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1.
We study the N=2 supersymmetric E6 models on the 6-dimensional space–time where the supersymmetry and gauge symmetry can be broken by the discrete symmetry. On the space–time M4×S1/(Z2×Z2′)×S1/(Z2×Z2′), for the zero modes, we obtain the 4-dimensional N=1 supersymmetric models with gauge groups SU(3)×SU(2)×SU(2)×U(1)2, SU(4)×SU(2)×SU(2)×U(1), and SU(3)×SU(2)×U(1)3 with one extra pair of Higgs doublets from the vector multiplet. In addition, considering that the extra space manifold is the annulus A2 and disc D2, we list all the constraints on constructing the 4-dimensional N=1 supersymmetric SU(3)×SU(2)×U(1)3 models for the zero modes, and give the simplest model with Z9 symmetry. We also comment on the extra gauge symmetry breaking and its generalization.  相似文献   

2.
We study N = 1 dualities in four-dimensional supersymmetric gauge theories as the world volume theory of D4 branes with one compact direction in type IIA string theory. We generalize the previous work for SO(Nc1) × Sp(Nc2) with the superpotential W = TrX4 to the case of W = TrX4(k+1) in terms of brane configuration. We conjecture that the new dualities for the product gauge groups of SO(Nc1) × Sp(Nc2) × SO(Nc3), SO(Nc1) × Sp(Nc2) × SO(Nc3) × Sp(Nc4) and higher multiple product gauge groups can be obtained by reversing the ordering of NS5 branes and D6 branes while preserving the linking numbers. We also describe the above dualities in terms of wrapping D6 branes around 3-cycles of Calabi-Yau threefolds in type IIA string theory. The theory with adjoint matter can be regarded as taking multiple copies of NS5 brane in the configuration of brane or geometric approaches.  相似文献   

3.
The spatially inhomogeneous decomposition and desorption reaction of oxide layers with coverage 1-0.3 monolayers (ML) from a silicon (100) surface has been studied using scanning tunneling microscopy (STM). After desorption, microscopic changes to the (2 × 1) reconstruction produce two variations on the dimer row reconstruction with decreased surface atom density. A (2 × n) vacancy chain reconstruction and a c(4 × 4) incomplete row reconstruction were observed; a structure for the latter is proposed. Both reconstructions are metastable, reforming the (2 × 1) reconstruction upon heating. At greater length scales during desorption from an initial 1.0 ML coverage, the mesoscopic changes to the surface structure include pitting and roughening, with up to a measured 20 fold increase in the edge density as compared to the clean Si(100) surface.

These structural changes suggest a reaction mechanism involving a substantial rearrangement of the substrate silicon. From an initial 1.0 ML oxygen coverage, using measured void size distributions at total desorption levels of 13% and below — before voids have begun to coalesce — the evolution of void sizes during initial desorption can be followed. A mechanism for desorption is proposed in which silicon atoms must diffuse from adjacent clean surface area to the oxide boundary, producing a reactive complex from which SiO is desorbed. Void growth rates derived from two rate limiting cases for this desorption reaction mechanism can be compared to measured results. We show that the measured void area evolution is consistent with a reaction mechanism where the rate limiting step for monolayer desorption is the promotion of a silicon atom in a lattice site to a mobile monomer within the void.  相似文献   


4.
The infinite-layer compound with nominal composition of Sr0.86Nd0.14CuO2 synthesized under high pressure has been investigated by high-resolution transmission microscopy as well as selected area electron diffraction techniques. The microtwin originating from the tetragonal-orthorhombic phase transformation and the 2×b superstructure are observed in such an infinite-layer compound for the first time. The n×c (n=2, 3, 4, …) superstructures and their origin are discussed. Computer image simulation reveals that the 2×c superstructure is due to the oxygen deficiency.  相似文献   

5.
We reconsider the Kaluza-Klein compactifications of D = 11 supergravity on AdS4 × (G/H)7 manifolds that were classified in the eighties, in the modern perspective of AdS4/CFT3 correspondence. We focus on one of the three N = 2 cases: (G/H)7 = M111 = SU(3) × SU(2) × U(1) /SU(2) × U(1)′ × U(1)′'. Relying on the systematic use of the harmonic analysis techniques developed in the eighties by one of us (P. Fré) with R. D'Auria, we derive the complete spectrum of long, short and massless Osp(2|4) × SU(3) × SU(2) unitary irreducible representations obtained in this compactification. Our result also provides a general scheme for the other N = 2 compactifications. Furthermore, it is a necessary comparison term in the AdS4/CFT3 correspondence: the complete AdS/CFT match of the spectra that we obtain will provide a much more stringent proof of the ACS/CFT correspondence than in the S7 case, since the structure of the superconformal field theory on the M2-brane world volume must be such as to reproduce, at the level of composite operators, the flavor group representations, the conformal dimensions and the hyperchanges that we obtain in the present article. The investigation of this match is left to future publications. Here we provide an exhaustive construction of the Kaluza-Klein side of our spectroscopy.  相似文献   

6.
We derive the quenched master field equations for constrained systems such as the O(N) non-linear sigma model, U(N)×U(N) chiral models, and U(N) lattice gauge theory. The master equations are algebraic, and involve quenching in both the space and “fifth” (Langevin) time directions. The quenched master field for the O(N) nonlinear sigma model is found exactly. The 0-dimensional unitary matrix model is solved perturbatively, and we recover the Gross-Witten result. The master equation for the U(N)×U(N) chiral model is set up for non-perturbative approximation methods, and some qualitative results are obtained.  相似文献   

7.
The reactions of H2S with predosed surface oxygen on Ni(110) surfaces were studied for a variety of coverage conditions. The primary reaction product is H2O, but the details of the water formation and desorption depends on the coverage of both O and H2S.

For high coverages of oxygen (p(2 × 1)−O; 0.5 ML), the reaction to form water is quantitative. The loss of oxygen from the surface (as measured by AES) is equal to the increase in sulfur coverage. XPS and HREELS measurements indicate the presence of chemisorbed H2O immediately following large exposures of H2S on the oxygen predosed surface at 110 K. Deuterium incorporation results suggest that the primary mechanism for these coverage conditions involves direct transfer of hydrogen from SH or H2S moieties to the oxygen.

A second mechanism involving reaction of surface hydroxyl groups with surface hydrogen was also identified. This mechanism is particularly important for high coverages of oxygen (0.5 ML) and low coverages of H2S (0.15 ML), where water desorption was observed at 235 K, but was not observed spectroscopically at 110 K. The sequential addition of two surface hydrogen atoms to surface oxygen is not an important mechanism in this system.

These reactions were modeled using a bond-order conservation method, and the model successfully reproduced the important mechanistic conclusions.  相似文献   


8.
The U(N) chiral model, when quenched using Parisi's rule, has a [U(1) × U(1)]N/U(1) global invariance. To determine whether this symmetry breaks spontaneously in weak coupling for N=∞, a one-loop calculation of the distribution of eigenvalues of the single U(N) matrix of the model is performed. This distribution is shown to be uniform on the unit circle and hence, no symmetry breaking occurs. Further, the order parameter | tr U|2/N2, which should be zero at N=∞ in the absence of spontaneous symmetry breaking, is evaluated in the weak coupling phase for one, two and three dimensions for N varying from 2 to 50 by Monte Carlo simulation of the quenched model. The data indicate that this parameter indeed goes to zero as N→∞ implying that the symmetry does not break.  相似文献   

9.
We obtain in a closed form the 1/N2 contribution to the free energy of the two Hermitian N×N random matrix model with nonsymmetric quartic potential. From this result, we calculate numerically the Yang–Lee zeros of the 2D Ising model on dynamical random graphs with the topology of a torus up to n=16 vertices. They are found to be located on the unit circle on the complex fugacity plane. In order to include contributions of even higher topologies we calculated analytically the nonperturbative (sum over all genus) partition function of the model for the special cases of N=1,2 and graphs with n≤20 vertices. Once again the Yang–Lee zeros are shown numerically to lie on the unit circle on the complex fugacity plane. Our results thus generalize previous numerical results on random graphs by going beyond the planar approximation and strongly indicate that there might be a generalization of the Lee–Yang circle theorem for dynamical random graphs.  相似文献   

10.
We show that the transfer matrix of the AN−1(1) open spin chair with diagonal boundary fields has the symmetry Uq(SU(l)) × Uq(SU(Nl)) × U(1), as well as a “duality” symmetry which maps lNl. We exploit these symmetries to compute exact boundary S-matrices in the regime with q real.  相似文献   

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