Unification of Gauge and Yukawa Couplings without Symmetry ∗

A natural gradual extension of the idea of Grand Unification is to attempt to relate the gauge and Yukawa couplings; Gauge-Yukawa Unification (GYU). However, within the framework of renormalizable field theories, there exists no realistic symmetry that leads to a GYU. Here we propose an approach to GYU which is based on the principle of the reduction of couplings and finiteness in supersymmetric Grand Unified Theories. We elucidate how the observed top-bottom mass hierarchy can be explained in terms of supersymmetric GYU by considering an example of the SU(5) Finite Unified Theory. It is expected that, when more accurate measurements of the top and bottom quark masses are available, it will be possible to discriminate among the various GYU models. ∗ Presented by J.K. at the 5 Hellenic School and Workshops on Elementary Particle Physics, September 3-24, 1995, Corfu, to appear in the proceedings. Partially supported by the Grants-in-Aid for Scientific Research from the Ministry of Education, Science and Culture (No. 40211213). On leave of absence from the Institute of Theoretical Physics, Warsaw University, ul. Hoza 69, 00-681 Warsaw, Poland. Partially supported by the Polish Committee for Scientific Research. ‡ Partially supported by C.E.C. projects, SC1-CT91-0729; CHRX-CT93-0319.