N = 1 superspace formulation of N = 2 and N = 4 super-Yang-Mills models with central charge

The component models of N = 2 and N = 4 supersymmetric Yang-Mills theories of Sohnius, Stelle and West are reformulated in terms of N = 1 superfields. The non-supersymmetric constraints are supersymmetrized generalizing the linear multiplet in the presence of the non-abelian gauge superfield and (in the N = 4 case) a doublet of chiral superfields. The extended supersymmetry transformations preserving constraints are explicitly given in terms of N = 1 superfields. We are able to introduce the constraints back into the lagrangian using superfield Lagrange multipliers. The on-shell equivalence of this formulation with the formulation of Fayet with one (for N = 2) and three (for N = 4) chiral superfields is shown. The abelian N = 2 model is worked out to show the connection between full superspace treatment and the N = 1 superfield formulation.     

N = 2 supergravity action in terms of N = 1 superfields

We construct the full N = 2 supergravity action in terms of N = 1 supergravity and matter fields.     

Noncompact N=2 supergravity

A massive spin-one multiplet with central charge is coupled to N=2 supergravity. Compared to conventional gauge fields the anomalous magnetic moment of the spin-one particles is of the opposite sign. The construction of this theory is based on an N=2 supersymmetric gauge theory associated with the noncompact group SO(2,1). As a byproduct we present a convenient expression for the N=2 Einstein-Yang-Mills lagrangian.     

Doubly excited resonances of the helium sequence associated with N=4 hydrogenic thresholds

Several lower-lying doubly excited resonances associated with N=4 hydrogenic thresholds for two electron atoms have been calculated using a method of complex rotation.     

N = 4 Yang-Mills theory in terms of N = 3 and N = 2 light-cone superfields

The N = 4 Yang-Mills theory is truncated to an N = 3 Yang-Mills theory and to an N = 2 Yang-Mills theory coupled to an N = 2 Wess-Zumino field. The whole procedure is performed in the light-cone gauge. It is then shown that these theories are unique even if we only insist on N = 3 or N = 2 supersymmetry respectively. Finally we show in detail how the introduction of the fermionic Wess-Zumino field renders the one-loop self-energy finite.     

The complete N =2, d = 10 supergravity

The alternative N = 2, d = 10 supergravity, which is not derivable by dimensional reduction from the N = 1, d = 11 theory, is constructed at the full non-linear level. The transformation laws of the component fields and the equations of motion are derived and shown to be consistent. The derivation makes use of superspace techniques and exploits the fact that the scalars belong to the coset space SU(1,1)/U(1).     

Linearized N = 2 superfield supergravity

We present the formulation of linearized SU(2) supergravity and U(2) conformal supergravity in terms of unconstrained N = 2 superfields: the gauge superfield, compensating superfields, gauge transformations, supertensors, actions and covariant derivatives.     

Shell-model study on magnetic dipole excitation of N = 28 isotones

Magnetic dipole excitation of N = 28 isotones — ⁴⁸Ca, ⁵⁰Ti, ⁵²Cr, ⁵⁴Fe and ⁵¹V — is studied in terms of the shell model by assuming $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}{}^{\mathrm{n?m}}\text{(}\text{p}\text{3}\text{2}\text{p}\text{1}\text{2}\text{f}\text{5}\text{2}\text{)}{}^{\mathrm{m}}$ configurations with m = 0, 1 and 2 on an inert ⁴⁰Ca core. Strength distributions observed in (e,e′) and (p,p′) experiments are fairly well reproduced. Interference of proton and neutron excitations enhances B(M1) values around E_x = 10 MeV and reduces those of low-lying states. The strength for T = T₀ + 1 states substantially increases when orbital magnetization is not taken into account, whereas no appreciable consequences can be seen for T = T₀ states. In comparison with single-particle model predictions with m = 0, about 20–30% reduction of the total strength is obtained due to ground-state configuration mixing. It is shown that the isoscalar spin component is reduced as well as the isovector one. However, the theoretical total strength is still much larger than experimental values, and coupling with high-lying configurations and possible delta-hole excitation might be required in order to account for the discrepancy. In an odd-mass nucleus ⁵¹V, the ground-state transition strength is distributed continuously over a wide energy range, being very strongly fragmented.     

N = 8 supergravity

The complete structure of N = 8 supergravity is presented with an optional local SO(8) invariance. The SO(8) gauge interactions break E₇ invariance, but leave the local SU(8) unaffected. Exploiting E₇ × SU(8) invariance and using explicit lowest order results, we first derive the complete action and transformation laws. Subsequently, we introduce local SO(8) invariance and prove the consistency of the theory. Possible implications of our results are discussed.     

N = 4 supergravity coupled to N = 4 matter and hidden symmetries

We present the N = 1 supergravity in 10 dimensions obtained by truncating the reduced N = 1 supergravity from 11 dimensions. This is further reduced to 4 dimensions to give SU(4) supergravity coupled to six SO(4) vector multiplets. As the reduction is from 10 dimensions, the theory is expected to have the symmetry SL(6R)_global×SO(6)_local, but we give a theoretical argument that this can be extended to SO(6,6)×SU(1,1)_global and SO(6)×SO(6)×U(1)_local.     

Radiative muon capture for N = Z nuclei

The commonly used elementary hamiltonian of radiative muon capture has been confirmed, while the alternative Hwang-Primakoff approach is shown not to be gauge invariant.In the inclusive process on N = Z nuclei, the closure approximation is avoided by using a realistic nuclear excitation spectrum.The study is exemplified by a detailed application to ⁴⁰Ca. Predictions are given for the high-energy photon spectrum, circular polarization and asymmetry with respect to the muon polarization for various values of the pseudoscalar coupling constant g_p. A semi-quantitative agreement is found with the data on the spectrum; more precise experiments are necessary to determine g_p.     

N = 2, D = 10 non-chiral supergravity and its spontaneous compactification

The non-chiral N = 2, D = 10 supergravity theory is constructed using dimensional reduction from N = 1, D = 11 supergravity. It is shown that this theory may spontaneously compactify, yielding S⁴ × S², CP² × S² and S² × S² × S² spaces for the extra dimensions.     

Towards a finite N = 2 susy GUT

We consider finite, N = 2 supersymmetric GUTs based on gauge groups SU(n) and SO(n). As an example, we discuss a semirealistic model based on SO(12). We argue that in finite, N = 2 supersymmetric GUTs, gauge symmetry breaking should occur dynamically. We present a heuristic picture in which this is induced by soft, finiteness preserving SUSY breaking terms. The bound states formed cause a very rapid evolution of the SO(12) coupling constant and break SO(12) into SU(4)×SU(3)_C×U(1).     

Bound states in N = 8 supergravity and N = 4 supersymmetric Yang-Mills theories

We present a study of possible bound states in N = 8 supergravity. We find evidence for the existence of multiplets of two-body bound states and expect that many-body bound states may exist as well. Our study is based on a calculation of Regge trajectories in the two-body scattering amplitudes of the lagrangian field theory. We also study Regge trajectories in N = 4 Yang-Mills theory and find evidence for a possible spin zero, SU(4) and gauge singlet, massless bound state. If such a state actually exists and supersymmetry is not broken, it may be a member of a supersymmetric multiplet which includes the graviton.     

Group manifold first-order formulation of N=2, d=4 supergravity theory

In this paper, the so far lacking first-order formulation of N = 2 supergravity is obtained in the group manifold rheonomic symmetry approach. In order for the theory to be non-trivial it must contain, besides the pseudoconnection, also a 0-form matter multiplet which, moreover, provides the mechanism to generate the spin-l field kinetic term. It is explicitly shown how the O(2)～U(1) symmetry is realized not by a linear gauge transformation, rather by a rheonomic one.     

Line strengths,collision strengths and excitation rates for multiply-charged silicon ions

Line strengths, collision strengths and excitation rates have been calculated for a variety of transitions in multicharged silicon ions from Si(Vi) to Si(XIV). The collision strengths were evaluated in an LS coupling scheme in the distorted wave approximation neglecting exchange except for the helium-like transitions. Excitation rates were then obtained by integrating the collision strength over a Maxwellian velocity distribution function. These results are then described by a simple two-parameter fit for the rates.     

Instanton effects in N = 2 supersymmetric quantum mechanics

Supersymmetric quantum mechanics with several bosonic and fermionic dynamic variables is considered. Two different N = 2 supersymmetric models involving instantons are discussed in detail. Instantons fail to break supersymmetry in one of the models considered. The vacuum state is degenerate in this model which generally results in spontaneous breaking of internal left-right symmetry. In another model supersymmetry is destroyed dynamically due to special complex instanton solutions. Possible implications for SUSY field theories are discussed.     

The improved tensor multiplet in N = 2 supergravity

We construct a scale-invariant action for the N = 2 tensor multiplet which can be coupled to conformal supergravity. In spite of its non-polynomial form the action describes a free massless hypermultiplet. When used as a compensating multiplet it leads to a new minimal formulation of N = 2 Poincaré or de Sitter supergravity. We discuss its consequences and present a comparison with previous off-shell formulations.     

Low energy constraints on N = 2 supersymmetric models

We derive constraints on the masses of mirror particles in N = 2 supersymmetric theories. We consider the K_L?K_S mass difference, the π → ev/π → μv branching ratio and the anomalous magnetic moment of the muon. The K_L?K_S mass difference gives a lower bound of 15 TeV on the mirror gauge scalar and mirror gauge fermion masses, under suitable assumptions.