The Atrium of San Marco in Venice. The Genesis of the Genesis Mosaics and their Medieval Reality

Bericht der Organisatoren: Die Tagung wollte ein Zeichen setzen: ein Zeichen, dass es geboten sei, sich erneut der Cotton Genesis und ihrem ausdrücklichsten mittelalterlichen Nachfahren, den Schöpfungsmosaiken der Vorhalle von San Marco in Venedig, zuzuwenden. Die Diskussion dieser Verbindung von frühchristlichen Illuminationen, die nur noch in wenigen verkohlten Fragmenten überliefert sind, mit den mittelalterlichen Mosaiken ist seit der Entdeckung durch Johan Jakob Tikkanen 1889 geführt worden. Sie kam 1986 mit der Edition der Cotton Genesis durch Kurt Weitzmann und Herbert Kessler zu einem vorläufigen Abschluss. Die Mosaiken erschienen als weitgehend getreue Kopie der Buchmalereien der Handschrift, die dabei allein redaktionelle, aber keine konzeptionelle Veränderungen durch die Mosaizisten erfahren hätten..

Le Regard du mauvais (œil)

Cet article reconsidère la distinction faite par Meyer Schapiro entre l’art en tant qu’objet esthétique (« objet pour l’œil ») et l’art en tant que « véhicule de doctrine ». Il étudie en particulier un triptyque en ivoire du xiie siècle (actuellement au Museo nazionale del Bargello à Florence) où figure d’une part le Christ terrassant les bêtes et d’autre part saint Michel tuant le Démon. D’après son analyse du paradigme du mauvais œil dans l’art médiéval, qui protège contre le « désir des yeux », l’auteur avance que ce paradigme s’appuie sur une interaction réflexive entre les deux modèles présentés par Schapiro et conclut en disant que : « Regarder l’art roman est une psychomachia, une bataille pour l’âme du spectateur ».This article looks over Meyer Schapiro's distinction between art as an aesthetic object ("object for the eye") and art as a "vehicle of doctrine". More precisely, it examines a XIIth century ivory triptych (currently at the Museo Nazionale del Bargello in Florence), where on one side Christ bombarded the animals and on the other St Michael killed the Demon. According to his analysis of the paradigm of the evil eye in medieval art, as a protection against the "desire of the eyes", the author proposes that this paradigm is based on a reflexive interaction between the two models presented by Schapiro and concludes by saying that "to look at Romanesque art is a psychomachia, a battle for the soul of the spectator"

"Contra os judeus, hereges e sarracenos que dizem que nós adoramos ídolos": a arte como ortodoxia

Writings about art and indeed art itself during the Middle Ages often targeted Jews, and to a lesser extent Muslims, when defending material images. This paper explores a third group, heretics, by analyzing the arguments about the use of art advanced at the Council of Arras in 1025 and depictions related to them.Escritos sobre a arte, assim como as próprias obras de arte, frequentemente atacavam os judeus e, em uma medida menor, os muçulmanos, na defesa das imagens materiais durante a Idade Média. Este artigo explora um terceiro grupo, os hereges, analisando os argumentos a respeito do uso da arte propostos no Concílio de Arras, em 1025, figurações relacionadas a eles

Propagating mode-I fracture in amorphous materials using the continuous random network (CRN) model

We study propagating mode-I fracture in two dimensional amorphous materials using atomistic simulations. We used the continuous random network (CRN) model of an amorphous material, creating samples using a two dimensional analogue of the WWW (Wooten, Winer & Weaire) Monte-Carlo algorithm. For modeling fracture, molecular-dynamics simulations were run on the resulting samples. The results of our simulations reproduce the main experimental features. In addition to achieving a steady-state crack under a constant driving displacement (which had not yet been achieved by other atomistic models for amorphous materials), the runs show micro-branching, which increases with driving, transitioning to macro-branching for the largest drivings. Beside the qualitative visual similarity of the simulated cracks to experiment, the simulation also succeeds in explaining the experimentally observed oscillations of the crack velocity

Front Propagation up a Reaction Rate Gradient

We expand on a previous study of fronts in finite particle number reaction-diffusion systems in the presence of a reaction rate gradient in the direction of the front motion. We study the system via reaction-diffusion equations, using the expedient of a cutoff in the reaction rate below some critical density to capture the essential role of fl uctuations in the system. For large density, the velocity is large, which allows for an approximate analytic treatment. We derive an analytic approximation for the front velocity depe ndence on bulk particle density, showing that the velocity indeed diverge s in the infinite density limit. The form in which diffusion is impleme nted, namely nearest-neighbor hopping on a lattice, is seen to have an essential impact on the nature of the divergence

Does the continuum theory of dynamic fracture work?

We investigate the validity of the Linear Elastic Fracture Mechanics approach to dynamic fracture. We first test the predictions in a lattice simulation, using a formula of Eshelby for the time-dependent Stress Intensity Factor. Excellent agreement with the theory is found. We then use the same method to analyze the experiment of Sharon and Fineberg. The data here is not consistent with the theoretical expectation.Comment: 4 page

Nonlinear lattice model of viscoelastic Mode III fracture

We study the effect of general nonlinear force laws in viscoelastic lattice models of fracture, focusing on the existence and stability of steady-state Mode III cracks. We show that the hysteretic behavior at small driving is very sensitive to the smoothness of the force law. At large driving, we find a Hopf bifurcation to a straight crack whose velocity is periodic in time. The frequency of the unstable bifurcating mode depends on the smoothness of the potential, but is very close to an exact period-doubling instability. Slightly above the onset of the instability, the system settles into a exactly period-doubled state, presumably connected to the aforementioned bifurcation structure. We explicitly solve for this new state and map out its velocity-driving relation

Arrested Cracks in Nonlinear Lattice Models of Brittle Fracture

We generalize lattice models of brittle fracture to arbitrary nonlinear force laws and study the existence of arrested semi-infinite cracks. Unlike what is seen in the discontinuous case studied to date, the range in driving displacement for which these arrested cracks exist is very small. Also, our results indicate that small changes in the vicinity of the crack tip can have an extremely large effect on arrested cracks. Finally, we briefly discuss the possible relevance of our findings to recent experiments.Comment: submitted to PRE, Rapid Communication

Phase-Field Model of Mode III Dynamic Fracture

We introduce a phenomenological continuum model for mode III dynamic fracture that is based on the phase-field methodology used extensively to model interfacial pattern formation. We couple a scalar field, which distinguishes between ``broken'' and ``unbroken'' states of the system, to the displacement field in a way that consistently includes both macroscopic elasticity and a simple rotationally invariant short scale description of breaking. We report two-dimensional simulations that yield steady-state crack motion in a strip geometry above the Griffith threshold.Comment: submitted to PR

Steady-State Cracks in Viscoelastic Lattice Models

We study the steady-state motion of mode III cracks propagating on a lattice exhibiting viscoelastic dynamics. The introduction of a Kelvin viscosity $\eta$ allows for a direct comparison between lattice results and continuum treatments. Utilizing both numerical and analytical (Wiener-Hopf) techniques, we explore this comparison as a function of the driving displacement $\Delta$ and the number of transverse sites $N$. At any $N$, the continuum theory misses the lattice-trapping phenomenon; this is well-known, but the introduction of $\eta$ introduces some new twists. More importantly, for large $N$ even at large $\Delta$, the standard two-dimensional elastodynamics approach completely misses the $\eta$-dependent velocity selection, as this selection disappears completely in the leading order naive continuum limit of the lattice problem.Comment: 27 pages, 8 figure