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arXiv 0705.0827hep-thgr-qcmath.DG
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一阶以上Worldsheet西格玛模型梯度RG流的度量

A Metric for Gradient RG Flow of the Worldsheet Sigma Model Beyond First Order

T. Oliynyk, V. Suneeta, E. Woolgar

摘要:

Tseytlin最近提出,存在一个作用泛函,其梯度在微扰论中生成所有阶的世界面西格玛模型中目标空间度规的重整化群流。梯度是相对于一个度量的空间上的耦合常数,这是明确已知的,只有领先的秩序,在微扰理论,但在该秩序是半正定的,如下从佩雷尔曼的工作里奇流。这就产生了一个单调性公式的流量,预计失败,只有当β函数扰动系列未能收敛,这可能会发生,如果曲率或其衍生物增长大。通过明确计算耦合常数空间上度规中的二阶项,检验了微扰论中次首阶单调性公式的有效性。在这个顺序,这个度量被发现不是半正定的。在这种情况下,这可能破坏单调性,曲率的导数变得足够大,高阶微扰校正是显着的。

英文摘要:

Tseytlin has recently proposed that an action functional exists whose gradient generates to all orders in perturbation theory the Renormalization Group (RG) flow of the target space metric in the worldsheet sigma model. The gradient is defined with respect to a metric on the space of coupling constants which is explicitly known only to leading order in perturbation theory, but at that order is positive semi-definite, as follows from Perelman's work on the Ricci flow. This gives rise to a monotonicity formula for the flow which is expected to fail only if the beta function perturbation series fails to converge, which can happen if curvatures or their derivatives grow large. We test the validity of the monotonicity formula at next-to-leading order in perturbation theory by explicitly computing the second-order terms in the metric on the space of coupling constants. At this order, this metric is found not to be positive semi-definite. In situations where this might spoil monotonicity, derivatives of curvature become large enough for higher order perturbative corrections to be significant.

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