I explain how to construct noncommutative BPS configurations in four and lower dimensions by solving linear matrix equations. Examples are instantons in D=4 Yang-Mills, monopoles in D=3 Yang-Mills-Higgs, and (moving) solitons in D=2+1 YangMills-Higgs. Some emphasis is on the latter as a showcase for the dressing method.
Self-duality and BPS equationsIn this talk I shall present a powerful method for and results of constructing classical field configurations with finite action or energy in four-dimensional noncommutative gauge theory and its lower-dimensional descendants:I am setting up the formalism in such a way that it is completely transparent to the (Moyal-type) noncommutative deformation. In other words, the noncommutative equations below differ from the commutative ones merely in the interpretation of the symbols or their product (stars are suppressed). This will be briefly explained in Section 6. The Yang-Mills field equations are implied by first-order (self-duality or BPS) equations:where F and φ are u(n) valued and Greek indices run from 1 to 4 while Latin ones stop at 3. In complex coordinates (note the signs!) y = x 1 +ix 2 and z = x 3 ∓ix 4 the self-duality equationwhere the upper and lower signs belong to the signatures (4,0) and (2,2), respectively. Dimensional reduction to D=3 is accomplished via