Staggered fermion is a technical subtlety that arises when fermion

Fermion

In particle physics, a fermion is any particle which obeys the Fermi–Dirac statistics . Fermions contrast with bosons which obey Bose–Einstein statistics....

ic fields are included in lattice gauge theory

Lattice gauge theory

In physics, lattice gauge theory is the study of gauge theories on a spacetime that has been discretized into a lattice. Gauge theories are important in particle physics, and include the prevailing theories of elementary particles: quantum electrodynamics, quantum chromodynamics and the Standard...

. When one does so, many new unphysical fermionic excitations corresponding to alternating fermionic fields occur in the spectrum. This is known as the fermion doubling problem. A particular way to resolve this problem, first proposed by Lenny Susskind and John Kogut, is the staggered fermion approach where a new nonlocal action is constructed where the Dirac operator

Dirac operator

In mathematics and quantum mechanics, a Dirac operator is a differential operator that is a formal square root, or half-iterate, of a second-order operator such as a Laplacian...

is treated as a square root.