Lattice Monte Carlo Study Research Articles

Self-diffusion in polymer solutions using the bond-fluctuation MC-algorithm

A lattice Monte Carlo study of the self-diffusion of polymer chains in an athermal solution of equal chains is presented. The examined chain lengths, N (= 20–200), and volume fractions, φ (= 0.025-0.5), cover the range from dilute solution to concentrated solution, respectively. The dynamics show a gradual crossover from Rouse to reptation-like behaviour. Analysing the data according to a scaling theory and taking into account the density dependence of the microscopic length and time-scales, an almost perfect scaling of the self-diffusion coefficient is achieved. The high statistical accuracy of the data (10 3–10 4 chains per parameter combination) was obtainable by using a transputer-based parallel computer.

Distribution of the color fields around static quarks: Lattice sum rules.

A lattice Monte Carlo study of the color fields in the sector of static {ital q{bar q}} pairs is reported. Lattice sum rules relating these observables to the {ital q{bar q}} potential are tested in detail. As a by-product the {beta} function of the SU(2) Yang-Mills theory is determined with high accuracy.

Formation and stability of quantised (non-abelian) magnetic monopoles: A lattice Monte Carlo study

We put the Georgi-Glashow model on a lattice, and use Monte Carlo techniques to investigate the quantum physics of its monopoles. For appropriate bare couplings the monopoles are stable (suggesting that theories in which the Higgs scalars are composite will also generate monopoles). We show how the history of a monopole depends on the volume of space-time in which it is originally created; anti-monopoles usually appear in “hot spots” on the domain wall separating the monopole from the rest of the universe, and these may annihilate with the monopole, or they may form a quasi-stable system. We observe how a condensation of “(anti)-monopole” vacuum fluctuations can restore the broken symmetry. We also observe that in the BPS limit quantum fluctuations restore the symmetry, so that in that limit there are no monopoles.