Gravitational binding in 4D dynamical triangulation

In the dynamical triangulation model of four dimensional euclidean quantum gravity we investigate gravitational binding. Two scalar test particles (quenched approximation) have a positive binding energy, thereby showing that the model can represent gravitational attraction.Comment: 19 pages, LaTeX2e, version as accepted by Nucl Phys

Absence of barriers in dynamical triangulation

Due to the unrecognizability of certain manifolds there must exist pairs of triangulations of these manifolds that can only be reached from each other by going through an intermediate state that is very large. This might reduce the reliability of dynamical triangulation, because there will be states that will not be reached in practice. We investigate this problem numerically for the manifold $S^5$, which is known to be unrecognizable, but see no sign of these unreachable states.Comment: 8 pages, LaTeX2e source with postscript resul

New Developments in Treacherous Points of Light-Front Dynamics

Light-front dynamics(LFD) plays an important role in hadron phenomenology. Last few years, however, it has been emphasized that treacherous points such as zero-mode contributions should be taken into account for successful LFD applications to hadron phenomenology. We discuss examples of treacherous points and present new progresses made last few years to handle them correctly.Comment: 5 pages, espcrc1.sty. proceedings of FB XVIII (August 2006, Brazil), to be published in Nucl. Phys.

Further evidence that the transition of 4D dynamical triangulation is 1st order

We confirm recent claims that, contrary to what was generally believed, the phase transition of the dynamical triangulation model of four-dimensional quantum gravity is of first order. We have looked at this at a volume of 64,000 four-simplices, where the evidence in the form of a double peak histogram of the action is quite clear.Comment: 12 pages, LaTeX2

Revealing treacherous points for successful light-front phenomenological applications

Light-front dynamics(LFD) plays an important role in hadron phenomenology as evidenced from recent development of generalized parton distributions and other quantities involving hadrons. For successful LFD applications to hadron phenomenology, however, treacherous points such as zero-mode contributions should be taken into account. For a concrete example of zero-mode contribution, we present Standard Model analysis of vector anomaly in the CP-even form factors of W^{\pm} gauge bosons. Main distinguished features of LFD is discussed in comparison with other Hamiltonian dynamics. We also present a power counting method to correctly pin down which hadron form factors receive the zero-mode contribution and which ones do not. Indications from our analysis to hadron phenomenology are discussed.Comment: 6 pages; requires espcrc2.sty; to appear in the proceedings of Workshop on Light-Cone QCD and Nonperturbative Hadron Physics 2005 (LC 2005), Cairns, Queensland, Australia, 7-15 Jul 200

Resonance and morphological stability of tidal basins

The paper describes the concept of a network model for the morphological behaviour of a near-resonant multiple-inlet tidal basin, as part of a model system which includes the barrier island coasts and the outer deltas. It addresses the question whether a small interference somewhere in such a basin can have major effects on sediment transport and morphology elsewhere in the system.\ud \ud In order to explain the basic ideas of the model, only the main tidal constituent (M2) and the associated topography-induced residual current are considered, not the overtides. Furthermore, the model concerns only non-cohesive sediment (sand).\ud \ud In spite of these simplifications, the model concept is shown to be effective, in that it results in a morphological evolution equation for each branch of the network and a picture of the influence of each branch on the resonance-sensitivity of the system as a whole

Metric Semantics and Full Abstractness for Action Refinement and Probabilistic Choice

This paper provides a case-study in the field of metric semantics for probabilistic programming. Both an operational and a denotational semantics are presented for an abstract process language L_pr, which features action refinement and probabilistic choice. The two models are constructed in the setting of complete ultrametric spaces, here based on probability measures of compact support over sequences of actions. It is shown that the standard toolkit for metric semantics works well in the probabilistic context of L_pr, e.g. in establishing the correctness of the denotational semantics with respect to the operational one. In addition, it is shown how the method of proving full abstraction --as proposed recently by the authors for a nondeterministic language with action refinement-- can be adapted to deal with the probabilistic language L_pr as well

Students and instant messaging: a survey of current use and demands for higher education

Instant messaging (IM) is the term used to describe the technology through which ‘users can set up a list of partners who will be able to receive notes that pop up on their screens the moment one of them writes and hits the send button’. While early use could be described as mainly for fun, IM today is a serious communication medium. Remarkably, it seems that educational institutions have been doing very little with it, while several studies indicate that it could indeed be a valuable tool in education. As a first step towards a better understanding of the educational use of IM, we want to gain insights in how students currently use IM and what opportunities they themselves see for the medium. To that end we conducted a survey among students of the Fontys University of Applied Sciences in The Netherlands. A large majority of the participating students indicated using IM for their studies. Also, when asked about their demands for a possible educational implementation, the majority were positive

More on the exponential bound of four dimensional simplicial quantum gravity

A crucial requirement for the standard interpretation of Monte Carlo simulations of simplicial quantum gravity is the existence of an exponential bound that makes the partition function well-defined. We present numerical data favoring the existence of an exponential bound, and we argue that the more limited data sets on which recently opposing claims were based are also consistent with the existence of an exponential bound.Comment: 10 pages, latex, 2 figure