Trigonometry of spacetimes: a new self-dual approach to a curvature/signature (in)dependent trigonometry

A new method to obtain trigonometry for the real spaces of constant curvature and metric of any (even degenerate) signature is presented. The method encapsulates trigonometry for all these spaces into a single basic trigonometric group equation. This brings to its logical end the idea of an absolute trigonometry, and provides equations which hold true for the nine two-dimensional spaces of constant curvature and any signature. This family of spaces includes both relativistic and non-relativistic homogeneous spacetimes; therefore a complete discussion of trigonometry in the six de Sitter, minkowskian, Newton--Hooke and galilean spacetimes follow as particular instances of the general approach. Any equation previously known for the three classical riemannian spaces also has a version for the remaining six spacetimes; in most cases these equations are new. Distinctive traits of the method are universality and self-duality: every equation is meaningful for the nine spaces at once, and displays explicitly invariance under a duality transformation relating the nine spaces. The derivation of the single basic trigonometric equation at group level, its translation to a set of equations (cosine, sine and dual cosine laws) and the natural apparition of angular and lateral excesses, area and coarea are explicitly discussed in detail. The exposition also aims to introduce the main ideas of this direct group theoretical way to trigonometry, and may well provide a path to systematically study trigonometry for any homogeneous symmetric space.Comment: 51 pages, LaTe

L'umano nell'uomo: Vasilij Grossman tra ideologie e domande eterne

Vasilij Grossman (1905-1964) s'impone solo ora, con il recente successo delle ripubblicazioni in diverse lingue del suo capolavoro postumo Vita e destino, come una delle figure artistiche e filosofiche pi\uf9 interessanti del XX secolo. La dimensione letteraria di Grossman che affonda le radici nella pi\uf9 alta tradizione russa - \ue8 votata ad un realismo classico, aperto all'universale, costantemente teso all'espressione di domande ultime ed eterne che affermano l'uomo e la sua libert\ue0 contro il potere dell'ideologia. L'umano nell'uomo \ue8 questo nucleo originale presente in ogni uomo che impedisce al potere di schiacciare il singolo nella morsa dell'omologazione. Tra i meandri oscuri della storia del Novecento, la risposta di Grossman non \ue8 da intendersi solo in senso intellettuale: \ue8 una strada reale che la letteratura, nella sua bellezza "incarnata", manifesta come possibilit\ue0 aperta all'esperienza di ciascuno. I saggi che compongono questo volume il secondo di studi collettanei su Grossman - rappresentano un passo decisivo verso una conoscenza completa della vita e dell'opera del grande autore russo e ne documentano l'appartenenza ai classici della letteratura di ogni tempo

Cultura e ideologia nei vocabolari. Lessicografia russa e italiana a confronto

Il volume prende in esame la relazione fra lingua, cultura e ideologia nella lessicografia italiana e russa, evidenziando l'imprescindibilit\ue0 della conoscenza del contesto culturale per la ricostruzione inferenziale degli impliciti culturali del lessicografo. Particolare attenzione viene inoltre rivolta ai possibili usi manipolatori delle voci dizionariali, attraverso l'analisi delle voci lessicografiche di parole ideologicamente sensibili.The volume highlights the relationship between language, culture and ideology in Italian and Russian lexicography, with a focus on the relevance of the knowledge of the cultural context for the inferential reconstruction of the lexicographer's implicit cultural presuppositions. Possible manipulative uses of dictionary entries are also exploited through an in-depth analysis of the lexicographic voice of ideologically sensitive words

Openstate: Programming platform-independent stateful openflow applications inside the switch

Software Defined Networking envisions smart centralized controllers governing the forwarding behavior of dumb low-cost switches. But are "dumb" switches an actual strategic choice, or (at least to some extent) are they a consequence of the lack of viable alternatives to OpenFlow as programmatic data plane forwarding interface? Indeed, some level of (programmable) control logic in the switches might be beneficial to offload logically centralized controllers (de facto complex distributed systems) from decisions just based on local states (versus network-wide knowledge), which could be handled at wire speed inside the device itself. Also, it would reduce the amount of flow processing tasks currently delegated to specialized middleboxes. The underlying challenge is: can we devise a stateful data plane programming abstraction (versus the stateless OpenFlow match/action table) which still entails high performance and remains consistent with the vendors' preference for closed platforms? We posit that a promising answer revolves around the usage of extended finite state machines, as an extension (super-set) of the OpenFlow match/action abstraction. We concretely turn our proposed abstraction into an actual table-based API, and, perhaps surprisingly, we show how it can be supported by (mostly) reusing core primitives already implemented in OpenFlow devices

Cultura e ideologia nei vocabolari. Lessicografia russa e italiana a confronto

Il volume si pone il duplice obiettivo di illuminare la relazione fra lingua, cultura e ideologia nella lessicografia italiana e russa, e di offrire uno strumento per la consultazione dei vocabolari russi e bilingui, mostrando quanto essa richieda sia competenza tecnica (familiarità con i tecnicismi, con numerose categorie semantiche e grammaticali, sigle ecc.) sia acutezza ermeneutica, basata sulla conoscenza del contesto culturale in cui sono stati prodotti i testi a cui il vocabolario fa riferimento, così da ricostruire in modo inferenziale gli impliciti culturali del lessicografo, presenti nel suo processo interpretativo. Scopo del libro è mostrare che le parole, per il fatto stesso di circoscrivere concetti, interpretano la realtà, veicolano un certo modo di vederla e, dunque, una certa cultura; inoltre, quando le componenti implicite vengono imposte in modo occulto dal lessicografo mediante la compilazione delle voci dizionariali, senza essere condivise dai parlanti, nei vocabolari si attua una manipolazione ideologica del lessico. Ciò viene mostrato dagli autori analizzando le voci lessicografiche di lessemi ideologicamente sensibili, di cui è possibile esporre la semantica in modo strumentale e parziale

Micro SIDs: A Solution for Efficient Representation of Segment IDs in SRv6 Networks

The Segment Routing (SR) architecture is based on source routing. Within an SR enabled network, a list of instructions called segments can be added to the packet headers to influence the forwarding and the processing of the packets. In SRv6 (Segment Routing over IPv6 data plane) the segments are represented with IPv6 addresses, which are 16 bytes long. There are some SRv6 service scenarios that may require to carry a large number of segments in the IPv6 packet headers. Reducing the size of these overheads is useful to minimize the impact on MTU (Maximum Transfer Unit) and to enable SRv6 on legacy hardware devices with limited processing capabilities that could suffer from the long headers. In this paper we present the Micro SID solution for the efficient representation of segment identifiers. The proposed Micro SID solution has been implemented on three different architectures (VPP, Linux, P4) and interoperability tests have been performed. We also analyze the reduction of the header size that can be achieved with Micro SIDs and compare it with other proposals for segment list compression. Our results show that the header size can be reduced up to 75%. Finally, we mention that a fundamental asset of the proposed Micro SID solution is the full compatibility and seamless interoperability with existing SRv6 architecture

Micro SIDs: A solution for Efficient Representation of Segment IDs in SRv6 Networks

The Segment Routing (SR) architecture is based on loose source routing. A list of instructions, called segments can be added to the packet headers, to influence the forwarding and the processing of the packets in an SR enabled network. In SRv6 (Segment Routing over IPv6 data plane) the segments are represented with IPv6 addresses, which are 16 bytes long. There are some SRv6 service scenarios that may require to carry a large number of segments in the IPv6 packet headers. Reducing the size of these overheads is useful to minimize the impact on MTU (Maximum Transfer Unit) and to enable SRv6 on legacy hardware devices with limited processing capabilities that could suffer the long headers. In this paper we present the Micro SID solution for the efficient representation of segment identifiers. With this solution, the length of the segment list can be drastically reduced