In discrete-time dynamical systems arising from economic problems, the length of the period (henceforth simply "period") separating two successive values of the state variables may play an essential role in determining the type of dynamics followed by the system. In economics, this fact is...

The recent nancial market turmoil has raised the question whether certain countries, in particular Italy and Spain, were facing a liquidity or a solvency problem. Some economists re{phrased this problem, by asking whether those countries' crisis was triggered by investors' self- fullling...