“…Contrary to the d = 4 Yang-Mills theory where the multi-instanton solutions are not available in an explicit form, in the CP Nc−1 model they are known explicitly, and for any 'number of colors' N c [4,5]. Moreover, the multi-instanton weight arising from integrating out quantum oscillations about instantons is also known [6,7,8]. In addition, the model is exactly solvable at large N c [5,9], and the spectrum is known for all N c [10].…”