Top quark physics at e+e- linear colliders

The profile of top quarks is described in the Standard Model and beyond, and the prospects for carrying out high precision measurements in the top quark sector at e+e- colliders are reviewed. (i) The steep rise of the cross section σ(e+e-→tanti t) near the treshold through the formation of toponium remnants allows the measurement of the Balmer top mass mt with an accuracy of better than 500 MeV. (ii) The properties of the standard top decay model t→b+W+ as well as [possibly rare] non-standard decays to charged Higgs bosons t→b+H+ or through the stop channel in supersymmetric models, t→t tilde + neutralino, can be investigated. (iii) Electroweak static parameters of the top quark, anomalous magnetic and electric dipole moments, and the chirality of the (t, b) decay current can be explored through angular correlations between initial and final state particles. (iv) Higgs radiation off top quarks in e+e-→tanti tH or Higgs decay to top quarks in e+e-→ZH→Ztanti t may provide an almost unique opportunity to measure directly the Higgs-fermion coupling. (orig.)