Right eigenvalue equation in quaternionic quantum mechanics

We study the right eigenvalue equation for quaternionic and complex linear matrix operators defined in n-dimensional quaternionic vector spaces. For quaternionic linear operators the eigenvalue spectrum consists of n complex values. For these operators we give a necessary and sufficient condition for the diagonalization of their quaternionic matrix representations. Our discussion is also extended to complex linear operators, whose spectrum is characterized by 2n complex eigenvalues. We show that a consistent analysis of the eigenvalue problem for complex linear operators requires the choice of a complex geometry in defining inner products. Finally, we introduce some examples of the left eigenvalue equations and highlight the main difficulties in their solution.Comment: 24 pages, AMS-Te

Quaternionic potentials in non-relativistic quantum mechanics

We discuss the Schrodinger equation in presence of quaternionic potentials. The study is performed analytically as long as it proves possible, when not, we resort to numerical calculations. The results obtained could be useful to investigate an underlying quaternionic quantum dynamics in particle physics. Experimental tests and proposals to observe quaternionic quantum effects by neutron interferometry are briefly reviewed.Comment: 21 pages, 16 figures (ps), AMS-Te

Quaternionic Electroweak Theory and CKM Matrix

We find in our quaternionic version of the electroweak theory an apparently hopeless problem: In going from complex to quaternions, the calculation of the real-valued parameters of the CKM matrix drastically changes. We aim to explain this quaternionic puzzle.Comment: 8, Revtex, Int. J. Theor. Phys. (to be published

Resonant laser tunnelling

We propose an experiment involving a gaussian laser tunneling through a twin barrier dielectric structure. Of particular interest are the conditions upon the incident angle for resonance to occur. We provide some numerical calculations for a particular choice of laser wave length and dielectric refractive index which confirm our expectations.Comment: 15 pages, 6 figure

Relativistic tunneling through opaque barriers

We propose an analytical study of relativistic tunneling through opaque barriers. We obtain a closed formula for the phase time. This formula is in excellent agreement with the numerical simulations and corrects the standard formula obtained by the stationary phase method. An important result is found when the upper limit of the incoming energy distribution coincides with the upper limit of the tunneling zone. In this case, the phase time is proportional to the barrier width.Comment: 11 pages, 3 figure

Expertise locale et étrangère en Palestine: faiblesse, fragmentation et séduction des pratiques urbanistiques

Based on research and intervention direct experiences of the authors in the OPT, this paper offers a contribution about the circulation and exchange of knowledge in the framework of international cooperation, strictly related to the urban planning field of practices. By the effects of the Israeli occupation and the spatial nature of this conflict, in fact, Palestine could be considered as an extreme case of dependence by the International cooperation – above all from the point of view of public legitimacy and economic support – also for the ordinary activities in urban and regional planning and regulation of spaces. The long history of international cooperation, however, does not seem to have contributed so far to diminish weaknesses, fragmentation and the ability to intervene by professionals and local institutions that in this context are the desired outcome of the occupation itself. This poses a crucial question for theoretical reflections as well as for the international cooperation practices, which has led the authors to discuss the ways in which the knowledge of international experts is combined with local ones, starting from analogies and differences in the most widespread ways of thinking and to act in the context of international cooperation related to the planning of the city and the territory. Then 6 " portrait-type of planners", 3 of local planners and 3 of international planners were elaborated, to summarize references and experiences useful to highlight dynamics that seem peculiar and which try to reconnect the training paths, the available networks and the guidelines for action in order to highlight the critical elements of the most frequent and widespread practices. From the effort of synthesis of the peculiarities of the many subjects met and interviewed and the comparison between the portraits it is possible to trac

Sostenibilità & diseguaglianze: misurare senza perdere la complessità

Nell’ambito del lavoro che stiamo conducendo con il tandem ASVIS-Urban@it per la Città Metropolitana di Roma, entro l’opportunità di offrire il nostro supporto all’Ente metropolitano, ci siamo contestualmente proposti di approfondire il senso delle sfide offerte dai diversi Goal dell’Agenda 2030. Nella metodologia condivisa con ASviS stiamo conducendo, innanzitutto, un benchmarking sulle esperienze europee e internazionali, con particolare attenzione alla ricognizione degli obiettivi contenuti nelle strategie, nei piani e nelle politiche europee, nazionali (a partire dalla SNSvS) e regionali, nel quadro dell’Agenda Onu 2030, comprensiva degli strumenti e delle misure atte alla loro attuazione. Ma, proprio entro questo quadro, un primo approfondimento sul Goal 10-Ridurre le diseguaglianze (pensato nelle sue relazioni con il Goal 1-Combattere la povertà) appare particolarmente sfidante per quel che riguarda la misurazione e, quindi, l’effettivo perseguimento degli obiettivi di sviluppo sostenibile alla scala metropolitana. In una fase nella quale diseguaglianze e povertà paiono crescere senza sosta nelle nostre città e nostri territori, i Goal 1 e 10 dell’Agenda 2030 mostrano, forse più di altri, la necessità di essere opportunamente interpretati proprio alla scala delle città europee, dove il tema della povertà e delle diseguaglianze non può essere limitato al confronto tra gli stati ma deve riguardare i diversi territori all’interno dei singoli stati

Packed Memory Arrays – Rewired

The physical memory layout of a tree-based index structure deteriorates over time as it sustains more updates; such that sequential scans on the physical level become non-sequential, and therefore slower. Packed Memory Arrays (PMAs) prevent this by managing all data in a sequential sparse array. PMAs have been studied mostly theoretically but suffer from practical problems, as we show in this paper. We study and fix these problems, resulting in an improved data structure: the Rewired Memory Array (RMA). We compare RMA with the main previous PMA implementations as well as state-of-the-art tree index structures and show on a wide variety of data and query distributions that RMA can reach competitive update and point lookup performance, while always providing superior scan performance – close to dense column scans

Comparison of different techniques to study the nanostructure and the microstructure of cementitious materials with and without superabsorbent polymers

It is difficult to study the microstructural porosity in time without destroying the samples and stopping hydration. Current techniques mainly involve mercury intrusion porosimetry and microscopic analysis. These destructive techniques are able to give information on the microstructure, but the nanostructure is affected due to sample preparation. Dynamic vapour sorption is a technique which is not often used to study the nanostructure of cementitious materials and requires the application of different models. Furthermore, nuclear magnetic resonance can be applied to non-destructive study not only the total water content but also the pore size distribution by comparing the T2 relaxation times, and can be combined with cryoporometry. In this paper, these different measuring techniques are compared and linked to each other. The obtained nano- and microstructures are compared to different models found in literature. Pore sizes in the range of 1.5–2 nm and of 8–12 nm are found, reflecting the gel pores. In addition, some bigger capillary pores are found. The measuring techniques are complementary to each other as they study different pore size ranges and are based on different phenomena.</p

Extending SQL for computing shortest paths

Reachability and shortest paths are among two of the most common queries realized on graphs. While graph frameworks and property graph databases provide an extensive and convenient built-in support for these operations, it is still both clunky and inefficient to perform on standard SQL DBMSs. In this paper, we present an extension to the standard SQL language to compute both reachability predicates and many-to-many shortest path queries. We first describe a methodology to represent a directed graph starting from virtual table expressions. Second, we introduce a new type of operator to compute shortest