TY - JOUR AU - Oset, E. PY - 2013 DA - 2013// TI - On the ambiguities of sign determination of the S-matrix from energy levels in a finite box T2 - Eur. Phys. J. A JO - European Physical Journal A SP - 32 EP - 4pp VL - 49 IS - 3 PB - Springer AB - In a recent paper the authors make a study on the determination of the S-matrix elements for scattering of particles in the infinite volume from the energy levels in a finite box for the case of multiple channels. The study is done with a toy model in 1+1 dimension and the authors find that there is some ambiguity in the sign of nondiagonal matrix elements, casting doubts on whether the needed observables in the infinite volume can be obtained from the energy levels of the box. In this paper I present an easy derivation, confirming the ambiguity of the sign and argue that this, however, does not put restrictions in the determination of observables. SN - 1434-6001 UR - http://arxiv.org/abs/1211.3985 UR - https://doi.org/10.1140/epja/i2013-13032-9 DO - 10.1140/epja/i2013-13032-9 LA - English N1 - WOS:000317855000004 ID - Oset2013 ER -