The Heisenberg ferromagnet in spin coherent state representation

A new approach to Heisenberg ferromagnet using the spin coherent state representation is developed. The differential operator representation of spin angular momentum operators is used to derive thec-number analogs of the basic quantum mechanical equations, viz., the Schrödinger, Bloch and Liouville equations for the Heisenberg ferromagnet. As an important illustration of our formulation, which has noad hoc assumptions and does not use any boson representation, the excitation spectrum for one, two and three spin waves is obtained. In these cases it is also shown that eigenvalue spectrum can be obtained by completely ignoring the kinematical interactions.     

Semi-classical approach to antiproton-nucleus scattering

The similarities and differences between antiproton-nucleus scattering and heavyion-nucleus scattering are examined. It is found that the one-turning point approach viz Wentzel, Kramers and Brillouin (WKB) approximation can be applied to the analysis of antiproton-nucleus scattering. Using this approximation, a closed form expression for the nuclear phase shift is deduced from the corresponding expression for the heavy-ion scattering phase shift derived by Shastry and the method is illustrated by carrying out the cross-section calculation of atE _lab = 46·8 MeV.     

Increasing average period lengths by switching of robust chaos maps in finite precision

The direct measurement of the gluon polarization in the nucleon at the COMPASS experiment is discussed. Three complementary analyses are considered. All of them study ΔG/G using method based on selection of events originating from the Photon Gluon Fusion process. Most precise preliminary value of ΔG/G is obtained from the high p _T pair channel for the Q ² < 1 (GeV/c)² region: ΔG/G = 0.016 ± 0.058 (stat.) ± 0.055 (syst.). on behalf of the COMPASS collaboration     

Topological field patterns in the Yang-Mills theory

We present a formalism where the topological configurations of pure Yang-Mills theory are characterised using gauge fields alone. Here, we obtain an expression for the charges of these topologicalSO(3) gauge field configurations in terms of the Abelian vector potentials. In this formalism we analyse the ’t Hooft-Polyakov monopole solution.     

Quantum Integrability in Systems with Finite Number of Levels

We consider the problem of defining quantum integrability in systems with finite number of energy levels starting from commuting matrices and construct new general classes of such matrix models with a given number of commuting partners. We argue that if the matrices depend on a (real) parameter, one can define quantum integrability from this feature alone, leading to specific results such as exact solvability, Poissonian energy level statistics and to level crossings.     

Exact solution of a large class of interacting quantum systems exhibiting ground state singularities

We demonstrate how to construct a large class of interacting quantum systems for which an exact solution may be found for the ground state wave function and ground state energy for some range of interaction parameters. It is shown that the ground state exhibits singularities in these cases, and in some simple instances the exact ground state phase diagram and critical indices are also found.     

The 85Rb(p,d)84Rb reaction

The spectrum seen in single neutron pickup leading to the doubly odd nucleus ⁸⁴Rb is remarkably clean, with only five levels populated by l = 4 and six by l = 1 transitions. A simple 2J+1 weighting for the l = 4 data, combined with previous information on ⁸⁴Rb, allowed the J^π = 2^?–7^? states of the ($\text{v}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}{}^{\mathrm{?3}}\text{? π}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^{\mathrm{?3}}$) multiplet to be identified. These data are used to determine the two-hole $\text{π}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{-v}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}{}^{\mathrm{?}}$ interaction matrix elements.     

Atom resolved evidence for a defective chemisorbed oxygen state at a Mg(0001) surface

A chemisorbed oxygen state has been revealed for the first time by scanning tunnelling microscopy to be present at the interface between a (1 x 1)-O structure and overlying magnesium atoms; the step-height at the interface is between 0.14 and 0.15 nm and compatible with the presence of O delta- like states.