论文标题

蒙特卡洛的方法

A Monte Carlo approach to the conformal bootstrap

论文作者

Laio, Alessandro, Valenzuela, Uriel Luviano, Serone, Marco

论文摘要

我们介绍了一种方法,以在任意维度中找到共形场理论(CFTS)的截短引导方程的近似数值解。该方法基于通过一个由动作$ s $引导的大都市算法的随机搜索,该算法是单个标量场相关器的截断bootstrap方程的对数。尽管基于半准编程的数值共形性引导方法在CFTS上具有严格的排除界限,但此方法寻找近似解决方案,这些解决方案对应于$ s $的局部最小值,而存在,并且甚至可能远离极端性区域。通过此协议,我们发现,如果对操作员的缩放维度没有限制,则$ s $具有一个最低限度,与自由理论相对应。但是,如果我们修复了外部操作员尺寸,我们会遇到可以使用我们的方法研究的最小值。施加保守的压力调整器,$ \ mathbf {z} _2 $对称性和一个相关的标量,我们确定了存在$ s $的本地最小值的两个区域。当投影在$(δ_σ,δ_ε)$ - 平面,$σ$和$ε$的外部和最轻的交换运算符时,这些区域之一与以前的Bootstrap研究中发现的极端线相吻合。另一个区域沿着$ d = 2 $中的广义免费理论,而低于$ d = 3 $和$ d = 4 $。我们从经验上证明,发现的一些最小值与已知理论有关,包括$ 2D $和$ 3D $ ISING理论和$ 2D $ Yang-Lee型号。

We introduce an approach to find approximate numerical solutions of truncated bootstrap equations for Conformal Field Theories (CFTs) in arbitrary dimensions. The method is based on a stochastic search via a Metropolis algorithm guided by an action $S$ which is the logarithm of the truncated bootstrap equations for a single scalar field correlator. While numerical conformal bootstrap methods based on semi-definite programming put rigorous exclusion bounds on CFTs, this method looks for approximate solutions, which correspond to local minima of $S$, when present, and can be even far from the extremality region. By this protocol we find that if no constraint on the operator scaling dimensions is imposed, $S$ has a single minimum, corresponding to the Free Theory. If we fix the external operator dimension, however, we encounter minima that can be studied with our approach. Imposing a conserved stress-tensor, a $\mathbf{Z}_2$ symmetry and one relevant scalar, we identify two regions where local minima of $S$ are present. When projected in the $(Δ_σ, Δ_ε)$-plane, $σ$ and $ε$ being the external and the lightest exchanged operators, one of these regions essentially coincides with the extremality line found in previous bootstrap studies. The other region is along the generalized free theories in $d = 2$ and below that in both $d = 3$ and $d = 4$. We empirically prove that some of the minima found are associated to known theories, including the $2d$ and $3d$ Ising theories and the $2d$ Yang-Lee model.

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