Secular increase of the astronomical unit and perihelion precessions as tests of the Dvali-Gabadadze-Porrati multi-dimensional braneworld scenario

An unexpected secular increase of the astronomical unit, the length scale of the Solar System, has recently been reported by three different research groups (Krasinsky and Brumberg, Pitjeva, Standish). The latest JPL measurements amount to 7 +/- 2 m cy(-1). At present, there are no explanations able to accommodate such an observed phenomenon, either in the realm of classical physics or in the usual four-dimensional framework of the Einsteinian general relativity. The Dvali-Gabadadze-Porrati braneworld scenario, which is a multi-dimensional model of gravity aimed at providing an explanation of the observed cosmic acceleration without dark energy, predicts, among other things, a perihelion secular shift, due to Lue and Starkman, of 5 x 10(-4) arcsec cy(-1) for all the planets of the Solar System. It yields a variation of about 6 m cy(-1) for the Earth-Sun distance which is compatible with the observed rate of change for the astronomical unit. The recently measured corrections to the secular motions of the perihelia of the inner planets of the Solar System are in agreement with the predicted value of the Lue-Starkman effect for Mercury, Mars and, at a slightly worse level, the Earth.