Pseudo-Riemannian Universe from Euclidean bulk

Abstract: I develop the idea that our world is a brane-like object embedded in Euclidean bulk. In its ground state, the brane constituent matter is assumed to be homogeneous and isotropic, and of negligible influence on the bulk geometry. The analysis of this paper is model independent, in the sense that action functional of bulk fields is not specified. Instead, the behavior of the brane is derived from the universally valid conservation equation of the bulk stress tensor. The present work studies the behavior of a $3$-sphere in the $5$-dimensional Euclidean bulk. The sphere is made of bulk matter characterized by the equation of state $p=\alpha\rho$. It is shown that stability of brane vibrations requires $\alpha < 0$. Then, the stable brane perturbations obey Klein-Gordon-like equation with an effective metric of Minkowski signature. The argument is given that it is this effective metric that is detected in physical measurements. The corresponding effective Universe is analyzed for all the values of $\alpha<0$. In particular, the effective metric is shown to be a solution of Einstein's equations coupled to an effective perfect fluid. The effective energy density and pressure at the present epoch are calculated. So are the age of the Universe, and the effective cosmological constant. All the results are presented in two tables. As an illustration, one simple choice of the brane constituent matter is studied in detail.