COMPOSITE QUASI-PARTICLE FORMATION AND THE LOW-ENERGY EFFECTIVE-HAMILTONIANS FOR THE ONE-DIMENSIONAL AND 2-DIMENSIONAL HUBBARD-MODEL

We investigate the effect of hole doping on the strong-coupling Hubbar d model at half filling in spatial dimensions D greater than or equal to 1. We start with an antiferromagnetic mean-field description of the insulating state, and show that doping creates solitons in the antife rromagnetic background. In one dimension, the soliton is topological, spinless, and decoupled from the background antiferromagnetic fluctuat ions at low energies. In two dimensions and above, the soliton is nont opological, has spin quantum number 1/2, and is strongly coupled to th e antiferromagnetic fluctuations. We derive the effective action gover ning the quasiparticle motion, study the properties of a single carrie r, and comment on a possible description at finite concentration.