Multigravity in six dimensions: Generating bounces with flat positive tension branes

We present a generalization of the five dimensional multigravity models to six dimensions. The key characteristic of these constructions is that that we obtain solutions which do not have any negative tension branes while at the same time the branes are kept flat. This is due to the fact that in six dimensions the internal space is not trivial and its curvature allows bounce configurations with the above feature. These constructions give for the first time a theoretically and phenomenologically viable realization of multigravity.Comment: 27 pages, 13 figures, typos correcte

Multiprocessor interrupting and synchronizing concepts in the parallel SIMULA machine and their representation by Petri-Nets

Large-scale discrete time simulation is an application area which demands high speed processing. This specific application area requires the design of new machine architectures which are feasible as a result of the current technological advances. These machine architectures can be implemented by multiprocessor structures so as to provide high performance by exploiting parallelism which characterizes many dynamic simulation models. SIMULA 67 is a powerful general purpose programming language which includes features for advanced and complex software simulation products. The process structure of SIMULA allows for the definition of concurrent tasks which can be executed in parallel by a multiprocessor configuration. Such configurations support a high degree of synchronization and interrupt mechanisms to control the evolution of parallel processes. This paper elaborates the synchronizing and interrupting concepts incorporated in the design of a parallel SIMULA machine and represents these concepts by their corresponding Petri-Net equivalents. © 1985

Nonlinear propagation dynamics of finite-energy Airy beams

The nonlinear dynamics of intense truncated Airy beams in Kerr ionizing media are investigated from numerical simulations and experiments. We show numerically that a competition between the linear and nonlinear effects takes place and may be modified by tuning the width of the main lobe of the Airy beam and the size of the truncating diaphragm. Our analysis shows that the acceleration of the Airy peak, an inherent feature of linear Airy beam propagation, is preserved only for powers in the main Airy lobe below a certain threshold. Nonlinear propagation of intense Airy beams with low power in the main lobe is sustained by a continuous energy flux from its neighbors, similarly to the mechanism sustaining nonlinear Bessel beam propagation. Airy beams with higher powers in the main lobe are reshaped into a multifilamentary pattern induced by Kerr and multiphoton nonlinearities. The nucleation of new filaments and their interaction affect the acceleration of the main Airy lobes. We finally show that the size of the truncation constitutes a control parameter for the energy flux that features the Airy beam acceleration. Experiments performed in water corroborate the existence of these two distinct nonlinear propagation regimes