We consider the most general scale invariant radial Hamiltonian allowing for anisotropic scaling between space and time. We formulate a renormalisation group analysis of this system and demonstrate the existence of a universal quantum phase transition from a continuous scale invariant phase to a discrete scale invariant phase. Close to the critical point, the discrete scale invariant phase is characterised by an isolated, closed, attracting trajectory in renomalisation group space (a limit cycle). Moving in appropriate directions in the parameter space of couplings this picture is altered to one controlled by a quasi periodic attracting trajectory (a limit torus) or fixed points. We identify a direct relation between the critical point, the renormalisation group picture and the power laws characterising the zero energy wave functions.Classical symmetries broken at the quantum level are termed anomalous. Since their discovery [1][2][3][4], anomalies have become a very active field of research in physics. One class of anomalies describes the breaking of continuous scale invariance (CSI). In the generic case, quantisation of a classically scale invariant Hamiltonian is ill-defined and necessitates the introduction of a regularisation scale [5] which breaks CSI altogether. Recently, a sub-class of scale anomalies has been discovered in which a residual discrete scale invariance (DSI) remains after regularisation. Models exhibiting this phenomenon include a non-relativistic particle in the presence of an attractive, inverse square radial potential H S = p 2 /2m − λ/r 2 [6][7][8][9][10][11][12][13][14], the charged and massless Dirac fermion in an attractive Coulomb potential H D = γ 0 γ j p j − λ/r [15] and a class of one dimensional Lifshitz scalars [16] withĤ L = p 2 /2m N − λ/x 2N [17].Any system described by these classically scale invariant Hamiltonians exhibits an abrupt transition in the spectrum at some λ = λ c . For λ < λ c , the spectrum contains no bound states close to E = 0, however, as λ goes above λ c , an infinite sequence of bound (quasi bound forĤ D ) states appears. In addition, in this "over-critical" regime, the states surprisingly form a geometric sequenceaccumulating at E = 0 where n ∈ Z, α > 0 and E 0 is a number that depends on the regularisation. The existence and structure of the levels is 'universal', that is, it does not rely on the details of the potential close to its source. This feature is a signature of residual DSIThus, * danny.brattan@gmail.com † somrie@campus.technion.ac.il ‡ eric@physics.technion.ac.il a quantum phase transition occurs at λ c between a continuous scale invariant (CSI) phase and a discrete scale invariant phase (DSI). This transition has been associated with Berezinskii-Kosterlitz-Thouless (BKT) transitions [13, 18-23] and has found applications in the Efimov effect [24-26], graphene [15], QED3 [27] and other phenomena [18,[28][29][30][31][32][33][34][35].A useful tool in the characterisation of this phenomenon is the renormalisation group (RG) [36]. For the case o...