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Massless and massive monopoles carrying nonabelian magnetic charges

Description: The properties of BPS monopoles carrying nonabelian magnetic charges are investigated by following the behavior of the moduli space of solutions as the Higgs field is varied from a value giving a purely abelian symmetry breaking to one that leaves a nonabelian subgroup of the gauge symmetry unbroken. As the limit of nonabelian unbroken symmetry is reached, some of the fundamental abelian monopoles remain massive but acquire nonabelian magnetic charges. The BPS mass formula indicates that others should because massless in this limit. These do not correspond to distinct solitons, but instead are manifested as a ``nonabelian cloud`` surrounding the massive monopoles, with their position and phase degrees of freedom being transformed into parameters characterizing the cloud.
Date: October 1, 1996
Creator: Weinberg, E.J.
Partner: UNT Libraries Government Documents Department

Quark model calculations of symmetry breaking in parton distributions

Description: Using a quark model, we calculate symmetry breaking effects in the valence quark distributions of the nucleon. In particular, we examine the breaking of the quark model SU(4) symmetry by color magnetic effects, and find that color magnetism provides an explanation for deviation of the ratio d{sub v}({chi})/u{sub v}({chi}) from 1/2. Additionally, we calculate the effect of charge symmetry breaking in the valence quark distributions of the proton and neutron and find, in contrast to other authors, that the effect is too small to be seen experimentally.
Date: September 1, 1995
Creator: Benesh, C.J.; Goldman, J.T. & Stephenson, G.J.
Partner: UNT Libraries Government Documents Department

Petite unification: an alternative viewpoint

Description: It is assumed that at some distance scale, not too many orders of magnitude less than the compton wavelength of intermediate bosons W/sup + -/ and Z/sup 0/, the SU(3)/sub c/ x SU(2)/sub L/ x U(1)/sub Y/ gauge theory, characterized by three coupling constants, becomes embedded in a gauge theory G/sub S/ x G/sub W/ characterized by only two coupling constants, g/sub S/ and g/sub W/. The strong group G/sub S/ and weak group G/sub W/ are assumed each to be either simple or pseudo-simple i.e. a direct product of simple groups with identical coupling strengths. Such a possibility is caled petite unification. Any subsequent unification of the strong force with the weak at still shorter distances is left unconsidered. A building-up procedure is adopted, that is to say the available inputs from the low-energy theory SU(3)/sub c/ x SU(2)/sub L/ x U(1)/sub Y/ are used to restrict the choices of G/sub S/ and G/sub W/. The inputs used are the experimental value of sin/sup 2/theta/sub W/ and the known fermion representations. The choices of G/sub W/ are found to be quite restricted. The smallest acceptable G/sub W/ turns out to be (SU(2))/sup 4/, and the most efficient choice of a strong group is SU(4) built a la Pati and Salam, which is the simplest case for which the electroweak U(1)/sub Y/ generator is a linear combination of both G/sub S/ and G/sub W/ generators. Furthermore, leptons provide the fourth color degree of freedom achieving thus an early quark-lepton unification. The phenomenology of the minimal petite unification model SU(4) x (SU(2))/sup 4/ is examined in detail.
Date: May 1, 1981
Creator: Hung, P.Q.
Partner: UNT Libraries Government Documents Department

Determination of the chiral SU(4) x SU(4) breaking parameters

Description: Broken chiral SU(4) x SU(4) symmetry: from the observed mass spectrum of pseudoscalar charmed mesons the symmetry breakig parameters of the theory could be solved. It is found that both vacuum and Hamiltonian breaking play an important role as far as charmed states are concerned. Purely from the masses of D and F mesons the current algebra mass ratio m/sub c//m/sub s/ < 5 is deduced. This differs greatly from values obtained using linear or quadratic mass formulas. Considering eta, eta', and eta/sub c/ mixing a good solution with m/sub c//m/sub s/ approx. 3.2 and (anti cc)/anti uu) approx. 5.67 is further obtained. 18 references
Date: June 1, 1978
Creator: Das, K.P. & Deshpande, N.G.
Partner: UNT Libraries Government Documents Department

Unpaired nucleons as probes of core collective fields

Description: Field theory techniques are applied to the study of interacting boson systems. A dynamical quasiparticle theory derived by the equations of motion method is compared with IBFM as a means of coupling an odd particle to IBM cores. For a single j-shell, the two models are found to be roughly equivalent on a phenomenological level. This equivalence requires that the IBFM parameter ..lambda../sub 0/ is a function of the core, SU(5) vs. SU(3) or O(6), but not an explicit function of the Fermi level. IBFM is found to Coriolis attenuate in strong-coupled bands - partly decoupled cases must be investigated further. The dynamical quasiparticle method has advantages with respect to (i) the physical significiance of the pairing ..delta.. as opposed to the IBFM ..lambda..jj' 's, (ii) particle transfer at least in principle, and (iii) easy generalizability. In an application of static mean field theory, the ..cap alpha..-cluster interpretation of the SU(4) model for the Ra isotopes is tested. It is found that a larger cluster would be required to account for experimental odd-nucleon decoupling factors. 38 references.
Date: January 1, 1984
Creator: Leander, G.A.; Semmes, P.B. & Doenau, F.
Partner: UNT Libraries Government Documents Department