Interacting Dirac Materials

We investigate the extent to which the class of Dirac materials in two-dimensions provides general statements about the behavior of both fermionic and bosonic Dirac quasiparticles in the interacting regime. For both quasiparticle types, we find common features for the interaction induced renormalization of the conical Dirac spectrum. We perform the perturbative renormalization analysis and compute the self-energy for both quasiparticle types with different interactions and collate previous results from the literature whenever necessary. Guided by the systematic presentation of our results in Table~\ref{Summary}, we conclude that long-range interactions generically lead to an increase of the slope of the single-particle Dirac cone, whereas short-range interactions lead to a decrease. The quasiparticle statistics does not qualitatively impact the self-energy correction for long-range repulsion but does affect the behavior of short-range coupled systems, giving rise to different thermal power-law contributions. The possibility of a universal description of the Dirac materials based on these features is also mentioned.Comment: 19 pages and 12 Figures; Contains 6 Appendice

Surface polaritons in two-dimensional left-handed photonic crystals

Using an extended plane-wave-based transfer-matrix method, the photonic band structures and the corresponding transmission spectrum of a two-dimensional left-handed photonic crystal are calculated. Comparisons between the periodic structure with a single left-handed cylindric rod are made, and many interesting similarities are found. It is shown that, due to the localized surface polaritons presented by an isolated left-handed rod, there exist many exciting physical phenomena in high-dimensional left-handed photonic crystals. As direct results of coupling of the localized surface polaritons of neighboring left-handed rod, a lot of almost dispersionless bands, anti-crossing behavior, and a zero $\bar{n}$ gap are exhibited in the left-handed periodic structure. Moreover, in a certain frequency region, except distorted by a lot of anti-crossing behavior, there exists a continual dispersion relation, which can be explained by the long-wavelength approximation. It is also pointed out that high-dimensional left-handed photonic crystals can be used to design narrow-band filter.Comment: sign errors in equation

Adaptation in the face of internal conflict:The paradox of the organism revisited

The paradox of the organism refers to the observation that organisms appear to function as coherent purposeful entities, despite the potential for within-organismal components like selfish genetic elements and cancer cells to erode them from within. While it is commonly accepted that organisms may pursue fitness maximisation and can be thought to hold particular agendas, there is a growing recognition that genes and cells do so as well. This can lead to evolutionary conflicts between an organism and the parts that reside within it. Here, we revisit the paradox of the organism. We first outline its conception and relationship to debates about adaptation in evolutionary biology. Second, we review the ways selfish elements may exploit organisms, and the extent to which this threatens organismal integrity. To this end, we introduce a novel classification scheme that distinguishes between selfish elements that seek to distort transmission versus those that seek to distort phenotypic traits. Our classification scheme also highlights how some selfish elements elude a multi-level selection decomposition using the Price equation. Third, we discuss how the organism can retain its status as the primary fitness-maximising agent in the face of selfish elements. The success of selfish elements is often constrained by their strategy and further limited by a combination of fitness alignment and enforcement mechanisms controlled by the organism. Finally, we argue for the need for quantitative measures of both internal conflicts and organismality

On the Security of the Algebraic Eraser Tag Authentication Protocol

The Algebraic Eraser has been gaining prominence as SecureRF, the company commercializing the algorithm, increases its marketing reach. The scheme is claimed to be well-suited to IoT applications but a lack of detail in available documentation has hampered peer-review. Recently more details of the system have emerged after a tag authentication protocol built using the Algebraic Eraser was proposed for standardization in ISO/IEC SC31 and SecureRF provided an open public description of the protocol. In this paper we describe a range of attacks on this protocol that include very efficient and practical tag impersonation as well as partial, and total, tag secret key recovery. Most of these results have been practically verified, they contrast with the 80-bit security that is claimed for the protocol, and they emphasize the importance of independent public review for any cryptographic proposal.Comment: 21 pages. Minor changes. Final version accepted for ACNS 201

The relation between gravity rate of change and vertical displacement in previously glaciated areas

The rate of change of surface gravity, dg/dt, and vertical deformation rate of the solid surface, du/dt, are two observables of glacial isostatic adjustment (GIA). They contribute with different information on the same phenomenon. Their relation contains information of the underlying physics and a trustworthy relation allows to combine these observations to strengthen the overall observational accuracy of the phenomenon. In this paper we investigate the predicted relation between dg/dt and du/dt in previously glaciated areas. We use the normal mode approach for one dimensional earth models and solutions of the sea level equation with time-dependent coastline geometry. Numerical predictions of dg/dt and du/dt are computed for Laurentia, Fennoscandia and the British Isles respectively, using six different earth models. Within each region a linear trend is then fitted using the relation dg/dt = C du/dt + dg_0/dt. The estimated C and dg_0/dt differ more between the regions than between different earth models within each region. For Fennoscandia C ≈ −0.163 μGal/mm and for Laurentia C ≈ −0.152 μGal/mm. Maximum residuals between the linear trend and spatially varying model predictions of dg/dt are 0.04 μGal/yr in Fennoscandia and 0.17 μGal/yr in Laurentia. For the British Isles the results are harder to interpret, mainly since this region is located on the zero uplift isoline of Fennoscandia. In addition, we show temporal variation of the relation since the last glacial maximum till present-day. The temporal and spatial variation of the relation between dg/dt and du/dt can be explained by (i) the elastic respectively viscous proportion of the total signal and (ii) the spectral composition of the regional signal. Additional local effects, such as the Newtonian attraction and elastic deformation from local sea level changes, are examined in a case study for six stations in the Nordic absolute gravity network. The influence of these local effects on the relation between View the dg/dt and du/dt is negligible except for extreme locations close to the sea

Scale-dependent groundwater contributions influence patterns of winter baseflow stream chemistry in boreal catchments

Funded by •KCS •Swedish Science Foundation (VR) SITES •European Research Council. Grant Number: GA 335910 VEWAPeer reviewedPublisher PD

The straight field line concept and applications

The straight field line mirror field is a marginal minimum B field with straight nonparallel field lines. This field gives optimal ellipticity, the drift surfaces lie on a magnetic surface, radiofrequency heating of the plasma is predicted to be efficient and MHD stability is provided by the minimum B property. One intended application of the magnetic field configuration is energy production and transmutation of spent nuclear fuel in a fusion-fission machine, where the mirror confined plasma is surrounded by a fission mantle. Reactor safety can be increased with a subcritical fission mantle, and the fission power can exceed the fusion power by as much as a factor of 150 with a reasonable condition for reactor safety margins, and this provides a basis for a compact reactor design. The straight field line mirror concept can also be of interest as a plasma source for synthesis of sophisticated materials.Магнітне поле пастки з прямими, але непаралельними силовими лініями має максимум в центрі. Таке поле має мінімальну еліптичність магнітних поверхонь, дрейфові поверхні співпадають з магнітними, високочастотний нагрів може мати високу ефективність, та МГД- стійкість забезпечена мінімумом В. Одне з можливих застосувань такої магнітної конфігурації – виробництво електроенергії та трансмутація відпрацьованого ядерного палива в умовах, коли пастка знаходиться усередині ядерного реактора. Підвищена безпека роботи реактора забезпечується його підкритичністю, і коефіцієнт підсилення потужності досягає значення 150 з дотриманням вимог безпеки. Концепція утримання з прямими силовими лініями магнітного поля може також бути використаною в плазмових джерелах для синтезу складних матеріалів.Магнитное поле ловушки с прямыми, но непараллельными силовыми линиями имеет минимум в центре. Такое поле обладает минимальной эллиптичностью магнитных поверхностей, дрейфовые поверхности совпадают с магнитными, высокочастотный нагрев может иметь высокую эффективность, и МГД- устойчивость обеспечена минимумом В. Одно из возможных применений такой магнитной конфигурации – производство электроэнергии и трансмутация отработанного ядерного топлива в условиях, когда ловушка находится внутри ядерного реактора. Повышенная безопасность работы реактора обеспечивается его подкритичностью, и коэффициент усиления мощности достигает величины 150 при соблюдении требований безопасности. Концепция удержания с прямыми силовыми линиями магнитного поля может также быть использована в источниках плазмы для синтеза сложных материалов

The electronic structure of poly(pyridine-2,5-diyl) investigated by soft x-ray absorption and emission spectroscopies

The electronic structure of the poly-pyridine conjugated polymer has been investigated by resonant and nonresonant inelastic X-ray scattering and X-ray absorption spectroscopies using synchrotron radiation. The measurements were made for both the carbon and nitrogen contents of the polymer. The analysis of the spectra has been carried out in comparison with molecular orbital calculations taking the repeat-unit cell as a model molecule of the polymer chain. The simulations indicate no significant differences in the absorption and in the non-resonant X-ray scattering spectra for the different isomeric geometries, while some isomeric dependence of the resonant spectra is predicted. The resonant emission spectra show depletion of the {\pi} electron bands in line with symmetry selection and momentum conservation rules. The effect is most vizual for the carbon spectra; the nitrogen spectra are dominated by lone pair n orbital emission of {\sigma} symmetry and are less frequency dependent.Comment: 11 pages, 7 figures, 1 table, http://www.sciencedirect.com/science/article/pii/S030101049800262

Estimating Discharge in Low-Order Rivers With High-Resolution Aerial Imagery

Remote sensing of river discharge promises to augment in situ gauging stations, but the majority of research in this field focuses on large rivers (\u3e50 m wide). We present a method for estimating volumetric river discharge in low-order (wide) rivers from remotely sensed data by coupling high-resolution imagery with one-dimensional hydraulic modeling at so-called virtual gauging stations. These locations were identified as locations where the river contracted under low flows, exposing a substantial portion of the river bed. Topography of the exposed river bed was photogrammetrically extracted from high-resolution aerial imagery while the geometry of the remaining inundated portion of the channel was approximated based on adjacent bank topography and maximum depth assumptions. Full channel bathymetry was used to create hydraulic models that encompassed virtual gauging stations. Discharge for each aerial survey was estimated with the hydraulic model by matching modeled and remotely sensed wetted widths. Based on these results, synthetic width-discharge rating curves were produced for each virtual gauging station. In situ observations were used to determine the accuracy of wetted widths extracted from imagery (mean error 0.36 m), extracted bathymetry (mean vertical RMSE 0.23 m), and discharge (mean percent error 7% with a standard deviation of 6%). Sensitivity analyses were conducted to determine the influence of inundated channel bathymetry and roughness parameters on estimated discharge. Comparison of synthetic rating curves produced through sensitivity analyses show that reasonable ranges of parameter values result in mean percent errors in predicted discharges of 12%–27%