There has been a lot of recent interest in so-called "steady state" genetic algorithms (GAs) which, among other things, replace only a few individuals (typically 1 or 2) each generation from a fixed size population of size N. Understanding the advantages and/or disadvantages of replacing only a fraction of the population each generation (rather than the entire population) was a goal of some of ...

In this paper, we derive principles of optimal cyclical monetary policy in an economy without capital, with a cash-in-advance restriction on household transactions, and monopolistic firms that set prices one period in advance. The only distortionary policy instruments are the nominal interest rate and the money supply. In this environment it is feasible to undo both the cash-in-advance and pric...

Through Bridging the Gaps, an internship program that links health-related service with interdisciplinary training, Penn Dental Medicine students reach out to Philadelphia's neediest neighborhoods--and receive huge rewards in return.

We define a direct translation from finite rooted trees to finite natural functions which shows that the Worm Principle introduced by Lev Beklemishev is equivalent to a very slight variant of the well-known Kirby-Paris’ Hydra Game. We further show that the elements in a reduction sequence of the Worm Principle determine a bad sequence in the well-quasi-ordering of finite sequences of natural nu...

An excess of events with a rapidity gap between jets, over what would be expected from non-diffractive processes, has been observed at HERA. A process based on a perturbative QCD calculation of colour singlet exchange has been added to HERWIG. With this addition, HERWIG is able to describe the number of events with a gap between jets over the number without a gap. This gap fraction is predicted...