5,617 research outputs found
Ferromagnetic Transition in One-Dimensional Itinerant Electron Systems
We use bosonization to derive the effective field theory that properly
describes ferromagnetic transition in one-dimensional itinerant electron
systems. The resultant theory is shown to have dynamical exponent z=2 at tree
leve and upper critical dimension d_c=2. Thus one dimension is below the upper
critical dimension of the theory, and the critical behavior of the transition
is controlled by an interacting fixed point, which we study via epsilon
expansion. Comparisons will be made with the Hertz-Millis theory, which
describes the ferromagnetic transition in higher dimensions.Comment: 4 pages. Presentation improved. Final version as appeared in PR
Zeeman and Orbital Effects of an in-Plane Magnetic Field in Cuprate Superconductors
We discuss the effects of a magnetic field applied parallel to the Cu-O
() plane of the high cuprate superconductors. After briefly reviewing
the Zeeman effect of the field, we study the orbital effects, using the
Lawrence-Doniach model for layered superconductors as a guide to the physics.
We argue that the orbital effect is qualitatively different for in-plane and
inter-layer mechanisms for superconductivity. In the case of in-plane
mechanisms, interlayer couplings may be modeled as a weak interlayer Josephson
coupling, whose effects disappear as ; in this case Zeeman
dominates the effect of the field. In contrast, in the inter-layer mechanism
the Josephson coupling {\em is} the driving force of superconductivity, and we
argue that the in-plane field suppresses superconductivity and provides an
upper bound for which we estimate very crudely.Comment: 4 pages with 1 embedded ps figure. Manuscript submitted to the MMM'99
conferenc
Disorder induced brittle to quasi-brittle transition in fiber bundles
We investigate the fracture process of a bundle of fibers with random Young
modulus and a constant breaking strength. For two component systems we show
that the strength of the mixture is always lower than the strength of the
individual components. For continuously distributed Young modulus the tail of
the distribution proved to play a decisive role since fibers break in the
decreasing order of their stiffness. Using power law distributed stiffness
values we demonstrate that the system exhibits a disorder induced brittle to
quasi-brittle transition which occurs analogously to continuous phase
transitions. Based on computer simulations we determine the critical exponents
of the transition and construct the phase diagram of the system.Comment: 6 pages, 6 figure
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