THE "ART OF WAR FRIEZE" IN URBINO: A BLEND OF VIRTUAL RECONSTRUCTION AND SCIENTIFIC ACCURACY

The Art of War Frieze was commissioned by Federico da Montefeltro, Duke of Urbino, to decorate the back of the «wing façade» of the Ducal palace. The Frieze decorated the façade from the time it was realised towards the end of the XVth century until 1756. The Frieze consists of a very particular series of seventy-two limestone bas-reliefs, whose iconographic repertoire represents numerous war and building machines as well as military and political symbols. After it broke away from the outdoor façade it was stored in different rooms in the Palace but despite the many documentary records available, the question of the original sequence of the basreliefs has never been resolved. The primary scope of this paper is to create a "virtual" reconstruction of the original sequence of the bas-reliefs, starting from historical and iconographic records, an analysis of the back and the individual panels using a laser scanner and fully automatic open source photo modelling technologies like the Arc3d, and photogrammetric systems like Image Master together with analyses of the state of conservation, type of degradation correlated to atmospheric parameters (sunlight, temperature, rain). Tests will then be carried out with different systems in order to confirm the accuracy of the model if it is decided to reproduce the individual panels using the rapid prototyping technique associated to a study of the execution techniques

A MULTIDISCIPLINARY DOCUMENTAL REPRESENTATION METHOD FOR KINETIC AND ENVIRONMENTAL ART

Abstract. The contribution addresses the definition of a new collaborative documental method for designing and managing the different phases of conservation of kinetic-programmed art. Our approach consists of developing a new representative model that includes both mechanical parts and spatial characteristics. The research stems from a specific case-study, Ambiente – Strutturazione a parametri virtuali (1969) by Gabriele Devecchi, permanently displayed at Museo del '900 in Milan since 2010. Starting from the dimensional and technical data, we obtained a graphical model of lamps 2D and 3D. They were enriched by a detailed abacus describing all the elements and by specific maps capturing all the phases of regular and extraordinary maintenance underwent by the environment. The second part was carried out with a report about physical motion. The goal has been representing speed and geometry of the movement inside the space. By merging the first part of the documenting process and the second one we've got a graphic digital model including information about the individual parts of the installation and their mechanical interaction. The third and last step is ongoing and tackles the challenge of using virtual technologies for the description of the whole environment. Thanks to a collaboration between technicians and theoretic scholars, we attempted to match the study of the physical motion and all data about the structural parts with the careful consideration of historical-artistic and perception-related features. The work led to the conclusion that a virtual, immersive reproduction of the environment is not enough for deeply understanding the experience enjoyed by users inside it, because it misses the embodied perception activated by the artwork. For this reason, this study may be considered as a step in a broader research path about documentation of complex environmental, immersive, kinetic works of art.</p

Infinite-Dimensional Representations of 2-Groups

A "2-group" is a category equipped with a multiplication satisfying laws like those of a group. Just as groups have representations on vector spaces, 2-groups have representations on "2-vector spaces", which are categories analogous to vector spaces. Unfortunately, Lie 2-groups typically have few representations on the finite-dimensional 2-vector spaces introduced by Kapranov and Voevodsky. For this reason, Crane, Sheppeard and Yetter introduced certain infinite-dimensional 2-vector spaces called "measurable categories" (since they are closely related to measurable fields of Hilbert spaces), and used these to study infinite-dimensional representations of certain Lie 2-groups. Here we continue this work. We begin with a detailed study of measurable categories. Then we give a geometrical description of the measurable representations, intertwiners and 2-intertwiners for any skeletal measurable 2-group. We study tensor products and direct sums for representations, and various concepts of subrepresentation. We describe direct sums of intertwiners, and sub-intertwiners--features not seen in ordinary group representation theory. We classify irreducible and indecomposable representations and intertwiners. We also classify "irretractable" representations--another feature not seen in ordinary group representation theory. Finally, we argue that measurable categories equipped with some extra structure deserve to be considered "separable 2-Hilbert spaces", and compare this idea to a tentative definition of 2-Hilbert spaces as representation categories of commutative von Neumann algebras

Group field theory and simplicial gravity path integrals: A model for Holst-Plebanski gravity

In a recent work, a dual formulation of group field theories as non-commutative quantum field theories has been proposed, providing an exact duality between spin foam models and non-commutative simplicial path integrals for constrained BF theories. In light of this new framework, we define a model for 4d gravity which includes the Immirzi parameter gamma. It reproduces the Barrett-Crane amplitudes when gamma goes to infinity, but differs from existing models otherwise; in particular it does not require any rationality condition for gamma. We formulate the amplitudes both as BF simplicial path integrals with explicit non-commutative B variables, and in spin foam form in terms of Wigner 15j-symbols. Finally, we briefly discuss the correlation between neighboring simplices, often argued to be a problematic feature, for example, in the Barrett-Crane model.Comment: 26 pages, 1 figur

Hidden Quantum Gravity in 4d Feynman diagrams: Emergence of spin foams

We show how Feynman amplitudes of standard QFT on flat and homogeneous space can naturally be recast as the evaluation of observables for a specific spin foam model, which provides dynamics for the background geometry. We identify the symmetries of this Feynman graph spin foam model and give the gauge-fixing prescriptions. We also show that the gauge-fixed partition function is invariant under Pachner moves of the triangulation, and thus defines an invariant of four-dimensional manifolds. Finally, we investigate the algebraic structure of the model, and discuss its relation with a quantization of 4d gravity in the limit where the Newton constant goes to zero.Comment: 28 pages (RevTeX4), 7 figures, references adde

La documentazione per una conservazione "sostenibile" come il digital può integrare il lavoro dei restauratori

I beni culturali sono spesso definiti i giacimenti inesauribili da cui l’Italia attinge. I cittadini che ogni giorno vivono il nostro patrimonio gli assegnano un significato collettivo e personale, caratterizzandolo di valori che si creano e si rigenerano nel tempo . Nella convinzione che questi valori siano la personalità e la qualità di una cittadinanza evoluta e contemporanea, la conservazione dei beni culturali è necessariamente argomento che interessa tutti, esperti e non. Il grande tema della salvaguardia del patrimonio diventa così argomento dell’intera società, che deve quotidianamente essere informata sul suo stato di salute, in un’ottica di partecipazione culturale e sociale a più livelli. Il mondo della conservazione deve integrare alle sue pratiche scientificamente consolidate l’approccio digitale, che prevede la progettazione di nuovi percorsi supportati dall’uso di nuovi strumenti. L’obiettivo ultimo si auspica sia la definizione di un modello documentale digitale che possa contenere al suo interno informazioni tecniche specifiche e dal quale partire per elaborare una comunicazione diretta e di immediata lettura. Il processo di restauro adempie così al suo scopo originale, di ri-accessibilità dell’arte e democratizzazione dei messaggi in essa contenuti

Non-commutative flux representation for loop quantum gravity

The Hilbert space of loop quantum gravity is usually described in terms of cylindrical functionals of the gauge connection, the electric fluxes acting as non-commuting derivation operators. It has long been believed that this non-commutativity prevents a dual flux (or triad) representation of loop quantum gravity to exist. We show here, instead, that such a representation can be explicitly defined, by means of a non-commutative Fourier transform defined on the loop gravity state space. In this dual representation, flux operators act by *-multiplication and holonomy operators act by translation. We describe the gauge invariant dual states and discuss their geometrical meaning. Finally, we apply the construction to the simpler case of a U(1) gauge group and compare the resulting flux representation with the triad representation used in loop quantum cosmology.Comment: 12 pages, matches published versio

Hidden Quantum Gravity in 3d Feynman diagrams

In this work we show that 3d Feynman amplitudes of standard QFT in flat and homogeneous space can be naturally expressed as expectation values of a specific topological spin foam model. The main interest of the paper is to set up a framework which gives a background independent perspective on usual field theories and can also be applied in higher dimensions. We also show that this Feynman graph spin foam model, which encodes the geometry of flat space-time, can be purely expressed in terms of algebraic data associated with the Poincare group. This spin foam model turns out to be the spin foam quantization of a BF theory based on the Poincare group, and as such is related to a quantization of 3d gravity in the limit where the Newton constant G_N goes to 0. We investigate the 4d case in a companion paper where the strategy proposed here leads to similar results.Comment: 35 pages, 4 figures, some comments adde

Quantum gravity as a group field theory: a sketch

We give a very brief introduction to the group field theory approach to quantum gravity, a generalisation of matrix models for 2-dimensional quantum gravity to higher dimension, that has emerged recently from research in spin foam models.Comment: jpconf; 8 pages, 9 figures; to appear in the Proceedings of the Fourth Meeting on Constrained Dynamics and Quantum Gravity, Cala Gonone, Italy, September 12-16, 200

Group field theory formulation of 3d quantum gravity coupled to matter fields

We present a new group field theory describing 3d Riemannian quantum gravity coupled to matter fields for any choice of spin and mass. The perturbative expansion of the partition function produces fat graphs colored with SU(2) algebraic data, from which one can reconstruct at once a 3-dimensional simplicial complex representing spacetime and its geometry, like in the Ponzano-Regge formulation of pure 3d quantum gravity, and the Feynman graphs for the matter fields. The model then assigns quantum amplitudes to these fat graphs given by spin foam models for gravity coupled to interacting massive spinning point particles, whose properties we discuss.Comment: RevTeX; 28 pages, 21 figure