In this paper we study the possibly existing anisotropy in the acceleration expansion by use of the full sample of Union2 data. Using the hemisphere comparison method to search for a preferred direction, we take the deceleration parameter q0 as the diagnostic to quantify the anisotropy level in the wCDM model. We find that the maximum accelerating expansion direction is $(l,b)=(314_{ +20^{ \circ}}^{ \circ-13^{ \circ}},28_{ +11^{ \circ}}^{ \circ-33^{ \circ}})$,with the maximum anisotropy level of $\delta q_{ 0,max}/\bar{ q}_0=0.79_{ +0.27}^{ -0.28}$, and that the anisotropy is more prominent when only low redshift data ($z\leq0.2$) are used. We also discuss this issue in the $CPL$ parameterized model, showing a similar result.
Categories: astro-ph.CO hep-ph