Casademunt, Jaume


Vol. 447, Issues 3-6, p.67-144 (2007)
Vol. 448, Issues 5-6, p.113-180 (2007)
Vol. 449, Issues 1-3, p.1-76 (2007)


Theory of pattern forming systems under traveling-wave forcing
Sten Rüdiger, Ernesto M. Nicola, Jaume Casademunt and Lorenz Kramer
Phys. Rep.  447, 73-111 ( 2007)

Dynamics of Domain Walls in Pattern Formation with Traveling-Wave Forcing 
S. Rüdiger, J. Casademunt, and L. Kramer 
We study dynamics of domain walls in pattern forming systems that are externally forced by a moving space-periodic modulation close to 2:1 spatial resonance. The motion of the forcing induces nongradient dynamics, while the wave number mismatch breaks explicitly the chiral symmetry of the domain walls. The combination of both effects yields an imperfect nonequilibrium Ising-Bloch bifurcation, where all kinks (including the Ising-like one) drift. Kink velocities and interactions are studied within the generic amplitude equation. For nonzero mismatch, a transition to traveling bound kink-antikink pairs and chaotic wave trains occurs.
Phys. Rev. Lett. 99, 028302 (2007)

Collective Dynamics of Interacting Molecular Motors 
O. Campàs, Y. Kafri, K. B. Zeldovich, J. Casademunt, and J.-F. Joanny 
The collective dynamics of N interacting processive molecular motors are considered theoretically when an external force is applied to the leading motor. We show, using a discrete lattice model, that the force-velocity curves strongly depend on the effective dynamic interactions between motors and differ significantly from those of a simple approach where the motors equally share the force. Moreover, they become essentially independent of the number of motors if N is large enough (N?5 for conventional kinesin). We show that a two-state ratchet model has a very similar behavior to that of the coarse-grained lattice model with effective interactions. The general picture is unaffected by motor attachment and detachment events.
Phys. Rev. Lett. 97, 038101 (2006)

Traveling-Stripe Forcing Generates Hexagonal Patterns 
D. G. Míguez, E. M. Nicola, A. P. Muñuzuri, J. Casademunt, F. Sagués, and L. Kramer 
We study the response of Turing stripe patterns to a simple spatiotemporal forcing. This forcing has the form of a traveling wave and is spatially resonant with the characteristic Turing wavelength. Experiments conducted with the photosensitive chlorine dioxide-iodine-malonic acid reaction reveal a striking symmetry-breaking phenomenon of the intrinsic striped patterns giving rise to hexagonal lattices for intermediate values of the forcing velocity. The phenomenon is understood in the framework of the corresponding amplitude equations, which unveils a complex scenario of dynamical behaviors.
Phys. Rev. Lett. 93, 048303 (2004)

Nonlinear Saffman-Taylor Instability 
E. Álvarez-Lacalle, J. Ortín, and J. Casademunt 
We show, both theoretically and experimentally, that the interface between two viscous fluids in a Hele-Shaw cell can be nonlinearly unstable before the Saffman-Taylor linear instability point is reached. We identify the family of exact elastica solutions [Nye et al., Eur. J. Phys. 5, 73 (1984)] as the unstable branch of the corresponding subcritical bifurcation which ends up at a topological singularity defined by interface pinchoff. We devise an experimental procedure to prepare arbitrary initial conditions in a Hele-Shaw cell. This is used to test the proposed bifurcation scenario and quantitatively asses its practical relevance.
Phys. Rev. Lett. 92, 054501 (2004)

Kinetic Roughening in Two-Phase Fluid Flow through a Random Hele-Shaw Cell 
Eduard Pauné and Jaume Casademunt 
A nonlocal interface equation is derived for two-phase fluid flow, with arbitrary wettability and viscosity contrast, c=(?1-?2)/(?1+?2), in a model porous medium defined as a Hele-Shaw cell with random gap b0+?b. Fluctuations of both capillary and viscous pressure are explicitly related to the microscopic quenched disorder, yielding conserved, nonconserved, and power-law correlated noise terms. Two length scales are identified that control the possible scaling regimes and which scale with capillary number Ca as l1~b0(cCa)-1/2 and l2~b0Ca-1. Exponents for forced fluid invasion are obtained from numerical simulation and compared with recent experiments.
Phys. Rev. Lett. 90, 144504 (2003)

Dynamics of Turing Patterns under Spatiotemporal Forcing 
S. Rüdiger, D. G. Míguez, A. P. Muñuzuri, F. Sagués, and J. Casademunt 
We study, both theoretically and experimentally, the dynamical response of Turing patterns to a spatiotemporal forcing in the form of a traveling-wave modulation of a control parameter. We show that from strictly spatial resonance, it is possible to induce new, generic dynamical behaviors, including temporally modulated traveling waves and localized traveling solitonlike solutions. The latter make contact with the soliton solutions of Coullet [Phys. Rev. Lett. 56, 724 (1986)] and generalize them. The stability diagram for the different propagating modes in the Lengyel-Epstein model is determined numerically. Direct observations of the predicted solutions in experiments carried out with light modulations in the photosensitive chlorine dioxide-iodine-malonic acid reaction are also reported.
Phys. Rev. Lett. 90, 128301 (2003)

Universality Class of Fluctuating Pulled Fronts 
Goutam Tripathy, Andrea Rocco, Jaume Casademunt, and Wim van Saarloos 
It has recently been proposed that fluctuating "pulled" fronts propagating into an unstable state should not be in the standard Kardar-Parisi-Zhang (KPZ) universality class for rough interface growth. We introduce an effective field equation for this class of problems, and show on the basis of it that noisy pulled fronts in d+1 bulk dimensions should be in the universality class of the ((d+1)+1)D KPZ equation rather than of the (d+1)D KPZ equation. Our scenario ties together a number of heretofore unexplained observations in the literature, and is supported by previous numerical results.
Phys. Rev. Lett. 86, 5215 (2001)

Brownian Motion of Spiral Waves Driven by Spatiotemporal Structured Noise 
I. Sendiña-Nadal, S. Alonso, V. Pérez-Muñuzuri, M. Gómez-Gesteira, V. Pérez-Villar, L. Ramírez-Piscina, J. Casademunt, J. M. Sancho, and F. Sagués 
Spiral chemical waves subjected to a spatiotemporal random excitability are experimentally and numerically investigated in relation to the light-sensitive Belousov-Zhabotinsky reaction. Brownian motion is identified and characterized by an effective diffusion coefficient which shows a rather complex dependence on the time and length scales of the noise relative to those of the spiral. A kinematically based model is proposed whose results are in good qualitative agreement with experiments and numerics.
Phys. Rev. Lett. 84, 2734 (2000)

Phase-field model for Theoretical approach Hele-Shaw flows with arbitrary viscosity contrast. I. 
R. Folch, J. Casademunt, A. Hernández-Machado, and L. Ramírez-Piscina 
We present a phase-field model for the dynamics of the interface between two inmiscible fluids with arbitrary viscosity contrast in a rectangular Hele-Shaw cell. With asymptotic matching techniques we check the model to yield the right Hele-Shaw equations in the sharp-interface limit, and compute the corrections to these equations to first order in the interface thickness. We also compute the effect of such corrections on the linear dispersion relation of the planar interface. We discuss in detail the conditions on the interface thickness to control the accuracy and convergence of the phase-field model to the limiting Hele-Shaw dynamics. In particular, the convergence appears to be slower for high viscosity contrasts.
Phys. Rev. E 60, 1724 (1999)

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