A covariant entropy bound conjecture on the dynamical horizon

As a compelling pattern for the holographic principle, our covariant entropy bound conjecture is proposed for more general dynamical horizons. Then we apply our conjecture to ΛCDM cosmological models, where we find it imposes a novel upper bound 10 on the cosmological constant for our own universe by taking into account the dominant entropy contribution from super-massive black holes, which thus provides an alternative macroscopic perspective to understand the longstanding cosmological constant problem. As an intriguing implication of this conjecture, we also discuss the possible profound relation between the present cosmological constant, the origin of mass, and the anthropic principle. ∗Honorable Mention Award Received from Gravity Research Foundation for 2008 Essay Competition.