1,487 research outputs found
Theory of site-disordered magnets
In realistic spinglasses, such as CuMn, AuFe and EuSrS, magnetic atoms are
located at random positions. Their couplings are determined by their relative
positions. For such systems a field theory is formulated. In certain limits it
reduces to the Hopfield model, the Sherrington-Kirkpatrick model, and the
Viana-Bray model. The model has a percolation transition, while for RKKY
couplings the ``concentration scaling'' T_g proportional to c occurs. Within
the Gaussian approximation the Ginzburg-Landau expansion is considered in the
clusterglass phase, that is to say, for not too small concentrations. Near
special points, the prefactor of the cubic term, or the one of the
replica-symmetry- breaking quartic term, may go through zero. Around such
points new spin glass phases are found.Comment: 26 pages Revtex, 6 figure
Multiple scattering of classical waves: from microscopy to mesoscopy and diffusion
A tutorial discussion of the propagation of waves in random media is
presented. In first approximation the transport of the multiple scattered waves
is given by diffusion theory, but important corrections are present. These
corrections are calculated with the radiative transfer or Schwarzschild-Milne
equation, which describes intensity transport at the ``mesoscopic'' level and
is derived from the ``microscopic'' wave equation. A precise treatment of the
diffuse intensity is derived which automatically includes the effects of
boundary layers. Effects such as the enhanced backscatter cone and imaging of
objects in opaque media are also discussed within this framework. In the second
part the approach is extended to mesoscopic correlations between multiple
scattered intensities which arise when scattering is strong. These correlations
arise from the underlying wave character. The derivation of correlation
functions and intensity distribution functions is given and experimental data
are discussed. Although the focus is on light scattering, the theory is also
applicable to micro waves, sound waves and non-interacting electrons.Comment: Review. 86 pages Latex, 32 eps-figures included. To appear in Rev.
Mod. Phy
Ginzburg-Landau theory of the cluster glass phase
On the basis of a recent field theory for site-disordered spin glasses a
Ginzburg-Landau free energy is proposed to describe the low temperatures glassy
phase(s) of site-disordered magnets. The prefactors of the cubic and dominant
quartic terms change gradually along the transition line in the
concentration-temperature phase diagram. Either of them may vanish at certain
points , where new transition lines originate. The new phases are
classifiedComment: 6 pages Revtex, 5 figures. To appear in J. Phys. A. Let
Third Cumulant of the total Transmission of diffuse Waves
The probability distribution of the total transmission is studied for waves
multiple scattered from a random, static configuration of scatterers. A
theoretical study of the second and third cumulant of this distribution is
presented. Within a diagrammatic approach a theory is developed which relates
the third cumulant normalized to the average, , to the normalized second cumulant . For a broad Gaussian beam profile it is found that .
This is in good agreement with data of optical experiments.Comment: 16 pages revtex, 8 separate postscript figure
Food, nutrition & behaviour : research for healthy eating, healthy living
This brochure illustrates this range of research activities in the domain of food and nutrition, lifestyle and health. It does so by providing examples of collaboration of Wageningen UR with partners in the public and private sector
On a Three-Dimensional Gravity Model with Higher Derivatives
The purpose of this work is to present a model for 3D massive gravity with
topological and higher-derivative terms. Causality and unitarity are discussed
at tree-level. Power-counting renormalizability is also contemplated.Comment: 9 pages, Latex, no figures; to be published in Gen. Rel. Gra
"Optical conductance fluctuations: diagrammatic analysis in Landauer approach and non-universal effects"
The optical conductance of a multiple scattering medium is the total
transmitted light of a diffuse incoming beam. This quantity, very analogous to
the electronic conductance, exhibits universal conductance fluctuations. We
perform a detailed diagrammatic analysis of these fluctuations. With a
Kadanoff-Baym technique all the leading diagrams are systematically generated.
A cancellation of the short distance divergencies occurs, that yields a well
behaved theory. The analytical form of the fluctuations is calculated and
applied to optical systems. Absorption and internal reflections reduce the
fluctuations significantly.Comment: 25 pages Revtex 3.0, 18 seperate postscript figure
Recovery in supported accommodations:A scoping review and synthesis of interventions for people with severe mental illness
Research on the recovery domains beside clinical recovery of people with severe mental illness in need of supported accommodations is limited. The aim of this study was (1) to investigate which recovery interventions exist for this group of people and (2) to explore the scientific evidence. We conducted a scoping review, including studies with different designs, evaluating the effectiveness the recovery interventions available. The search resulted in 53 eligible articles of which 22 focused on societal recovery, six on personal recovery, five on functional recovery, 13 on lifestyle-interventions, and seven on creative and spiritual interventions. About a quarter of these interventions showed added value and half of them initial promising results. The research in this area is still limited, but a number of recovery promoting interventions on other areas than clinical recovery have been developed and evaluated. Further innovation and research to strengthen and repeat the evidence are needed
Ehrenfest relations at the glass transition: solution to an old paradox
In order to find out whether there exists a thermodynamic description of the
glass phase, the Ehrenfest relations along the glass transition line are
reconsidered. It is explained that the one involving the compressibility is
always satisfied, and that the one involving the specific heat is principally
incorrect.
Thermodynamical relations are presented for non-ergodic systems with a
one-level tree in phase space. They are derived for a spin glass model, checked
for other models, and expected to apply, e.g., to glass forming liquids. The
second Ehrenfest relation gets a contribution from the configurational entropy.Comment: 4 pages revtex, to appear in Phys. Rev. Let
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