How good are projection methods for convex feasibility problems?

We consider simple projection methods for solving convex feasibility problems. Both successive and sequential methods are considered, and heuristics to improve these are suggested. Unfortunately, particularly given the large literature which might make one think otherwise, numerical tests indicate that in general none of the variants considered are especially effective or competitive with more sophisticated alternatives

Teaching statistical physics by thinking about models and algorithms

We discuss several ways of illustrating fundamental concepts in statistical and thermal physics by considering various models and algorithms. We emphasize the importance of replacing students' incomplete mental images by models that are physically accurate. In some cases it is sufficient to discuss the results of an algorithm or the behavior of a model rather than having students write a program.Comment: 21 pages, 4 figures, submitted to the American Journal of Physic

Real trade-weighted value of the dollar holds, despite fall against the yen and mark

International trade

Immigrant links to the home country: implications for trade, welfare and factor rewards

Human capital ; Emigration and immigration ; International trade

Has NAFTA changed North American trade?

The controversy over the success or failure of NAFTA is now bleeding over into discussion about the benefits of extending the trade accord to other countries in the Western Hemisphere. The NAFTA debate has typically focused on its impact on employment. But to understand the overall economic effects of NAFTA, it is important to first determine its impact on trade. In this article, David Gould explores NAFTA's effects on North America's trading patterns since its implementation in 1994. He finds that although it is difficult to distinguish any effect of NAFTA on trade between Canada and Mexico or Canada and the United States, trade between the United States and Mexico has significantly increased since 1994.North American Free Trade Agreement ; Free trade

Does the choice of nominal anchor matter?

The conventional wisdom on nominal anchors is that exchange rate-based inflation stabilizations lead to economic booms while monetary-based stabilizations lead to recessions. This study finds strong evidence against this view. Rather than determining the path of economic growth, the choice of nominal anchor appears to be endogenously determined by the state of the economy. To peg or manage the exchange rate, a high level of international reserves is important, especially when a government's credibility is low after a period of high inflation. After controlling for the level of international reserves and the rate of inflation, growth after monetary-based stabilizations does not significantly differ from that following exchange rate-based stabilizations. ; Economic Research Working Paper 9914Inflation (Finance)

R-matrices and Tensor Product Graph Method

A systematic method for constructing trigonometric R-matrices corresponding to the (multiplicity-free) tensor product of any two affinizable representations of a quantum algebra or superalgebra has been developed by the Brisbane group and its collaborators. This method has been referred to as the Tensor Product Graph Method. Here we describe applications of this method to untwisted and twisted quantum affine superalgebras.Comment: LaTex 7 pages. Contribution to the APCTP-Nankai Joint Symposium on "Lattice Statistics and Mathematical Physics", 8-10 October 2001, Tianjin, Chin

Finding a point in the relative interior of a polyhedron

A new initialization or `Phase I' strategy for feasible interior point methods for linear programming is proposed that computes a point on the primal-dual central path associated with the linear program. Provided there exist primal-dual strictly feasible points - an all-pervasive assumption in interior point method theory that implies the existence of the central path - our initial method (Algorithm 1) is globally Q-linearly and asymptotically Q-quadratically convergent, with a provable worst-case iteration complexity bound. When this assumption is not met, the numerical behaviour of Algorithm 1 is highly disappointing, even when the problem is primal-dual feasible. This is due to the presence of implicit equalities, inequality constraints that hold as equalities at all the feasible points. Controlled perturbations of the inequality constraints of the primal-dual problems are introduced - geometrically equivalent to enlarging the primal-dual feasible region and then systematically contracting it back to its initial shape - in order for the perturbed problems to satisfy the assumption. Thus Algorithm 1 can successfully be employed to solve each of the perturbed problems.\ud We show that, when there exist primal-dual strictly feasible points of the original problems, the resulting method, Algorithm 2, finds such a point in a finite number of changes to the perturbation parameters. When implicit equalities are present, but the original problem and its dual are feasible, Algorithm 2 asymptotically detects all the primal-dual implicit equalities and generates a point in the relative interior of the primal-dual feasible set. Algorithm 2 can also asymptotically detect primal-dual infeasibility. Successful numerical experience with Algorithm 2 on linear programs from NETLIB and CUTEr, both with and without any significant preprocessing of the problems, indicates that Algorithm 2 may be used as an algorithmic preprocessor for removing implicit equalities, with theoretical guarantees of convergence

Bounding the Tau Neutrino Magnetic Moment from Single Photon Searches at LEP

We show that single photon searches at LEP constrain the tau neutrino magnetic moment to be less than ${\cal O}(10^{-6})~\mu_B$. This bound is competitive with low energy ($s\simeq (30~GeV)^2$) single photon searches.Comment: 5 pgs. LaTeX, one reference fixed in revised version, JHU-TIPAC-940004, UM-TH-94-1