R. J. Rivers

Dual PT-symmetric quantum field theories

Abstract Some quantum field theories described by non-Hermitian Hamiltonians are investigated. It is shown that for the case of a free fermion field theory with a γ 5 mass term the Hamiltonian is PT -symmetric. Depending on the mass parameter this symmetry may be either broken or unbroken. When the PT symmetry is unbroken, the spectrum of the quantum field theory is real. For the PT -symmetric version of the massive Thirring model in two-dimensional space–time, which is dual to the PT -symmetric scalar sine-Gordon model, an exact construction of the C operator is given. It is shown that the PT -symmetric massive Thirring and sine-Gordon models are equivalent to the conventional Hermitian massive Thirring and sine-Gordon models with appropriately shifted masses.

The Theran eruption and Minoan palatial collapse: new interpretations gained from modelling the maritime network

What was the effect on Late Minoan civilisation of the catastrophic destruction of Akrotiri on Thera (Santorini) by volcanic eruption? Not much, according to the evidence for continuing prosperity on Crete. But the authors mobilise their ingenious mathematical model (published in Antiquity 82: 1009–1024), this time to show that the effects of removing a major port of call could have impacted after an interval, as increased costs of transport gradually led to ever fewer routes and eventual economic collapse.

Zurek-Kibble mechanism for the spontaneous vortex formation in Nb-Al/Al(ox)/Nb Josephson tunnel junctions: new theory and experiment.

New scaling behavior has been both predicted and observed in the spontaneous production of fluxons in quenched Nb-Al/Al(ox)/Nb annular Josephson tunnel junctions (JTJs) as a function of the quench time, tau(Q). The probability f(1) to trap a single defect during the normal-metal-superconductor phase transition clearly follows an allometric dependence on tau(Q) with a scaling exponent sigma = 0.5, as predicted from the Zurek-Kibble mechanism for realistic JTJs formed by strongly coupled superconductors. This definitive experiment replaces one reported by us earlier, in which an idealized model was used that predicted sigma = 0.25, commensurate with the then much poorer data. Our experiment remains the only condensed matter experiment to date to have measured a scaling exponent with any reliability.

DYNAMICS VERSUS SELECTION RULES IN DIFFRACTION DISSOCIATION.

Abstract In a diffraction model arising from duality, and in related models, the Morrison and other selection rules for diffraction dissociation are shown not to hold. An examination of experimental data also indicates a failure of these rules. The consequences of the model for the helicity structure of A 1 πϱ couplings are explored.

Using Statistical Physics to Understand Relational Space: a case study from Mediterranean Prehistory

Spatial relationships among entities across a range of scales are fundamental in many of the social sciences, not least in human geography, physical geography, and archaeology. However, space has received a surprisingly uneven treatment; in archaeology, for example, spatial analysis only really came to the fore in the 1960s and 70s, through the influence of the ‘New Geography’ (Haggett, 1965; Chorley & Haggett, 1967). David Clarke (1968, 1977), one of the principal exponents of spatial analysis in New Archaeology, described three levels of resolution in spatial archaeology: the micro level, the semi-micro or meso level and the macro level, the last of these representing relationships between sites (Clarke, 1977, p. 13). Yet, despite the clear implication that these levels should articulate, many subsequent studies have tended to aim at just one level. World-systems theory, for example, forms the basis for core-periphery models that examine macro-level spatial relationships (e.g., Schortman & Urban, 1992; Peregrine, 1996; McGuire, 1996; Chase-Dunn & Hall, 1997; Stein, 1998; Kardulias, 1999). While Clarke’s emphasis on different spatial scales has the advantage of clarity, his general approach, and indeed that of much spatial analysis of this kind, has been criticized for its overly deterministic approach to space. The idea that space has absolute geometric properties has been increasingly challenged by scholars arguing that space is a relative construct, a process that emerges out of social practices. In geography this critique already has a long history (e.g., Harvey, 1973), which has been taken up by increasingly diverse and influential voices (e.g., Lefebvre, 1991; Harvey, 1996; Soja, 1996; Thrift, 1996; Hetherington, 1997; Murdoch, 2006). This ‘spatial turn’ has also been experienced in archaeology, where approaches to space were ‘relationalized’ through the influence of phenomenology in landscape studies (Bender, 1993; Tilley, 1994; Knapp & Ashmore, 1999; Smith, 2003; Blake, 2002, 2004).

Spontaneous Fluxoid Formation in Superconducting Loops

We report on the experimental verification of the Zurek-Kibble scenario in an isolated superconducting ring over a wide parameter range. The probability of creating a single flux quantum spontaneously during the fast normal-superconducting phase transition of a wide Nb loop clearly follows a scaling relation on the quenching time

Zurek-Kibble Domain Structures: The Dynamics of Spontaneous Vortex Formation in Annular Josephson Tunnel Junctions

{\ensuremath{\tau}}_{Q}

Interactions In Space For Archaeological Models

, as one would expect if the transition took place as fast as causality permits. However, the observed Zurek-Kibble scaling exponent

Testing the kibble-zurek scenario with annular josephson tunnel junctions

\ensuremath{\sigma}=0.62\ifmmode\pm\else\textpm\fi{}0.15

Interactions between U(1) cosmic strings: An analytical study.

is two times larger than anticipated for large loops. Assuming Gaussian winding number densities we show that this doubling is well founded for small annuli.