Role of finite-size effects in the critical behavior of itinerant fermions

We study the role of finite-size effects on critical behavior near a metallic q=0 critical point and compare the results with a recent extensive quantum Monte Carlo (QMC) study [Y. Schattner, Phys. Rev. X 6, 031028 (2016)2160-330810.1103/PhysRevX.6.031028]. This study found several features in both bosonic and fermionic responses, in disagreement with the expected critical behavior with a dynamical exponent z=3. We show that finite-size effects are particularly strong for z=3 criticality and give rise to a behavior different from that of an infinite system, over a wide range of momenta and frequencies. We argue that by taking finite-size effects into account, the QMC results can be explained within z=3 theory.