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arXiv 1802.07151cond-mat.stat-mechhep-th
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具有淬火无序的$O(N)$模型的精确结果

Exact results for the $O(N)$ model with quenched disorder

Gesualdo Delfino, Noel Lamsen

摘要:

利用标度不变散射理论精确确定了二维淬火无序$O(N)$对称模型的重整化群不动点线。随机不动点的特征在于两个无序参数:接近纯情况时消失的模量和相位角。临界线分为三类,这取决于无序模量的值。除了对应于纯情况的类,第二类具有最大值的无序模,并包括Nishimori-like多临界点以及零温度不动点。第三类包含在$N$变化时在前两类之间插值的临界线。对于正$N$,它包含一条红外固定点线,其范围为从$\sqrt{2}-1$到$1$的$N$值。沿着这条线,能量密度算符的对称扇区是超普适的(即与$N$无关)。对于$N=2$,一条不动点线只存在于纯粹的情况下,但也解释了在无序存在下观察到的Berezinskiii-Kosterlitz-无相。

英文摘要:

We use scale invariant scattering theory to exactly determine the lines of renormalization group fixed points for $O(N)$-symmetric models with quenched disorder in two dimensions. Random fixed points are characterized by two disorder parameters: a modulus that vanishes when approaching the pure case, and a phase angle. The critical lines fall into three classes depending on the values of the disorder modulus. Besides the class corresponding to the pure case, a second class has maximal value of the disorder modulus and includes Nishimori-like multicritical points as well as zero temperature fixed points. The third class contains critical lines that interpolate, as $N$ varies, between the first two classes. For positive $N$, it contains a single line of infrared fixed points spanning the values of $N$ from $\sqrt{2}-1$ to $1$. The symmetry sector of the energy density operator is superuniversal (i.e. $N$-independent) along this line. For $N=2$ a line of fixed points exists only in the pure case, but accounts also for the Berezinskii-Kosterlitz-Thouless phase observed in presence of disorder.

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