Probing the dynamical behavior of dark energy

We investigate dynamical behavior of the equation of state of dark energy wde by employing the linear-spline method in the region of low redshifts from observational data (SnIa, BAO, CMB and 12 H(z) data). The redshift is binned and wde is approximated by a linear expansion of redshift in each bin. We leave the divided points of redshift bins as free parameters of the model, the best-fitted values of divided points will represent the turning positions of wde where wde changes its evolving direction significantly (if there exist such turnings in our considered region). These turning points are natural divided points of redshift bins, and wde between two nearby divided points can be well approximated by a linear expansion of redshift. We find two turning points of wde in z(0,1.8) and one turning point in z(0,0.9), and wde(z) could be oscillating around w = -1. Moreover, we find that there is a 2 Delta *s deviation of wde from around z = 0.9 in both correlated and uncorrelated estimates. Keywords->