Cosmic Strings and Quintessence

We present a new Lorentz gauge invariant U(1) topological field theory in Riemann-Cartan spacetime manifold U4. By virtue of the decomposition theory of U(1) gauge potential and the φ–mapping topological current theory, it is proved that the U(1) complex scalar field φ(x) can be looked upon as the order parameter field in our Universe, and the set of zero points of φ(x) create the cosmic strings as the spacetime defects in the early Universe. In the standard cosmology this complex scalar order parameter field possesses negative pressure, provides an accelerating expansion of Universe and be able to explain the inflation in the early Universe. Therefore this complex scalar field is not only the order parameter field created the cosmic strings, but also reasonably behaves as the quintessence, the dark energy.