; Zhang, Xinmin] Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
; [Li, Mingzhe] Nanjing Univ, Dept Phys, Nanjing 210093, Peoples R China
; [Zhang, Xinmin] Chinese Acad Sci, TPCSF, Beijing 100049, Peoples R China
; [Li, Mingzhe] Nanjing Univ, Purple Mt Observ, Joint Ctr Particle Nucl Phys & Cosmol, Nanjing 210093, Peoples R China
Determining the equation of state of dark energy with astronomical observations is crucially important to understand the nature of dark energy. In performing a likelihood analysis of the data, especially of the cosmic microwave background and large scale structure data the dark energy perturbations have to be taken into account both for theoretical consistency and for numerical accuracy. Usually, one assumes in the global fitting analysis that the dark energy perturbations are adiabatic. In this paper, we study the dark energy isocurvature per analytically and discuss its implications for the cosmic microwave background radiation and large scale structure. Furthermore, with the current astronomical observational data and by employing Markov Chain Monte Carlo method, we perform a global analysis of cosmological parameters assuming general Initial conditions for the dark energy perturbations. The results show that the dark energy isocurvature perturbations are very weakly constrained and that purely adiabatic initial conditions are consistent with the data.