2,186 research outputs found
Critical behaviour and ultrametricity of Ising spin-glass with long-range interactions
Ising spin-glass systems with long-range interactions () are considered. A numerical study of the critical behaviour is
presented in the non-mean-field region together with an analysis of the
probability distribution of the overlaps and of the ultrametric structure of
the space of the equilibrium configurations in the frozen phase. Also in
presence of diverging thermodynamical fluctuations at the critical point the
behaviour of the model is shown to be of the Replica Simmetry Breaking type and
there are hints of a non-trivial ultrametric structure. The parallel tempering
algorithm has been used to simulate the dynamical approach to equilibrium of
such systems.Comment: 15 pages and 12 figure
Re-enacting Early Video Art as a Research Tool for Media Art Histories
This paper will discuss re-enactment as a relevant tool for practice-based research to investigate pioneering video performances and video artworks from the 1970s and 1980s from a theoretical, art-historical and curatorial point of view. Since the early 2000s, the re-enactment of artists’ performance has been growing as an art practice internationally and has been investigated in several studies and exhibitions. In this paper, I will pro- pose that the re-enactment of early video artworks can open up critical analysis on the original work—its nature, form and content—as well as on collective and personal memory and mediation. Re-enactment becomes a research tool that investigates the nature of video which was at the time a relatively new medium. Re-enactment informs the research into the original piece, its documentation, the relationships between the artist and the body, the work and the viewer. It investigates the effects of analogue video on the viewer and the artist in comparison with the digital video employed in the re-enactment and its documentation. The paper will analyse case studies from the research projects REWIND, REWINDItalia and EWVA (European Women’s Video Art in the 70s and 80s)
Interventions, Productions and Collaborations:the relationship between RAI and visual artists
On 17 May 1952, before RAI Radiotelevisione Italiana Studios began their regular broadcast from Milan, the Spatialist painter and sculptor Lucio Fontana broadcast his own experimental 'artwork' on Italian television, beginning a fruitful relationship between RAI and visual artists. For some, such as the painter Mario Sasso and the Arte Povera artist Pino Pascali, it provided careers as designers and art directors. For others, such as Carlo Quartucci and Gianni Toti, who were given unique access to RAI's television apparatus, it was an opportunity to explore their own artistic experimentations with an expensive and exclusive medium. RAI also hosted seminal artists' performances on-screen including John Cage and Fabio Mauri. This article, based on documents and interviews collected during the Arts and Humanities Research Council-funded project REWINDItalia, discusses these and other seminal cases as well as tracing and assessing the history of this fruitful and complex exchange between RAI and visual artists
First Order Phase Transition and Phase Coexistence in a Spin-Glass Model
We study the mean-field static solution of the Blume-Emery-Griffiths-Capel
model with quenched disorder, an Ising-spin lattice gas with quenched random
magnetic interaction. The thermodynamics is worked out in the Full Replica
Symmetry Breaking scheme. The model exhibits a high temperature/low density
paramagnetic phase. When the temperature is decreased or the density increased,
the system undergoes a phase transition to a Full Replica Symmetry Breaking
spin-glass phase. The nature of the transition can be either of the second
order
(like in the Sherrington-Kirkpatrick model) or, at temperature below a given
critical value (tricritical point), of the first order in the Ehrenfest sense,
with a discontinuous jump of the order parameter and a latent heat. In this
last case coexistence of phases occurs.Comment: 4 pages, 8 figure
A simple spin model for three steps relaxation and secondary proccesses in glass formers
A number of general trends are known to occur in systems displaying secondary
processes in glasses and glass formers. Universal features can be identified as
components of large and small cooperativeness whose competition leads to excess
wings or apart peaks in the susceptibility spectrum. To the aim of
understanding such rich and complex phenomenology we analyze the behavior of a
model combining two apart glassy components with a tunable different
cooperativeness. The model salient feature is, indeed, based on the competition
of the energetic contribution of groups of dynamically relevant variables,
e.g., density fluctuations, interacting in small and large sets. We investigate
how the model is able to reproduce the secondary processes physics without
further ad hoc ingredients, displaying known trends and properties under
cooling or pressing.Comment: 11 Pages, 11 Figure
Complexity of waves in nonlinear disordered media
The statistical properties of the phases of several modes nonlinearly coupled
in a random system are investigated by means of a Hamiltonian model with
disordered couplings. The regime in which the modes have a stationary
distribution of their energies and the phases are coupled is studied for
arbitrary degrees of randomness and energy. The complexity versus temperature
and strength of nonlinearity is calculated. A phase diagram is derived in terms
of the stored energy and amount of disorder. Implications in random lasing,
nonlinear wave propagation and finite temperature Bose-Einstein condensation
are discussed.Comment: 20 pages, 11 Figure
Reply to Comment on ``Spherical 2+p spin-glass model: an analytically solvable model with a glass-to-glass transition''
In his Comment, Krakoviack [Phys. Rev. B (2007)] finds that the phase
behavior of the s+p spin-glass model is different from what proposed by
Crisanti and Leuzzi [Phys. Rev. B 73, 014412 (2006)] if s and p are larger than
two and are separated well enough. He proposes a trial picture, based on a one
step replica symmetry breaking solution, displaying a mode-coupling-like
glass-to-glass transition line ending in a A3 singularity. However, actually,
the physics of these systems changes when p-s is large, the instability of
which the one step replica symmetry breaking glassy phase suffers turns out to
be so wide ranging that the whole scenario proposed by Krakoviack must be
seriously reconsidered.Comment: 4 pages, 5 figure; reply to arXiv:0705.3187. To be published in Phys
Rev B 76 (2007
The K-sat problem in a simple limit
We compute the thermodynamic properties of the 3-satisfiability problem in
the infinite connectivity limit. In this limit the computations can be strongly
simplified and the thermodynamical properties can be obtained with an high
accuracy. We find evidence for a continuous replica symmetry breaking in the
region of high number of clauses, .Comment: 9 pages, 6 figures. To appear in J. Stat. Phys. Minor change
The disordered Backgammon model
In this paper we consider an exactly solvable model which displays glassy
behavior at zero temperature due to entropic barriers. The new ingredient of
the model is the existence of different energy scales or modes associated to
different relaxational time-scales. Low-temperature relaxation takes place by
partial equilibration of successive lower energy modes. An adiabatic scaling
solution, defined in terms of a threshold energy scale \eps^*, is proposed.
For such a solution, modes with energy \eps\gg\eps^* are equilibrated at the
bath temperature, modes with \eps\ll\eps^* remain out of equilibrium and
relaxation occurs in the neighborhood of the threshold \eps\sim \eps^*. The
model is presented as a toy example to investigate conditions related to the
existence of an effective temperature in glassy systems and its possible
dependence on the energy sector probed by the corresponding observable.Comment: 24 pages, 11 figure
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