Distributed PC Based Routers: Bottleneck Analysis and Architecture Proposal

Recent research in the different functional areas of modern routers have made proposals that can greatly increase the efficiency of these machines. Most of these proposals can be implemented quickly and often efficiently in software. We wish to use personal computers as forwarders in a network to utilize the advances made by researchers. We therefore examine the ability of a personal computer to act as a router. We analyze the performance of a single general purpose computer and show that I/O is the primary bottleneck. We then study the performance of distributed router composed of multiple general purpose computers. We study the performance of a star topology and through experimental results we show that although its performance is good, it lacks flexibility in its design. We compare it with a multistage architecture. We conclude with a proposal for an architecture that provides us with a forwarder that is both flexible and scalable.© IEE

Magnetic field generation by pointwise zero-helicity three-dimensional steady flow of incompressible electrically conducting fluid

We introduce six families of three-dimensional space-periodic steady solenoidal flows, whose kinetic helicity density is zero at any point. Four families are analytically defined. Flows in four families have zero helicity spectrum. Sample flows from five families are used to demonstrate numerically that neither zero kinetic helicity density, nor zero helicity spectrum prohibit generation of large-scale magnetic field by the two most prominent dynamo mechanisms: the magnetic $\alpha$-effect and negative eddy diffusivity. Our computations also attest that such flows often generate small-scale field for sufficiently small magnetic molecular diffusivity. These findings indicate that kinetic helicity and helicity spectrum are not the quantities controlling the dynamo properties of a flow regardless of whether scale separation is present or not.Comment: 37 pages, 11 figures, 54 reference

Network Friendly P2P-TV: The Napa-Wine Approach

DEMO Sessio

Branching rules of semi-simple Lie algebras using affine extensions

We present a closed formula for the branching coefficients of an embedding p in g of two finite-dimensional semi-simple Lie algebras. The formula is based on the untwisted affine extension of p. It leads to an alternative proof of a simple algorithm for the computation of branching rules which is an analog of the Racah-Speiser algorithm for tensor products. We present some simple applications and describe how integral representations for branching coefficients can be obtained. In the last part we comment on the relation of our approach to the theory of NIM-reps of the fusion rings of WZW models with chiral algebra g_k. In fact, it turns out that for these models each embedding p in g induces a NIM-rep at level k to infinity. In cases where these NIM-reps can be be extended to finite level, we obtain a Verlinde-like formula for branching coefficients.Comment: 11 pages, LaTeX, v2: one reference added, v3: Clarified proof of Theorem 2, completely rewrote and extended Section 5 (relation to CFT), added various references. Accepted for publication in J. Phys.

Charges of Exceptionally Twisted Branes

The charges of the exceptionally twisted (D4 with triality and E6 with charge conjugation) D-branes of WZW models are determined from the microscopic/CFT point of view. The branes are labeled by twisted representations of the affine algebra, and their charge is determined to be the ground state multiplicity of the twisted representation. It is explicitly shown using Lie theory that the charge groups of these twisted branes are the same as those of the untwisted ones, confirming the macroscopic K-theoretic calculation. A key ingredient in our proof is that, surprisingly, the G2 and F4 Weyl dimensions see the simple currents of A2 and D4, respectively.Comment: 19 pages, 2 figures, LaTex2e, complete proofs of all statements, updated bibliograph