3,904 research outputs found
Fracture surfaces of heterogeneous materials: a 2D solvable model
Using an elastostatic description of crack growth based on the Griffith
criterion and the principle of local symmetry, we present a stochastic model
describing the propagation of a crack tip in a 2D heterogeneous brittle
material. The model ensures the stability of straight cracks and allows for the
study of the roughening of fracture surfaces. When neglecting the effect of the
non singular stress, the problem becomes exactly solvable and yields analytic
predictions for the power spectrum of the paths. This result suggests an
alternative to the conventional power law analysis often used in the analysis
of experimental data.Comment: 4 pages, 4 figure
Complex temperatures zeroes of partition function in spin-glass models
An approximate method is proposed for investigating complex-temperature
properties of real-dimensional spin-glass models. The method uses the
complex-temperature data of the ferromagnetic model on the same lattice. The
universality line in the complex-temperature space is obtained.Comment: latex, corrected some misprint
Entropy of Open Lattice Systems
We investigate the behavior of the Gibbs-Shannon entropy of the stationary
nonequilibrium measure describing a one-dimensional lattice gas, of L sites,
with symmetric exclusion dynamics and in contact with particle reservoirs at
different densities. In the hydrodynamic scaling limit, L to infinity, the
leading order (O(L)) behavior of this entropy has been shown by Bahadoran to be
that of a product measure corresponding to strict local equilibrium; we compute
the first correction, which is O(1). The computation uses a formal expansion of
the entropy in terms of truncated correlation functions; for this system the
k-th such correlation is shown to be O(L^{-k+1}). This entropy correction
depends only on the scaled truncated pair correlation, which describes the
covariance of the density field. It coincides, in the large L limit, with the
corresponding correction obtained from a Gaussian measure with the same
covariance.Comment: Latex, 28 pages, 4 figures as eps file
The political import of deconstructionâDerridaâs limits?: a forum on Jacques Derridaâs specters of Marx after 25 Years, part I
Jacques Derrida delivered the basis of The Specters of Marx: The State of the Debt, the Work of Mourning, & the New International as a plenary address at the conference âWhither Marxism?â hosted by the University of California, Riverside, in 1993. The longer book version was published in French the same year and appeared in English and Portuguese the following year. In the decade after the publication of Specters, Derridaâs analyses provoked a large critical literature and invited both consternation and celebration by figures such as Antonio Negri, Wendy Brown and Frederic Jameson. This forum seeks to stimulate new reflections on Derrida, deconstruction and Specters of Marx by considering how the futures past announced by the book have fared after an eventful quarter century. Maja Zehfuss, Antonio VĂĄzquez-Arroyo and Dan Bulley and Bal Sokhi-Bulley offer sharp, occasionally exasperated, meditations on the political import of deconstruction and the limits of Derridaâs diagnoses in Specters of Marx but also identify possible paths forward for a global politics taking inspiration in Derridaâs work of the 1990s
Directed polymer in a random medium of dimension 1+1 and 1+3: weights statistics in the low-temperature phase
We consider the low-temperature disorder-dominated phase of the
directed polymer in a random potentiel in dimension 1+1 (where )
and 1+3 (where ). To characterize the localization properties of
the polymer of length , we analyse the statistics of the weights of the last monomer as follows. We numerically compute the probability
distributions of the maximal weight , the probability distribution of the parameter as well as the average values of the higher order
moments . We find that there exists a
temperature such that (i) for , the distributions
and present the characteristic Derrida-Flyvbjerg
singularities at and for . In particular, there
exists a temperature-dependent exponent that governs the main
singularities and as well as the power-law decay of the moments . The exponent grows from the value
up to . (ii) for , the
distribution vanishes at some value , and accordingly the
moments decay exponentially as in . The
histograms of spatial correlations also display Derrida-Flyvbjerg singularities
for . Both below and above , the study of typical and
averaged correlations is in full agreement with the droplet scaling theory.Comment: 13 pages, 29 figure
Spectral Degeneracies in the Totally Asymmetric Exclusion Process
We study the spectrum of the Markov matrix of the totally asymmetric
exclusion process (TASEP) on a one-dimensional periodic lattice at ARBITRARY
filling. Although the system does not possess obvious symmetries except
translation invariance, the spectrum presents many multiplets with degeneracies
of high order. This behaviour is explained by a hidden symmetry property of the
Bethe Ansatz. Combinatorial formulae for the orders of degeneracy and the
corresponding number of multiplets are derived and compared with numerical
results obtained from exact diagonalisation of small size systems. This
unexpected structure of the TASEP spectrum suggests the existence of an
underlying large invariance group.
Keywords: ASEP, Markov matrix, Bethe Ansatz, Symmetries.Comment: 19 pages, 1 figur
Linguistic incompetence: giving an account of researching multilingually
This paper considers the place of linguistic competence and incompetence in the context of researching multilingually. It offers a critique of the concept of competence and explores the performative dimensions of multilingual research and its narration, through the philosophy of Judith Butler, and in particular her study Giving an account of oneself. It explores aspects of risk, justice, narrative limit and a morality of multilingualism in emergent multilingual research frameworks. These theoretical dimensions are explored through consideration of âlinguistically incompetentâ ethnographic work with refugees and asylum seekers, in contexts of hospitality and in life long learning research in the Gaza Strip, and of early attempts to learn new languages. The paper offers a prospect of a relational approach to researching multilingually and affirms the vulnerability at the heart of linguistic hospitality
Gaussian field theories, random Cantor sets and multifractality
The computation of multifractal scaling properties associated with a critical
field theory involves non-local operators and remains an open problem using
conventional techniques of field theory. We propose a new description of
Gaussian field theories in terms of random Cantor sets and show how universal
multifractal scaling exponents can be calculated. We use this approach to
characterize the multifractal critical wave function of Dirac fermions
interacting with a random vector potential in two spatial dimensions. We show
that the multifractal scaling exponents are self-averaging.Comment: Extensive modifications of previous version; exact results replace
numerical calculation
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