Probing the dynamical behavior of dark energy

We investigate dynamical behavior of the equation of state of dark energy w_de 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 w_de 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 w_de where w_de 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 w_de between two nearby divided points can be well approximated by a linear expansion of redshift. We find two turning points of w_de in z∊(0,1.8) and one turning point in z∊(0,0.9), and w_de(z) could be oscillating around w = −1. Moreover, we find that there is a 2σ deviation of w_de from around z = 0.9 in both correlated and uncorrelated estimates.