On adiabatic N-soliton interactions and trace identities

We compare the Hamiltonian properties of the N-soliton solutions of the NLSE in the adiabatic approximation and show how it matches the Hamiltonian formulation for the complex Toda chain which describes the adiabatic N-soliton interactions. Received 21 October 2001 Published online 2 October 2002 RID="a" ID="a"e-mail: gerjikov@inrne.bas.bg     

solitons in quantum Hall systems

We present here an elementary pedagogical introduction to CP_N solitons in quantum Hall systems. We begin with a brief introduction to both CP_N models and to quantum Hall (QH) physics. We then focus on spin and layer-spin degrees of freedom in QH systems and point out that these are in fact CP_N fields for N = 1 and N = 3. Excitations in these degrees of freedom will be shown to be topologically non-trivial soliton solutions of the corresponding CP_N field equations. We conclude with a brief summary of our own recent work in this area, done with Sankalpa Ghosh. Received 17 November 2001 Published online 2 October 2002 RID="a" ID="a"e-mail: doug0700@mail.jnu.ac.in     

Some geometric aspects of maps

In this talk we introduce a Weierstrass-like system of equations corresponding to CP N -1 fields in two dimensions. Then using this representation we introduce a vector in R N 2-1 and treating this vector as the radius vector of a surface immersed in R N 2-1 we discuss to what extent the associated metric describes the geometry of the CP N -1 maps. We show that for the holomorphic maps - the correspondence is exact; while for the more general fields we have to go beyond the Weierstrass system and add extra terms. Received 1st August 2001 / Received in final form 18 October 2001 Published online 2 October 2002 RID="a" ID="a"Work done in collaboration with M. Grundland e-mail: w.j.zakrzewski@durham.ac.uk     

Lattice effects in the quasiparticle dynamics and kinetics

In this work we present a full selfconsistent set of nonlinear equations which unifies the nonlinear elasticity theory equations, the Boltzmannn transport theory and the Maxwell equations for quasiparticles with arbitrary dispersion laws in nonstationarily deformed crystals with arbitrary (but linear) constitutive relations. Transformations to replace the Galilean ones are obtained, the quasiparticle mechanics in a Hamiltonian form is deduced, and a Boltzmann-type transport equation (valid in the whole Brillouin zone) is derived. The theory may be applied to metals, semiconductors, quantum crystals, low-dimensional structures etc. Received 20 October 2001 Published online 2 October 2002 RID="a" ID="a"e-mail: dipushk@issp.bas.bg     

New localized Superluminal solutions to the wave equations with finite total energies and arbitrary frequencies

By a generalized bidirectional decomposition method, we obtain new Superluminal localized solutions to the wave equation (for the electromagnetic case, in particular) which are suitable for arbitrary frequency bands; several of them being endowed with finite total energy. We construct, among the others, an infinite family of generalizations of the so-called “X-shaped" waves. Results of this kind may find application in the other fields in which an essential role is played by a wave-equation (like acoustics, seismology, geophysics, gravitation, elementary particle physics, etc.). Received 23 June 2002 Published online 24 September 2002 RID="a" ID="a"Work partially supported by MIUR and INFN (Italy), and by FAPESP (Brazil). This paper did first appear as e-print physics/0109062 [and as preprint INFN/FM-01/02 (I.N.F.N.; Frascati, 2001)]. RID="b" ID="b"e-mail: recami@mi.infn.it     

Three-body decays of light nuclei: 6Be, 8Li, 9Be, 12O, 16Ne, and 17Ne

The theoretical approach to the two-proton radioactivity and three-body decays developed in (L.V. Grigorenko, R.C. Johnson, I.G. Mukha, I.J. Thompson, M.V. Zhukov, Phys. Rev. Lett. 85, 22 (2000) and to be published in Phys. Rev. C) is applied to the range of light nuclear systems. We study nuclear structures, widths, and momentum correlations for the decay fragments. Strong contradictions with experiment, as well as effects of special interest, are found in ¹²O and ¹⁶Ne nuclei. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: l.grigorenko@surrey.ac.uk     

Properties of supersymmetric integrable systems of KP type

The recently proposed supersymmetric extensions of reduced Kadomtsev-Petviashvili (KP) integrable hierarchies in N = 1, 2 superspace are shown to contain in the purely bosonic limit new types of ordinary non-supersymmetric integrable systems. The latter are coupled systems of several multi-component non-linear Schr?dinger-like hierarchies whose basic nonlinear evolution equations contain additional quintic and higher-derivative nonlinear terms. Also, we obtain the N = 2 supersymmetric extension of Toda chain model as Darboux-B?cklund orbit of the simplest reduced N = 2 super-KP hierarchy and find its explicit solution. Received 13 September 2001 Published online 2 October 2002 RID="a" ID="a"e-mail: nissimov@inrne.bas.bg RID="b" ID="b"e-mail: svetlana@inrne.bas.bg     

Comment on¶“On the relationship between the entropy and enthalpy of interfacial segregation” by L. Rubinovich and M. Polak

The paper of L. Rubinovich and M. Polak [Eur. Phys. J. B 22, 267 (2001)] contains some controversial items. The notation “excess” in connection with various thermodynamic quantities describing solute segregation on the basis of the Langmuir-McLean isotherm is used in a meaning contradictory to general thermodynamics. The approach used to interpret the linear relationship between segregation entropy and enthalpy results in rather strange conclusions. These items are discussed, and it is shown how a formulation with standard terms is in accordance with general thermodynamics. Received 14 January 2002 / Received in final form 27 September 2002 Published online 14 February 2003 RID="a" ID="a"e-mail: lejcekp@fzu.cz     

On N-wave type systems and their gauge equivalent

The class of nonlinear evolution equations (NLEE) - gauge equivalent to the N-wave equations related to the simple Lie algebra are derived and analyzed. They are written in terms of (x, t) ∈ satisfying r = rank nonlinear constraints. The corresponding Lax pairs and the time evolution of the scattering data are found. The Zakharov-Shabat dressing method is appropriately modified to construct their soliton solutions. Received 20 October 2001 / Received in final form 30 April 2002 Published online 2 October 2002 RID="a" ID="a"e-mail: gerjikov@inrne.bas.bg     

Covalent magnetism in the RFe <Emphasis Type="Bold">6</Emphasis>Ge <Emphasis Type="Bold">6</Emphasis> series

The electronic structure of the RFe ₆ Ge ₆ compounds ( R = Sc, Lu, Ti, Zr, Hf and Nb) of HfFe ₆ Ge ₆ -type structure has been studied using the muffin-tin Korringa-Kohn-Rostoker method in a non-relativistic approach. The chemical bonding is analyzed based on the l-decomposed site projected densities of states. Spin-dependent changes in the R nd- Fe 3d covalent bond are shown to be responsible for the experimentally observed rise in the Fe moment and hyperfine field upon increasing the R valency. The limited quantitative agreement between theoretical and experimental values is interpreted as being due to a non-negligible orbital moment and to a significant asphericity in the spin density at the iron site. The theoretical results also forecast a strong increase of the Ge(2e) transferred hyperfine field with the R valency. Received 20 December 2002 Published online 4 June 2003 RID="a" ID="a"e-mail: Thomas.Mazet@lcsm.uhp-nancy.fr RID="b" ID="b"Associé au CNRS (UMR 7555)     

The high-pressure <Emphasis Type="Bold">α/β</Emphasis> phase transition in lead sulphide (PbS)

The high-pressure behaviour of PbS was investigated by angular dispersive X-ray powder diffraction up to pressures of 6.8 GPa. Experiments were accompanied by first principles calculations at the density functional theory level. By combining both methods reliable data for the elastic properties of rock-salt type α- and high-pressure β-PbS could be obtained. β-PbS could be determined to crystallise in the CrB-type (B33), with space group Cmcm. The reversible ferro-elastic α/β transition is of first order. It is accompanied by a large volume discontinuity of about 5% and a coexistence region of the two phases. A gliding mechanism of {001} bilayers along one of the cubic 〈110〉 directions governs the phase transition which can be described in terms of group/subgroup relationships via a common subgroup, despite its reconstructive character. The quadrupling of the primitive unit cell indicates a wave vector (0, 0,π/ a ) on the Δ-line of the Brillouin zone. Received 11 October 2002 Published online 14 February 2003 RID="a" ID="a"Also at: Institute of Physics of the Czech Academy of Sciences, Cukrovarnicka 10, 16253 Praha 6, Czech Republic e-mail: knorr@min.uni-kiel.de RID="b" ID="b"Present address: University of Cambridge, Cavendish Laboratory (TCM), Madingley Road, Cambridge CB3 0HE, UK RID="c" ID="c"Present address: Johann-Wolfgang Goethe Universit?t, Mineralogisches Institut, Kristallographie, Senckenberganlage 30, D 60054 Frankfurt a.M., Germany     

Some experimental and theoretical studies on the Mn magnetic moment in Y ( Ni 1 - x Mn x ) 2 B 2 C

The magnetic moment of the Mn impurities was obtained from magnetization measurements of Y ( Ni _{1 - x} Mn _x ) ₂ B ₂ C as a function of the concentration x less than 0.15. Using the coherent potential approximation and starting from 3 d density of states, obtained from the first principles calculations, the magnetic moments are obtained within a two sublattice model. For adequately estimated values of the Coulomb interactions U, the position of the energy level of Mn and adopting values for the intersublattice hybridization term, a qualitative agreement with the observed experimental data is obtained. Received 23 April 2001 and Received in final form 29 October 2001     

High-spin structure of the neutron-rich odd-odd 106, 108 45Rh and 110, 112 47Ag isotopes

The ^{106, 108}Rh and ^{110, 112}Ag nuclei have been produced as fission fragments following the fusion reaction ²⁸Si + ¹⁷⁶Yb at 145 MeV bombarding energy and studied with the Eurogam2 array. The yrast high-spin states of these four odd-odd nuclei, which are observed for the first time, consist of rotational bands in which the odd proton occupies the πg _9/2 subshell and the odd neutron the νh _11/2 subshell. Their behaviour as a function of spin values does not vary with the number of neutrons: as observed in the odd-N neighbouring nuclei, the motion of the odd neutron remains decoupled from the motion of the core, from N = 61 to N = 65. Moreover, the staggering observed in the yrast bands of odd-odd isotopes is strongly reduced as compared to the large values displayed by the rotational bands built on the πg _9/2 subshell in the odd-A Rh and Ag isotopes. The results of particle-rotor calculations indicate that this reduction is related to a change of the core deformation. Received: 1 June 2001 / Accepted: 23 July 2002 / Published online: 10 December 2002 RID="a" ID="a"e-mail: porquet@csnsm.in2p3.fr RID="b" ID="b"Present address: CSNSM IN2P3-CNRS and Université Paris-Sud 91405 Orsay, France. RID="c" ID="c"Present address: NAC, Faure, ZA 7131, South Africa. RID="d" ID="d"Present address: Department of Nuclear Physics, ANU, Canberra ACT 0200, Australia. Communicated by D. Schwalm     

High resolution laser spectroscopy of NaAr: Improved interaction potential for the ground state

The absorption spectrum of NaAr has been investigated with high resolution using a supersonic beam of molecules and a tunable dye laser. About 3 300 absorption lines due to the transition A ² Π ← X and B ² Σ ← X have been observed. In addition, we observed the spectral distribution of the fluorescence for a particular absorption line. From all experimental data the X ² Σ ⁺ interaction potential has been deduced in a fully quantum-mechanical method of approach. The potential is given in terms of an analytical Hartree-Fock-Dispersion function. For the equilibrium parameters of the X state we get R _e = 5.01(1) ? and D _e = 41.6(2) cm ^-1 . Received 28 August 2002 / Received in final form 15 October 2002 Published online 17 December 2002 RID="a" ID="a"Now at Knick Elektronische Messger?te, Beuckestr. 22, 14163 Berlin, Germany. RID="b" ID="b"e-mail: dz@kalium.physik.tu-berlin.de     

Isomorphous phase transition and orientational freezing in hexagonal mixed crystal C 70(1 - x) C60x. A pseudospin model

A four-state pseudospin model is constructed for the isomorphous phase transition hcp-2↦hcp-1 in pure C₇₀ and in C₇₀-rich mixed crystal C _{70(1 - x)} C_60x. With the specific anisotropic pseudospin interactions adapted to the C₇₀ crystal the model is equivalent to a two-state Ising model in a temperature-dependent field. Replica symmetric state of the model is shown to approach the critical point when the width of distribution of random fields and/or of random bonds increases. The temperature of the phase transition and the phase equilibrium temperature then are practically constant, whereas the experiment shows their strong decrease with x. The main effect of dilution resides in an x-dependence of the model parameters. Dilatometric data on the hexagonal C _{70(1 - x)} C_60x are used to fit these parameters. A metastable disordered phase subsisting below the phase transition is discovered in a range of the model parameters and is shown to be responsible for the macroscopic behaviour of the system. A good agreement with experimental data is obtained for the spontaneous strain and for the x-dependence of the hysteresis. Received 20 April 2001 and Received in final form 26 September 2001     

Broad-band dielectric spectroscopy of Ba 2NaNb 5O 15 single crystal

Barium sodium niobate (BNN) single crystals are studied by IR spectroscopy, time-domain THz transmission spectroscopy, HF coaxial wave-guide technique and LF dielectric spectroscopy to cover the frequency range 10²-10¹⁴ Hz in a wide temperature interval. The dielectric response parallel and perpendicular to the polar c-axis is discussed. The ferroelectric transition at T _c = 830 K is driven by a relaxational soft mode coupled with another central-mode type relaxation which both gradually disappear on cooling in the ferroelectric phase. Below T _i the parameters of the expected IR active amplitudon were estimated. The low-temperature permittivity increase on cooling for the field direction has been explained by an incipient proper ferroelectric-ferroelastic transition driven by an IR and Raman active B₂-symmetry soft mode. Received 24 August 2002 Published online 19 December 2002 RID="a" ID="a"e-mail: buixader@fzu.cz     

In-beam spectroscopy of 253, 254No

In-beam conversion electron spectroscopy experiments have been performed on the transfermium nuclei ^{253, 254}No using the conversion electron spectrometer SACRED in nearly collinear geometry in conjunction with the gas-filled separator RITU at the University of Jyv?skyl?. The experimental setup is discussed and the spectra are compared to Monte Carlo simulations. The implications for the ground-state configuration of ²⁵³No are discussed. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: rdh@ns.ph.liv.ac.uk RID="b" ID="b"Present address: GANIL, F-14021 Caen, France. RID="c" ID="c"Permanent address: IReS Strasbourg, IN2P3-CNRS, F-67037-Strasbourg, France. RID="d" ID="d"Present address: CEA/DIF DCRE/SDE/LDN F-91680 Bruyeres-le-Chatel. RID="e" ID="e"Present address: Daresbury Laboratory, Daresbury WA4 4AD, UK. RID="f" ID="f"Permanent address: IPN Lyon, IN2P3-CNRS, F-69037 Lyon, France.     

Quasi-periodic and periodic solutions for dynamical systems related to Korteweg-de Vries equation

We consider quasi-periodic and periodic (cnoidal) wave solutions of a set of n-component dynamical systems related to Korteweg-de Vries equation. Quasi-periodic wave solutions for these systems are expressed in terms of Novikov polynomials. Periodic solutions in terms of Hermite polynomials and generalized Hermite polynomials for dynamical systems related to Korteweg-de Vries equation are found. Received 15 October 2001 / Received in final form 6 March 2002 Published online 2 October 2002 RID="a" ID="a"e-mail: nakostov@ie.bas.bg     

Coexistence of superconductivity and spin density wave orderings in the organic superconductor (TMTSF) 2 PF 6

The phase diagram of the organic superconductor (TMTSF)₂PF₆has been revisited using transport measurements with an improved control of the applied pressure. We have found a 0.8 kbar wide pressure domain below the critical point (9.43 kbar, 1.2 K) for the stabilisation of the superconducting ground state featuring a coexistence regime between spin density wave (SDW) and superconductivity (SC). The inhomogeneous character of the said pressure domain is supported by the analysis of the resistivity between T _SDW and T _SC and the superconducting critical current. The onset temperature T _SC is practically constant ( 1.20±0.01 K) in this region where only the SC/SDW domain proportion below T _SC is increasing under pressure. An homogeneous superconducting state is recovered above the critical pressure with T _SC falling at increasing pressure. We propose a model comparing the free energy of a phase exhibiting a segregation between SDW and SC domains and the free energy of homogeneous phases which explains fairly well our experimental findings. Received 3 September 2001 and Received in final form 9 November 2001