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arXiv 0901.0450hep-thcond-mat.stat-mech
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重参数化不变性与RG方程:局部势近似的推广

Reparameterisation Invariance and RG equations: Extension of the Local Potential Approximation

H. Osborn, D. E. Twigg

摘要:

方程相关的Polchinski版本的精确重整化群方程的标量场的局部势近似扩展到一阶导数展开,并保持reparameterisation不变性,假设。重新参数化不变性确保方程明确地确定反常维数eta,并且方程使得结果对于任何多临界不动点的ε展开精确到O(ε ^2)。用数值方法确定eta也很简单。当维数d=3时,在具有O(N)对称性的理论中获得了宽范围的临界指数的数值结果,对于各种N和η的范围,在局部势近似下获得。从这里描述的导数近似得出的相关η对于不同的N被发现。并对方程的大N极限进行了分析。相应的讨论也给出了一个微扰RG框架和尺度维数的导数算子计算到第一阶的。

英文摘要:

Equations related to the Polchinski version of the exact renormalisation group equations for scalar fields which extend the local potential approximation to first order in a derivative expansion, and which maintain reparameterisation invariance, are postulated. Reparameterisation invariance ensures that the equations determine the anomalous dimension eta unambiguously and the equations are such that the result is exact to O(epsilon^2) in an epsilon-expansion for any multi-critical fixed point. It is also straightforward to determine eta numerically. When the dimension d=3 numerical results for a wide range of critical exponents are obtained in theories with O(N) symmetry, for various N and for a ranges of eta, are obtained within the local potential approximation. The associated eta, which follow from the derivative approximation described here, are found for various N. The large N limit of the equations is also analysed. A corresponding discussion is also given in a perturbative RG framework and scaling dimensions for derivative operators are calculated to first order in epsilon.

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