This article explains the idea of unified field theories in particle physics. It starts with a historical review of two successful theories which unified two apparently distinct forces: Maxwell’s theory of electromagnetism and Glashow–Salam–Weinberg theory of electroweak forces. Then it describes known four forces in Nature: gravitational, electromagnetic, weak and strong forces, and what their...

In the grand-unified models based on SU(15) and SU(16) in which the quarks and leptons are un-unified at the intermediate stages, we show that BR (KL → μe) ≤ 10−14 and BR (K → πμe) ≤ 10−14 despite the presence of leptoquark gauge bosons. Thus, the observation of these processes in the ongoing or upcoming experiments will rule out the models. PACS numbers: 12.10.Dm, 13.20.Eb, 11.30.Hv Experiment...

Grand unification is an attractive idea and enables the unification of forces and the (partial) unification of quarks and leptons in each family.1) The introduction of supersymmetry (SUSY) increases the reality of grand unification. In the minimal supersymmetric standard model (MSSM), the gauge couplings meet at MX = 2.1× 1016GeV if the superpartners and Higgs particles exist below or around O(...

We discuss supersymmetic SO(10) unified theories constructed in 6 dimensions. The breaking of SO(10) group is achieved by the orbifold compactification. In 4 dimensions we obtain a N = 1 supersymmetric standard model which gauge group is enlarged by an additional U(1) symmetry. This unbroken gauge group is obtained as intersection of the Pati-Salam and the Georgi-Glashow subgroups of SO(10). Th...

We study the boundary conditions in topologically twisted Chern-Simons matter theories with the Lie 3-algebraic structure. We find that the supersymmetric boundary conditions and the gauge invariant boundary conditions can be unified as complexified gauge invariant boundary conditions which lead to supergroup WZW models. We propose that the low-energy effective field theories on the two-dimensi...

Abstract In the first lecture, the Standard Model is reviewed, with the aim of seeing how its successes constrain possible extensions, the significance of the apparently low Higgs mass indicated by precision electroweak experiments is discussed, and defects of the Standard Model are examined. The second lecture includes a general discussion of the electroweak vacuum and an introduction to super...