Sets and C^n; Quivers and A-D-E; Triality; Generalized Supersymmetry; and D4-D5-E6

The relation between Geisteswissenschaft and Naturwissenschaft has been discussed by Munster in hep-th/9305104. The plan of this paper is to begin with the empty set; use it to form sets and quivers (sets of points plus sets of arrows between pairs of points); and then use them to make complex vector spaces and to get the A-D-E Coxeter-Dynkin diagrams. The Dn Spin(2n) Lie algebras have spinor representations to describe fermions. D4 Spin(8) triality gives automorphisms among its vector and two half-spinor representations. D5 Spin(10) contains both Spin(8) and the complexification of the vector representation of Spin(8). E6 contains both Spin(10) and the two half-spinor representations of Spin(10), and therefore contains the adjoint representation of Spin(8) and the complexifications of the vector and the two half-spinor representations of Spin(8). E6 is the basis for construction of a fundamental model of physics that is consistent with experiment (see hep-th/9302030, hep-ph/9301210).Comment: 1+22 pages, THEP-93-5, LaTe

Random and systematic measurement errors in acoustic impedance as determined by the transmission line method

The effect of random and systematic errors associated with the measurement of normal incidence acoustic impedance in a zero-mean-flow environment was investigated by the transmission line method. The influence of random measurement errors in the reflection coefficients and pressure minima positions was investigated by computing fractional standard deviations of the normalized impedance. Both the standard techniques of random process theory and a simplified technique were used. Over a wavelength range of 68 to 10 cm random measurement errors in the reflection coefficients and pressure minima positions could be described adequately by normal probability distributions with standard deviations of 0.001 and 0.0098 cm, respectively. An error propagation technique based on the observed concentration of the probability density functions was found to give essentially the same results but with a computation time of about 1 percent of that required for the standard technique. The results suggest that careful experimental design reduces the effect of random measurement errors to insignificant levels for moderate ranges of test specimen impedance component magnitudes. Most of the observed random scatter can be attributed to lack of control by the mounting arrangement over mechanical boundary conditions of the test sample

Commodity Markets: Rational Expectations in Markets With Irrational Investors

The "financialization" of commodity markets have become a concern for policy makers and market participants. What was once a market for the hedging of holding physical commodities has expanded to become a market for the diversification of financial assets. When financial assets diversification goals are decoupled from the fundamental factors that affect producers and consumers of physical goods futures markets may not be as efficient in aggregating information concerning the economics of the underlying commodity. Theoretical understanding of whether commodity futures market function well under exogenous shifts in demand for futures contracts depend on our assumptions of how market participants behave, including their level of risk aversion. This paper builds a competitive storage model with an explicit futures market that incorporates irrational shocks to demand for futures contracts. This model is flexible enough to investigate the impact of the "financialization" of commodity futures markets and the resulting impacts.commodity, futures, financialization, competitive storage, rational expectations, Agricultural and Food Policy, Agricultural Finance, Financial Economics, Risk and Uncertainty,

Transport characteristics of L-point and Г-point electrons through GaAs-Ga_(1-x)Ai_xAs-GaAs(111} double heterojunctions

We present here a study on the transport characteristics of L‐point and Γ‐point derived electrons through abrupt GaAs–Ga_(1−x)Al_xAs–GaAs(111) double heterojunctions. The use of complex‐k band structures in the tight‐binding approximation and transfer matrices provide a reasonably accurate description of the wave function at the GaAs–Ga_(1−x)Al_xAs interface. A representation of the wave function in terms of bulk complex‐k Bloch states is used in the GaAs regions where the potential is bulklike. A representation of the wave function in terms of planar orbitals is used in the central Ga_(1−x)Al_xAs region where the potential deviates from its bulk value (i.e., interfacial region). Within this theoretical framework, realistic band structure effects are taken into account and no artificial rules regarding the connection of the wave function across the interface are introduced. The ten‐band tight‐binding model includes admixture in the total wave function of states derived from different extrema of the GaAs conduction band. States derived from the same extremum of the conduction band appear to couple strongly to each other, whereas states derived from different extrema are found to couple weakly. Transport characteristics of incoming L‐point and Γ‐point Bloch states are examined as a function of the energy of the incoming state, thickness of the Ga_(1−x)Al_xAs barrier, and alloy composition x. Transmission through the Ga_(1−x)Al_xAs barrier is either tunneling or propagating depending on the nature of the Bloch states available for strong coupling in the alloy. Since Bloch states derived from different extrema of the conduction band appear to couple weakly to each other, it seems possible to reflect the low velocity L‐point component of the current while transmitting the high velocity Γ‐point component

An experimental study of the effects of water repellant treatment on the acoustic properties of Kevlar

The treatment consisted of immersing samples of Kevlar in a solution of distilled water and Zepel. The samples were then drained, dried in a circulating over, and cured. Flow resistance tests showed approximately one percent decrease in flow resistance of the samples. Also there was a density increase of about three percent. It was found that the treatment caused a change in the texture of the samples. There were significant changes in the acoustic properties of the treated Kevlar over the frequency range 0.5 to 3.5 kHz. In general it was found that the propagation constant and characteristic impedance increased with increasing frequency. The real and imaginary components of the propagation constant for the treated Kevlar exhibited a decrease of 8 to 12 percent relative to that for the untreated Kevlar at the higher frequencies. The magnitude of the reactance component of the characteristic impedance decreased by about 40 percent at the higher frequencies