On the Universality of Matrix Models for Random Surfaces

We present an alternative procedure to eliminate irregular contributions in the perturbation expansion of c=0-matrix models representing the sum over triangulations of random surfaces, thereby reproducing the results of Tutte [1] and Brezin et al. [2] for the planar model. The advantage of this method is that the universality of the critical exponents can be proven from general features of the model alone without explicit determination of the free energy and therefore allows for several straightforward generalizations including cases with non-vanishing central charge c< 1.Comment: 9 pages, 3 figure

Perturbative analysis on infrared aspects of noncommutative QED on R^4

Here we examine the noncommutative counterpart of QED, which is called as noncommutative QED. The theory is obtained by examining the consistent minimal coupling to noncommutative U(1) gauge field. The *-product admits the coupling of the matter with only three varieties of charges, i.e., 0, +1 and -1. Ultraviolet divergence can be absorbed into the rescaling of the fields and the parameters at least at one loop level. To examine the infrared aspect of the theory the anomalous magnetic dipole moment is calculated. The dependence on the direction of photon momentum reflects the Lorentz symmetry violation of the system. The explicit calculation of the finite part of the photon vacuum polarization shows the singularity ln({q C^TC q}) (C^{\mu\nu} is a noncommutative parameter.) in the infrared side which also exists in noncommutative Yang-Mills theory. It is associated with the ultraviolet behavior of the theory. We also consider the extension to chiral gauge theory in the present context, but the requirement of anomaly cancellation allows only noncommutative QED.Comment: 10 pages, LaTEX2e, A part of results changed, reference adde

Quantum Zeno Features of Bistable Perception

A generalized quantum theoretical framework, not restricted to the validity domain of standard quantum physics, is used to model the dynamics of the bistable perception of ambiguous visual stimuli. The central idea is to treat the perception process in terms of the evolution of an unstable two-state quantum system, yielding a quantum Zeno type of effect. A quantitative relation between the involved time scales is theoretically derived. This relation is found to be satisfied by empirically obtained cognitive time scales relevant for bistable perception.Comment: 19 pages, 1 figur

Search for Scaling Dimensions for Random Surfaces with c=1

We study numerically the fractal structure of the intrinsic geometry of random surfaces coupled to matter fields with $c=1$. Using baby universe surgery it was possible to simulate randomly triangulated surfaces made of 260.000 triangles. Our results are consistent with the theoretical prediction $d_H = 2+\sqrt{2}$ for the intrinsic Hausdorff dimension.Comment: 10 pages, (csh will uudecode and uncompress ps-file), NBI-HE-94-3

Systematic errors due to linear congruential random-number generators with the Swendsen-Wang algorithm: A warning

We show that linear congruential pseudo-random-number generators can cause systematic errors in Monte Carlo simulations using the Swendsen-Wang algorithm, if the lattice size is a multiple of a very large power of 2 and one random number is used per bond. These systematic errors arise from correlations within a single bond-update half-sweep. The errors can be eliminated (or at least radically reduced) by updating the bonds in a random order or in an aperiodic manner. It also helps to use a generator of large modulus (e.g. 60 or more bits).Comment: Revtex4, 4 page

Der Pandemie-bedingte Lockdown legt Strukturkonservativismen im System Schule offen

Ausgerechnet die Krise der exzessiven COVID-19-Pandemie und die damit einhergehenden Lockdowns avanciert zu einer Bestandsaufnahme in Sachen Steuerung und Umsetzung der digitalen Transformation von Schule und Unterricht. Allerorts wird kontrovers darüber diskutiert, wie die ad hoc eingeführten ‚Online-Unterricht‘-, ‚Distance Learning‘- und/oder ‚Hybrid-Unterricht‘-Arrangements zu bewerten sind und welche Folgen und Konsequenzen diese für die „Generation Corona“ zeitigen. Der Beitrag berichtet über das virtuelle Online-Forum „Qualitätsstandards für das Lernen mit digitalen Medien“, welches das Ministerium für Bildung, Wissenschaft und Kultur des Landes Schleswig-Holstein, Deutschland, in Kiel am 06.02.2021 veranstaltete. Der Ablauf der thematisch einschlägigen Konferenz wird detailliert nachgezeichnet und kritisch im Kontext des sogenannten „digitalen Lernens“ auf dem sachlich gebotenen Weg zu einer digitalen Schulkultur und schulischen Medienkultur verortet. Schlussendlich legt das digital-unterstützte Lernen unter Pandemie-Bedingungen einen bedenklichen Strukturkonservativismus im Bildungssystem offen