arXiv subjects

A. Bode

Publications and source records attributed to A. Bode.

8 recordsLinked to original sources

arXiv2001

O(a) improved QCD: The 3-loop beta-function, and the critical hopping parameter

We calculate the 3-loop bare $β$-function of QCD, formulated on the lattice with the clover fermionic action. The dependence of our result on the number of colors $N$, the number of fermionic flavors $N_f$, and the clover parameter $c_{SW}$, is shown explicitly. A direct outcome of our calculation is the two-loop relation between the bare coupling constant $g_0$ and the one renormalized in the MS-bar scheme. Further, we can immediately derive the three-loop correction to the relation between the lattice $Λ$-parameter and $g_0$, which turns out to be very pronounced. We also calculate the critical value of the hopping parameter, $κ_c$, in the clover action, to two loops in perturbation theory. This quantity is an additive renormalization; as such, it exhibits a linear divergence in the lattice spacing. We compare our results to non perturbative evaluations of $κ_c$ coming from MC simulations.

hep-lat↗

arXiv2001

The three-loop beta-fuction of QCD with the clover action

We calculate, to 3 loops in perturbation theory, the bare $β$-function of QCD, formulated on the lattice with the clover fermionic action. The dependence of our result on the number of colors $N$, the number of fermionic flavors $N_f$, as well as the clover parameter $c_{SW}$, is shown explicitly. A direct outcome of our calculation is the two-loop relation between the bare coupling constant $g_0$ and the one renormalized in the MS-bar scheme. Further, we can immediately derive the three-loop correction to the relation between the lattice $Λ$-parameter and $g_0$, which is important in checks of asymptotic scaling. For typical values of $c_{SW}$, this correction is found to be very pronounced.

hep-lat↗

arXiv2001

Two loop lattice expansion of the Schroedinger functional coupling in improved QCD

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 MSbar-coupling. By taking into account all improvement coefficients we are able to improve the Schroedinger functional to two loop order.

hep-lat↗

arXiv1998

Two-Loop Computation of the Schroedinger Functional in Pure SU(3) Lattice Gauge Theory

We compute the Schroedinger functional (SF) for the case of pure SU(3) gauge theory at two-loop order in lattice perturbation theory. This allows us to extract the three-loop beta-function in the SF-scheme. These results are required to compute the running coupling, the Lambda-parameter and quark masses by finite size techniques with negligible systematic errors. In addition, we can now implement two-loop O(a) improvement in simulations and extend and study series in alternative ("tadpole-improved") bare couplings.

hep-lat↗

arXiv1995

Hyper-Systolic Parallel Computing

A new class of parallel algorithms is introduced that can achieve a complexity of O(n^3/2) with respect to the interprocessor communication, in the exact computation of systems with pairwise mutual interactions of all elements. Hitherto, conventional methods exhibit a communicational complexity of O(n^2). The amount of computation operations is not altered for the new algorithm which can be formulated as a kind of h-range problem, known from the mathematical field of Additive Number Theory. We will demonstrate the reduction in communicational expense by comparing the standard-systolic algorithm and the new algorithm on the connection machine CM5 and the CRAY T3D. The parallel method can be useful in various scientific and engineering fields like exact n-body dynamics with long range forces, polymer chains, protein folding or signal processing.

hep-lat↗

arXiv1995

Monopoles in Compact U(1) -- Anatomy of the Phase Transition

We present evidence that the existence of a first order phase transition in compact U(1) with Wilson action is not related to monopole loops wrapping around the toroidal lattice, as has been previously suggested. Our analysis is based on the suppression of such loops by `soft boundary conditions' that correspond to an infinitely large chemical potential for the monopoles on the boundary, during the updating process. It is observed that the double peak structure characteristic for the first order phase transition reappears at sufficiently large lattice sizes and separations from the lattice boundary.

hep-lat↗

arXiv1995

First-Order Signals in Compact QED with Monopole Suppressed Boundaries

Pure gauge compact QED on hypercubic lattices is considered with periodically closed monopole currents suppressed. We compute observables on sublattices which are nested around the centre of the lattice in order to locate regions where translation symmetry is approximately recovered. Our Monte Carlo simulations on $24^4$-lattices give indications for a first-order nature of the U(1) phase transition.

hep-lat↗

arXiv1993

Monopole clusters and critical dynamics in four-dimensional U(1)

We investigate monopoles in four-dimensional compact U(1) with Wilson action. We focus our attention on monopole clusters as they can be identified unambiguously contrary to monopole loops. We locate the clusters and determine their properties near the U(1) phase transition. The Coulomb phase is characterized by several small clusters, whereas in the confined phase the small clusters coalesce to one large cluster filling up the whole system. We find that clusters winding around the periodic lattice are absent within both phases and during the transition. However, within the confined phase, we observe periodically closed monopole loops if cooling is applied.

hep-lat↗