Comment on ``Stripe Glasses: Self-Generated Randomness in a Uniformly Frustrated System''

comment on J. Schmalian and P. Wolynes, Phys. Rev. Lett. {\bf 85}, 836 (2000).Comment: 1 page, 1 Figure, accepted in Phys. Rev. Letter

Non glassy ground-state in a long-range antiferromagnetic frustrated model in the hypercubic cell

We analize the statistical mechanics of a long-range antiferromagnetic model defined on a D-dimensional hypercube, both at zero and finite temperatures. The associated Hamiltonian is derived from a recently proposed complexity measure of Boolean functions, in the context of neural networks learning processes. We show that, depending of the value of D, the system either presents a low temperature antiferromagnetic stable phase or the global antiferromagnetic order disappears at any temperature. In the last case the ground state is an infinitely degenerated non-glassy one, composed by two equal size anti-aligned antiferromagnetic domains. We also present some results for the ferromagnetic version of the model.Comment: 8 pages, 5 figure

Langevin dynamics of the Coulomb frustrated ferromagnet: a mode-coupling analysis

We study the Langevin dynamics of the soft-spin, continuum version of the Coulomb frustrated Ising ferromagnet. By using the dynamical mode-coupling approximation, supplemented by reasonable approximations for describing the equilibrium static correlation function, and the somewhat improved dynamical self-consistent screening approximation, we find that the system displays a transition from an ergodic to a non-ergodic behavior. This transition is similar to that obtained in the idealized mode-coupling theory of glassforming liquids and in the mean-field generalized spin glasses with one-step replica symmetry breaking. The significance of this result and the relation to the appearance of a complex free-energy landscape are also discussed.Comment: 13 pages, 11 figures, submitted to Phys. Rev.

Evidence of polariton induced transparency in a single organic quantum wire

The resonant interaction between quasi-one dimensional excitons and photons is investigated. For a single isolated organic quantum wire, embedded in its single crystal monomer matrix, the strong exciton-photon coupling regime is reached. This is evidenced by the suppression of the resonant excitonic absorption arising when the system eigenstate is a polariton. These observations demonstrate that the resonant excitonic absorption in a semiconductor can be understood in terms of a balance between the exciton coherence time and the Rabi period between exciton-like and photon-like states of the polariton.Comment: 9 pages and 4 figure

Evidence for "fragile" glass-forming behavior in the relaxation of Coulomb frustrated three-dimensional systems

We show by means of a Monte Carlo simulation study that three-dimensional models with long-range frustration display the generic phenomena seen in fragile glassforming liquids. Due to their properties (absence of quenched disorder, physical motivation in terms of structural frustration, and tunable fragility), these systems appear as promising minimal theoretical models for describing the glass transition of supercooled liquids.Comment: 4 pages, 4 figure

Microphase Separation and modulated phases in a Coulomb frustrated Ising ferromagnet

We study a 3-dimensional Ising model in which the tendency to order due to short-range ferromagnetic interactions is frustrated by competing long-range (Coulombic) interactions. Complete ferromagnetic ordering is impossible for any nonzero value of the frustration parameter, but the system displays a variety of phases characterized by periodically modulated structures. We have performed extensive Monte-Carlo simulations which provide strong evidence that the microphase separation transition between paramagnetic and modulated phases is a fluctuation-induced first-order transition. Additional transitions to various commensurate phases may also occur when further lowering the temperature.Comment: 6 pages, 4 figures, accepted in Europhys. Letter

The frustrated spherical model: an alternative to Ginzburg-Landau Hamiltonians with competing interactions

We solve analytically the Langevin dynamics of the classic spherical model considering the ferromagnetic exchange and a long-range antiferromagnetic interaction. Our results in the asymptotic regime, shows an equivalence in the functionality of the spatial and self-correlations between this model and the recently studied Ginzburg-Landau frustrated model within the Hartree approximation. A careful discussion is done about the low temperature behavior in the context of glassy dynamics. The appearance of interesting features regarding the establishment of the ferromagnetic phase is also analyzed in view of the effects of the spherical restriction. We propose a new variant of the spherical model in which the global restriction is substituted by an infinite set of restrictions over finite size regions. This modification leads to a new dynamical equation that suggests the appearance of the low temperature phase transition even in the non-frustrated case were the classic spherical model fails

Etude de la variabilité d'un agent pathogène, Xanthomonas campestris pv manihotis, par l'analyse factorielle multiple

International audienc

Locally Preferred Structure and Frustration in Glassforming Liquids: A Clue to Polyamorphism?

We propose that the concept of liquids characterized by a given locally preferred structure (LPS) could help in understanding the observed phenomenon of polyamorphism. ``True polyamorphism'' would involve the competition between two (or more) distinct LPS, one favored at low pressure because of its low energy and one favored at high pressure because of its small specific volume, as in tetrahedrally coordinated systems. ``Apparent polyamorphism'' could be associated with the existence of a poorly crystallized defect-ordered phase with a large unit cell and small crystallites, which may be illustrated by the metastable glacial phase of the fragile glassformer triphenylphosphite; the apparent polyamorphism might result from structural frustration, i. e., a competition between the tendency to extend the LPS and a global constraint that prevents tiling of the whole space by the LPS.Comment: 11, 6 figures, Proceedings of the Conference "Horizons in Complex Systems", Messina; in honor of the 60th birthday of H.E. Stanle