RT Journal Article T1 Position-dependent noncommutative products: classical construction and field theory A1 Ruiz Ruiz, Fernando A1 Gayral, V. A1 Gracia Bondía, José Mariano AB We look in Euclidean R-4 for associative star products realizing the commutation relation [x(mu), x(upsilon)] i Theta(mu upsilon)(x), where the noncommutativity parameters Theta(mu upsilon) depend on the position coordinates x. We do this by adopting Rieffel's deformation theory (originally formulated for constant Theta and which includes the Moyal product as a particular case) and find that, for a topology R-2 x R-2, there is only one class of such products which are associative. It corresponds to a noncommutativity matrix whose canonical form has components Theta(12) = -Theta(21) = 0 and Theta(34) = -Theta(43) = theta(x(1), x(2)), with theta(x (1), x(2)) an arbitrary positive smooth bounded function. In Minkowski space-time, this describes a position-dependent space-like or magnetic noncommutativity. We show how to generalize our construction to n >= 3 arbitrary dimensions and use it to find traveling noncommutative lumps generalizing noncommutative solitons discussed in the literature. Next we consider Euclidean lambda phi(4) field theory on such a noncommutative background. Using a zeta-like regulator, the covariant perturbation method and working in configuration space, we explicitly compute the UV singularities. We find that, while the two-point UV divergences are nonlocal, the four-point UV divergences are local, in accordance with recent results for constant Ѳ. PB Elsevier Science BV SN 0550-3213 YR 2005 FD 2005-11-07 LK https://hdl.handle.net/20.500.14352/51009 UL https://hdl.handle.net/20.500.14352/51009 LA eng NO © 2005 Elsevier B.V. All rights reserved.The authors thank J.C. Várilly for helpful comments. V.G. wishes to acknowledge the hospitality of the Department of Theoretical Physics of Universidad Complutense de Madrid, where this work was started. J.M.G.B. is very grateful to B. Booss-Bavnbek for making available to him unpublished notes on the Duhamel expansion. He also thanks MEC, Spain for support through a ‘Ramón y Cajal’ contract. F.R.R. is grateful to MEC, Spain for financial support through grant No. BFM2002-00950. NO MEC DS Docta Complutense RD 10 abr 2025