Logarithmic time-like Liouville quantum field theory has a generalized PT invariance, where T is the time-reversal operator and P stands for an S-duality reflection of the Liouville field φ. In Euclidean space the Lagrangian of such a theory, L = 1 2 (∇φ) 2 − igφ exp(iaφ), is analyzed using the techniques of PT -symmetric quantum theory. It is shown that L defines an infinite number of unitarily inequivalent sectors of the theory labeled by the integer n. In one-dimensional space (quantum mechanics) the energy spectrum is calculated in the semiclassical limit and the mth energy level in the nth sector is given by Em,n ∼ (m + 1/2) 2 a 2 /(16n 2 ).PACS numbers: 11.30. Er, 03.70.+k Motivated by studies of time-like logarithmic Liouville quantum field theory, we examine here the interaction −igφ exp(iaφ) in field theory and its quantummechanical analog −igx exp(iax). This remarkable interaction gives rise to a countably infinite number of inequivalent quantum theories.The interaction −igφ exp(iaφ) has its origin in conformal field theory (CFT) of Liouville type, whose interaction has the form e αφ [1][2][3][4][5][6]. This exponential arises in string theory and in two-dimensional gravity, which are defined on two-dimensional manifolds. Using general coordinate invariance, one can show that the metric tensor g µν for these theories can be reduced locally to g µν = η µν e αφ , where η µν is the Minkowski metric. String theory and two-dimensional gravity are conformally invariant at the classical level, but quantum effects can produce an anomaly that destroys conformal invariance. Conformal symmetry is restored if the field φ is governed by the Liouville actionRecoil effects for zero-dimensional D-branes scattering off closed strings are described by the interaction φe αφ in addition to the usual Liouville interaction e αφ [7]. Such pairs of operators define a logarithmic CFT [8]. Logarithmic CFTs also arise in descriptions of quenched disordered condensed matter systems [9,10]. Supercritical strings [11] and the condensation of tachyons [12,13] is studied in the context of time-like Liouville theories, whose interaction term has α replaced by ia. Thus, combining the ideas of Liouville and logarithmic CFT, we are led to consider the d-dimensional Euclidean Lagrangianwhere φ is a scalar field and a, g, and h are treated as positive real parameters.The Lagrangian (1) is not Hermitian and one cannot make such a theory Hermitian by adding its Hermitian conjugate because this would destroy the conformality property of the theory. Nevertheless, the techniques of PT quantum theory [14] can be used to study this field theory. The Lagrangian is not obviously PT invariant because in Liouville theory the field φ is assumed to transform as a scalar, so it does not change sign under space reflection. [If φ were a pseudoscalar field, the Lagrangian would be PT invariant because under parity reflection P, φ would change sign Pφ(x, t)P = −φ(−x, t), and under time reversal T , i changes sign T iT = −i.] However, we let P represent a...