<p>The multicritical generalizations of the Lee-Yang universality class arise as renormalization-group fixed points of scalar field theories with complex <i>iφ</i><sup>2<i>n</i>+1</sup> interaction, <i>n</i> ∈ ℕ, just below their upper critical dimension. It has been recently conjectured that their continuation to two dimensions corresponds to the non-unitary conformal minimal models ℳ(2<i>,</i> 2<i>n</i> + 3). Motivated by that, we revisit the functional renormalization group approach to complex 𝒫𝒯-symmetric scalar field theories in the Local Potential Approximation, without or with wavefunction renormalization (LPA and LPA’ respectively), aiming to explore the fate of the <i>iφ</i><sup>2<i>n</i>+1</sup> theories from their upper critical dimension to two dimensions. The <i>iφ</i><sup>2<i>n</i>+1</sup> fixed points are identified using a perturbative expansion of the functional fixed-point equation near their upper critical dimensions, and they are followed to lower dimensions by numerical integration of the full equation. A peculiar feature of the complex 𝒫𝒯-symmetric potentials is that the fixed points are characterized by real but negative anomalous dimensions <i>η</i>, and in low dimension <i>d</i>, this can lead to a change of sign of the scaling dimensions ∆ = (<i>d</i> − 2 + <i>η</i>)<i>/</i>2, thus requiring a novel analysis of the analytical properties of the functional fixed-point equations. We are able to follow the Lee-Yang universality class (<i>n</i> = 1) down to two dimensions, and numerically determine the scaling dimension of the fundamental field as a function of <i>d</i>. On the other hand, within the LPA’, multicritical Lee-Yang fixed points with <i>n &gt;</i> 1 cannot be continued to <i>d</i> = 2 due to the existence of unexpected non-perturbative fixed points that annihilate with the <i>iφ</i><sup>2<i>n</i>+1</sup> fixed points.</p>

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Critical and multicritical Lee-Yang fixed points in the local potential approximation

  • Dario Benedetti,
  • Fanny Eustachon,
  • Omar Zanusso

摘要

The multicritical generalizations of the Lee-Yang universality class arise as renormalization-group fixed points of scalar field theories with complex 2n+1 interaction, n ∈ ℕ, just below their upper critical dimension. It has been recently conjectured that their continuation to two dimensions corresponds to the non-unitary conformal minimal models ℳ(2, 2n + 3). Motivated by that, we revisit the functional renormalization group approach to complex 𝒫𝒯-symmetric scalar field theories in the Local Potential Approximation, without or with wavefunction renormalization (LPA and LPA’ respectively), aiming to explore the fate of the 2n+1 theories from their upper critical dimension to two dimensions. The 2n+1 fixed points are identified using a perturbative expansion of the functional fixed-point equation near their upper critical dimensions, and they are followed to lower dimensions by numerical integration of the full equation. A peculiar feature of the complex 𝒫𝒯-symmetric potentials is that the fixed points are characterized by real but negative anomalous dimensions η, and in low dimension d, this can lead to a change of sign of the scaling dimensions ∆ = (d − 2 + η)/2, thus requiring a novel analysis of the analytical properties of the functional fixed-point equations. We are able to follow the Lee-Yang universality class (n = 1) down to two dimensions, and numerically determine the scaling dimension of the fundamental field as a function of d. On the other hand, within the LPA’, multicritical Lee-Yang fixed points with n > 1 cannot be continued to d = 2 due to the existence of unexpected non-perturbative fixed points that annihilate with the 2n+1 fixed points.