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arXiv 1710.03310hep-th
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作为WKB精确泛函积分的外场中弦对产生的Worldsheet瞬子和振幅

Worldsheet Instantons and the amplitude for string pair production in an external field as a WKB exact functional integral

James Gordon, Gordon W. Semenoff

摘要:

我们重新讨论了在恒定外部电场中带电弦对的产生问题。弦态是有质量的,从真空中产生对是一个隧穿过程,类似于由电场产生带电粒子-反粒子对的施温格过程。我们在世界面西格玛模型中发现了引起隧穿事件的瞬子。我们评估的西格玛模型分函数在多瞬子部门的WKB近似,保持经典的行动和集成的二次波动的解决方案。我们发现,在所有多瞬子扇区的结果的总和再现已知的振幅。这表明必须取消对WKB限制的更正。为了证明它们确实是相互抵消的,我们确定了西格玛模型的费米子对称性,它发生在瞬子扇区中,并与集体坐标相关联。我们证明了作用是对称的,相互作用是一个精确的形式。这些条件足以使世界面泛函积分局部化到其WKB极限。

英文摘要:

We revisit the problem of charged string pair creation in a constant external electric field. The string states are massive and creation of pairs from the vacuum is a tunnelling process, analogous to the Schwinger process where charged particle-anti-particle pairs are created by an electric field. We find the instantons in the worldsheet sigma model which are responsible for the tunnelling events. We evaluate the sigma model partition function in the multi-instanton sector in the WKB approximation which keeps the classical action and integrates the quadratic fluctuations about the solution. We find that the summation of the result over all multi-instanton sectors reproduces the known amplitude. This suggests that corrections to the WKB limit must cancel. To show that they indeed cancel, we identify a fermionic symmetry of the sigma model which occurs in the instanton sectors and which is associated with collective coordinates. We demonstrate that the action is symmetric and that the interaction action is an exact form. These conditions are sufficient for localization of the worldsheet functional integral onto its WKB limit.

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