H. C. Pauli

Power-law wave functions and generalized parton distributions for the pion

We propose a model for generalized parton distributions of the pion based on the power-law ansatz for the effective light-cone wave function.

DLCQ bound states of N = ( 2 , 2 ) super-Yang-Mills theory at finite and large N

We consider the 1+1 dimensional N = (2,2) supersymmetric matrix model which is obtained by dimensionally reducing N = 1 super Yang-Mills from four to two dimensions. The gauge groups we consider are U(Nc) and SU(Nc), where Nc is finite but arbitrary. We adopt light-cone coordinates, and choose to work in the light-cone gauge. Quantizing this theory via Discretized Light-Cone Quantization (DLCQ) introduces an integer, K, which restricts the light-cone momentum-fraction of constituent quanta to be integer multiples of 1/K. Solutions to the DLCQ bound state equations are obtained for K=2,3,...,6 by discretizing the light-cone supercharges, which results in a supersymmetric spectrum. Our numerical results imply the existence of normalizable massless states in the continuum limit K ->infinity, and therefore the absence of a mass gap. The low energy spectrum is dominated by string-like (or many parton) states. Our results are consistent with the claim that the theory is in a screening phase.

DLCQ spectrum ofN=(8,8)super Yang-Mills theory

We consider the 1+1 dimensional N = (8,8) supersymmetric matrix field theory obtained from a dimensional reduction of ten dimensional N = 1 super Yang-Mills. The gauge groups we consider are U(N) and SU(N), where N is finite but arbitrary. We adopt light-cone coordinates, and choose to work in the light-cone gauge. Quantizing this theory via Discretized Light-Cone Quantization (DLCQ) introduces an integer, K, which restricts the light-cone momentum-fraction of constituent quanta to be integer multiples of 1/K. Solutions to the DLCQ bound state equations are obtained for K=2,3 and 4 by discretizing the light-cone super charges, which preserves supersymmetry manifestly. We discuss degeneracies in the massive spectrum that appear to be independent of the light-cone compactification, and are therefore expected to be present in the decompactified limit K ->infinity. Our numerical results also support the claim that the SU(N) theory has a mass gap.

On the mass distribution in Time-Dependent Hartree-Fock calculations of heavy-ion collisions

Structural limitations in the Time-Dependent Hartree-Fock formalism when applied to heavy-ion collisions are discussed. These severely impair the ability of the method to correctly predict mass distributions and mass-to-charge ratios for the resulting fragments.

A simple approach to the nuclear dynamics

We propose an approach to the nuclear dynamics which enables us to understand the relations between the time-dependent Hartree-Fock method and the quantumstatistical approach to the heavy ion reactions. The same formalism allows us to generalize the random phase approximation in order to include the spreading width of collective states.

Single particle models in the shell correction approach

We investigate the dependence of the shell correction energy on the parameters as they occur in the Nilsson model and the single particle model with a Woods-Saxon potential. We give criteria, how these parameters should be chosen in order that the shell correction energies become fairly model-independent. The different models yield now a value of about −20 MeV for208Pb, substantially larger than in previous work. Its relation to the remainder of the mass formula fit is discussed. We find that shell energies have an extremum. The minimum occurs close to the conventional parameter values (except the potential diffuseness of the protons) and close to the minimum of the total binding energy. The minimum in shell energy corresponds to a maximum bunching of single particle states. The gross properties of these extremal shells agree considerably better with the experimental spectra (for both the neutrons and the protons) than those of conventional model parameters.

A semiclassical description of Fermions with spin-dependent forces

It is shown how to generalize the semiclassical treatment of dense Fermi gases in the presence of spin-dependent forces. One constructs the Wigner transform of the singlet density matrix in that representation in which the position operator and thez component of the spin operator are diagonal. This way one obtains a matrix in the spin indices which is a function of the semiclassicalp andq variables. Rules are then given how to calculate with this matrix, theμ-matrix. Next, this matrix is explicitly evaluated for independent Fermions in a spherically symmetrical potential, subject to spin-orbit forces. Finally a brief discussion is given about the nature of this matrix and possible uses are proposed.

Effect of zero modes on the bound-state spectrum in light-cone quantisation

Abstract We study the role of bosonic zero modes in light-cone quantisation on the invariant mass spectrum for the simplified setting of two-dimensional SU(2) Yang-Mills theory coupled to massive scalar adjoint matter. Specifically, we use discretised light-cone quantisation where the momentum modes become discrete. Two types of zero momentum mode appear – constrained and dynamical zero modes. In fact only the latter type of modes turn out to mix with the Fock vacuum. Omission of the constrained modes leads to the dynamical zero modes being controlled by an infinite square-well potential. We find that taking into account the wavefunctions for these modes in the computation of the full bound state spectrum of the two dimensional theory leads to 21% shifts in the masses of the lowest lying states.

Dynamic excitation in fission

Abstract The excitation mechanism of the fission process is studied in terms of a model of particles moving in a deformed time-dependent potential. A residual interaction of the pairing type is incorporated by means of the BCS approximation. Only two-quasi-particle excitations up to some cutoff energy are included. The separation of the total excitation energy into intrinsic and translational parts is made at the scission point. The present calculations for 240 Pu show that, in the framework of this model, most of the available energy at scission is transformed into intrinsic excitation energy. However the convergence of the calculated value for the cutoff energy is unsatisfactory, and hence a description in terms of a better model space is needed. The fact that very many channels are involved suggests that a statistical treatment may be useful.

Short-range forces and surface tension in nuclei

Consider an atomic nucleus, or any closed system of Fermions under the influence of a saturating short-range interaction. If the range is sufficiently short, one finds that the thickness of the surface layer is not determined by the range of this force, but by a new,quantum mechanical characteristic length, L=(ħ2/8mF)1/3, whereF is the restoring force generated at the boundary by the self-consistent potential acting on the most energetic particles. Moreover, in equilibrium, thisforce adjusts itself in such a manner thatkFL ∼ 1 wherekF is the Fermi wave number. As a consequence, one is now able to compute the binding energy, and thus the volume and surface energy coefficients in an explicit analytical fashion as a function of the coupling constants of the interaction, which in the present case is a modified Skyrme interaction. In addition, speculations are made on the existence ofsurface isomers. These are nuclei at several hundred MeV excitation with essentially the same central density, but with an increased surface region.