科研之友
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摘要
We consider the decay of cosmic strings that are trapped in the false vacuum in a theory of scalar electrodynamics in 3 + 1 dimensions. This paper is the 3 + 1-dimensional generalization of the 2 + 1-dimensional decay of false vortices which we have recently completed [2]. We restrict our analysis to the case of thin-walled cosmic strings which occur when large magnetic flux is trapped inside the string. Thus the string looks like a tube of fixed radius, at which it is classically stable. The core of the string contains magnetic flux in the true vacuum, while outside the string, separated by a thin wall, is the false vacuum. The string decays by tunneling to a configuration which is represented by a bulge, where the region of true vacuum within is ostensibly enlarged. The bulge can be described as the meeting of a kink soliton-antisoliton pair along the length of the string. It can be described as a bulge appearing in the initial string, starting from the string of small, classically stable radius, expanding to a fat string of large, classically unstable (to expansion) radius and then returning back to the string of small radius along its length. This configuration is the bounce point of a corresponding O(2) symmetric instanton, which we can determine numerically. Once the bulge appears it explodes in real time. The paired soliton and antisoliton recede from each other along the length of the string with a velocity that quickly approaches the speed of light, leaving behind a fat tube. At the same time the radius of the fat tube that is being formed expands (transversely) as it is no longer classically stable, converting false vacuum to the true vacuum with ever-diluting magnetic field within. The rate of this expansion is determined by the energy difference between the true vacuum and the false vacuum. Our analysis could be applied to a network of cosmic strings formed in the very early Universe or vortex lines in a superheated superconductor.
- 出版日期2013-11-8
