Gauge symmetries change the number of Dp-brane dimensions

It is known that the presence of antisymmetric background field $B_{\mu\nu}$ leads to noncommutativity of Dp-brane manifold. Addition of the linear dilaton field in the form $\Phi(x)=\Phi_0+a_\mu x^\mu$, causes the appearance of the commutative Dp-brane coordinate $x=a_\mu x^\mu$. In the present article we show that for some particular choices of the background fields, $a^2\equiv G^{\mu\nu}a_\mu a_\nu=0$ and $\tilde a^2\equiv \ [ (G-4BG^{-1}B)^{-1} ]^{\mu\nu}a_\mu a_\nu=0$, the local gauge symmetries appear in the theory. They turn some Neuman boundary conditions into the Dirichlet ones, and consequently decrease the number of the Dp-brane dimensions. The physical Dp-brane is just the gauge invariant part of the initial, naive brane. The noncommutativity parameter has standard form in the physical Dp-brane. It is proportional to the induced antisymmetric field with indices raised by the open and closed string metrics induced in the gauge invariant subspace