Can thermal inflation solve the monopole problem.pdfVIP

a r X i v : h e p - p h / 9 8 0 8 2 6 0 v 1 7 A u g 1 9 9 8 Can thermal inflation solve the monopole problem ? R. Jeannerot Centre for Theoretical Physics, University of Sussex, Falmer, Brighton BN1 9QH, UK Abstract It is shown that thermal inflation arises naturally in rank greater than five unified theories when non-renormalisable terms are introduced. Thermal in- flation is driven by two Higgs fields ΦB?L and ΦB?L which also break U(1)B?L when acquiring vevs at the end of inflation. The inflationary period provides enough e-foldings to solve the monopole problem for MB?L ≥ 1012 GeV. We point out that observations suggest that MB?L ? 1014 GeV. I. INTRODUCTION Supersymmetric grand unified theories (GUTs) of the strong, weak and electromagnetic interactions have received lots of interests since it has been shown that the three gauge cou- pling constants of the minimal supersymmetric standard model (MSSM), when interpolated to high energies, meet in a single point at 2×1016 GeV [1]. GUT theories can also be viewed as low energy limits of a more fundamental theory. If this more fundamental theory is su- perstrings theory, GUTs could explain the discrepancy which exists between the string scale and the scale at which all fundamental interactions other than gravity merge. Therefore the idea of GUT is an idea which stands on its own, whether we believe or not in the existence of an ultimate theory of nature; and all problems which GUT theories have to deal with, such as the monopole problem, still have to be solved. If we do believe in the existence of an ultimate theory, which is probably a theory of quantum gravity , then we may want to include Planck suppressed operators (or operators suppressed by some very high energy scale) when building a GUT model. These operators then underline the fact that the GUT emerges from a more fundamental theory, but without any assumption upon the nature of this more fundamental theory. A problem which all GUTs have to face, wheth