The low-temperature specific heat anomaly of the SU(2) invariant 1D Heisenberg antiferromagnet of spin S in a small magnetic field

It is expected that the specific heat of the SU(2)-invariant 1D Heisenberg antiferromagnet of spin S is linear to the temperature at low T with the linear coefficient gamma _s being a function of field H. The author's main result is that lim_{H to O gamma s}=¹/₃(1+ square root S Gamma (S)(e/S)^s/ pi ) not= lim_T to _O lim_{H to O gamma s}=2S/(1+S). This extends the previous result for S=¹/₂ to other spin values. The author also provides an approximate interpolation formula between these two limits as a function of H/T for very small H and T.