Duality and symmetry tests for multiparticle production models

Two-body absorptive parts generated by unitarity from multi-Regge particle production models are tested with respect to duality and symmetry structure (suppression of exotics and exchange degeneracy in output). A multi-Regge model with production of only stable particles generates exotic and non-exotic outputs of equal strength; resonances (clusters) are needed to pass these symmetry tests. Two complementary approaches are used, explicit S-matrix models and duality diagrams; the connection between dynamical assumptions and different duality diagram rules is discussed. C-parity plays a crucial role; using C-conserving duality diagrams we show that standard manipulations lead to a topological pomeron which has secondary terms; one, with C_t = ?1, cancels the topological ω₁ meson, another one, with C_t = +1, cancels the topological ?₁ meson.     

An analysis of runs tests as indicators of nonstatistical structure in the compound nucleus

Runs tests were applied to computer-generated elastic-scattering excitation functions in order to examine their sensitivity to nonstatistical structure in the compound nucleus. The scattering amplitudes were either purely statistical or else they included contributions from additional resonances about 1 MeV broad. Our aim was to determine whether the runs tests could distinguish between the two cases. The tests were successful once trends producing correlations between the datum points were removed. Spurious nonstatistical effects were thus eliminated, demonstrating that if the trend-reduction problem is dealt with propertly, runs tests are effective in searches for nonstatistical structure beneath the compound-nucleus fluctuations in experimental excitation functions.     

Pseudospin symmetry as an accidental symmetry in the relativistic framework

We analyse the arguments used in the relativistic context to base the quasi-degeneracy of pseudospin doublets (PSDs) observed in atomic nuclei on the smallness of the single-particle central potential (Σ _S + Σ₀), discussing, especially, the implications of the results obtained in the limit (Σ _S + Σ₀ = 0. We study also the transition from a relativistic model, where Σ _S + Σ₀ is a harmonic-oscillator potential and exhibits degenerate PSDs, to a more realistic one with broken pseudospin symmetry. We examine, in particular, the effect of the corresponding pseudospin symmetry-breaking term on the Dirac spinors of the PSDs. An extension of the Nilsson model to the relativistic case is also considered. Communicated by V. Vento     

The nucleus as a multiquark system

Model calculations for nuclear properties such as shell structure, magnetic moments and charge distributions are presented where quarks instead of nucleons are used as the fundamental nuclear constituents. It is shown that such a new picture is able to reproduce the gross properties of the classical theory. Nucleons and nuclearΔ-resonances show, however, a partial quark deconfinemement which leads to Pauli-blocking.     

光电信息工程实验教学的思考与改革

面对急剧变化的世界,工程知识本身的有效期变得越来越短,社会对学生各种素质的要求越来越高。如何定位大学工程教育本身的角色?如何在光电工程实验教学中培养社会对学生所提出的各种要求?结合对这些问题的思考,讨论了光电信息工程专业实验教学所面临的挑战,以及为应对这些挑战所进行的教学改革实践。     

The lead nucleus as a miniature surrogate for a neutron star

The nucleus of ²⁰⁸Pb, a system 18 orders of magnitude smaller and 55 orders of magnitude lighter than a neutron star, may be used as a miniature surrogate to establish important correlations between its neutron skin and several neutron-star properties. Indeed, models with a thicker neutron skin in ²⁰⁸Pb generate larger neutron stars that have a lower liquid-to-solid transition density. Further, we illustrate how the correlation between the neutron skin in ²⁰⁸Pb and the radius of a 1.4 solar-mass neutron star may be used to place important constraints on the equation of state of neutron-rich matter and how it may help elucidate the existence of a phase transition at the core of the star.     

Mixed symmetry states and isospin excitation in the N = Z nucleus 28Si

The interacting boson model with isospin (IBM-3) has been used to study the isospin excitation states and mixed symmetry states at low spin for 28Si. The theoretical calculations are in agreement with experimental data. The theoretical results show that the 81+ energy is 14.73 MeV.     

Sensitivity of laboratory tests of gravitation beyond the geometrical optics limit

A report is given of a laboratory experiment that reached the sensitivity attained so far in extraterrestrial tests of gravitation beyond the limit of geometrical optics. The sensitivity achieved here in searching for a hypothetical relative change in the velocity of light (δc/c ? 2 × 10^-12) seems, however, already near to the presumable maximum for experiments carried out on the earth's surface with static fields.     

Mixed symmetry states and electromagnetic transition in the N=Z nucleus ^28Si

The interacting boson model with isospin （IBM-3） has been used to study mixed symmetry states and electromagnetic transitions at low-lying states for a ^28Si nucleus. The theoretical calculations show that the 24^＋ state is the lowest mixed symmetry state in ^28Si and the 43＋ state is also a mixed symmetry state.     

Dynamical symmetry breaking as the origin of the pomeranchuk singularity

We consider the viewpoint that Reggeons are built out of Reggeized quarks and that an O(2) symmetry between two kinds of quarks (“heavy” and “light”) is dynamically broken by their interaction. The Goldstone boson thus generated is associated with the Pomeron, and it is argued that it naturally has a smaller slope than the other Reggeons which are ordinary bound states of the quarks.     

The representation theory of the symmetry group of lattice fermions as a basis for kinematics in lattice QCD

The symmetry group of staggered lattice fermions is discussed as a discrete subgroup of the symmetry group of the Dirac-Kähler equation. For the representation theory of this group, G. Mackey's generalization of E.P. Wigner's procedure for the construction of unitary representations of groups with normal subgroups is used. A complete classification of these irreducible representations by “momentum stars”, “flavour orbits” and “reduced spins” is given.     

The realization of dynamical symmetry for the shape invariant potentials

New realization of the dynamical symmetry of the Hamiltonians with shape invariant potentials is proposed. In this realization the operators of supersymmetric quantum mechanics are explicitly used. It is shown that the method can be used not only for the translationally shape invariant potentials but also for those arising when multiplication of the parameters is applied (self similar potentials).     

Quadratic bell inequalities as tests for multipartite entanglement

This Letter presents quantum mechanical inequalities which distinguish, for systems of n spin- 1 / 2 particles ( n>2), between fully entangled states and states in which at most n-1 particles are entangled. These inequalities are stronger than those obtained by Gisin and Bechmann-Pasquinucci [Phys. Lett. A 246, 1 (1998)] and by Seevinck and Svetlichny [quant-ph/0201046].     

The symmetry of the Hubbard model

The spectrum of the Hubbard model shows permanent degeneracy of levels with different symmetries, if one considers only symmetry operators independent of the coupling constant. This suggests the existence of symmetry operators which depend on the coupling constant. We find these highly nontrivial operators and show that they explain the degeneracies in the energy spectrum.Part of project No. P5588 of the Fonds zur Förderung der wissenschaftlichen Forschung in Österreich.     

Inductively Coupled Plasmas as Excitation Sources for Atomic Fluorescence Spectrometry

The inductively coupled Ar plasma (ICP) is introduced as a multielement excitation source for flame atomic fluorescence spectrometry. The ICP-excited and the EDL-excited atomic fluorescence detection limits are compared for 20 elements.