Lepton and quark symmetry in weak and electromagnetic interactions

We discuss a three-quark model motivated by lepton-quark analogy. An advantage of this model is that there is no hypercharge-changing neutral current, but Cabibbo suppression has to be explained by dynamical reason.     

Runge-Lenz vector, accidental SU(2) symmetry, and unusual multiplets for motion on a cone

We consider a particle moving on a cone and bound to its tip by 1/r or harmonic oscillator potentials. When the deficit angle of the cone divided by 2π is a rational number, all bound classical orbits are closed. Correspondingly, the quantum system has accidental degeneracies in the discrete energy spectrum. An accidental SU(2) symmetry is generated by the rotations around the tip of the cone as well as by a Runge-Lenz vector. Remarkably, some of the corresponding multiplets have fractional “spin” and unusual degeneracies.     

Global SO(3) × SO(3) × U(1) symmetry of the Hubbard model on bipartite lattices

In this paper the global symmetry of the Hubbard model on a bipartite lattice is found to be larger than SO(4). The model is one of the most studied many-particle quantum problems, yet except in one dimension it has no exact solution, so that there remain many open questions about its properties. Symmetry plays an important role in physics and often can be used to extract useful information on unsolved non-perturbative quantum problems. Specifically, here it is found that for on-site interaction U ≠ 0 the local SU(2) × SU(2) × U(1) gauge symmetry of the Hubbard model on a bipartite lattice with N_a^D sites and vanishing transfer integral t = 0 can be lifted to a global [SU(2) × SU(2) × U(1)]/Z₂² = SO(3) × SO(3) × U(1) symmetry in the presence of the kinetic-energy hopping term of the Hamiltonian with t > 0. (Examples of a bipartite lattice are the D-dimensional cubic lattices of lattice constant a and edge length L = N_aa for which D = 1, 2, 3,... in the number N_a^D of sites.) The generator of the new found hidden independent charge global U(1) symmetry, which is not related to the ordinary U(1) gauge subgroup of electromagnetism, is one half the rotated-electron number of singly occupied sites operator. Although addition of chemical-potential and magnetic-field operator terms to the model Hamiltonian lowers its symmetry, such terms commute with it. Therefore, its 4^N_aD energy eigenstates refer to representations of the new found global [SU(2) × SU(2) × U(1)]/Z₂² = SO(3) × SO(3) × U(1) symmetry. Consistently, we find that for the Hubbard model on a bipartite lattice the number of independent representations of the group SO(3) × SO(3) × U(1) equals the Hilbert-space dimension 4^N_aD. It is confirmed elsewhere that the new found symmetry has important physical consequences.     

On the connection of matrix elements of the SU (1,1) discrete series representations with SU (2) matrix elements

The purpose of this note is to establish the connection between the matrix elements of representations of two simplest groups: representations of the discrete series of the non-compact SU (1,1) group and the corresponding representations of the compact SU (2) group.     

Representations of the Sugawara SU(2) current algebra

The Sugawara SU(2) current algebra is exponentiated in order to obtain the group. Further, the representations of the current algebra are recovered from the representations of the group.Generators of the three-dimensional Euclidean group E, (space translations and space relations) are constructed. An example showing the relation with Yang-Mills theory is presented.     

Monte Carlo estimates of the SU(2) mass gap

Combining Monte Carlo and variational techniques, we compute the mass gap (or glueball mass) in the SU(2) lattice gauge theory. We obtain the estimate $\text{m}{}_{\mathrm{g}}\text{=(2.4 ± 0.6)}\text{K}\text{, K}$ being the string tension. We also discuss previous results derived by numerical or strong coupling methods and present Monte Carlo data on the second moment of the correlation length.     

Semi-leptonic weak and electromagnetic interactions in nuclei:: Parity violations in electron scattering and weak neutral currents

A general result for the difference in differential cross sections for electron scattering between any two nuclear levels with incident longitudinally polarized right- and left-handed electrons is derived. This difference must involve the parity-violating weak interaction at least linearly and can be used to study weak neutral currents as pointed out by Feinberg. A V — A structure for the weak neutral currents is assumed with a semi-leptonic current-current interaction, and the electromagnetic interaction is treated in the one-photon-exchange approximation. The result is expressed in terms of the same set of reduced matrix elements of the multipoles of the nuclear currents which govern all electromagnetic and weak transitions between these levels. A previously developed unified analysis of semi-leptonic weak and electromagnetic interactions in nuclei which determines one-body transition densities, including their spin and spatial dependences, through electron scattering provides nuclear transitions to serve as known analyzers in testing the structure of this part of the weak interaction. Examples are given using Weinberg's model of the weak neutral currents. Feinberg's result for elastic scattering from spin-0 nuclei is rederived and two new examples using previously determined one-body densities are discussed : the 1⁺0 → 0⁺1 (3.56 MeV) transition in ⁶Li and the 0⁺0 → 1⁺ 1(15.1 MeV) transition in ¹²C.     

A universal covering group of SU(p, q)

A universal covering group of SU(p, q) is parametrized and its groups law in this parametrization is established.     

On asymptotic properties of a quantum number ω in a system with SU(3) symmetry

The asymptotic properties of the basic vectors for the (λμ) irreducible representations of the SU(3)-group in the SU(3)?SO(3) reduction (Elliott's basis) are investigated for large values of λ or μ. The matrix of the Bargmann-Moshinsky operator Ω in Elliott's basis is analysed for the same limiting case. Approximate expressions for the eigenvalues and eigenvectors of the operator Ω are found. They demonstrate the asymptotic properties of the operator Ω to be very close to those of the rigid quantum top.     

Self dual solutions of the temperature SU(2) Yang-Mills theory

Continuing previous work we elaborate on the method of “heating” the self-dual axially symmetric fields of the SU(2) Yang-Mills theory to finite temperature. Heating consists of performing—in certain Ansatz functions which are two-dimensional (2D) conformally invariant—a 2D conformal transformation x = x₀ + i ∥x∥ → y(x), where the analytic function y(x) is periodic in the Euclidean time variable x₀. Solutions are preserved by this manipulation, which automatically changes zero-temperature fields into finite temperature ones. One can exploit this simple fact in various ways. The Harrington-Shepard caloron solution of the temperature Yang-Mills theory can be gotten from the T = 0 instanton by the transformation y(x) = (πT)^?1 tan πTx. One can generate a multicaloron solution from the T = 0 one instanton solution by a conformal transformation. Generally, self-dual axially symmetric Yang-Mills fields can be heated without spoiling self duality. The caloron and three other temperature solutions are studied in some detail. One of the new solutions is a generalized caloron with interesting properties. Our study reveals a remarkable property of the self-dual sector of the temperature Yang-Mills theory: it is full of Wu-Yang (color) monopoles at high temperature. At low temperature these monopoles disappear.     

Two dimensional gases of weight charges and SU(N) fermino theories

We analyze two dimensional gases composed of particles interacting via a Coulomb or Yakawa potential through their “non-Abelian” charges. These charges are taken to be elementary weight or root vectors of SU(N). The grand partition function of these gases is shown to be equivalent to the generating functional of sine-Gordon models with weight vectors and hence to that of SU(N) fermion models. The fermion field creates or annihilates topological solitons which have elementary weight vectors as topological quantum numbers. Then, we discuss the confinement of fermions in the SU(N) Higgs models, where instantons (Z_N vortices) constitute a Yukawa gas of weight charges. We prove that fermions are confirmed by the effects of instantons in the SU(N) Higgs models in contrast with the Abelian Higgs model.     

A systematic search for a realistic SU(n) tumbling gauge model

Within the framework of the dynamical symmetry breaking and the tumbling ideas, a systematic search was carried out in SU(n) groups with the ultimate aim of determining if a realistic and phenomenologically acceptable model exists which tumbles down to SU(3)_c ? U(1), or a suitable large group. To do so all the anomaly free and the asymptotically free fermion contents for any SU(n) were first determined. In order to have nontrivial tumbling the real and the pseudo-real representations have been eliminated, and the tumbling patterns of all the allowed complex ones in detail have been examined. No such realistic model has been found. These results combined with those of Srednicki's concerning the SO(4n + 2) and E₆ groups establish the fact that there cannot be any realistic tumbling gauge model within the context of the original tumbling hypotheses. Having thus established the need for a change of these hypotheses some suggestions and comment on various ways of remedying the problem are made.     

Four-baryon weak interactions with ΔS = 1 and SU (6) symmetry

Relations are found among the amplitudes for four-baryon processes with S = 1 under the assumption that the Lagrangian for s-wave weak interactions has the transformation properties of a component of the SU(6) 35-plet. In particular, it is found that the amplitudes for the¹S₀ ¹S₀ and³S₁ ³S₁ transitions for the p pn reaction are the same, within a sign.Translated from Izvestiya VUZ. Fizika, No. 10, pp. 70–77, October, 1969.     

SL(4) as a common symmetry group of electromagnetic and gravitational interactions

A theory of electromagnetic and gravitational interactions between elementary particles is proposed, based upon the symmetry groupSL(4). According to this theory, gravitational fields are formed as the result of interactions between charged particles with opposite charge.     

The conflict between natural flavor conservation of Higgs couplings and cabibbo mixing in SU(2)L × U(1)

The general problem of conservation of strangeness and other quark flavors by the exchange of several neutral Higgs mesons is investigated in SU(2)_L × U(1). We find that the horizontal symmetries necessary to enforce this conservation conflict with the known Cabibbo mixing. In particular, if the quarks form an irreducible representation of the horizontal symmetry, the mixing angles are all trivial (i.e., 0 or $\text{π}\text{2}$); if they form a reducible representation, it is possible to have some nontrivial mixing angles, but only if there are several unmixed generations of quarks with exactly the same relative pattern of masses and mixings.     

Z2 × Z2 Discrete Symmetry in the Left-Right Symmetric Model SU(2)L × SU(2)R × U(l)B-L

From the point that the Higgs fields can be regarded as the gauge fields on a discrete group, we construct a gauge theory of the leftright symmetric model SU(2)_L × SU(2)_R × U(1)_B-L (LRSM) over Z₂ ⊙ Z₂ discrete symmetry.     

SU(3) as gauge group of the vectorlike weak and electromagnetic interactions

A scheme of the weak and electromagnetic interactions based on the group SU(3) as well as on six quark flavours and eight leptons is presented. Several aspects of the weak interactions are discussed, in particular the presence of new right-handed currents, the neutral current, the generation of the Cabibbo angle, and the dominant non-leptonic weak interaction.     

Limits on P and T violating neutral current weak interactions

It is pointed out that presently available limits on the electric dipole moments of atoms and molecules require that the coupling constants for any scalar-pseudoscalar or tensor pseudo tensor interaction between electrons and nucleons be at least three orders of magnitude less than the Fermi constant.