Power-law spin correlations in pyrochlore antiferromagnets

The ground state ensemble of the highly frustrated pyrochlore-lattice antiferromagnet can be mapped to a coarse-grained ``polarization'' field satisfying a zero-divergence condition From this it follows that the correlations of this field, as well as the actual spin correlations, decay with separation like a dipole-dipole interaction ($1/|R|^3$). Furthermore, a lattice version of the derivation gives an approximate formula for spin correlations, with several features that agree well with simulations and neutron-diffraction measurements of diffuse scattering, in particular the pinch-point (pseudo-dipolar) singularities at reciprocal lattice vectors. This system is compared to others in which constraints also imply diffraction singularities, and other possible applications of the coarse-grained polarization are discussed.Comment: 13 pp, revtex, two figure

Vortex lines or sheets - what is formed in dynamic drives?

In isotropic macroscopic quantum systems vortex lines can be formed while in anisotropic systems also vortex sheets are possible. Based on measurements of superfluid 3He-A, we present the principles which select between these two competing forms of quantized vorticity: sheets displace lines if the frequency of the external field exceeds a critical limit. The resulting topologically stable state consists of multiple vortex sheets and has much faster dynamics than the state with vortex lines.Comment: RevTex, 5 pages, sumbitted to Phys. Rev. Let

Cosmology, Particle Physics and Superfluid 3He

Many direct parallels connect superfluid 3He with the field theories describing the physical vacuum, gauge fields and elementary fermions. Superfluid $^3$He exhibits a variety of topological defects which can be detected with single-defect sensitivity. Modern scenarios of defect-mediated baryogenesis can be simulated by the interaction of the 3He vortices and domain walls with fermionic quasiparticles. Formation of defects in a symmetry-breaking phase transition in the early Universe, which could be responsible for large-scale structure formation and for microwave-background anisotropy, also may be modelled in the laboratory. This is supported by the recent observation of vortex formation in neutron-irradiated 3He-B where the "primordial fireball" is formed in an exothermic nuclear reaction.Comment: Invited talk at LT-21 Conference, 20 pages, 3 figures available at request, compressed ps file of the camera-ready format with 3 figures is at ftp://boojum.hut.fi/pub/publications/lowtemp/LTL-96006.ps.g

Sport, War and Democracy in Classical Athens

This article concerns the paradox of athletics in classical Athens. Democracy may have opened up politics to every class of Athenian but it had little impact on sporting participation. The city’s athletes continued to drawn predominantly from the upper class. It comes as a surprise then that lower-class Athenians actually esteemed athletes above every other group in the public eye, honoured them very generously when they won, and directed a great deal of public and private money to sporting competitions and facilities. In addition athletics escaped the otherwise persistent criticism of upper-class activities in the popular culture of the democracy. The research of social scientists on sport and aggression suggests this paradox may have been due to the cultural overlap between athletics and war under the Athenian democracy. The article concludes that the practical and ideological democratization of war by classical Athens legitimized and supported upper-class sport

Olympic legacies in the IOC's 'Celebrate Humanity' campaign: ancient or modern?

The Olympics is a global event that acts as a carrier of cultural meanings that are available to international audiences and markets. Though the heritage of the Olympics is claimed to be derived from the ancient world, in fact the contemporary legacy is very modern. Indeed, such meanings, and the legacy thereby attached, are re-represented, distributed, and marketed by a media-sport complex predicated less on the concept of arete and much more on a consumption ethos. Here, the initial formulation, development and use of the 'Celebrate Humanity' programme is investigated. The programme was framed by the IOC marketing department as a way both to deflect criticism of the IOC and as one means by which to provide 'added-value' to the Olympic Partner (TOP) programme sponsors. This programme, and the wider Olympic movement, highlights the basic contradiction between the ideals of 'Olympism' and the realities of the modern Olympics in practice. The 'legacy' of the modern games is consumption. The legacy 'message' becomes embedded in a broader process of commerce whereby the media/marketing/advertising/corporate nexus is concerned less with the values underpinning Olympism per se and more with how such values can help build markets, construct and enhance brand awareness, and create 'glocal' consumers/identities. Celebrate Humanity is no exception