论文标题
RG限制周期和扰动QFT中的非常规固定点
RG Limit Cycles and Unconventional Fixed Points in Perturbative QFT
论文作者
论文摘要
我们在$3-ε$尺寸中研究了量子场理论,其中标量字段$ ϕ^{ab} $形成了$ o(n)^2 $或$ o(n)$ global Symmetry group下的不可约表示。我们计算beta功能最高四环阶,并找到重新归一化组的固定点。在大型$ n $等价的示例中,父$ o(n)^2 $理论及其反对称投影表现出相同的大$ n $ beta函数,具有真实的固定点。但是,对于$ o(n)$的对称对称的无术表示,大型$ n $等价是由于出现未从父理论中继承而来的附加双重跟踪操作员而违反的。在这个女儿理论的大$ n $固定点中,我们发现了复杂的CFT。当分析继续以$ n $的小型非全能值时,对称的无术$ o(n)$模型也表现出非常有趣的现象。在这里,我们发现非常规的固定点,我们称之为“怪异”。它们位于耦合常数$ g^i $的实际值,但是雅各布矩阵$ \ partialβ^i/\ partial g^j $的两个特征值很复杂。当这些复杂的共轭特征值越过虚轴时,会发生HOPF分叉,从而产生RG限制周期。对于$ n _ {\ rm Crit} \大约4.475 $,并且对于高于此值的$ n $范围,我们发现RG流量会导致限制周期。
We study quantum field theories with sextic interactions in $3-ε$ dimensions, where the scalar fields $ϕ^{ab}$ form irreducible representations under the $O(N)^2$ or $O(N)$ global symmetry group. We calculate the beta functions up to four-loop order and find the Renormalization Group fixed points. In an example of large $N$ equivalence, the parent $O(N)^2$ theory and its anti-symmetric projection exhibit identical large $N$ beta functions which possess real fixed points. However, for projection to the symmetric traceless representation of $O(N)$, the large $N$ equivalence is violated by the appearance of an additional double-trace operator not inherited from the parent theory. Among the large $N$ fixed points of this daughter theory we find complex CFTs. The symmetric traceless $O(N)$ model also exhibits very interesting phenomena when it is analytically continued to small non-integer values of $N$. Here we find unconventional fixed points, which we call "spooky." They are located at real values of the coupling constants $g^i$, but two eigenvalues of the Jacobian matrix $\partial β^i/\partial g^j$ are complex. When these complex conjugate eigenvalues cross the imaginary axis, a Hopf bifurcation occurs, giving rise to RG limit cycles. This crossing occurs for $N_{\rm crit} \approx 4.475$, and for a small range of $N$ above this value we find RG flows which lead to limit cycles.