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arXiv 1808.08129hep-latcond-mat.stat-mech
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梯度流作用下二维O(3)模型的拓扑敏感性

Topological Susceptibility of the 2d O(3) Model under Gradient Flow

Wolfgang Bietenholz, Philippe de Forcrand, Urs Gerber, Héctor Mejía-Díaz, Ilya O. Sandoval

摘要:

2d O(3)模型被广泛用作铁磁性和量子色动力学的玩具模型。与后者,它的股票-在其他基本方面-财产的连续功能积分分裂成拓扑部门。拓扑也可以定义在其晶格正则化的版本,但半经典的参数表明,拓扑磁化率$χ_{\rm t}$不朝着有限的连续极限。以前的数值研究证实,数量$χ_{\rm t}\, ξ^{2}$发散在大的相关长度$ξ$。在这里,我们调查的问题是否这种分歧仍然存在时,配置平滑的梯度流(GF)。GF破坏了部分拓扑绕组;在精细格上,这大大减少了$χ_{\rm t}$。然而,即使当流动时间很长,GF的影响范围-或平滑半径-达到$ξ/2$,我们仍然没有观察到连续标度的证据。

英文摘要:

The 2d O(3) model is widely used as a toy model for ferromagnetism and for Quantum Chromodynamics. With the latter it shares --- among other basic aspects --- the property that the continuum functional integral splits into topological sectors. Topology can also be defined in its lattice regularised version, but semi-classical arguments suggest that the topological susceptibility $χ_{\rm t}$ does not scale towards a finite continuum limit. Previous numerical studies confirmed that the quantity $χ_{\rm t}\, ξ^{2}$ diverges at large correlation length $ξ$. Here we investigate the question whether or not this divergence persists when the configurations are smoothened by the Gradient Flow (GF). The GF destroys part of the topological windings; on fine lattices this strongly reduces $χ_{\rm t}$. However, even when the flow time is so long that the GF impact range --- or smoothing radius --- attains $ξ/2$, we do still not observe evidence of continuum scaling.

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