What we take from Einstein?
Ruslan A. Sharipov.
The “3D-brane universe model” is the name of a new non-Einsteinian theory of gravity. This theory is based on criticism and denial of the space-time as a material entity. However, it does not deny all the achievements of Einstein's theory and strives to digest and incorporate everything that is possible from Einstein's theory. In this article we analyze the elements of continuity between the two theories.
In Einstein's theory gravity is described by a four-dimensional metric. It can be understood as a 4x4 matrix, which is shown in the figure to the left of the arrow. The components of this matrix depend on coordinates and time.
Space-time in the new theory is subdivided into a foliation of 3D-branes. Each of these branes corresponds to one of the moments in the evolution of the real three-dimensional universe. The foliation of 3D-branes determines the choice of special coordinates, which are called comoving coordinates, and a special time, which is called membrane time. In these coordinates and in this time, the matrix of Einstein's metric becomes block-diagonal with diagonal blocks of the sizes 1×1 and 3×3. The content of the 1x1 diagonal block is interpreted in the new theory as a scalar field. The content of the 3x3 diagonal block in the new theory is understood as the three-dimensional metric of the real three-dimensional universe. Components of Einstein's metric that do not fall into these blocks are excluded from the new theory. They are painted over in the figure with gray rectangles.
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