Ground state and low excitations of an integrable chain with alternating spins

An anisotropic integrable spin chain, consisting of spins s = 1 and s = 1/2, is investigated. It is characterized by two real parameters anti c and c, the coupling constants of the spin interactions. For the case anti c < 0 and c < 0 the ground state configuration is obtained by means of thermodynamic Bethe ansatz. Furthermore the low excitations are calculated. It turns out, that apart form free magnon states being the holes in the ground state rapidity distribution, there exist bound states given by special string solutions of Bethe ansatz equations (BAE) in analogy to [13]. The dispersion law of these excitations is calculated numerically. (orig.)SIGLEAvailable from TIB Hannover: RR 1596(179) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman