The exponents for the uniaxial case d=3, N=m=1 are in good agreement with recent Monte Carlo simulations for the ANNNI model.Comment: 48 pages, no figures, two typos fixe

Topological Dilatonic Supergravity Theories

We present a central extension of the $(m,n)$ super-Poincar\'e algebra in two dimensions. Besides the usual Poincar\'e generators and the $(m,n)$ supersymmetry generators we have $(m,n)$ Grassmann generators, a bosonic internal symmetry generator and a central charge. We then build up the topological gauge theory associated to this algebra. We can solve the classical field equations for the fields which do not belong to the supergravity multiplet and to a Lagrange multiplier multiplet. The resulting topological supergravity theory turns out to be non-local in the fermionic sector.Comment: 11 pages, plain TeX, IFUSP-P/112

Doenças do girassol.

Mancha de Alternaria - Alternaria spp.; Podridao branca - Sclerotinia sclerotiorum (Lib.) de Bary; Mildio - Plasmopara halstedii (Farl.) Berl. & de Toni; Ferrugem - Puccinia helianthi Schw.; Bolha branca - Albugo tragopogi (Pers.) Schroet; Oidio - Erysiphe cichoracearum DC; Mancha cinzenta da haste - Phomopsis helianthi Munth. - Cvet. et al.; Mancha preta da haste - Phoma oleracea var. helianthi tuberosi Sacc.; Outras podridoes radiculares e murchas - Sclerotium rolfsii Sacc., Macrophomina phaseolina (Tass.) Goid e Verticillium dahliae Klebahn; Podridao cinza do capitulo - Botrytis cinerea Pers. ex Fr.; Mancha bacteriana e crestamento bacteriano - Pseudomonas syringae pv. helianthi (Kawamura) Dye, Wilkie et Young; Pseudomonas cichorii (Swingle) Stapp; Podridao da medula da haste - Erwinia sp.; Mosaico comum do girassol - virus do mosaico do picao ("sunflower mosaic virus"); Controle de doencas.bitstream/item/40506/1/Doencas-do-girassol.pd