Top quark flavor changing couplings at a muon collider

There is growing interest in the development of a muon collider that would make it possible to produce lepton collisions at energies of several TeV. Among others, there can be significant contributions to electroweak gauge boson, Higgs boson and top quark physics. In this work we pay attention to the latter, in particular, effective flavor-changing (FC) top-quark interactions. We discuss the flavor changing $t \bar q$ ($q=u,c$) production processes that can be a good probe of the dimension-six top quark four-fermion and fermion-boson operators in the SMEFT. We consider all sixteen operators that can generate flavor-changing top quark couplings. After comparing with the current LHC bounds, we find potential limits three or four orders of magnitude stronger for four-fermion operators. Concerning fermion-boson couplings, for the tensor operators $Q_{uW}$ and $Q_{uB}$ we obtain the highest sensitivity. We also observe that the effective $W$ approximation (EWA) does not apply with $Q_{uB}$.