[en] It is shown that of the four parameters in the low-energy part of the theory, which is based on the supergravitational theory of grand unification (SUGRA GUT), only three (m₃/sub //₂, γequivalentM/m₃/sub //₂, and A) depend on the details of the gravitational theory, while the fourth (B) is determined by the grand unification model

[en] The Grand Unification Theory with the (SU₅ circle-times U₁)circle-times(SU₃ circle-times U₁)_H gauge group, in which (SU₃ circle-times U₁)_H is the horizontal symmetry of quark-lepton generations, is considered within the framework of the approach using a four-dimensional superstring with free fermions. The horizontal hypercharge Y_H is used to quantize electromagnetic charges of quarks and leptons within the framework of standard SO₁₀ 16-plets. In the authors approach, construction of the horizontal gauge symmetry leads to the appearance of a new massive SO₁₀ 16-plet, which is a singlet with respect to the horizontal group. The resulting Higgs sector may enable the hidden gauge group to be suppressed significantly and to break the flip SU₅ circle-times U₁ symmetry first to SM and then to SU^c₃ circle-times U^em₁. The Q_em construction allows the authors to avoid states with exotic charges (Q^ex_em = 1/nQ_em), whose emergence is characteristic of the approach using four-dimensional superstrings. In the authors approach, the horizontal group can be violated in the low-energy limit, which offers a possibility for the existence of a superweaklike mechanism of CP violation in the gauge sector of the SU_3H group. 19 refs., 2 tabs

[en] At the beginning of the universe the fundamental forces of the standard model (the electro-magnetic interaction, the weak and strong nuclear interactions) are supposed to be unified because it was the domain of very high energy. When the universe cooled down the symmetry associated to this unique interaction broke generating topological defects called cosmic strings. Cosmic strings have nothing to do with the string theory. Cosmic strings form a cosmological network that evolve with time, cosmic strings moving at the speed of light. Simulations have shown that cosmic strings have a 10^-30 m long characteristic radius and a linear density of about 10²¹ kg/m. Because of the high value of the linear density, cosmic strings could be detected via gravitational effects like the deviation of light rays or the detection of specific gravitational waves. Detection attempts have been made in the past 2 years but no cosmic string has been detected so far. (A.C.)

[en] The relationships among the many specialized areas of physics are discussed. The historical aspects are briefly covered, and the relevance of the superconducting super collider is emphasized

[en] If a grand Unified Theory with a compact unifying group G is spontaneously broken to H, magnetic monopoles are created. The fate of such an H-monopole under a subsequent breaking to K is contained in H is shown to depend on the behaviour of its non-Abelian charge Q introduced by Goddard, Nuyts, Olive: if Q belongs to the Lie algebra k of K, the monopole survives: if Q can be H-rotated to k, it can be converted. A necessary condition for an H-monopole to survie is that its Higgs charge satisfy a topological constraint

[en] A brief description of the principal features of Grand Unified Monopoles is given. This is followed by an extended overview of the current terrestrial, astrophysical and cosmological bounds on their existence

[en] The grand unification of forces based on SU(5) is discussed. Like other grand unified theories, the above theory suffers from the defects that: (i) it has too many parameters even after reducing three couplings to one and (ii) it does not obey naturalness condition which every workable theory has to satisfy. It is suggested that further development in this area will be through supersymmetry. (M.G.B.)

No abstract available

[en] The proceedings includes two lectures given at the Winter School on High Energy Physics held Puri, India between 3-17 January 1988 on the following topics: complex manifolds and string theory. A separate abstract was prepared for each of these lectures. Refs, figs and tabs

[en] Some recent developments with respect to the resolution of the gauge hierarchy problem in grand unified theories by supersymmetry are presented. A general argument is developed to show how global supersymmetry maintains the stability of the different mass-scales under perturbative effects. (author)