We suggest that vacuum entanglement energy associated with the entanglement entropy of the universe is the origin of dark energy. The observed properties of dark energy can be explained by using the nature of entanglement energy without modification of gravity or exotic matter. From the number of degrees of freedom in the standard model, we obtain the equation of state parameter ω 0 Λ ≃ −0.93 and d ≃ 0.95 for the holographic dark energy, which are consistent with current observational data at the 95% confidence level. * Electronic address: scikid@kias.re.kr

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Rotating charged Gauss-Bonnet black hole solutions in higher dimensional (d > 4), asymptotically anti-de Sitter spacetime are obtained in the small angular momentum limit. The angular momentum, magnetic dipole moment, and the gyromagnetic ratio of the black holes are calculated and it turns out that the Gauss-Bonnet term does not affect to the gyromagnetic ratio.

We construct a quantum field theory in noncommutative spacetime by twisting the algebra of quantum operators (especially, creation and annihilation operators) of the corresponding quantum field theory in commutative spacetime. The twisted Fock space and S-matrix consistent with this algebra have been constructed. The resultant S-matrix is consistent with that of Filk [37]. We find from this formulation that the spin-statistics relation is not violated in the canonical noncommutative field theories.