No abstract available

No abstract available

[en] The clover coefficient c_sw is computed at one loop order of perturbation theory for improved gluon actions including six-link loops. The O(a) improvement coefficients for the dimension three isovector composite operators bilinear in the quark fields are also calculated

[en] The 7-particle form factors of the fundamental spin field of the O(3) non-linear σ-model are constructed. We calculate the corresponding contribution to the spin-spin correlation function, and compare with predictions from the spectral density scaling hypothesis. The resulting approximation to the spin-spin correlation function agrees well with that computed in renormalized (asymptotically free) perturbation theory in the expected energy range. Further we observe simple lower and upper bounds for the sum of the absolute square of the form factors which may be of use for analytic estimates

[en] The contributions of the improved fermion action of Sheikholeslami and Wohlert to the two loop coefficient of the expansion of the Schroedinger functional coupling in terms of the lattice coupling are calculated for the gauge group SU(3). These coefficients are required for the second order relation of lattice data to the MS-bar-coupling. By taking into account all improvement coefficients we are able to improve the Schroedinger functional to two loop order

[en] We review the various computations of the ratio of the mass gap M to the Λ-parameter entering the perturbative computations of amplitudes at high energies in the O(n) non-linear σ-model. In particular we reproduce from original notes of H. Lehmann his computation of this ratio in the (next-to) leading order of the 1/n expansion. (orig.)

[en] The origin of the discrepancy between recent calculations of the connection between the Λ-parameters of lattice and continuum pure gauge theory is explained. The calculation is extended to include fermions. (orig.)

[en] Symanzik's programme for constructing a lattice action with improved continuum limit behaviour is considered for the case of pure Yang-Mills theory. The structure of the action is proposed and discussed in detail to lowest order perturbation theory. (orig.)

[en] Symanzik's programme for constructing a lattice action with improved continuum limit behaviour is considered for the case of pure Yang-Mills theory. The structure of the action is proposed and discussed in detail to lowest order in perturbation theory. (orig.)

[en] Wilson loops are calculated to one-loop order using lattice actions including 6-link loops. The static potential is extracted and its small-a expansion performed using coefficients determined at tree level. The Λ-parameter for Symanzik's improved action is thereby obtained and constraints placed on the coefficients appearing in the action at order g². (orig.)