A Conjecture on the Origin of Dark Energy

A conjecture on the origin of the dark energy in our universe is proposed. The analysis indicates that the dark energy may originate from the quantum fluctuations of space--time limited in our universe. Applying both the uncertainty principle and the holographic principle, the author finds that the density of such quantum fluctuation energy is ρ _V = 3c⁴ /32GL_H ², where L_H is the size of the event horizon of our universe and G is the gravitational constant. Using this dark energy model which contains no adjustable parameters, we obtain the current fraction Ω_Λ≡ ρ_V/ρ_c π/4 and the corresponding equation of state w(z) approximate - 1 + (1 - π /4)z with ρ_c being the critical energy density. These theoretical results are perfectly consistent with the recent cosmological observations. The striking coincidence implies that the quantum fluctuation energy of space--time may be the only source of dark energy. In addition, the analysis shows that the vacuum fluctuation energy does exist, but it comes from space--time rather than matter. This may have some deep implications for discrete space--time and quantum gravity.