  We investigate the large-volatility dynamics in financial markets, based on
the minute-to-minute and daily data of the Chinese Indices and German DAX. The
dynamic relaxation both before and after large volatilities is characterized by
a power law, and the exponents $p_\pm$ usually vary with the strength of the
large volatilities. The large-volatility dynamics is time-reversal symmetric at
the time scale in minutes, while asymmetric at the daily time scale. Careful
analysis reveals that the time-reversal asymmetry is mainly induced by
exogenous events. It is also the exogenous events which drive the financial
dynamics to a non-stationary state. Different characteristics of the Chinese
and German stock markets are uncovered.

Statistical Finance;Physics and Society