ESR in quasi 2-d ferromagnets: The coexistence of paramagnetic excitations and magnetostatic spin waves and new interference effects

The quasi 2-dimensional layer structures (C_nH_2n+1NH₃)₂CuCl₄ with n = 1,2 have been investigated by electron spin resonance. New phenomena arise for samples with well defined natural surfaces: (i) well resolved magnetostatic volume and surface spin wave modes at 4.2 K comparable in quality with spectra of YIG, (ii) a magnetostatic spin wave spectrum which is coincident with the paramagnetic resonance over a wide temperature range, (iii) interference effects between these two types of resonances.     

Vibrational spectra oftrans-dichlorodiiodoethylene

The infrared spectra oftrans-dichlorodiiodoethylene as a solid and in solution were recorded in the region 4000–25 cm^–1. Raman spectra of the compound were obtained and semiquantitative polarization data were calculated.The mutual exclusion between the infrared and Raman frequencies are in agreement with the expectedC _2h (2/m) symmetry for this molecule. The fundamentals have been assigned and a normal coordinate analysis carried out. Thermodynamic functions and the root mean square amplitudes of vibration have been obtained.The authors wish to acknowledge financial support from theNorwegian Research Council for Science and the Humanities.     

An algorithm for the construction of exceptional modules over tubular canonical algebras

Let Λ be a tubular canonical algebra of quiver type. We describe an algorithm, which for numerical data computes all regular exceptional Λ-modules, or more generally all indecomposable modules in exceptional tubes. The input for the algorithm is a quadruple consisting of the slope, the number of the tube, the quasi-socle and the quasi-length, the output are explicit matrices for the module with the data above.     

On the membrane approximation in isothermal film casting

In this work, a one-dimensional model for isothermal film casting is studied. Film casting is an important engineering process to manufacture thin films and sheets from a highly viscous polymer melt. The model equations account for variations in film width and film thickness, and arise from thinness and kinematic assumptions for the free liquid film. The first aspect of our study is a rigorous discussion of the existence and uniqueness of stationary solutions. This objective is approached via the argument principle, exploiting the homotopy invariance of a family of analytic functions. As our second objective, we analyze the linearization of the governing equations about stationary solutions. It is shown that solutions for the associated boundary-initial value problem are given by a strongly continuous semigroup of bounded linear operators. To reach this result, we cast the relevant Cauchy problem in a more accessible form. These transformed equations allow us insight into the regularity of the semigroup, thus yielding the validity of the spectral mapping theorem for the semigroup and the spectrally determined growth property.     

On semibounded restrictions of self-adjoint operators

After the von Neumann's remark [10] about pathologies of unbounded symmetric operators and an abstract theorem about stability domain [9], we develope here a general theory allowing to construct semibounded restrictions of selfadjoint operators in explicit form. We apply this theory to quantum-mechanical momentum (position) operator to describe corresponding stability domains. Generalization to the case of measurable functions of these operators is considered. In conclusion we discuss spectral properties of self-adjoint extensions of constructed self-adjoint restrictions.