243 research outputs found

    Memory effects in classical and quantum mean-field disordered models

    Full text link
    We apply the Kovacs experimental protocol to classical and quantum p-spin models. We show that these models have memory effects as those observed experimentally in super-cooled polymer melts. We discuss our results in connection to other classical models that capture memory effects. We propose that a similar protocol applied to quantum glassy systems might be useful to understand their dynamics.Comment: 24 pages, 12 figure

    Thermodynamics of black holes: an analogy with glasses

    Full text link
    The present equilibrium formulation of thermodynamics for black holes has several drawbacks, such as assuming the same temperature for black hole and heat bath. Recently the author formulated non-equilibrium thermodynamics for glassy systems. This approach is applied to black holes, with the cosmic background temperature being the bath temperature, and the Hawking temperature the internal temperature. Both Hawking evaporation and absorption of background radiation are taken into account. It is argued that black holes did not form in the very early universe.Comment: 4 pages revtex; submitted to Phys. Rev. Let

    Thermodynamic picture of the glassy state

    Full text link
    A picture for thermodynamics of the glassy state is introduced. It assumes that one extra parameter, the effective temperature, is needed to describe the glassy state. This explains the classical paradoxes concerning the Ehrenfest relations and the Prigogine-Defay ratio. As a second part, the approach connects the response of macroscopic observables to a field change with their temporal fluctuations, and with the fluctuation-dissipation relation, in a generalized non-equilibrium way.Comment: Proceedings of the Conference "Unifying Concepts in Glass Physics", ICTP, Trieste, 15 - 18 September 199

    The Glass Transition Temperature of Water: A Simulation Study

    Full text link
    We report a computer simulation study of the glass transition for water. To mimic the difference between standard and hyperquenched glass, we generate glassy configurations with different cooling rates and calculate the TT dependence of the specific heat on heating. The absence of crystallization phenomena allows us, for properly annealed samples, to detect in the specific heat the simultaneous presence of a weak pre-peak (``shadow transition''), and an intense glass transition peak at higher temperature. We discuss the implications for the currently debated value of the glass transition temperature of water. We also compare our simulation results with the Tool-Narayanaswamy-Moynihan phenomenological model.Comment: submitted to Phys. Re

    Minimal model for beta relaxation in viscous liquids

    Get PDF
    Contrasts between beta relaxation in equilibrium viscous liquids and glasses are rationalized in terms of a double-well potential model with structure-dependent asymmetry, assuming structure is described by a single order parameter. The model is tested for tripropylene glycol where it accounts for the hysteresis of the dielectric beta loss peak frequency and magnitude during cooling and reheating through the glass transition.Comment: Phys. Rev. Lett. (in press

    Observation of Fluctuation-Dissipation-Theorem Violations in a Structural Glass

    Full text link
    The fluctuation-dissipation theorem (FDT), connecting dielectric susceptibility and polarization noise was studied in glycerol below its glass transition temperature Tg. Weak FDT violations were observed after a quench from just above to just below Tg, for frequencies above the alpha peak. Violations persisted up to 10^5 times the thermal equilibration time of the configurational degrees of freedom under study, but comparable to the average relaxation time of the material. These results suggest that excess energy flows from slower to faster relaxing modes.Comment: Improved discussion; final version to appear in Phys. Rev. Lett. 4 pages, 5 PS figures, RevTe

    De hygiënehypothese onder de loep

    Get PDF
    The hygiene hypothesis states that as a result of improved hygiene and reduction of childhood diseases, the human immune system overreacts to relatively harmless stimuli, offering an explanation for the increase in the prevalence of eczema, asthma and allergies in the industrialised world. On the 20th of September 2018, a debate on the hygiene hypothesis took place in ARTIS-Micropia, Amsterdam. Experts in the fields of microbiology, immunology and infection prevention debated with each other and with the audience about 5 statements regarding the hygiene hypothesis. The first 3 statements dealt with the use of the name ‘hygiene hypothesis’, whether we can confirm or disprove the hypothesis and whether prevention of allergies by administration of micro-organisms is effective. The last 2 statements stated that intensive contact with micro-organisms prevents an overactive immune system and that playing outside and having a certain dietary pattern can prevent autoimmune and allergic diseases. The experts in the panel reached consensus about the importance of exposure to a high diversity of micro-organisms in early life to prevent an overactive immune system. They agreed that more research is needed in the coming years to be able to substantiate effective and practical interventions in our daily lives

    Individual Rights, Economic Transactions, and Recognition: A Legal Approach to Social Economics

    Get PDF
    Modernity brought the idea of individual property rights as a com- plex phenomenon. However, economics adopted a simplistic view of property as a fundamental institution, understating the complex interaction of different rights and obligations that frame the legal environment of economic processes with an insufficiently elaborated tool. Here, a more elaborate view of legal elements will be propose

    Computer Simulations of Supercooled Liquids and Glasses

    Full text link
    After a brief introduction to the dynamics of supercooled liquids, we discuss some of the advantages and drawbacks of computer simulations of such systems. Subsequently we present the results of computer simulations in which the dynamics of a fragile glass former, a binary Lennard-Jones system, is compared to the one of a strong glass former, SiO_2. This comparison gives evidence that the reason for the different temperature dependence of these two types of glass formers lies in the transport mechanism for the particles in the vicinity of T_c, the critical temperature of mode-coupling theory. Whereas the one of the fragile glass former is described very well by the ideal version of mode-coupling theory, the one for the strong glass former is dominated by activated processes. In the last part of the article we review some simulations of glass formers in which the dynamics below the glass transition temperature was investigated. We show that such simulations might help to establish a connection between systems with self generated disorder (e.g. structural glasses) and quenched disorder (e.g. spin glasses).Comment: 37 pages of Latex, 11 figures, to appear as a Topical Review article in J. Phys.: Condens. Matte
    corecore