THE WAVELENGTH OF GRAVITATIONAL WAVES PRODEUCED BY EXTENDED INFLATION

In contrast to conventional belief that extended inflation ends when the Universe percolates, we find inflation may continue at least many Hubble times even after the Universe percolates. What is observed is that inflation will not stop unless the global equation of state changes from inflationary one into radiation one. Thus the energy density of shorter wavelength gravitational waves induced by bubble collision at near the end of inflation should be at least Order $(10^2)\~O(10^3)$ times greater than previous estimation of Turner and Wilcek(TW).