Higher representation infinite algebras from McKay quivers of metacyclic groups

For each prime number $s$ we introduce examples of $(s-1)$- and $s$-representation infinite algebras in the sense of Herschend, Iyama and Oppermann, which arise from skew group algebras of some metacyclic groups embedded in $\mathrm{SL}(s,\mathbb{C})$ and $\mathrm{SL}(s+1,\mathbb{C})$. For this purpose, we give a description of the McKay quiver with a superpotential of such groups. Moreover we show that for $s=2$ our examples correspond to the classical tame hereditary algebras of type $\tilde{D}$.Comment: 38 pages, 9 figures. v2: minor changes to the exposition, added examples. To appear in Comm. Algebr

Skew group algebras of Jacobian algebras

For a quiver with potential $(Q,W)$ with an action of a finite cyclic group $G$, we study the skew group algebra $\Lambda G$ of the Jacobian algebra $\Lambda = \mathcal P(Q, W)$. By a result of Reiten and Riedtmann, the quiver $Q_G$ of a basic algebra $\eta( \Lambda G) \eta$ Morita equivalent to $\Lambda G$ is known. Under some assumptions on the action of $G$, we explicitly construct a potential $W_G$ on $Q_G$ such that $\eta(\Lambda G) \eta\cong \mathcal P(Q_G , W_G)$. The original quiver with potential can then be recovered by the skew group algebra construction with a natural action of the dual group of $G$. If $\Lambda$ is self-injective, then $\Lambda G$ is as well, and we investigate this case. Motivated by Herschend and Iyama's characterisation of 2-representation finite algebras, we study how cuts on $(Q,W)$ behave with respect to our construction.Comment: 34 pages, comments welcome. Final version, to appear in Journal of Algebr

Cavity control of Excitons in two dimensional Materials

We propose a robust and efficient way of controlling the optical spectra of two-dimensional materials and van der Waals heterostructures by quantum cavity embedding. The cavity light-matter coupling leads to the formation of exciton-polaritons, a superposition of photons and excitons. Our first principles study demonstrates a reordering and mixing of bright and dark excitons spectral features and in the case of a type II van-der-Waals heterostructure an inversion of intra and interlayer excitonic resonances. We further show that the cavity light-matter coupling strongly depends on the dielectric environment and can be controlled by encapsulating the active 2D crystal in another dielectric material. Our theoretical calculations are based on a newly developed non-perturbative many-body framework to solve the coupled electron-photon Schr\"odinger equation in a quantum-electrodynamical extension of the Bethe-Salpeter approach. This approach enables the ab-initio simulations of exciton-polariton states and their dispersion from weak to strong cavity light-matter coupling regimes. Our method is then extended to treat van der Waals heterostructures and encapsulated 2D materials using a simplified Mott-Wannier description of the excitons that can be applied to very large systems beyond reach for fully ab-initio approaches.Comment: 32 pages. 10 figures, 2 tabl

On some examples in higher Auslander-Reiten theory

Questa tesi è dedicata allo studio di alcuni esempi di algebre d-representation finite e infinite. Queste algebre sono la generalizzazione delle classiche algebre di tipo di rappresentazione finito e infinito nel contesto della teoria di Auslander-Reiten in dimensione superiore, introdotta da Iyama negli anni 2000. Nella prima parte della tesi introduciamo nuovi esempi di algebre d-representation infinite sfruttando la loro relazione con le algebre bimodulo (d+1)-Calabi-Yau di parametro di Gorenstein 1. Per prima cosa richiameremo alcuni risultati di Bocklandt, Schedler e Wemyss, e di Herschend, Iyama e Oppermann, che mostrano alcuni esempi dati da skew group algebre di sottogruppi finiti di gruppi lineari generali. Come generalizzazione delle classiche algebre ereditarie tame di tipo A, Herschend, Iyama e Oppermann hanno introdotto le algebre d-representation infinite di tipo A considerando sottogruppi abeliani di SL(d+1,C). Nel nostro lavoro otteniamo una costruzione simile per alcuni sottogruppi non abeliani. Più precisamente, studiamo la skew group algebra di alcuni sottogruppi metaciclici immersi in SL(s,C) e SL(s+1,C), quando s è un numero primo. A tale scopo diamo una descrizione dei quiver di McKay con superpotenziale di tali gruppi, e ne consideriamo dei grading ottenuti da tagli. Inoltre, mostriamo che per s=2 i nostri esempi corrispondono alle classiche algebre ereditarie tame di tipo D. La seconda parte della tesi tratta di skew group algebre di algebre Jacobiane. Dimostriamo che, se un gruppo ciclico finito agisce sull'algebra Jacobiana P(Q,W) di un quiver con potenziale (Q,W) soddisfando alcune assunzioni, allora la skew group algebra P(Q,W)*G è Morita equivalente all'algebra Jacobiana di un altro quiver con potenziale(Q_G,W_G), che è descritto esplicitamente. Il quiver con potenziale originale può essere quindi recuperato tramite una costruzione di skew group algebra rispetto a un'azione naturale del gruppo duale di G. Una delle motivazioni per questo lavoro risiede in un teorema di Herschend e Iyama, che mette in relazione i quiver con potenziale auto-iniettivi alle algebre 2-representation finite. Alla luce di ciò, studiamo il comportamento dei tagli su tali quiver sotto la nostra costruzione, allo scopo di ottenere nuovi esempi di algebre 2-representation finite da quelli già conosciuti. Presentiamo alcuni esempi dove la nostra costruzione può essere applicata, come i quiver con potenziale planari dove il gruppo agisce per rotazioni, e in particolare quelli auto-iniettivi che sono ottenuti da diagrammi di Postnikov

Is there a need for greater integration and shift in policy to tackle food waste? Insights from a review of European Union legislations

Within the European Union, there is an increasing recognition about the negative environmental impacts of food waste making it a prominent policy issue. But there is no clarity whether policies aimed at food waste minimisation are based on sound legislative frameworks that actually empower the relevant actors. By carefully reviewing existing European Union legislations that are linked directly or indirectly to food waste, we identify the difficulties encountered by stakeholders and assess whether adaptations to the rules-in-use are beneficial and desirable. Our general finding is that liability for donated foodstuffs, date marking provisions, the flexibility principle provided by the European Union Hygiene Package and fiscal rules are the main policy elements affecting, either positively or negatively, food waste generation and management. Food donation for charitable purposes emerges as the predominant Pan-European Union waste management solution. While removing existing barriers for food donors and banks is fundamental—as it makes redistribution more effective—this does not tackle prevention of excess food generation. We conclude that while there are several European Union food legislations which include and impact food waste management options, they are hardly direct. Moreover, they often generate incentives that are at odds across stakeholders, thereby dampening the intended impact. There is, therefore, need for an integrated policy framework to tackle food waste specifically. For that to happen though, a pre-requisite is lot more empirical research on the interaction effects of various food waste legislations

Indoor real-time localisation for multiple autonomous vehicles fusing vision, odometry and IMU data

Due to the increasing usage of service and industrial autonomous vehicles, a precise localisation is an essential component required in many applications, e.g. indoor robot navigation. In open outdoor environments, differential GPS systems can provide precise positioning information. However, there are many applications in which GPS cannot be used, such as indoor environments. In this work, we aim to increase robot autonomy providing a localisation system based on passive markers, that fuses three kinds of data through extended Kalman filters. With the use of low cost devices, the optical data are combined with other robots’ sensor signals, i.e. odometry and inertial measurement units (IMU) data, in order to obtain accurate localisation at higher tracking frequencies. The entire system has been developed fully integrated with the Robotic Operating System (ROS) and has been validated with real robots

Estabelecimento e desenvolvimento das macrofitas aquáticas "scirpus californicus, typha subulata e zizaniopsis bonariensis" sob condições experimentais de regimes hidricos diferenciados

Este experimento procurou obter informações básicas sobre macrófitas aquáticas visando a construção e recuperação de banhados. As espécies Scirpus californicus, Typha subulata e Zizaniopsis bonariensis foram estudadas em condições experimentais sob três regimes hídricos: (i) lâmina d' água permanente de 10 cm acima do substrato, (ii) lâmina oscilante de 3 ± 2 cm acima do substrato, (iii) inundações e drenagens alternadas, sendo as inundações dos dois últimos a cada 48 horas. O primeiro regime hídrico, foi o mais favorável ao desenvolvimento de Typha subulata e Zizaniopsis bonariensis. O segundo, superou ao final das observações o primeiro em relação ao desenvolvimento de Scirpus californicus. As variáveis respostas de desenvolvimento observadas (espessura à meia-altura da folha ou haste mais alta por planta; largura à meia-altura da folha ou haste mais alta por planta; altura da folha ou haste mais alta por planta; número de folhas ou hastes verdes por planta; número de brotos por planta; sobrevivência das folhas ou hastes originais do propágulo) foram descritores satisfatórios de crescimento e desenvolvimento diferenciado da parte aérea relacionado aos regimes hídricos. A variação dos descritores evidenciou plasticidade das proporções morfológicas e das opções fisiológicas de desenvolvimento, as quais, nas condições deste experimento foram diferenciadas nas três espécies. Scirpus californicus alocou recursos tanto para reprodução vegetativa como para a sexuada e teve maior crescimento. Typha subulata e Zizaniopsis bonariensis alocaram recursos somente para reprodução vegetativa e crescimento, no período das observações. As três espécies mostraram sobrevivência e desenvolvimento satisfatórios em substrato tipo subsolo mesmo nas condições de regime hídrico e compactação mais desfavoráveis. Isto as torna adequadas para plantio em áreas degradadas como plantas pioneiras para reconstrução ou construção de ecossistemas.This experiment aimed to obtain basic information on aquatic macrophytes for wetland construction and recovery of degraded wetlands. The species Scirpus californicus, Typha subulata and Zizaniopsis bonariensis were evaluated under experimental conditions and three hydric regimes: (i) continuosly flooded with water levei at 10 cm above substractum, (ii) alternated flooding with water levei at 3 ± 2 cm above substractum, (iii) alternated flooding and drainage, being the floodings of the last two hydric regimes, made every 48 hours. The first hydric regime, was best suited to the development of Typha subulata and Zizaniopsis bonariensis. The second one, by the end of observations, surpassed the first one, in relation to the development of Scirpus californicus. The observed response variables of development (thickness at half lenght of the tallest leaf or stem per plant; width at half lenght of the tallest leaf or stem per plant; heíght of tallest leaf or stem per plant; number of green leaves os stems per plant; number of shoots per plant; survival of propagules original leaves or stems) were satisfactory descriptors to differentiate growth and development of above ground parts as related to water regimes. The descriptors variation demonstrated plasticity of the morphological proportions and of the physiological options of development, which were differentiated for the three species under the conditions of this experíment. Scirpus californicus allocated as much resources to vegetative reproduction as to sexual reproduction, and had greater growth. Typha subulata and Zizaniopsis bonariensis allocated resources only for vegetative reproduction and growth in the period of observations. The three species showed satisfactory survival and development in subsoil like substractum, even under the most unfavourable conditions of hydric regimes and soil compaction. It makes them suitable for planting in degraded areas as pioneer plants for construction and redevelopment of ecossystems

Controlling Rayleigh-Backscattering-Induced Distortion in Radio over Fiber Systems for Radioastronomic Applications

Radio over Fiber (RoF) Systems exploiting a direct modulation of the laser source are presently utilized within important Radioastronomic scenarios. Due to the particular operating conditions of some of these realizations, the phenomena which typically generate nonlinearities in RoF links for telecommunications applications can be here regarded as substantially harmless. However, these same operating conditions can make the RoF systems vulnerable to different kinds of nonlinear effects, related to the influence of the Rayleigh Backscattered signal on the transmitted one. A rigorous description of the phenomenon is performed, and an effective countermeasure to the problem is proposed and demonstrated, both theoretically and experimentally.Comment: Accepted for publication in IEEE/OSA Journal of Lightwave Technolog

An End-to-End Solution for Enabling Urban Cyclability: The Bike2Work Experience

Mobility plays a fundamental role in modern cities. How citizens experience the city, access its core services, and participate in city life, strongly depends on its mobility organization and efficiency. The challenges that municipalities face are very ambitious: on the one hand, administrators must guarantee their citizens the right to mobility and to easily access local services; on the other hand, they need to minimize the economic, social, and environmental costs of the mobility system. Municipalities are increasingly facing problems of traffic congestion, road safety, energy dependency and air pollution, and therefore encouraging a shift towards sustainable mobility habits based on active mobility is of central importance. Active modes, such as cycling, should be particularly encouraged, especially for local recurrent journeys (i.e., home-to-school, home-to-work). In this context, addressing and mitigating commuter-generated traffic requires engaging public and private stakeholders through innovative and collaborative approaches that focus not only on supply (e.g., roads and vehicles) but also on transportation demand management. In this paper, we propose an end-to-end solution for enabling urban cyclability. It supports the companies' Mobility Managers (MMs) acting on the promotion of active mobility for home-to-work commuting, helps the city administrators to understand the needed urban planning interventions, and motivates the citizens to sustainable mobility. To evaluate the effectiveness of the proposed solution we developed two analyses: the first to accurately analyze the user experience and any behaviour change related to the BIKE2WORK initiative, and the second to demonstrate how exploiting the collected data we can inform and possible guide the involved municipality (i.e., Ferrara, a city in Northern Italy) in improving the urban cyclability.Comment: 12 pages, 11 figure