Spectrum of light nuclei in a finite volume

Lattice quantum chromodynamics calculations of multibaryon systems with physical quark masses would start a new age of ab initio predictions in nuclear physics. Performed on a finite grid, such calculations demand extrapolation of their finite-volume numerical results to free-space physical quantities. Such extraction of the physical information can be carried out fitting effective field theories (EFTs) directly to the finite-volume results or utilizing the Luscher free-space formula or its generalizations for extrapolating the lattice data to infinite volume. To understand better the effect of periodic boundary conditions on the binding energy of few-nucleon systems we explore here light nuclei with physical masses in a finite box and in free space. The stochastic variational method is used to solve the few-body systems. Substantial optimizations of the method are introduced to enable efficient calculations in a periodic box. With the optimized code, we perform accurate calculations of light nuclei A <= 4 within leading-order pionless EFT. Using Luscher formula for the two-body system, and its generalization for three- and fourbody systems, we examine the box effect and explore possible limitations of these formulas for the considered nuclear systems.

Automated summary

Lattice quantum chromodynamics calculations provide a new approach for ab initio predictions in nuclear physics, by extrapolating finite-volume results to free-space physical quantities. We investigated the effect of periodic boundary conditions on the binding energy of light nuclei using the stochastic variational method, and examined the limitations of the Luscher formula for different nuclear systems.