Lattice QCD without topology barriers

Understand

As the continuum limit is approached, lattice QCD simulations tend to get trapped in the topological charge sectors of field space and may consequently give biased results in practice.

• We propose to bypass this problem by imposing open (Neumann) boundary conditions on the gauge field in the time direction.
• The topological charge can then flow in and out of the lattice, while many properties of the theory (the hadron spectrum, for example) are not affected.
• Extensive simulations of the SU(3) gauge theory, using the HMC and the closely related SMD algorithm, confirm the absence of topology barriers if these boundary conditions are chosen.