W. Schirmacher

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PACS. 03.65Sq – Quantum mechanics: Semiclassical theories and applications. PACS. 05.45+b – Theory and models of chaotic systems. PACS. 72.20−i – Conductivity phenomena in semiconductors and insulators. Abstract. – We investigate the semiclassical scattering amplitude for systems, where the classical dynamics is non-hyperbolic, i.e. where islands of KAM(More)
A theory for the vibrational dynamics in disordered solids [W. Schirmacher, Europhys. Lett. 73, 892 (2006), based on the random spatial variation of the shear modulus, has been applied to determine the wave vector (k) dependence of the Brillouin peak position (Omega(k)) and width (Gamma(k)), as well as the density of vibrational states [g(omega)], in(More)
a r t i c l e i n f o Available online xxxx We present measurements of the vibrational spectrum of a binary niobium-phosphate glass in the THz frequency range using inelastic neutron and Raman scattering. The spectra of these glasses show a low-frequency enhancement of the vibrational density of states (" boson peak "). Using a recently developed theory of(More)
The nonexponential closed-time distributions observed for ionic channels have been explained recently by quasi-one-dimensional models of structural diffusion (Millhauser, G. L., E. E. Salpeter, and R. E. Oswald. 1988. Proc. Natl. Acad. Sci. USA. 85: 1503-1507; Condat, C. A., and J. Jäckle. 1989. Biophys. J. 55: 915-925; Levitt, D. G. 1989. Biophys. J. 55:(More)
Magnetic properties of thin composite films, consisting of non-interacting polystyrene-coated γ-Fe(2)O(3) (maghemite) nanoparticles embedded into polystyrene-block-polyisoprene P(S-b-I) diblock-copolymer films are investigated. Different particle concentrations, ranging from 0.7 to 43 wt%, have been used. The magnetization measured as a function of external(More)
Raman gain for all-optical amplification depends significantly on the cross section for spontaneous Raman scattering. We present measurements of the Raman spectrum of binary niobium-phosphate glasses in the frequency range from 5 – 1300 cm-1. The spectra of these glasses show a low-frequency enhancement of the vibrational density of states ('Boson peak')(More)
We consider the phase transition in a ferromagnet with line defects that introduce a local variation of the critical temperature V (r) / r ? ? , leading to a correlator hV (0)V (r)i / r ?(22?d) ?. We discuss conditions of both local and global character that lead to diierent scenarios for the transition, ranging from a \conventional" transition into a(More)
We investigate the high-frequency behavior of the density of vibrational states in three-dimensional elasticity theory with spatially fluctuating elastic moduli. At frequencies well above the mobility edge, instanton solutions yield an exponentially decaying density of states. The instanton solutions describe excitations, which become localized due to the(More)
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