RT Journal Article T1 Paramagnetic dominance, the sign of the beta function and UV/IR mixing in non-commutative U(1) A1 Ruiz Ruiz, Fernando A1 Pérez Martín, Carmelo AB U(1) gauge theory on non-commutative Minkowski spacetime in the Feynman-'t Hooft background gauge is studied. In particular, UV divergences and non-commutative IR divergent contributions to the two, three and four-point functions are explicitly computed at one loop. We show that the negative sign of the beta function results from paramagnetism – producing UV charge anti-screening prevailing over diamagnetism - giving rise to UV charge screening. This dominance in the field theory setting corresponds to tachyon magnification dominance in the string theory framework. Our calculations provide an explicit realization of UV/IR mixing and lead to an LR renormalization of the coupling constant, where now paramagnetic contributions produce screening and diamagnetic contributions anti-screening. PB Elsevier Science Bv SN 0550-3213 YR 2001 FD 2001-03-12 LK https://hdl.handle.net/20.500.14352/59002 UL https://hdl.handle.net/20.500.14352/59002 LA eng NO © 2001 Elsevier Science B.V. All rights reserved.The authors are grateful to E. López for pointing them out that the relative sign in the dispersion relation (6.1) in a previous version of this paper was wrong. They also thank CICyT, Spain for financial support through grant No. PB98 0842. NO CICyT DS Docta Complutense RD 7 jun 2025