Global calculation of two-neutrino double- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>β</mml:mi></mml:math> decay within the finite amplitude method in nuclear density functional theory

Two-neutrino double-beta $(2\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta})$ decay has been used to constrain the neutron-proton part of effective interactions, which in turn is compute nuclear matrix elements for neutrinoless decay, observation would have important consequences fundamental physics. We carefully examine $2\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ within proton-neutron quasiparticle random-phase approximation with energy density functionals. work functionals that are fit globally single-beta-decay half-lives and charge-exchange giant-resonance energies, but not themselves, evaluate all nuclei, including those whose yet measured. Such a comprehensive evaluation large model spaces without configuration truncation requires an efficient computational scheme; we employ double contour integration finite amplitude method. The results generally reproduce element extracted from well, use any fitting procedure. present predictions total 27 nuclei still unmeasured.