Dark Energy and Dark Matter in Emergent Gravity

We suggest that dark energy and dark matter may be a cosmic ouroboros of quantum gravity due to the coherent vacuum structure of spacetime. We apply the emergent gravity to a large $N$ matrix model by considering the vacuum in the noncommutative (NC) Coulomb branch satisfying the Heisenberg algebra. We observe that UV fluctuations in the NC Coulomb branch are always paired with IR fluctuations and these UV/IR fluctuations can be extended to macroscopic scales. We show that space-like fluctuations give rise to the repulsive gravitational force while time-like fluctuations generate the attractive gravitational force. When considering the fact that the fluctuations are random in nature and we are living in the (3+1)-dimensional spacetime, the ratio of the repulsive and attractive components will end in $\frac{3}{4}: \frac{1}{4}=75:25$ and this ratio curiously coincides with the dark composition of our current Universe. If one includes ordinary matters which act as the attractive force, the emergent gravity may explain the dark sector of our Universe more precisely.Comment: v3; two appendices and references are added, 20 page

Communication with SIMP dark mesons via Z'-portal

We consider a consistent extension of the SIMP models with dark mesons by including a dark U(1)_D gauge symmetry. Dark matter density is determined by a thermal freeze-out of the $3\to2$ self-annihilation process, thanks to the Wess-Zumino-Witten term. In the presence of a gauge kinetic mixing between the dark photon and the SM hypercharge gauge boson, dark mesons can undergo a sufficient scattering off the Standard Model particles and keep in kinetic equilibrium until freeze-out in this SIMP scenario. Taking the SU(N_f)xSU(N_f)/SU(N_f) flavor symmetry under the SU(N_c) confining group, we show how much complementary the SIMP constraints on the parameters of the dark photon are for current experimental searches for dark photon.Comment: 16 pages, 6 figures, To appear in Phys. Lett.