Observed changes in hurricane-driven waves explain the dynamics of modern cuspate shorelines

A comparison between historical and recent shoreline-change rates on the U.S. east coast (based on observed shoreline positions from the last century and a half) shows that emergent, large-scale, cuspate coastline features are changing shape, becoming more asymmetrical. This change in coastline shape arises from spatial shifts in the location of erosion and accretion zones. Using a numerical model of coastline change forced by wave-driven alongshore sediment flux, we show that a previously identified shift in hurricane-generated wave climate explains the patterns of coastline change we observe. Our results reveal a previously unrecognized type of large-scale, chronic landscape response to changing forcing. Though demonstrated here for a cuspate coastline, similar large-scale morphological adjustments are likely to occur along coastlines of varying morphology in the future - as global warming continues, along with the associated intensification of storms. Our approach allows for constraining and predicting future shifts in coastline shape

Relativistic quantum clocks

The conflict between quantum theory and the theory of relativity is exemplified in their treatment of time. We examine the ways in which their conceptions differ, and describe a semiclassical clock model combining elements of both theories. The results obtained with this clock model in flat spacetime are reviewed, and the problem of generalizing the model to curved spacetime is discussed, before briefly describing an experimental setup which could be used to test of the model. Taking an operationalist view, where time is that which is measured by a clock, we discuss the conclusions that can be drawn from these results, and what clues they contain for a full quantum relativistic theory of time.Comment: 12 pages, 4 figures. Invited contribution for the proceedings for "Workshop on Time in Physics" Zurich 201

Some Relations between Twisted K-theory and E8 Gauge Theory

Recently, Diaconescu, Moore and Witten provided a nontrivial link between K-theory and M-theory, by deriving the partition function of the Ramond-Ramond fields of Type IIA string theory from an E8 gauge theory in eleven dimensions. We give some relations between twisted K-theory and M-theory by adapting the method of Diaconescu-Moore-Witten and Moore-Saulina. In particular, we construct the twisted K-theory torus which defines the partition function, and also discuss the problem from the E8 loop group picture, in which the Dixmier-Douady class is the Neveu-Schwarz field. In the process of doing this, we encounter some mathematics that is new to the physics literature. In particular, the eta differential form, which is the generalization of the eta invariant, arises naturally in this context. We conclude with several open problems in mathematics and string theory.Comment: 23 pages, latex2e, corrected minor errors and typos in published versio

Family and identity. Catholic and non-Catholic intermarriage: attitudes to children, identity and sharing household responsibilities

info:eu-repo/semantics/publishe

A Farewell to Liouvillians

We examine the Liouvillian approach to the quantum Hall plateau transition, as introduced recently by Sinova, Meden, and Girvin [Phys. Rev. B {\bf 62}, 2008 (2000)] and developed by Moore, Sinova and Zee [Phys. Rev. Lett. {\bf 87}, 046801 (2001)]. We show that, despite appearances to the contrary, the Liouvillian approach is not specific to the quantum mechanics of particles moving in a single Landau level: we formulate it for a general disordered single-particle Hamiltonian. We next examine the relationship between Liouvillian perturbation theory and conventional calculations of disorder-averaged products of Green functions and show that each term in Liouvillian perturbation theory corresponds to a specific contribution to the two-particle Green function. As a consequence, any Liouvillian approximation scheme may be re-expressed in the language of Green functions. We illustrate these ideas by applying Liouvillian methods, including their extension to $N_L > 1$ Liouvillian flavors, to random matrix ensembles, using numerical calculations for small integer $N_L$ and an analytic analysis for large $N_L$. We find that behavior at $N_L > 1$ is different in qualitative ways from that at $N_L=1$. In particular, the $N_L = \infty$ limit expressed using Green functions generates a pathological approximation, in which two-particle correlation functions fail to factorize correctly at large separations of their energy, and exhibit spurious singularities inside the band of random matrix energy levels. We also consider the large $N_L$ treatment of the quantum Hall plateau transition, showing that the same undesirable features are present there, too

Learning from the world? Horizontal knowledge flows and geopolitics in international consulting firms

This paper examines the nature of the contemporary multinational corporation (MNC) through a study of the use of knowledge management systems (KMS) in four major international consulting firms. In particular, we explore whether and how such systems facilitate horizontal (inter-subsidiary) flows of knowledge, as described in the network view of the MNC. Our analysis reveals the presence of horizontal flows within the four firms, but flows that are contextually constrained and partly shaped by geopolitical power relations. Thus, our study gives some support to the image of the MNC as a network whilst highlighting the contextual limits of horizontal knowledge transfer and, importantly, the geopolitical conditions under which such knowledge transfer takes place. At the same time, it challenges the claim that consulting firms are model organizations in the area of knowledge management as well as the more negative view that questions the ability of KMS to facilitate knowledge transfer

A plan for administrative computing at ANL FY1991 through FY1993

In July of 1988, Argonne National Laboratory management approved the restructuring of Computing Services into the Computing and Telecommunications Division, part of the Physical Research area of the Laboratory. One major area of the Computing and Telecommunications Division is Management Information Systems (MIS). A significant aspect of Management Information Systems' work is the development of proposals for new and enhanced administrative computing systems based on an analysis of informational needs. This document represent the outcome of the planning process for FY1991 through FY1993. The introduction of the FY1991 through FY1993 Long-Range Plan assesses the state of administrative computing at ANL and the implications of FY1991 funding recommendations. It includes a history of MIS planning for administrative data processing. This document discusses the strategy and goals which are an important part of administrative data processing plans for the Laboratory. It also describes the management guidelines established by the Administrative Data Processing Oversight Committee for the proposal and implementation of administrative computing systems. Summaries of the proposals for new or enhanced administrative computing systems presented by individual divisions or departments with assistance of Management Information Systems, to the Administrative Data Processing Oversight Committee are given. The detailed tables in this paper give information on how much the resources to develop and implement a given systems will cost its users. The tables include development costs, computing/operations costs, software and hardware costs, and efforts costs. They include both systems funded by Laboratory General Expense and systems funded by the users themselves

Gerbes, M5-Brane Anomalies and E_8 Gauge Theory

Abelian gerbes and twisted bundles describe the topology of the NS-NS 3-form gauge field strength H. We review how they have been usefully applied to study and resolve global anomalies in open string theory. Abelian 2-gerbes and twisted nonabelian gerbes describe the topology of the 4-form field strength G of M-theory. We show that twisted nonabelian gerbes are relevant in the study and resolution of global anomalies of multiple coinciding M5-branes. Global anomalies for one M5-brane have been studied by Witten and by Diaconescu, Freed and Moore. The structure and the differential geometry of twisted nonabelian gerbes (i.e. modules for 2-gerbes) is defined and studied. The nonabelian 2-form gauge potential living on multiple coinciding M5-branes arises as curving (curvature) of twisted nonabelian gerbes. The nonabelian group is in general $\tilde\Omega E_8$, the central extension of the E_8 loop group. The twist is in general necessary to cancel global anomalies due to the nontriviality of the 11-dimensional 4-form G field strength and due to the possible torsion present in the cycles the M5-branes wrap. Our description of M5-branes global anomalies leads to the D4-branes one upon compactification of M-theory to Type IIA theory.Comment: 19 page

The low-lying excitations of polydiacetylene

The Pariser-Parr-Pople Hamiltonian is used to calculate and identify the nature of the low-lying vertical transition energies of polydiacetylene. The model is solved using the density matrix renormalisation group method for a fixed acetylenic geometry for chains of up to 102 atoms. The non-linear optical properties of polydiacetylene are considered, which are determined by the third-order susceptibility. The experimental 1Bu data of Giesa and Schultz are used as the geometric model for the calculation. For short chains, the calculated E(1Bu) agrees with the experimental value, within solvation effects (ca. 0.3 eV). The charge gap is used to characterise bound and unbound states. The nBu is above the charge gap and hence a continuum state; the 1Bu, 2Ag and mAg are not and hence are bound excitons. For large chain lengths, the nBu tends towards the charge gap as expected, strongly suggesting that the nBu is the conduction band edge. The conduction band edge for PDA is agreed in the literature to be ca. 3.0 eV. Accounting for the strong polarisation effects of the medium and polaron formation gives our calculated E(nBu) ca. 3.6 eV, with an exciton binding energy of ca. 1.0 eV. The 2Ag state is found to be above the 1Bu, which does not agree with relaxed transition experimental data. However, this could be resolved by including explicit lattice relaxation in the Pariser- Parr-Pople-Peierls model. Particle-hole separation data further suggest that the 1Bu, 2Ag and mAg are bound excitons, and that the nBu is an unbound exciton.Comment: LaTeX, 23 pages, 4 postscript tables and 8 postscript figure

Wildlife trail or systematic? Camera trap placement has little effect on estimates of mammal diversity in a tropical forest in Gabon

peer reviewedCamera traps (CTs) have been increasingly used for wildlife monitoring worldwide. In the tropics, most CT inventories target wildlife‐friendly sites, and CTs are commonly placed towards wildlife trails. However, it has been argued that this placement strategy potentially provides biased results in comparison to more systematic or randomized approaches. Here, we investigated the impact of CT placement on the remotely sensed mammal diversity in a tropical forest in Gabon by comparing pairs of systematically placed and wildlife‐trail‐oriented CTs. Our survey protocol consisted of 15–17 sampling points arranged on a 2 km2 grid and left for one month in the field. This protocol was replicated sequentially in four areas. Each sampling point comprised a CT pair: the ‘systematic CT’, installed at the theoretical point and systematically oriented towards the most uncluttered view; and the ‘trail CT’, placed within a 20‐m radius and facing a wildlife trail. For the vast majority of species, the detection probabilities were comparable between placements. Species average capture rates were slightly higher for trail‐based CTs, though this trend was not significant for any species. Therefore, the species richness and composition of the overall community, such as the spatial distribution patterns (from evenly spread to site‐restricted) of individual species, were similarly depicted by both placements. Opting for a systematic orientation ensures that pathways used preferentially by some species—and avoided by others—will be sampled proportionally to their density in the forest undergrowth. However, trail‐based placement is routinely used, already producing standardised data within large‐scale monitoring programmes. Here, both placements provided a comparable picture of the mammal community, though it might not be necessarily true in depauperate areas. Both types of CT data can nevertheless be combined in multi‐site analyses, since methods now allow accounting for differences in study design and detection bias in original CT data.Programme de Promotion de l’Exploitation Certifiée des Forêts (PPECF