39,223 research outputs found

    Interfaces (and Regional Congruence?) in Spin Glasses

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    We present a general theorem restricting properties of interfaces between thermodynamic states and apply it to the spin glass excitations observed numerically by Krzakala-Martin and Palassini-Young in spatial dimensions d=3 and 4. We show that such excitations, with interface dimension smaller than d, cannot yield regionally congruent thermodynamic states. More generally, zero density interfaces of translation-covariant excitations cannot be pinned (by the disorder) in any d but rather must deflect to infinity in the thermodynamic limit. Additional consequences concerning regional congruence in spin glasses and other systems are discussed.Comment: 4 pages (ReVTeX); 1 figure; submitted to Physical Review Letter

    Marketing images and consumers' experiences in selling environments

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    In a well-functioning market, consumers exert choices not just in purchases of products but also in selections of locations to enjoy shopping. Scholarly research has demonstrated that retail atmospheres impact on shoppers’ pleasurable shopping experiences. Demonstrating the marketing concept in action, shoppers consistently respond to this empowerment by for example, spending more time shopping and spending more money in retail facilities that are perceived to offer a pleasanter atmosphere and experience. This research pivots round an in-depth qualitative study that evaluated the impact of a plasma screens and specific informational content on shopping centre user behaviour. A phenomenological study of the effects of the medium, and the way in which these systems influence behaviour, permitted a far deeper investigation of our sample group vis-àvis increased browsing time and the propensity to spend. A series of eight focus discussions were conducted with local user groups of varying age and gender. Key themes drawn from the group discussions using axial coding indicated that the influence created by the images varied with subjects and settings. The general consensus was that such ‘screens’ created a certain ambience that influenced the way our subjects felt about the selling environment under study. Moreover, for our sample groups, there was clearly a link between the screened images and modern expectations of a selling environment. The plasma screens provided added enjoyment to shoppers’ experiences, providing them with more information enabling more informed shopping choices. The research concludes with implications for strategic marketing, theory and practice

    Metastates in mean-field models with random external fields generated by Markov chains

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    We extend the construction by Kuelske and Iacobelli of metastates in finite-state mean-field models in independent disorder to situations where the local disorder terms are are a sample of an external ergodic Markov chain in equilibrium. We show that for non-degenerate Markov chains, the structure of the theorems is analogous to the case of i.i.d. variables when the limiting weights in the metastate are expressed with the aid of a CLT for the occupation time measure of the chain. As a new phenomenon we also show in a Potts example that, for a degenerate non-reversible chain this CLT approximation is not enough and the metastate can have less symmetry than the symmetry of the interaction and a Gaussian approximation of disorder fluctuations would suggest.Comment: 20 pages, 2 figure

    Realistic spin glasses below eight dimensions: a highly disordered view

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    By connecting realistic spin glass models at low temperature to the highly disordered model at zero temperature, we argue that ordinary Edwards-Anderson spin glasses below eight dimensions have at most a single pair of physically relevant pure states at nonzero low temperature. Less likely scenarios that evade this conclusion are also discussed.Comment: 18 pages (RevTeX; 1 figure; to appear in Physical Review E

    Numerical design of streamlined tunnel walls for a two-dimensional transonic test

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    An analytical procedure is discussed for designing wall shapes for streamlined, nonporous, two-dimensional, transonic wind tunnels. It is based upon currently available 2-D inviscid transonic and boundary layer analysis computer programs. Predicted wall shapes are compared with experimental data obtained from the NASA Langley 6 by 19 inch Transonic Tunnel where the slotted walls were replaced by flexible nonporous walls. Comparisons are presented for the empty tunnel operating at a Mach number of 0.9 and for a supercritical test of an NACA 0012 airfoil at zero lift. Satisfactory agreement is obtained between the analytically and experimentally determined wall shapes

    The electrical conductivity of a collisionless magnetoplasma in a weakly turbulent magnetic field

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    Electrical conductivity of collisionless magnetoplasma in nearly turbulent magnetic fiel

    Zero-Temperature Dynamics of Plus/Minus J Spin Glasses and Related Models

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    We study zero-temperature, stochastic Ising models sigma(t) on a d-dimensional cubic lattice with (disordered) nearest-neighbor couplings independently chosen from a distribution mu on R and an initial spin configuration chosen uniformly at random. Given d, call mu type I (resp., type F) if, for every x in the lattice, sigma(x,t) flips infinitely (resp., only finitely) many times as t goes to infinity (with probability one) --- or else mixed type M. Models of type I and M exhibit a zero-temperature version of ``local non-equilibration''. For d=1, all types occur and the type of any mu is easy to determine. The main result of this paper is a proof that for d=2, plus/minus J models (where each coupling is independently chosen to be +J with probability alpha and -J with probability 1-alpha) are type M, unlike homogeneous models (type I) or continuous (finite mean) mu's (type F). We also prove that all other noncontinuous disordered systems are type M for any d greater than or equal to 2. The plus/minus J proof is noteworthy in that it is much less ``local'' than the other (simpler) proof. Homogeneous and plus/minus J models for d greater than or equal to 3 remain an open problem.Comment: 17 pages (RevTeX; 3 figures; to appear in Commun. Math. Phys.
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