Revolving D-branes and Spontaneous Gauge Symmetry Breaking
  We propose a new mechanism of spontaneous gauge symmetry breaking in the
world-volume theory of revolving D-branes around a fixed point of orbifolds. In
this paper, we consider a simple model of the T6/Z3 orbifold on which we put
D3-branes, D7-branes and their anti-branes. The configuration breaks
supersymmetry, but the R-R tadpole cancellation conditions are satisfied. A set
of three D3-branes at an orbifold fixed point can separate from the point, but
when they move perpendicular to the anti-D7-branes put on the fixed point, they
are forced to be pulled back due to an attractive interaction between the D3
and anti-D7 branes. In order to stabilize the separation of the D3-branes at
nonzero distance, we consider revolution of the D3-branes around the fixed
point. Then the gauge symmetry on D3-branes is spontaneously broken, and the
rank of the gauge group is reduced. The distance can be set at our will by
appropriately choosing the angular momentum of the revolving D3-branes, which
should be determined by the initial condition of the cosmological evolution of
D-brane configurations. The distance corresponds to the vacuum expectation
values of brane moduli fields in the world-volume theory and, if it is written
as M/Ms^2 in terms of the string scale Ms, the scale of gauge symmetry breaking
is given by M. Angular momentum conservation of revolving D3-branes assures the
stability of the scale M against Ms.
