Truncation,picture-changing operation and space time supersymmetry in Neveu-Schwarz-Ramond string field theory

The representation of the inverse picture-changing operator in terms of an appropriate truncation operator is found, which means that truncated Ramond string fields are inherent to the Witten construction. Equivalence of the Witten supertransformations and the supertransformations acting on the old truncated fields is established.     

Investigation of a non-renormalizable Lagrangian model invariant under supertransformations

A non-renormalizable Lagrangian model invariant under supertransformations is studied in the one-loop approximation, and a remarkable cancellation of divergences is found.     

The Binary Cascade

The Binary Cascade introduces a novel approach towards intra-nuclear cascade calculations. Like many QMD codes, it uses a detailed 3-dimensional model of the nucleus, and is based exclusively on binary scattering between reaction participants and nucleons within this nuclear model. Like a classical cascade, it uses optical potentials to describe the time evolution of particles passing through the nuclear medium. In the present paper we introduce the model, and investigate its predictive power for hadron spectra in nucleon nuclear reactions final states.Received: 19 December 2003, Revised: 5 March 2004, Published online: 7 September 2004PACS: 21.60.Ka Nuclear structure: Monte Carlo models - 24.10.Lx Nuclear reactions: general: Monte Carlo simulations (including hadron and parton cascades and string breaking models)     

Revisiting the quantum group symmetry of diatomic molecules

We propose a q-deformed model of anharmonic vibrations in diatomic molecules. We study the applicability of the model to the phenomenological Dunham expansion by comparison with experimental data. In contrast with other applications where it is difficult to find a physical interpretation for the deformation parameter, q, in our analysis it is directly related to the third-order coefficient in the Dunham expansion. We study the consistency of the parameters that determine the q-deformed system by comparing them with the vibrational terms fitted to 161 electronic states of diatomic molecules. We show how to include both positive and negative anharmonicities in a simple and systematic way.Received: 16 July 2004, Published online: 24 August 2004PACS: 33.15.Mt Rotation, vibration, and vibration-rotation constants - 02.20.Uw Quantum groups - 31.15.Hz Group theory - 03.65.Fd Algebraic methods - 02.20.-a Group theoryV.K. Dobrev: Permanent address, and after 30 April 2004: Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 1784, Sofia, Bulgaria     

Superfluidity in the inner crust of neutron stars

We present a mean-field quantum calculation of the specific heat in the inner crust of neutron stars, taking into account the inhomogeneous character of the system, in which a lattice of neutron-rich nuclei coexists with a gas of unbound neutrons.Received: 10 December 2002, Published online: 24 February 2004PACS: 21.60.-n Nuclear structure models and methods - 26.60. + c Nuclear matter aspects of neutron stars - 97.60.Jd Neutron stars     

Experimental puzzle of <Superscript>5</Superscript><Emphasis Type="Italic">H</Emphasis>

The experimental evidences for ⁵H are discussed. The results of the recent experiments are controversial. We make a comparison of the experimental data with theoretical calculations (L.V. Grigorenko, N.K. Timofeyuk, M.V. Zhukov, Eur. Phys. J. A 19, 181 (2004)) and try to find a consistent explanation for the current experimental situation. We conclude that more detailed experimental information is required to resolve the existing experimental ambiguity.Received: 22 April 2003, Revised: 8 November 2003, Published online: 18 June 2004PACS: 21.45. + v Few-body systems - 21.60.Gx Cluster models - 25.10. + s Nuclear reactions involving few-nucleon systems     

Symmetry in physics

The role of symmetry in Physics, especially in Nuclear Physics, is briefly reviewed.Received: 31 January 2003, Published online: 17 February 2004PACS: 02.20.Sv Lie algebras and Lie groups - 21.60.Fw Models based on group theory     

New descriptions of phase/shape transition regions in nuclei

Phase transitional behavior, critical-point symmetries, and the low-energy nuclear phase diagram are discussed, with emphasis on the behavior of simple spectroscopic observables. A perspective on the low-energy nuclear phase diagram from the standpoint of Landau theory is presented as well.Received: 4 November 2002, Published online: 23 March 2004PACS:   21.60.-n Nuclear structure models and methods     

On the nucleon self-energy in nuclear matter

We consider the nucleon self-energy in nuclear matter in the absence of Pauli blocking. It is evaluated using the partial-wave analysis of scattering data. Our results are compared with that of a realistic calculation to estimate the effect of this blocking. It is also possible to use our results as a check on the realistic calculations.PACS: 21.30.-x Nuclear forces - 21.65. + f Nuclear matter     

Electron scattering on <Superscript>3</Superscript>He --A playground to test nuclear dynamics

The electron-induced processes on ³He are analyzed using the Faddeev formalism with modern nucleon-nucleon and three-nucleon forces as well as exchange currents. The kinematical region is restricted to a mostly nonrelativistic one where the three-nucleon c.m. energy is below the pion production threshold and the three-momentum of the virtual photon is sufficiently below the nucleon mass. Comparisons with available data are shown and cases of agreement and disagreement are found. It is argued that new and precise data are needed to systematically check the present-day dynamical ingredients.Received: 6 February 2004, Published online: 17 August 2004PACS: 21.45. + v Few-body systems - 21.10.-k Properties of nuclei; nuclear energy levels - 25.10. + s Nuclear reactions involving few-nucleon systems - 25.20.-x Photonuclear reactions     

Non-extensive resonant reaction rates in astrophysical plasmas

We study two different physical scenarios of thermonuclear reactions in stellar plasmas proceeding through a narrow resonance at low energy or through the low-energy wing of a wide resonance at high energy. Correspondingly, we derive two approximate analytical formulae in order to calculate thermonuclear resonant reaction rates inside very coupled and non-ideal astrophysical plasmas in which non-extensive effects are likely to arise. Our results are presented as simple first-order corrective factors that generalize the well-known classical rates obtained in the framework of Maxwell-Boltzmann statistical mechanics. As a possible application of our results, we calculate the dependence of the total corrective factor with respect to the energy at which the resonance is located, in an extremely dense and non-ideal carbon plasma.Received: 7 January 2004, Revised: 9 March 2004, Published online: 14 September 2004PACS: 24.30.-v Resonance reactions - 26.50. + x Nuclear physics aspects of novae, supernovae, and other explosive environments - 05.90. + m Other topics in statistical physics, thermodynamics, and nonlinear dynamical systems     

Neutron excess in analytical expressions for fusion barrier parameters

The neutron excess dependence of heavy-ion fusion barriers is investigated, guided by predictions of different ion-ion potentials. We develop phenomenological expressions for the fusion barrier radii and heights, involving both the entrance channel mass asymmetry and neutron excess of the projectile and target. Compared to commonly used formulas, the developed expressions reproduce theoretical barrier parameters with a higher accuracy. Furthermore, they provide a means to assess the importance of the neutron excess degree of freedom implied by each potential.Received: 1 April 2003, Revised: 31 January 2004, Published online: 10 August 2004PACS: 24.10.-i Nuclear reaction models and methods - 25.70.-z Low and intermediate energy heavy-ion reactions - 25.70.Jj Fusion and fusion-fission reactions - 25.60.Pj Fusion reactions     

Proton- and neutron-induced fission on uranium carbide target

In the frame of the R&D program for the SPES project of the Legnaro Laboratories, the production yields of Rb, In and Cs isotopes have bean measured at the synchrocyclotron of the Petersburg Nuclear Physics Institute (PNPI) of Gatchina (Russia). Production yields for direct proton fission and neutron-induced fission on a high-density UC₂ powder target are compared. The overall efficiencies as a function of the target temperature have been measured.Received: 3 July 2003, Revised: 2 October 2003, Published online: 27 January 2004PACS: 24.75. + i General properties of fission - 25.85.Ec Neutron-induced fission     

Structure of the isovector dipole resonance in neutron-rich <Superscript>60</Superscript><Emphasis Type="Italic">Ca</Emphasis> nuclei and direct decay from pygmy resonance

The structure of the isovector dipole resonance in neutron-rich calcium isotope, ⁶⁰Ca, has been investigated by implementing a careful treatment of the differences of neutron and proton radii in the continuum random phase approximation (RPA). The calculations have taken into account the current estimates of the neutron skin. The estimates of the escape widths for direct neutron decay from the pygmy-dipole resonance (PDR) were shown rather wide, implicating a strong coupling to the continuum. The width of the giant-dipole resonance (GDR) was evaluated, bringing on a detailed discussion about its microscopic structure.Received: 22 September 2003, Revised: 9 February 2004, Published online: 7 September 2004PACS: 21.10.Pc Single-particle levels and strength functions - 21.60.-n Nuclear structure models and methods - 24.30.Cz Giant resonances - 24.30.Gd Other resonances     

Challenges in nuclear dynamics and thermodynamics

The purpose and contents of this topical issue, Dynamics and Thermodynamics with Nuclear Degrees of Freedom, which grew out of a series of workshops in the years 2004 and 2005, are introduced. The central topics are the nuclear density functional, nuclear multi-fragmentation, and nuclear phase transitions.     

A precision measurement of pp elastic scattering cross-sections at intermediate energies

We have measured differential cross-sections for elastic scattering with internal fiber targets in the recirculating beam of the proton synchrotron COSY. Measurements were made continuously during acceleration for projectile kinetic energies between 0.23 and 2.59 GeV in the angular range . Details of the apparatus and the data analysis are given and the resulting excitation functions and angular distributions presented. The precision of each data point is typically better than 4%, and a relative normalization uncertainty of only 2.5% within an excitation function has been reached. The impact on phase shift analysis as well as upper bounds on possible resonant contributions in lower partial waves are discussed.Received: 24 March 2004, Published online: 19 October 2004PACS: 25.40.Cm Elastic proton scattering - 13.75.Cs Nucleon-nucleon interactions (including antinucleons, deuterons, etc.) - 13.85.Dz Elastic scattering - 21.30.-x Nuclear forces     

Fragmentation of Si clusters studied by a dynamical Hartree-Fock method at semi-empirical level

This study describes fragmentation of silicon clusters of size . Fragmentation is produced by the increase of the kinetic energy E_k of the nuclear system and a time-dependent Hartree-Fock method, with a semi-empirical Hamiltonian is used for the evaluation of the transient ensuing the energy input. A typical channel of fragmentation has been observed which consists on the emission of small (from 1 to 5) groups of atoms. Due to these losses, the fragmentation remnants for reach a size equal to 1/2-1/4 of the original one. These trends are in agreement with the experimental ones. Furthermore the critical energies obtained from fragmentation calculations are discussed in the light of the binding energies evaluated for the stationary state.Received: 12 August 2003, Published online: 9 April 2004PACS: 21.60.-n Nuclear structure models and methods - 31.15.Ct Semi-empirical and empirical calculations (differential overlap, Hückel, PPP methods, etc.) - 79.60.Jv Interfaces; heterostructures; nanostructures     

Broad states beyond the neutron drip line

Theoretical studies of broad states in the few-body systems beyond the neutron drip line have been performed. We introduce a theoretical model which allows to incorporate the initial structure of colliding nuclei, reaction mechanism, few-body effects and final-state interactions in studies of broad unbound states. The model is directly related to the sudden-removal approximation for high-energy knock-out or break-up reactions. We apply this model to qualitative studies of some general properties of broad few-body states including correlations for emitted fragments. The theoretical ideas are illustrated mainly using the example of ⁵H. The prospect for observation of broad continuum structures corresponding to the tetraneutron ⁴n is also discussed.Received: 9 April 2003, Revised: 21 August 2003, Published online: 26 January 2004PACS: 21.45. + v Few-body systems - 21.60.Gx Cluster models - 25.10. + s Nuclear reactions involving few-nucleon systems     

A systematic study of neutrino mixing and <Emphasis Type="Italic">CP</Emphasis>-violationfrom lepton mass matrices with six texture zeros

We present a systematic study of 400 combinations of the charged lepton and neutrino mass matrices with six vanishing entries or texture zeros. Only 24 of them, which can be classified into a few distinct categories, are found to be compatible with current neutrino oscillation data at the level. A peculiar feature of the lepton mass matrices in each category is that they have the same phenomenological consequences. Taking account of a simple seesaw scenario for six parallel patterns of the charged lepton and Dirac neutrino mass matrices with six zeros, we show that it is possible to fit the experimental data at or below the level. In particular, the maximal atmospheric neutrino mixing can be reconciled with a strong neutrino mass hierarchy in the seesaw case. Numerical predictions are also obtained for the neutrino mass spectrum, flavor mixing angles, CP-violating phases and effective masses of the tritium beta decay and the neutrinoless double beta decay.Received: 28 September 2004, Revised: 14 October 2004, Published online: 1 December 2004PACS: 12.15.Ff, 12.10.Kt