Llanes Estrada, Felipe JoséBicudo, PD2023-06-202023-06-2020030556-282110.1103/PhysRevD.68.094014https://hdl.handle.net/20.500.14352/58813© 2003 The American Physical Society. The authors acknowledge useful discussions with S. Cotanch, F. Kleefeld, B. Hiller, P. Maris, J. R. Pelaez, A. Dobado, A. Gomez Nicola, and specially E. Ribeiro. This work was partially supported by Univ. Complutense on a travel grant, and by grants FPA 2000-0956 and BFM 2002-01003 (Spain), F.J.L.-E. is thankful for the hospitality and scholarly atmosphere at IST Lisbon.Using a systematic expansion of the quark-antiquark Bethe Salpeter wave functions in the relativistic quark model and working to O(P-4) in the chiral limit, we are able to derive theoretical expressions relating the coefficients of the chiral Lagrangian l(1),l(2) to the underlying quark-antiquark wave functions and interaction kernels. This is accomplished by using a novel technique based on a Ward identity for the quark-antiquark ladder kernel which greatly simplifies the required effort. Numerical evaluations are performed in two simple specific models.engjournal articlehttp://dx.doi.org/10.1103/PhysRevD.68.094014http://prd.aps.orgopen access53P-3(0) Condensed VacuumPerturbation-TheorySymmetryModelQcdMesonsScatteringResonancesExpansionBreakingFísica (Física)22 Física