Solidity of viscous liquids. V. Long-wavelength dominance of the dynamics

This paper is the fifth in a series exploring the physical consequences of the solidity of glass-forming liquids. Paper IV proposed a model where the density field is described by a time-dependent Ginzburg-Landau equation of the nonconserved type with rates in $k$ space of the form $\Gamma_0+Dk^2$. The model assumes that $D\gg\Gamma_0a^2$ where $a$ is the average intermolecular distance; this inequality expresses a long-wavelength dominance of the dynamics which implies that the Hamiltonian (free energy) to a good approximation may be taken to be ultralocal. In the present paper we argue that this is the simplest model consistent with the following three experimental facts: 1) Viscous liquids approaching the glass transition do not develop long-range order; 2) The glass has lower compressibility than the liquid; 3) The alpha process involves several decades of relaxation times shorter than the mean relaxation time. The paper proceeds to list six further experimental facts characterizing equilibrium viscous liquid dynamics and shows that these are readily understood in terms of the model; some are direct consequences, others are quite natural when viewed in light of the model

Geotecnologias para suporte à agricultura de precisão em agroecossistemas de terras baixas.

Neste documento são apresentadas as atividades realizadas durante o primeiro ano do projeto e se discute a aplicação de geotecnologias relacionadas às atividades de pesquisa desenvolvidas nas UPs do projeto AP2, na Estação Experimental Terras Baixas (ETB) da Embrapa Clima Temperado, envolvendo o uso de imagens orbitais de baixo custo, manuseio de GPS para efetivar modelos digitais de elevação e processamento dos dados segundo malha regular, sendo disponibilizados resultados preliminares obtidos pela equipe do arroz irrigado.bitstream/item/78794/1/documento-336-.pd

Fluctuation-dissipation ratio of a spin glass in the aging regime

We present the first experimental determination of the time autocorrelation $C(t',t)$ of magnetization in the non-stationary regime of a spin glass. Quantitative comparison with the response, the magnetic susceptibility $\chi(t',t)$, is made using a new experimental setup allowing both measurements in the same conditions. Clearly, we observe a non-linear fluctuation-dissipation relation between $C$ and $\chi$, depending weakly on the waiting time $t'$. Following theoretical developments on mean-field models, and lately on short range models, it is predicted that in the limit of long times, the $\chi(C)$ relationship should become independent on $t'$. A scaling procedure allows us to extrapolate to the limit of long waiting times.Comment: 4 pages, 3 figure

Universal and non-universal features of glassy relaxation in propylene carbonate

It is demonstrated that the susceptibility spectra of supercooled propylene carbonate as measured by depolarized-light-scattering, dielectric-loss, and incoherent quasi-elastic neutron-scattering spectroscopy within the GHz window are simultaneously described by the solutions of a two-component schematic model of the mode-coupling theory (MCT) for the evolution of glassy dynamics. It is shown that the universal beta-relaxation-scaling laws, dealing with the asymptotic behavior of the MCT solutions, describe the qualitative features of the calculated spectra. But the non-universal corrections to the scaling laws render it impossible to achieve a complete quantitative description using only the leading-order-asymptotic results.Comment: 37 pages, 16 figures, to be published in Phys. Rev.

Slow dynamics and aging in spin-glasses

Contribution presented by Eric Vincent in the Conference `Complex Behaviour of Glassy Systems', Sitges, Barcelona, Spain, June, 1996. It contains a review of the experimental results on Slow dynamics and aging in spin-glasses. It also presents their comparison with recent theoretical developments in the description of the out of equilibrium dynamics of disordered systems; namely, the trap model and the mean-field theory.Comment: 35 pages, 12 figures, macro lmamult.sty (included

Quantum Algebraic Approach to Refined Topological Vertex

We establish the equivalence between the refined topological vertex of Iqbal-Kozcaz-Vafa and a certain representation theory of the quantum algebra of type W_{1+infty} introduced by Miki. Our construction involves trivalent intertwining operators Phi and Phi^* associated with triples of the bosonic Fock modules. Resembling the topological vertex, a triple of vectors in Z^2 is attached to each intertwining operator, which satisfy the Calabi-Yau and smoothness conditions. It is shown that certain matrix elements of Phi and Phi^* give the refined topological vertex C_{lambda mu nu}(t,q) of Iqbal-Kozcaz-Vafa. With another choice of basis, we recover the refined topological vertex C_{lambda mu}^nu(q,t) of Awata-Kanno. The gluing factors appears correctly when we consider any compositions of Phi and Phi^*. The spectral parameters attached to Fock spaces play the role of the K"ahler parameters.Comment: 27 page