The K-process on a tree as a scaling limit of the GREM-like trap model

We introduce trap models on a finite volume $k$-level tree as a class of Markov jump processes with state space the leaves of that tree. They serve to describe the GREM-like trap model of Sasaki and Nemoto. Under suitable conditions on the parameters of the trap model, we establish its infinite volume limit, given by what we call a $K$-process in an infinite $k$-level tree. From this we deduce that the $K$-process also is the scaling limit of the GREM-like trap model on extreme time scales under a fine tuning assumption on the volumes.Comment: Published in at http://dx.doi.org/10.1214/13-AAP937 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Structure constants of planar N =4 Yang Mills at one loop

We study structure constants of gauge invariant operators in planar N=4 Yang-Mills at one loop with the motivation of determining features of the string dual of weak coupling Yang-Mills. We derive a simple renormalization group invariant formula characterizing the corrections to structure constants of any primary operator in the planar limit. Applying this to the scalar SO(6) sector we find that the one loop corrections to structure constants of gauge invariant operators is determined by the one loop anomalous dimension Hamiltonian in this sector. We then evaluate the one loop corrections to structure constants for scalars with arbitrary number of derivatives in a given holomorphic direction. We find that the corrections can be characterized by suitable derivatives on the four point tree function of a massless scalar with quartic coupling. We show that individual diagrams violating conformal invariance can be combined together to restore it using a linear inhomogeneous partial differential equation satisfied by this function.Comment: 52 pages, 12 figures, Typos fixed, reference adde

Towards a string bit formulation of N=4 super Yang-Mills

We show that planar cal N=4 Yang-Mills theory at zero 't Hooft coupling can be efficiently described in terms of 8 bosonic and 8 fermionic oscillators. We show that these oscillators can serve as world-sheet variables, the string bits, of a discretized string. There is a one to one correspondence between the on shell gauge invariant words of the free Y-M theory and the states in the oscillators' Hilbert space, obeying a local gauge and cyclicity constraints. The planar two-point functions and the three-point functions of all gauge invariant words are obtained by the simple delta-function overlap of the corresponding discrete string world sheet. At first order in the 't Hooft coupling, i.e. at one-loop in the Y-M theory, the logarithmic corrections of the planar two-point and the three-point functions can be incorporated by nearest neighbour interactions among the discretized string bits. In the SU(2) sub-sector we show that the one-loop corrections to the structure constants can be uniquely determined by the symmetries of the bit picture. For the SU(2) sub-sector we construct a gauged, linear, discrete world-sheet model for the oscillators, with only nearest neighbour couplings, which reproduces the anomalous dimension Hamiltonian up to two loops. This model also obeys BMN scaling to all loops.Comment: 64 pages, 6 figures, typos fixed, references adde

Duality Symmetries in N=2 Heterotic Superstring

We review the derivation and the basic properties of the perturbative prepotential in N=2 compactifications of the heterotic superstring. We discuss the structure of the perturbative monodromy group and the embedding of rigidly supersymmetric monodromies associated with enhanced gauge groups, at both perturbative and non-perturbative level.Comment: Based on talks presented at several conferences. 12 pages, LaTe

Estudio comparativo entre el Fondaparinux y la Nadroparina en la prevención del tromboembolismo venoso tras artroplastias de rodillas

El fondaparinux pertenece a una nueva clase de agentes antitrombóticos, los inhibidores selectivos del factor Xa. Nuestro estudio se propone analizar las diferencias entre las complicaciones originadas por la utilización de fondaparinux sódico y una heparina de bajo peso molecular, la nadroparina en la profilaxis tras artroplastia total de rodilla. Hemos realizado un estudio prospectivo que incluyó a 40 pacientes con el diagnóstico de gonartrosis primaria, en 20 se indicó profilaxis con fondaparinux y en otros 20 con nadroparina. En ningún paciente se presentaron signos o síntomas compatibles con TEV o embolismo pulmonar. No se objetivó hemorragia inusual por la herida, no fue preciso reintervención quirúrgica en ningún paciente ni se anotaron efectos adversos de ningún tipo. Sin embargo al analizar las cantidades recogidas en los drenajes y la cuantificación de las cifras de hemoglobina postoperatoria inmediata y en el control a los tres días encontramos diferencias entre los ambos grupos de pacientes, aunque estas diferencias no fueron estadísticamente significativas. El grupo de pacientes tratado con fondaparinux presentó un mayor sangrado reflejado a través del volumen recogido por los drenajes así como por la hemoglobina de control que se realizó a los tres días del período postoperatorio.The fondaparinux is a new type of antithrombotic drugs, the selective inhibitors anti factor Xa activity. Our study proposes analyzing the differences between the complications originated for sodium fondaparinux utilization and a low molecular weight heparin, the nadroparina, in the prophylaxis after total knee arthroplasty. A prospective study was made of 40 patients with osteoarthritis of the knee as primary diagnosis that were operated to implant a total knee replacement. In 20 patients we indicate prophylaxis with fondaparinux and in others 20 with nadroparina. In any patients we found signs or compatible symptoms of venous thromboembolism or pulmonary embolism. We did not observe unusual blood loss in the wound. Revision surgery was not necessary neither we noted any type of adverse effects. However when we analyze the quantities collected in the drains and the quantification of postoperative immediate haemoglobins and in the three days control we find differences between both patient’s groups, although these differences were not statistically significant. In the fondaparinux group we observed a big blood loss in the drains and less levels in the three days control haemoglobin

Influência da compactação do solo na produtividade da rebrota de eucalipto.

Normalmente, as áreas de rebrota sofrem a influência das operações de colheita, aplicação de herbicidas, adubos e resíduos, que concorrem para a compactação do solo. Em solos de texturas diferentes em áreas da Cia. Suzano de Papel e Celulose, nos municípios de Itatinga, SP, e São Miguel Arcanjo, SP, foram selecionadas 30 linhas de plantio para determinação da produtividade de eucalipto (Eucalyptus grandis Hill ex Maiden) aos sete anos de idade, bem como atributos físico-hídricos do solo a 50 cm da linha de plantio. Foram obtidas amostras indeformadas de solo em três profundidades: 0 a 10, 10 a 20 e 20 a 30 cm; a resistência do solo foi obtida com penetrômetro – SC 60 – até 60 cm de profundidade. As linhas de eucaliptos foram separadas, segundo a intensidade de movimentação das máquinas de colheita, em corte, galhada e tráfego. A redução da produtividade do eucalipto chegou até dois terços, comparando-se linhas de tráfego intenso das máquinas e sem tráfego. A camada superficial do solo (0 a 10 cm) recuperou parcialmente a estrutura durante os sete anos. A compactação foi máxima na camada de 10 a 20 cm, no solo argiloso e na camada de 20 a 30 cm, no solo arenoso. Houve correlação negativa (r² = 0,86) entre a densidade global, na profundidade de 10 a 20 cm, e o volume de madeira das linhas de eucalipto no solo arenoso. No solo argiloso, essa correlação (r² = 0,77) negativa ocorreu na profundidade de 20 a 30 cm

Multiloop divergences in the closed bosonic string theory

The structure of the divergences in the multiloop vacuum diagrams for the closed bosonic strings in the framework of the Polyakov covariant formalism is discussed. It is found, by an explicit computation, that all the divergences in the theory may be interpreted as due to tadpole diagrams in which the dilaton goes into the vacuum

Modificações nos atributos físicos de solos submetidos a dois sistemas de preparo em rebrota de Eucalyptus saligna.

Este trabalho teve como objetivos avaliar o efeito do revolvimento do solo das entrelinhas na produtividade de rebrota de Eucalyptus saligna, por meio das modificações em alguns atributos físicos do solo, e estabelecer qual profundidade de revolvimento apresenta maior ganho em produtividade em solos de texturas distintas, no Estado de São Paulo. Os sistemas de preparo foram: grade até 20 cm de profundidade e subsolador até 30 cm. Foram obtidas amostras indeformadas do solo nas seguintes profundidades: 0 a 10, 10 a 20 e 20 a 30 cm, em nove repetições por tratamento; nos mesmos pontos foram coletadas amostras de solo para análise da fertilidade. Os seguintes atributos físicos do solo foram determinados: densidade do solo, porosidade total e de aeração, macro e microporosidade e da planta: altura e DAP (Diâmetro à Altura do Peito). No solo de textura média não houve efeito do preparo do solo no crescimento das plantas, sendo estabelecido correlação negativa entre a porosidade de aeração, na profundidade de 10 - 20 cm, e o incremento em DAP (r2= 0,74). Essa mesma correlação foi positiva no solo de textura argilosa (r2 = 0,78). No solo de textura argilosa, os dois sistemas de preparo de solo apresentaram maiores incrementos em altura e DAP do que a testemunha, diferindo estatisticamente no nível de 1%, pelo teste de Tukey

D-Brane Topology Changing Transitions

We study D-branes on three-dimensional orbifold backgrounds that admit topologically distinct resolutions differing by flop transitions. We show that these distinct phases are part of the vacuum moduli space of the super Yang-Mills gauge theory describing the D-brane dynamics. In this way we establish that D-branes --- like fundamental strings --- allow for physically smooth topology changing transitions.Comment: 16 pages, 3 figures, Harvma