"Tunneling" Amplitudes of a Massless Quantum Field
Abstract
We propose a method for the approximate computation of the Green function of a scalar massless field subjected to potential barriers of given size and shape in spacetime. The potential of the barriers has the form V(phi)=xi(phi2-phi02)2; xi is very large and phi0 very close to zero, the product (xi phi02) being finite and small. This is equivalent to the insertion of a suitable constraint in the functional integral for phi. The Green function contains a double Fourier transform of the characteristic function of the region where the potential has support.
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