Observables on hypergraphs

Observables on hypergraphs are described by event-valued measures. We first distinguish between finitely additive observables and countably additive ones. We then study the spectrum, compatibility, and functions of observables. Next a relationship between observables and certain functionals on the set of measures M(H) of a hypergraph H is established. We characterize hypergraphs for which every linear functional on M(H) is determined by an observable. We define the concept of an effect and show that observables are related to effect-valued measures. Finally, we define operational transformations from M(H) to itself and show that they can be described as a certain combination of effects.On leave from University of Berne, Institute of Mathematical Statistics, Sidlerstrasse 5, CH-3012 Berne, Switzerland.     

Bianchi type-V perfect fluid models

A study of the nontilted diagonal Bianchi type-V perfect fluid models is undertaken in the nonlocally rotationally symmetric case. It is shown that in such a model, the singularity is necessarily velocity dominated and the upper bound for the ratio of the shear to the expansion is 1/3. A class of such exact models is also presented; the structure of the singularity and the effect of the anisotropy on the scale are discussed. Lastly, an attempt is made to solve exactly the equations of motion for the coordinates of the null geodesics.     

Signals for compositeness atep colliders: “Leptogluons” and exotic colored vectorbosons

Production rates and signals for coloroctet leptonsl ₈ atep machines like Hera and a \(\sqrt s = 2\) TeV collider are presented. In case of very heavy leptogluons:m ₈≈0(100 GeV) we argue that rates based on direct electron-gluon fusion are possibly strongly overestimated in the literature. In composite models the appearance of leptogluons always implies the existence of color exotic vectorbosons. Therefore we considerl ₈ production in electron-quark scatterings. We find that even at HERA energies such reactions should be detectable if there is nearby compositeness (Λ _H ～ several TeV) and the mass of the coloroctet neutrinom _v8<180 GeV. From such events it would be possible to extract information on the deeper structure of the preon model.     

Study of diffusion creep accompanying superplastic deformation of the alloy ZhS6KP

The development of diffusion creep (DC) accompanying superplastic deformation (SPD) of the highly doped nickel alloy ZhS6KP is studied based on an investigation of the redistribution of dispersed intragrain deposits of the phase of Ni₃(Al, Ti). Deposit-free zones (DFZ) are formed in the alloy, held at the temperature of SPD and accompanying deformation at the grain boundaries. The contribution of DC to the deformation was determined from a comparative analysis of the width of the DFZ in the deformed and undeformed parts of the samples for different grain sizes and rates of DC taking into account diffusion accommodation. It was established that for the optimum rate of SPD the upper limit of the contribution of DC to deformation for 2-m grains does not exceed 11%. It is concluded, based on the distribution of DFZ, that the effect of DC accompanying SPD is determined by diffusion fluxes, associated with the local concentration of stress accompanying the development of grain-boundary slipping.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 40–45, June, 1986.In conclusion, we thank Yu. M. Mishin for a useful discussion of the results.     

Field dependent critical fluctuations aboveT g in the ESR line width of the spin glassAgMn

The ESR of the spin glassAgMn (2.7 and 9.6 at %) has been investigated below and aboveT _g(0.1T _g<T<5T _g) at various microwave frequencies. The analysis yields:1) No explicit frequency dependence but strong magnetic field effects, inherent with ESR-experiments.2) Part of the excess line width is identified as critical spin fluctuations, following a power law. However, because of the presence of the applied field, the reduced temperaturet is not a good scaling variable. We choose the non-linear susceptibility X _s divided byH ², which scales as the order parameter susceptibility. The experiment yieldsW _ex(X _s /H ²) ^p ,p=0.42. From this we deduce z3.     

Structural changes of Zr x Cu100-x metallic glasses investigated by low temperature specific heat measurements

Amorphous alloys of Zr _x Cu_100–x (55x72) quenched from the melt are investigated by low temperature specific heat measurements. The influence of concentrationx, temperature of the melt before the quenching process and heat treatment on the electronic density of states, the Debye temperature and the superconducting transition temperature is examined. The latter one is the most affected value by structural relaxation while the specific heat in the normal conducting region remains nearly unchanged.     

Mössbauer effect of iodine at pressures to 30 GPa

We report the first high pressure¹²⁹I Mössbauer measurements with elemental iodine at pressures to 30 GPa. A 20 mg/cm^{2 129}I₂ absorber was mounted in a diamond anvil cell with an effective diameter of 0.21 mm. The source used was Mg₃ ^129mTeO₆. Experiments were performed mainly at 4 K and the pressure was monitored by the ruby fluorescence method. With increasing pressure we observe a gradual decrease in ¦e²qQ¦ and an increase in IS and values of the low pressure, molecular phase; at 16 GPa a new phase (HP1) is detected characterized by a change in sign of e²qQ and a smaller value of ¦e²qQ¦, and a substantial increase in . At 24 GPa a new phase (HP2) is formed that is characterized by a smaller value of . In general the population of the molecular phase decreases from 1.0 near 15 GPa to a value of 0.4 at 30 GPa. The fraction of the high pressure phase (HP1 + HP2) increases at the expense of the molecular phase and that of the HP2 at the expense of the HP1 phase. These observations are discussed in relation to the onset of a metallic phase near 16 GPa and recent x-ray diffraction studies.Work performed under the auspices of the U.S. Department of Energy.     

Influence of a continuous quenching procedure on the initial stages of spinodal decomposition

Instead of the standard assumption in the theory of phase separation where an instantaneous quench from an initial equilibrium state to the final state in the two-phase region is assumed, we consider the more realistic situation that the change of the external control parameter (e.g. temperature) can only be performed with finite rates. During the initial stages of spinodal decomposition the system then has some memory of the states intermediate between the initial and the final one. This influence of the finite quench rate in continuous quenching procedures is studied within the linearized theory of spinodal decomposition, with the Langer-Baron-Miller decoupling, and with Monte Carlo simulations. Both the case of thermally activated mobilities (applicable to solid metallic alloys) and the case of nearly temperature-independent mobilities (applicable to fluid polymer mixtures) are treated, and possible experimental applications are discussed. We find drastic deviations from the standard instantaneous quench situations in all cases of experimental interest.     

Low temperature anharmonicity in Sn(CH3)4 due to methyl group reorientation: A Mössbauer study

The detailed temperature variation of the Mössbauer spectral intensity in Sn(CH₃)₄ displays a pronounced drop of the Debye temperature from _D 96K below the transition temperature (T _t 43K) to _D 76K above it. The transition atT _t is discussed in terms of recent INS and NMR results where increased motion of inequivalent CH₃ groups has been observed around the temperatureT _t .Supported by the U.S.-Israel Binational Science Foundation