Recurrence Plot and Recurrence Quantification Analysis Techniques for   Detecting a Critical Regime. Examples from Financial Market Indices
  Recurrence Plot (RP) and Recurrence Quantification Analysis (RQA) are signal numerical analysis methodologies able to work with non linear dynamical systems and non stationarity. Moreover they well evidence changes in the states of a dynamical system. We recall their features and give practical recipes. It is shown that RP and RQA detect the critical regime in financial indices (in analogy with phase transition) before a bubble bursts, whence allowing to estimate the bubble initial time. The analysis is made on DAX and NASDAQ daily closing price between Jan. 1998 and Nov. 2003. DAX is studied in order to set-up overall considerations, and as a support for deducing technical rules. The NASDAQ bubble initial time has been estimated to be on Oct. 19, 1999. 
A. Fabretti (Dpt Mathematics for Economy, Insurances and Finance   Applications, U. Roma 1), M. Ausloos (Supratecs, U. Liege)