Misleading inferences from discretization of empty spacetime: Snyder-noncommutativity case study

Alternative approaches to the study of the quantum-gravity problem are handling the role of spacetime very differently. Some are focusing on the analysis of one or another novel formulation of "empty spacetime", postponing to later stages the introduction of particles and fields, while other approaches assume that spacetime should only be an emergent entity. We here argue that recent progress in the covariant formulation of quantum mechanics suggests that empty spacetime is not physically meaningful. We illustrate our general thesis in the specific context of the noncommutative Snyder spacetime, which is also of some intrinsic interest, since hundreds of studies were devoted to its analysis. We show that empty Snyder spacetime, described in terms of a suitable kinematical Hilbert space, is discrete, but this is only a formal artifact: the discreteness leaves no trace on the observable properties of particles on the physical Hilbert space.Comment: 6 page

Biosystematics of European species of carnivorous genus Utricularia (Lamiales, angiosperms)

Utricularia is a genus of carnivorous plants catching its preys using small traps. In Europe, seven aquatic species occur. They rarely flower and the species identification, using only vegetative parts, is difficult. Except flowers, according to literature, teeth on the lateral margin of the ultimate leaf segments should discriminate U. australis from U. vulgaris (“U. vulgaris aggregate”). Concerning U. intermedia/U. ochroleuca/U. stygia complex (“U. intermedia aggregate”), the number of teeth on the leaf margin, the ultimate leaf segment apex shape and the quadrifid gland features are considered crucial for species distinction. However, the reliability of these features has never been tested from a quantitative and statistical perspective. About quadrifid glands inside traps, previous authors stated that all the Scandinavian species might be distinguished by their features. The present study was focused on morphological and geometric morphometric investigations in order to quantitatively test the reliability of the features of vegetative parts reported as diagnostic in literature. Also, molecular analysis were performed to the search for DNA barcodes and to reconstruct the phylogenetic relationships, using nuclear ITS and plastidial trnL-F IGS and rps16 intron markers. Some morphological characters revealed to be potentially useful for species discrimination (e.g. teeth on leaf margin in U. intermedia aggregate), while others resulted unreliable. Morphometric analysis of the quadrifid glands was not able to discriminate between the whole set of species, but may be diagnostic for species in U. intermedia aggregate. Generally, Barcoding approach failed to discriminate species, even if it could be of some help in U. minor aggregate. Indeed, with few exceptions, U. bremii shows peculiar DNA regions different from U. minor for both plastidial markers investigated. However, interesting hypotheses could be derived from phylogenetic networks and trees obtained, including hybridization events to explain the rise of the mostly sterile species, such as U. stygia. This species clusters with the other species of U. intermedia aggregate in plastidial phylogenies, while it is closely related to species of U. minor aggregate in ITS phylogeny. Also U. ochroleuca shows some incongruences considering the different markers, at least for some accessions, pointing to the possible occurrence of hybrids

Indagini biosistematiche volte a chiarire l'origine del giacinto di Webb (Bellevalia webbiana Parl.)

Il seguente lavoro sperimentale si pone l’obiettivo di fare luce sull’origine del giacinto di Webb (Bellevalia webbiana Parl.), specie endemica dell’Italia centrale, tetraploide con 2n=4x=16. Sono state valutate le possibilità di origine autopoliploide o allopoliploide, compiendo analisi di tipo filogenetico molecolare e di tipo citogenetico. In particolare,è stata ricostruita la filogenesi delle specie italiane del genere Bellevalia tramite il marcatore plastidiale trnL-trnF (spaziatore intergenico tra il gene codificante il trna della leucina e quello della fenilalanina) e sono state utilizzate la tecnica GISH (Genomic In Situ Hybridization), per valutare l’eventuale contributo di alcune specie (B. boissieri, B. trifoliata e B. ciliata) alla formazione allopoliploide di B. webbiana, e la tecnica FISH (Fluorescence In Situ Hybridization), applicata alle regioni 45S e 5S dei cromosomi di B. webbiana, per una migliore caratterizzazione del cariotipo da confrontare con quello delle presunte specie parentali. I risultati ottenuti confermano una forte affinità tra il giacinto di Webb e le presunte specie parentali considerate, per cui si può sostenere, con buona probabilità, un coinvolgimento di alcune di queste, se non di tutte, in un evento di allopoliploidia. La specie B. boissieri appare come la candidata più solida, anche se si dovesse riconsiderare l’ipotesi di un’origine autopoliploide, non smentita dai risultati ottenuti. Si riscontrano rapporti filogenetici diversi tra B. trifoliata e B. webbiana, a seconda che si consideri l’analisi plastidiale qui prodotta e l’analisi nucleare (marcatore ITS) prodotta in altro studio. Mettendo insieme tutti i dati esistenti su queste specie, si può formulare un’ipotesi di allopoliploidia, con B. boissieri specie donatrice di ovuli e B. trifoliata specie donatrice di polline

Taxonomy, typification and karyology of Crepis lacera (Asteraceae)

Crepis lacera is a diploid species (2n = 8), mostly occurring in Italy, with a disjunct population in Albania. The names C. lacera, C. latialis and C. lacera f. titani are here lectotypified, and their taxonomic value is discussed. For the latter name, based on morphological, biogeographical and karyological results, we propose here the subspecific rank (C. lacera subsp. titani stat. nov.). In addition, basal leaf morphology variation, the main distinguishing feature between the two subspecies, is discussed in the light of paedomorphosis, and a distribution map for both subspecies is presented

Relative locality in a quantum spacetime and the pregeometry of κ\kappa-Minkowski

We develop a new description of the much-studied $\kappa$-Minkowski noncommutative spacetime, centered on representing on a single Hilbert space not only the $\kappa$-Minkowski coordinates, but also the associated differential calculus and the $\kappa$-Poincar\'e symmetry generators. In this "pregeometric" representation the relevant operators act on the kinematical Hilbert space of the covariant formulation of quantum mechanics, which we argue is the natural framework for studying the implications of the step from commuting spacetime coordinates to the $\kappa$-Minkowski case, where the spatial coordinates do not commute with the time coordinate. The empowerment provided by this kinematical-Hilbert space representation allows us to give a crisp characterization of the "fuzziness" of $\kappa$-Minkowski spacetime, whose most striking aspect is a relativity of spacetime locality. We show that relative locality, which had been previously formulated exclusively in classical-spacetime setups, for a quantum spacetime takes the shape of a dependence of the fuzziness of a spacetime point on the distance at which an observer infers properties of the event that marks the point.Comment: 10 pages. This is a more polished version of the manuscript. Technical results and Fig.1 unchanged. A Fig.2 has been added highlighting an analogy between relative simultaneity and relative localit

Genetic differentiation among populations of the threatened Bellevalia webbiana (Asparagaceae) and its consequence on conservation

The narrow central Italian endemic and threatened Webb's hyacinth (Bellevalia webbiana), a perennial herb, is a clear example of a species that has disappeared from several localities due to the de..

Chromosome numbers for the Italian flora: 8

In this contribution, new chromosome data obtained on material collected in Italy are presented. It includes three chromosome counts from two taxa endemic to Southern Italy (Centaurea subtilis and Onobrychis alba subsp. echinata) and one species (Poa ligulata) occurring in Italy with only one recently discovered population

Gravity's weight on worldline fuzziness

We investigate a connection between recent results in 3D quantum gravity, providing an effective noncommutative-spacetime description, and some earlier heuristic descriptions of a quantum-gravity contribution to the fuzziness of the worldlines of particles. We show that 3D-gravity-inspired spacetime noncommutativity reflects some of the features suggested by previous heuristic arguments. Most notably, gravity-induced worldline fuzziness, while irrelevantly small on terrestrial scales, could be observably large for propagation of particles over cosmological distances.Comment: 8 pages. This essay received an honorable mention in the 2012 Essay Competition of the Gravity Research Foundatio