Sánchez Soto, Luis LorenzoMonzón Serrano, Juan José2023-06-192023-06-1920142073-899410.3390/sym6020396https://hdl.handle.net/20.500.14352/35546Received: 24 February 2014 / Revised: 12 May 2014 / Accepted: 14 May 2014 / Published: 22 May 2014 This article belongs to the Special Issue Physics based on Two-by-two Matrices.We give a simplified account of the properties of the transfer matrix for a complex one-dimensional potential, paying special attention to the particular instance of unidirectional invisibility. In appropriate variables, invisible potentials appear as performing null rotations, which lead to the helicity-gauge symmetry of massless particles. In hyperbolic geometry, this can be interpreted, via Möbius transformations, as parallel displacements, a geometric action that has no Euclidean analogy.engAtribución 3.0 Españajournal articlehttp://dx.doi.org/10.3390/sym6020396http://www.mdpi.com/2073-8994/6/2/396open access51-7:531.111.5535.31ΡT SymmetrySL(2C)Lorentz GroupHyperbolic GeometryÓptica (Física)Partículas2209.19 Óptica Física2208 Nucleónica