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arXiv 0907.3665hep-thhep-lat
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有质量伴随费米子的大N规范理论的有限体积相

Finite Volume Phases of Large N Gauge Theories with Massive Adjoint Fermions

Timothy J. Hollowood, Joyce C. Myers

摘要:

费米子在不同表象下的类QCD规范理论的相结构是一个有趣的但通常在分析上难以解决的问题。确保弱耦合的一种方法是将理论定义在一个小的有限体积中,在这种情况下是S^3 x S^1。真正的相变可以发生在大N理论中。在这里,我们使用这种方法来研究SU(N)规范理论,其中N_f个有质量的伴随值马约拉纳费米子在S^1附近具有非热边界条件。当N_f =1时,我们发现了一条跃迁线,它将束缚相和去束缚相的弱耦合类似物分开,使Wilson线的本征值密度从均匀分布转变为带隙分布。然而,当N_f >1时的情形要丰富得多,出现了一系列弱耦合的部分受限相类似物,它们留下了一个中心对称的Z_p子群。在这些Z_p相中,本征值密度有p个带隙,它们通过一级相变与限制相分离。我们证明了,对于足够小的mR(费米子的质量乘以S^3的半径),只有受限相存在。大N相图与有限N结果以及基于R^3 x S^1计算和晶格模拟的其他方法一致。

英文摘要:

The phase structure of QCD-like gauge theories with fermions in various representations is an interesting but generally analytically intractable problem. One way to ensure weak coupling is to define the theory in a small finite volume, in this case S^3 x S^1. Genuine phase transitions can then occur in the large N theory. Here, we use this technique to investigate SU(N) gauge theory with a number N_f of massive adjoint-valued Majorana fermions having non-thermal boundary conditions around S^1. For N_f =1 we find a line of transitions that separate the weak-coupling analogues of the confined and de-confined phases for which the density of eigenvalues of the Wilson line transform from the uniform distribution to a gapped distribution. However, the situation for N_f >1 is much richer and a series of weak-coupling analogues of partially-confined phases appear which leave unbroken a Z_p subgroup of the centre symmetry. In these Z_p phases the eigenvalue density has p gaps and they are separated from the confining phase and from one-another by first order phase transitions. We show that for small enough mR (the mass of the fermions times the radius of the S^3) only the confined phase exists. The large N phase diagram is consistent with the finite N result and with other approaches based on R^3 x S^1 calculations and lattice simulations.

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