Theoretical scenarios for 10(3) GeV to 10(19) GeV

Basic dogmas of particle physics are Some of their implications beyond the model are explored, Higgs sector of the standard model of electroweak interactions is the weakest link in the model, Elementary Higgs field makes the model 'unnatural' beyond about 10(3) GeV. Supersymmetry provides the most attractive framework wherein this problem can be addressed. This new symmetry, relating fermions and bosons, is expected to be operative at about 10(3) GeV, In addition, grand unification of the fundamental interactions can be studied consistently only within a supersymmetric formulation, Inclusion of gravity with other interactions leads to supergravity theories, which should emerge as a low energy description of a more fundamental theory, the string theory. Supersymmetry again is an essential feature of such a theory, Quantum gravity, with its characteristic scale of 10(19) GeV, may well be described by a superstring theory.