Stochastic oscillations of adaptive networks: application to epidemic modelling

Adaptive-network models are typically studied using deterministic differential equations which approximately describe their dynamics. In simulations, however, the discrete nature of the network gives rise to intrinsic noise which can radically alter the system's behaviour. In this article we develop a method to predict the effects of stochasticity in adaptive networks by making use of a pair-based proxy model. The technique is developed in the context of an epidemiological model of a disease spreading over an adaptive network of infectious contact. Our analysis reveals that in this model the structure of the network exhibits stochastic oscillations in response to fluctuations in the disease dynamic.Comment: 11 pages, 4 figure

Neutrino Oscillations, Fluctuations and Solar Magneto-gravity Waves

This review has two parts. The first part summarizes the current observational constraints on fluctuations in the solar medium deep within the solar Radiative Zone, and shows how the KamLAND and SNO-salt data combine to make the experimental determination of the neutrino oscillation parameters largely insensitive to prior assumptions about the nature of these oscillations. As part of a search for plausible sources of solar fluctuations to which neutrinos could be sensitive, the second part of the talk summarizes a preliminary analysis of the influence of magnetic fields on helioseismic waves. Using simplifying assumptions which should apply to modes in the solar radiative zone, we find a resonance between Alfven waves and helioseismic g-modes which potentially modifies the solar density profile fairly significantly over comparatively short distance scales, too narrow to be ruled out by present-day analyses of p-wave helioseismic spectra.Comment: Plenary talk presented at AHEP 2003, Valencia, Spain, October 200

CASE HISTORIES USING SYNTHETIC FIBER REINFORCED CONCRETE

Synthetic fiber reinforced concrete has been used in shotcrete for many years. This paper discusses select project case histories from around the world. The discussion focuses on why fibers are used and explains how there are many benefits, advantages, and features regarding the choice of fibers. Also discussed is why and how the fibers affect the overall project performance, schedule, costs, and construct-ability. Further discussion shows that the fiber choice is in the details. The best fiber choice must meet certain project criteria established by all the decision makers involved in the project. Lastly, the versatility in the use of a specific blend of synthetic fibers in shotcrete shows the potential for even more diverse applications of synthetic fiber reinforcement

Black Holes and the Super Yang-Mills diagram. II

The complete phase diagram of objects in M-theory compactified on tori $T^p$, $p=1,2,3$, is elaborated. Phase transitions occur when the object localizes on cycle(s) (the Gregory-Laflamme transition), or when the area of the localized part of the horizon becomes one in string units (the Horowitz-Polchinski correspondence point). The low-energy, near-horizon geometry that governs a given phase can match onto a variety of asymptotic regimes. The analysis makes it clear that the matrix conjecture is a special case of the Maldacena conjecture.Comment: 23 pages, latex; 3 eps figures; v2: references and minor comments added. v3: reference adde

‘Missing out’: Reflections on the positioning of ethnographic research within an evaluative framing

Contemporary approaches to evaluating ‘complex’ social and health interventions are opening up spaces for methodologies attuned to examining contextual complexities, such as ethnography. Yet the alignment of the two agendas – evaluative and ethnographic – is not necessarily comfortable in practice. I reflect on experiences of conducting ethnographic research alongside a public health evaluation of a community-based initiative in the UK, using the lens of ‘missing out’ to examine intersections between my own ethnographic concerns and those of the communities under study. I examine potential opportunities posed by the discomfort of ‘missing out’, particularly for identifying the processes and spaces of inclusion and exclusion that contributed both to my ethnographic experiences and to the realities of the communities engaging with the initiative. This reveals productive possibilities for a focus on ‘missing out’ as a form of relating for evaluations of the impacts of such initiatives on health and social inequalities

Superselectors: Efficient Constructions and Applications

We introduce a new combinatorial structure: the superselector. We show that superselectors subsume several important combinatorial structures used in the past few years to solve problems in group testing, compressed sensing, multi-channel conflict resolution and data security. We prove close upper and lower bounds on the size of superselectors and we provide efficient algorithms for their constructions. Albeit our bounds are very general, when they are instantiated on the combinatorial structures that are particular cases of superselectors (e.g., (p,k,n)-selectors, (d,\ell)-list-disjunct matrices, MUT_k(r)-families, FUT(k, a)-families, etc.) they match the best known bounds in terms of size of the structures (the relevant parameter in the applications). For appropriate values of parameters, our results also provide the first efficient deterministic algorithms for the construction of such structures

On-Shell Recursion Relations for Generic Theories

We show that on-shell recursion relations hold for tree amplitudes in generic two derivative theories of multiple particle species and diverse spins. For example, in a gauge theory coupled to scalars and fermions, any amplitude with at least one gluon obeys a recursion relation. In (super)gravity coupled to scalars and fermions, the same holds for any amplitude with at least one graviton. This result pertains to a broad class of theories, including QCD, N=4 SYM, and N=8 supergravity.Comment: 19 pages, 3 figure

Holographic Aspects of Fermi Liquids in a Background Magnetic Field

We study the effects of an external magnetic field on the properties of the quasiparticle spectrum of the class of 2+1 dimensional strongly coupled theories holographically dual to charged AdS$_4$ black holes at zero temperature. We uncover several interesting features. At certain values of the magnetic field, there are multiple quasiparticle peaks representing a novel level structure of the associated Fermi surfaces. Furthermore, increasing magnetic field deforms the dispersion characteristics of the quasiparticle peaks from non-Landau toward Landau behaviour. At a certain value of the magnetic field, just at the onset of Landau-like behaviour of the Fermi liquid, the quasiparticles and Fermi surface disappear.Comment: 18 pages, 10 figures. Revised some of the terminology: changed non-separable solutions to infinite-sum solution