共查询到20条相似文献,搜索用时 15 毫秒
1.
H. Levine 《Nuclear Physics B》1980,170(1):128-138
The two-dimensional non-abelian Higgs model is studied by employing a dilute gas of ZN vortices. The results obtained are similar to the corresponding results of the abelian model, studied by Callan, Dashen and Gross, and Raby and Ukawa. The most interesting conclusion is that in the presence of some number, NF, of massless fermion flavors, the theory behaves differently for N > Ncrit or N < Ncrit where Ncrit = NF/(NF?2). 相似文献
2.
We have computed the scale breaking Λ parameters of the euclidean and hamiltonian formulations of the lattice regulated O(N) and SU(N) × SU(N) spin systems in 1 + 1 dimensions in terms of the ΛPV parameters of the Pauli-Villars regulated continuum models. Using lattice perturbation theory, the renormalized mass gap has been determined in terms of ΛPV for each model. These results are compared to analogous calculations in SU(N) gauge theories. 相似文献
3.
《Nuclear Physics B》1996,469(3):419-444
The pressure and the energy density of the SU(3) gauge theory are calculated on lattices with temporal extent Nτ = 4, 6 and 8 and spatial extent Nσ = 16 and 32. The results are then extrapolated to the continuum limit. In the investigated temperature range up to five times Tc we observe a 15% deviation from the ideal gas limit. We also present new results for the critical temperature on lattices with temporal extent Nτ = 8 and 12. At the corresponding critical couplings the string tension is calculated on 324 lattices to fix the temperature scale. An extrapolation to the continuum limit yields Tc/√σ = 0.629(3). We furthermore present results on the electric and magnetic condensates as well as the temperature dependence of the spatial string tension. These observables suggest that the temperature dependent running coupling remains large even at T ≅ 5Tc. For the spatial string tension we find √σs/T=0.566(13)g22(T) with g2 (5Tc) ≅ 1.5. 相似文献
4.
《Physics letters. [Part B]》1988,205(1):1-6
The algebraic quantization of the SU(3) skyrmion is presented. We discuss the role of the number of colors (Nc) in QCD and the Wess-Zumino term in the quantization. Two distinct dynamical group chains are shown to correspond to different methods of semiclassical quantization. We obtain most of the SU(6) quark model predictions for the skyrmion quantized with Nc=3. 相似文献
5.
《Physics letters. [Part B]》1987,194(2):231-235
We describe a simple N = 1 supersymmetric GUT based on the group SU(5)×U(1) which has the following virtues: the gauge group is broken down to the SU(3)C×SU(2)L×U(1)Y of the standard model using just 10, Higgs representations, and doublet-triplet mass splitting problem is solved naturally by a very simple missing-partner mechanism. The successful supersymmetric GUT prediction for sin2θw can be maintained, whilst there are no fermion mass relations. The gauge group and representation structure of the model may be obtainable from the superstring. 相似文献
6.
Pierre van Baal 《Communications in Mathematical Physics》1982,85(4):529-547
We show how to prove and to understand the formula for the “Pontryagin” indexP for SU(N) gauge fields on the HypertorusT 4, seen as a four-dimensional euclidean box with twisted boundary conditions. These twists are defined as gauge invariant integers moduloN and labelled byN μv (=?N μv ). In terms of these we can write (ν∈#x2124;) $$P = \frac{1}{{16\pi ^2 }}\int {Tr(G_{\mu v} \tilde G_{\mu v} )d_4 x = v + \left( {\frac{{N - 1}}{N}} \right) \cdot \frac{{n_{\mu v} \tilde n_{\mu v} }}{4}} $$ . Furthermore we settle the last link in the proof of the existence of zero action solutions with all possible twists satisfying \(\frac{{n_{\mu v} \tilde n_{\mu v} }}{4} = \kappa (n) = 0(\bmod N)\) for arbitraryN. 相似文献
7.
G. E. Volovik 《JETP Letters》2003,78(11):691-694
The left-right symmetric Pati-Salam model of the unification of quarks and leptons is based on the SU(4) and SU(2)×SU(2) symmetry groups. These groups are naturally extended to include the classification of families of quarks and leptons. We assume that the family group (the group which unites the families) is also the SU(4) group. The properties of the fourth generation of fermions are the same as those of the ordinary-matter fermions in the first three generations except for the family charge of the SU(4)F group: F=(1/3, 1/3, 1/3, ?1), where F=1/3 for fermions of ordinary matter and F=?1 for the fourth-generation fermions. The difference in F does not allow mixing between ordinary and fourth-generation fermions. Because of the conservation of the Fcharge, the creation of baryons and leptons in the process of electroweak baryogenesis must be accompanied by the creation of fermions of the fourth generation. As a result, the excess n B of baryons over antibaryons leads to the excess n4ν=N?N? of neutrinos over antineutrinos in the fourth generation with n4ν=n B . This massive neutrino may form nonbaryonic dark matter. In principle, the mass density of the fourth neutrino n4νm N in the Universe can make the main contribution to dark matter, since the lower bound on the neutrino mass m N from the data on decay of the Z bosons is m N <m Z /2. The straightforward prediction of this model leads to the amount of cold dark matter relative to baryons, which is an order of magnitude higher than allowed by observations. This inconsistency may be avoided by nonconservation of the F charge. 相似文献
8.
9.
Paul J Steinhardt 《Annals of Physics》1981,132(1):18-31
Two-dimensional gauge theories with diagonal SU(N) color symmetry are analyzed in the limit of strong coupling using bosonization techniques. A spectrum of heavy mesons is found in addition to a spectrum of light baryon and baryonium states. Exotic behavior is also found for various values of the {Θi} parameters. 相似文献
10.
Satoshi Watamura 《Physics letters. [Part B]》1984,136(4):245-250
We examine the compactification of D=4+2N, Einstein-Maxwell-Dirac theory. It is shown that the manifold CPN × M4 is a solution of the equations of motion. The structure of the fermions, gauge bosons and their couplings in the four-dimensional effective theory is investigated. The scale of CPN is quantized by a generalized Dirac condition. When the results are applied to the solution with internal space CP1×CP2, the weak mixing angle and the ratio of the couplings of SU(3) (g3) and SU(2) (g2) are defined by two integers and a hypercharge. An SU(3)-triplet chiral fermion can appear in four-dimensional effective theory. 相似文献
11.
In this paper we show that D = 11 supergravity admits an infinite discrete class of solutions having the phenomenological group SU(3) ? SU(2) ? U(1) as a symmetry of the internal space M7. These solutions lead, in dimensional reduction, to SU(3) ? SU(2) ? U(1) gauge fields.In general all these spaces produce a complete breaking of supersymmetry except in one case where N = 2 supersymmetry survives. The parameter which classifies the solutions is a rational number q/p which describes the embedding of the stability subgroup SU(2) ? U(1) ? U(1) of M7 in SU(3) ? SU(2) ? U(1). For all q/p ≠ 1 the holonomy group is SO(7) and all supersymmetries are broken. For q/p = 1 the holonomy group is SU(3) and two supersymmetries survive. In this last case we can also find a solution with internal photon curl . It breaks all sypersymmetries. 相似文献
12.
We show that the usual three families of quarks and leptons are identifiable with quasi Nambu-Goldstone fermions in a supersymmetric non-linear realization of E7 corresponding to the Kähler manifold E7/SU(5) × SU(3) × U(1). So the triplication of families suggests the underlying preon theory realizing the global E7 linearly. Possible connections with N = 8 supergravity are also discussed. 相似文献
13.
Motivated by experiments in nanoscopic systems, we study a generalized Anderson, which consist of two spin degenerate doublets hybridized to a singlet by the promotion of an electron to two conduction bands, as a function of the energy separation δ between both doublets. For δ=0 or very large, the model is equivalent to a one-level SU(N) Anderson model, with N=4 and 2 respectively. We study the evolution of the spectral density for both doublets (ρ1σ(ω) and ρ2σ(ω)) and their width in the Kondo limit as δ is varied, using the non-crossing approximation (NCA). As δ increases, the peak at the Fermi energy in the spectral density (Kondo peak) splits and the density of the doublet of higher energy ρ2σ(ω) shifts above the Ferrmi energy. The Kondo temperature TK (determined by the half-width at half maximum of the Kondo peak in density of the doublet of lower energy ρ1σ(ω)) decreases dramatically. The variation of TK with δ is reproduced by a simple variational calculation. 相似文献
14.
After reviewing the euclidean formulation of the thermodynamics for quantum spin systems, we develop the corresponding formalism for SU(N) gauge fields on the lattice. The results are then evaluated for the SU(2) system, using Monte Carlo simulation on lattices of (space × temperature) size 103 × 2,3,4,5. At high temperature, the system exhibits Stefan-Boltzmann behaviour, with three gluonic colour degrees of freedom. At Tc ≈ 43ΛL (215 MeV), the transition to “hadronic” behaviour occurs, signalled by a sharp peak in the specific heat. From the behaviour below the deconfinement transition (T<Tc), we obtain mG ≈ 200ΛL (1000 MeV) for the mass of the lowest gluonium state (glueball). 相似文献
15.
《Physics letters. [Part B]》1987,199(3):380-388
A variety of heterotic string compactifications on the K3 surface, manifolds of SU(3) holomony, and higher holomony manifolds, are solved exactly. An example of the quintic hypersurface in CP4 is worked out in detail. It is conjectured, and demonstrated in part, that any supersymmetric compactification of the heterotic string with an N=2 superconformal theory is equivalent to a compactification on a manifold of SU(N) holonomy, and in particular an arbitrary gluing of the discrete models with c=9 gives a solvable heterotic string compactification on some Calabi-Yau manifold. Calabi-Yau compactifications are seen to be exact vacua of string theory, retaining their topological and geometrical characteristics. Previously unknown enhanced gauge symmetries are found to arise for certain backgrounds. 相似文献
16.
《Nuclear Physics B》1999,539(3):557-576
We calculate the critical amplitudes of the Polyakov loop and its susceptibility at the deconfinement transition of (3 + 1)-dimensional SU(2) gauge theory. To this end we study the corrections due to irrelevant exponents in the scaling functions. As a guiding line for determining the critical amplitudes we use envelope equations which we derive from the finite size scaling formulae of the observables. We have produced new high precision data on Nσ3 × 4 lattices for Nχ = 12, 18, 26 and 36. With these data we find different corrections to the asymptotic scaling behaviour above and below the transition. Our result for the universal ratio of the susceptibility amplitudes is C+/C− = 4.72(11) and thus in excellent agreement with a recent measurement for the 3d Ising model. 相似文献
17.
Y. Iwasaki 《Physics letters. [Part B]》1981,100(4):327-330
A possible explanation is proposed for the crossover from strong to weak coupling region in SU(N) lattice gauge theories. We predict the pointswhere the crossover takes place for all SU(N)M: For example, g2 ≈ 2.0 for SU(2), g2 ≈ 1.0 for SU(3) and limN→∞Ng2(SU(N) ≈ 2.0. 相似文献
18.
We compute in the standard model of SU(3)c×(SU(2)×U(1)) with massless quarks and leptons the two-loop anomalous dimensions of the four-fermion operators relevant to proton decay in process involving (u, d, e, νe). The calculation is carried out by the use of dimensional reduction, a variant of dimensional regularization. Our aim is to give a complete calculation within the SU(5) GUT model of the next-to-leading enhancement-suppression factor for nucleon decay due to renormalization effects arising from hard gluons, W's and B's in process which involve (u, d, e, νe). It turns out that the result is sensitive to the ratios x(i) = MH (i)/MX where MH(i) are the masses of the twelve superheavy Higgs scalars in the multiplet which breaks SU(5) → SU(3)×SU(2)×U(1). 相似文献
19.
D. Faiman 《Nuclear Physics B》1976,109(2):286-292
We point out that the intersection of the Berkeley-SLAC and Saclay signs of πN→?N resonant amplitudes are consistent with ?-broken SU(6)W if both the 70, LP = 1?and 56, LP = 2+ multiplets choose anti-SU(6)W solutions. The symmetry scheme still fails in that the πN→πΔ relative signs require an SU(6)W-like solution for the 56, LP = 2+. This failure however now rests on a single incorrect sign prediction among all N? and Δπ amplitudes. 相似文献
20.
Dieter Stoll 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(1):69-79
We demonstrate that using bosonization techniques in 1+1-dimensional QCD in the chiral limit a unique definition of baryons is possible for finiteN c despite the fact that mesons, baryons and anti-baryons are massless. The definition which is based on the construction of an SU(2)-algebra provides the basis for a new approach to investigate hadronic properties in the strong coupling limit. It is used to study the Fock-state decomposition and structure functions of baryons for various finite values ofN c . The results are discussed in comparison to similar calculations based on discretized lightcone quantization. 相似文献