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1.
《Physics letters. [Part B]》1987,194(3):385-389
A generalised Z-orbifold model is described in which, as a result of nonstandard embedding of the point group and nontrivial embedding of the discrete translations, the number of generations is reduced to three and the observable gauge group is broken to SUC(3)×SUL(3)×U2(1). Yukawa couplings in this model are also discussed. 相似文献
2.
《Physics letters. [Part B]》1986,178(1):15-20
The phenomenology of superstring theories in which the gauge symmetry after compactification is SO(10) × E′8, instead of E6 × E′8, is discussed. In particular, the generation of an intermediate scale, the radiative breaking of electroweak symmetry, and the supersymmetric particle spectrum are investigated. 相似文献
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《Physics letters. [Part B]》1988,215(4):669-673
We construct a possibly realistic four-generation Calabi-Yau manifold by dividing the algebraic variety in CP4 × CP4 with the Z2×Z2 symmetry. The nontrivial embedding of Z2×Z2 in E(6) allows physically intriguing intermediate symmetry based on the U(1)×SU(2)L×SU(2)R×SU(4)C group. Also, the group of honest symmetries GH of the manifold is identified. 相似文献
5.
A new mechanism for baryogenesis is proposed. It is argued that, after inflation, the scalar quarks and leptons of a supersymmetric GUT may have large expectation values. The subsequent evolution of such a system is shown to generate a significant baryon density. For typical values of the parameters, nB/nγ may be as large as 103. 相似文献
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Single field baryogenesis, a scenario for Dirac leptogenesis sourced by a time-dependent scalar condensate, is studied on a toy model. We compare the creation of the charge asymmetry by the perturbative decay of the condensate with the nonperturbative decay, a process of particle production commonly known in the context of inflation as preheating. Neglecting backreaction effects, we find that over a wide parametric range perturbative decay and preheating contribute by the same order of magnitude to the baryon asymmetry. 相似文献
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《Physics letters. [Part B]》1987,199(3):407-411
We study a superstring inspired E6 model based on the MAC hypothesis. We find two kinds of model in which the proton decay through the colored Higgs is naturally suppressed and every field in 27 of E6 carries a role; a pair of colored fields in 27 are necessary to cause the MAC condensation and two doublet fields in 27 cause the usual Higgs mechanism at the electroweak breaking. The fields left in 27 are identified with quarks and leptons adding to vLc. 相似文献
11.
C Premkumar Yesudian 《Pramana》1989,33(6):651-657
An extended technicolour grand unification model based on the gauge groupE
6×SU(7) extended technicolour is presented. The symmetry-breaking based on extended technicolour theory is discussed. It is
shown that the existing phenomenology is well explained by the model. The strangeness changing neutral currents may not be
a problem with this model. 相似文献
12.
《Physics letters. [Part B]》1986,173(3):251-256
The possibility is considered of achieving inflation in the field-theory limit of the E8 X E8 superstring model, which is an N = 1 supergravity theory possessing a “no-scale” SU(n, 1)/SU(n) × U(1) structure. It is shown that neither type I inflation (due to higher-derivative terms O(R2)), nor inflation due to a SUSY-breaking gaugino-condensation potential, is possible, essentially because of the absence of free dimensionless parameters. Kaluza-Klein type inflation is ruled out because the internal space is Ricci flat. The occurence of type II inflation (due to some gauge singlet “inflation” field φ) depends upon the form of the superpotential F and of the Kähler potential G, but this also seems not to be possible, unless the >SU(n, 1) symmetry can be broken in a particular way. Hence, some new type of compactification scheme may be called for, or a different type of inflation. 相似文献
13.
Motivated by a desire to find a useful 2d Lorentz-invariant reformulation of the AdS5×S5 superstring world-sheet theory in terms of physical degrees of freedom we construct the “Pohlmeyer-reduced” version of the corresponding sigma model. The Pohlmeyer reduction procedure involves several steps. Starting with a coset space string sigma model in the conformal gauge and writing the classical equations in terms of currents one can fix the residual conformal diffeomorphism symmetry and kappa-symmetry and introduce a new set of variables (related locally to currents but non-locally to the original string coordinate fields) so that the Virasoro constraints are automatically satisfied. The resulting equations can be obtained from a Lagrangian of a non-Abelian Toda type: a gauged WZW model with an integrable potential coupled also to a set of 2d fermionic fields. A gauge-fixed form of the Pohlmeyer-reduced theory can be found by integrating out the 2d gauge field of the gauged WZW model. The small-fluctuation spectrum near the trivial vacuum contains 8 bosonic and 8 fermionic degrees of freedom with equal mass. We conjecture that the reduced model has world-sheet supersymmetry and is ultraviolet-finite. We show that in the special case of the AdS2×S2 superstring model the reduced theory is indeed supersymmetric: it is equivalent to the N=2 supersymmetric extension of the sine-Gordon model. 相似文献
14.
《Nuclear Physics B》1988,295(2):277-295
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《Nuclear Physics B》1986,268(2):349-361
A simple model is proposed to describe a gas of free strings at very high energy density, particularly in connection with a recently discovered phase dominated by macroscopic strings. This phase appears at high energy density if open strings are forbidden. For oriented strings the probability density for strings in the energy interval (E, E + dE) is dE / E in this phase. If open strings are allowed no such phase appears. The model is compared with superstring calculations, and relevant quantities are shown to agree. The model gives a simple and intuitively appealing picture of dense, free string gases. The effective string tension is also discussed and shown to vanish at the critical temperature. 相似文献
16.
《Physics letters. [Part B]》1987,184(1):37-44
We work out details of a previously proposed senario for baryogenesis in a superstring model, based on the Affleck-Dine mechanism exploiting the decays of large expectation values for squark and slepton fields after inflation. We show how the coefficients of the relevant quartic scalar operators can aquire the necessary imaginary parts. We examine possible sources of entropy among the gauge-singlet scalar and fermion fields including the gravitino, as well as the low-energy SU(2)L × U(1)2 → SU(2)L × U(1)Y → U(1)em phase transitions. We argue that none of these dilute substantailly the baryon-to-entropy ratio, which can easily be in the range preferred by cosmology. This means, in particular, that the Polonyi and gravitino problems are solved. 相似文献
17.
《Nuclear Physics B》1986,268(2):397-405
We have constructed a version of the chiral three-preon model E6 × SO(10) that satisfies the condition of asymptotic freedom in the metacolor and composite color-flavor sectors. The construction is based on the global color-flavor symmetry group SU(18). By applying the 't Hooft anomaly matching condition to the subgroup SU(16) × SU(2) of SU(18), together with a few physical constraints, we obtain a unique solution that gives rise to precisely three generations of the spinorial representation 16 of SO(10) without exotics. Except for N = 18, no solution exists for the global color-flavor group satisfying metacolor asymptotic freedom (N < 22) when SU(N) breaks to SU(16) × SU(N − 16). 相似文献
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N. Toyota 《Zeitschrift fur Physik C Particles and Fields》1988,39(4):461-465
We reconsider Kalyniak and Sundaresan's (KS's) criticism about the models obtained by Breit et al. totally from a more phenomenological point of view. We study which fields inN f (27) must acquire the vacuum expectation value (vev) rather than ones in \(\delta (27 + \overline {27} )\) in order to break down toSU(3) c ×U(1)em symmetry without any extraU(1) at weak scale and endow quarks and leptons with masses. General sets of fields to acquire the vev are obtained. Further utilizing maximally the light components of \(\delta (27 + \overline {27} )\) , minimal sets of fields inN f (27) to acquire the vev is listed up in each case of Breit et al. Also applying the conditions given there to more general cases, we find that there is only model free from KS's criticism. 相似文献
20.
We discuss the quark-lepton phenomenology of a superstring model compactified on aCP 4-based Calabi-Yau manifold defined by? i Z i 5 = 5 c Z 1 Z 2 Z 3 Z 4 Z 5 leading to four fermion generations using the Yukawa couplings calculated by us in a previous paper. We note that maintaining supersymmetry implies that forc?1, one of theU(1)-subgroup ofE 6 must break at the Planck scale; on the other hand forc?10+4, an intermediate scale of about 1011 GeV or 1014 GeV may be generated without destabilizing the gauge hierarchy. The model may have problems with fast proton decay for some choice ofc; however, understanding small neutrino masses remains a problem. 相似文献