Systematics in nucleon matrix element calculations

Understand

The current status of calculations of simple nucleon structure observables is reviewed, with a focus on the axial charge.

• A major challenge is the combination of an exponentially decaying signal-to-noise ratio and the need for large source-sink separations to eliminate excited-state contributions; efforts to understand and deal with this problem are the focus of the largest section of this review.
• Finite-volume effects and chiral extrapolation are also briefly discussed.