Colour Fields Computed in SU(3) Lattice QCD for the Static Tetraquark System

The colour fields created by the static tetraquark system are computed in quenched SU(3) lattice QCD, in a 24^3 x 48 lattice at beta=6.2 corresponding to a lattice spacing a=0.07261(85) fm. We find that the tetraquark colour fields are well described by a double-Y, or butterfly, shaped flux tube. The two flux tube junction points are compatible with Fermat points minimizing the total flux tube length. We also compare the diquark-diantiquark central flux tube profile in the tetraquark with the quark-antiquark fundamental flux tube profile in the meson, and they match, thus showing that the tetraquark flux tubes are composed of fundamental flux tubes.