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arXiv 0705.2539hep-lat
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手征不变格点Higgs-Yukawa模型在小和大Yukawa耦合常数时的相结构

The phase structure of a chirally invariant lattice Higgs-Yukawa model for small and for large values of the Yukawa coupling constant

P. Gerhold, K. Jansen

摘要:

考虑了一个基于Neuberger重叠算子的手征不变格点Higgs-Yukawa模型。作为最终确定希格斯质量边界的第一步,我们研究了在大NF极限下的模型相图。本文给出了在小Yukawa和四次耦合常数范围内的树能级有效势的表达式,并确定了相变的顺序。在强Yukawa耦合的情况下,对于四次耦合常数的所有值,模型有效地变成O(4)对称非线性σ模型。这导致在汤川耦合常数较大的情况下也存在对称相位。然而,在有限和小晶格上,强的有限体积效应阻止了希格斯场的期望值消失,从而模糊了强汤川耦合下对称相的存在。

英文摘要:

We consider a chirally invariant lattice Higgs-Yukawa model based on the Neuberger overlap operator. As a first step towards the eventual determination of Higgs mass bounds we study the phase diagram of the model analytically in the large Nf-limit. We present an expression for the effective potential at tree-level in the regime of small Yukawa and quartic coupling constants and determine the order of the phase transitions. In the case of strong Yukawa couplings the model effectively becomes an O(4)-symmetric non-linear sigma-model for all values of the quartic coupling constant. This leads to the existence of a symmetric phase also in the regime of large values of the Yukawa coupling constant. On finite and small lattices, however, strong finite volume effects prevent the expectation value of the Higgs field from vanishing thus obscuring the existence of the symmetric phase at strong Yukawa couplings.

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