9,492 research outputs found

    On the Behavior of F2 and its Logarithmic Slopes

    Get PDF
    It is shown that the CKMT model for the nucleon structure function F2, taken as the initial condition for the NLO evolution equations in perturbative QCD, provides a good description of the HERA data when presented in the form of the logarithmic slopes of F2 vs x and Q2 (Caldwell-plot), in the whole available kinematic ranges. Also the results obtained for the behavior of the gluon component of a nucleon are presented.Comment: 16 pages, 10 figure

    Improved bounds for the number of forests and acyclic orientations in the square lattice

    Get PDF
    In a recent paper Merino and Welsh (1999) studied several counting problems on the square lattice LnL_n. The authors gave the following bounds for the asymptotics of f(n)f(n), the number of forests of LnL_n, and α(n)\alpha(n), the number of acyclic orientations of LnL_n: 3.209912limnf(n)1/n23.841613.209912 \leq \lim_{n\rightarrow\infty} f(n)^{1/n^2} \leq 3.84161 and 22/7limnα(n)3.7092522/7 \leq \lim_{n\rightarrow\infty} \alpha(n) \leq 3.70925. In this paper we improve these bounds as follows: 3.64497limnf(n)1/n23.741013.64497 \leq \lim_{n\rightarrow\infty} f(n)^{1/n^2} \leq 3.74101 and 3.41358limnα(n)3.554493.41358 \leq \lim_{n\rightarrow\infty} \alpha(n) \leq 3.55449. We obtain this by developing a method for computing the Tutte polynomial of the square lattice and other related graphs based on transfer matrices

    Discrete variational integrators and optimal control theory

    Get PDF
    A geometric derivation of numerical integrators for optimal control problems is proposed. It is based in the classical technique of generating functions adapted to the special features of optimal control problems.Comment: 17 page

    Geometric numerical integration of nonholonomic systems and optimal control problems

    Get PDF
    A geometric derivation of numerical integrators for nonholonomic systems and optimal control problems is obtained. It is based in the classical technique of generating functions adapted to the special features of nonholonomic systems and optimal control problems.Comment: 6 pages, 1 figure. Submitted to IFAC Workshop on Lagrangian and Hamiltonian Methods for Nonlinear Control, Sevilla 200

    Tulczyjew's triples and lagrangian submanifolds in classical field theories

    Get PDF
    In this paper the notion of Tulczyjew's triples in classical mechanics is extended to classical field theories, using the so-called multisymplectic formalism, and a convenient notion of lagrangian submanifold in multisymplectic geometry. Accordingly, the dynamical equations are interpreted as the local equations defining these lagrangian submanifolds.Comment: 29 page

    On the Moyal deformation of Nahm Equations in seven dimensions

    Full text link
    We show how the reduced (anti-)self-dual Yang-Mills equations in seven dimensions described by the Nahm equations can be carried over to the Weyl-Wigner-Moyal formalism. In the process some new solutions for the cases of gauge groups SU(2) and SL(2,R) are explicitly obtained.Comment: 16+1 pages, LaTeX, no figure
    corecore