BPST instanton
Introduction


In theoretical physics, the **BPST instanton** is the [instanton](/wiki/Instanton "Instanton") with [winding number](/wiki/Winding_number "Winding number") 1 found by [Alexander Belavin](/wiki/Alexander_Belavin "Alexander Belavin"), [Alexander Polyakov](/wiki/Alexander_Markovich_Polyakov "Alexander Markovich Polyakov"), [Albert Schwarz](/wiki/Albert_Schwarz "Albert Schwarz") and [Yu. S. Tyupkin](/wiki/Yu._S._Tyupkin "Yu. S. Tyupkin"). It is a classical solution to the equations of motion of SU(2\) [Yang–Mills theory](/wiki/Yang%E2%80%93Mills_theory "Yang–Mills theory") in Euclidean space\-time (i.e. after [Wick rotation](/wiki/Wick_rotation "Wick rotation")), meaning it describes a transition between two different [topological vacua](/wiki/Theta_vacuum "Theta vacuum") of the theory. It was originally hoped to open the path to solving the problem of [confinement](/wiki/Color_confinement "Color confinement"), especially since Polyakov had proven in 1975 that instantons are the cause of confinement in three\-dimensional compact\-QED. This hope was not realized, however.


Is there another way to solve the problem of confinement?