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We study collective self-organization of weakly magnetic active suspensions in a uniform external field by analyzing a mesoscopic continuum model that we have recently developed. Our model is based on a Smoluchowski equation for a particle…

Soft Condensed Matter · Physics 2020-10-28 Fabian R. Koessel , Sara Jabbari-Farouji

Depending on the involved physiobiological parameters, stable or unstable behavior in active fluids is observed. In this paper a rigorous analytical justification of (in-)stability within the corresponding regimes is given. In particular,…

Analysis of PDEs · Mathematics 2023-08-03 Christiane Bui , Christian Gesse , Jürgen Saal

Activity in nematics drives interfacial flows that lead to preferential alignment that is tangential or planar for extensile systems (pushers) and perpendicular or homeotropic for contractile ones (pullers). This alignment is known as…

Soft Condensed Matter · Physics 2021-09-21 Rodrigo C. V. Coelho , Nuno A. M. Araújo , Margarida M. Telo da Gama

We study the entanglement dynamics in the externally-driven single-mode Dicke model in the thermodynamic limit, when the field is in resonance with the atoms. We compute the correlations in the atoms-field ground state by means of the…

Mesoscale and Nanoscale Physics · Physics 2009-06-30 Victor M. Bastidas , John H. Reina , Tobias Brandes

The effect of strong anisotropy on the Fermi line of a system of correlated electrons is studied in two space dimensions, using renormalization group techniques. Inflection points change the scaling exponents of the couplings, enhancing the…

Strongly Correlated Electrons · Physics 2009-10-30 J. Gonzalez , F. Guinea , M. A. H. Vozmediano

Topological defects are ubiquitous on surfaces with orientational order fields. Here, we study equilibrium states generated by the feedback between geometry and nematic order on fluid membranes with an integer topological defect. When the…

Soft Condensed Matter · Physics 2024-11-14 D. J. G. Pearce , C. Thibault , Q. Chaboche , C. Blanch-Mercader

We study the instability properties of Nesterov's ODE in non-conservative settings, where the driving term is not necessarily the gradient of a potential function. While convergence properties under Nesterov's ODE are well-characterized for…

Optimization and Control · Mathematics 2025-10-09 Daniel E. Ochoa , Mahmoud Abdelgalil , Jorge I. Poveda

We describe a numerical investigation of a continuum model of an active nematic, concentrating on the regime of active turbulence. Results are presented for the effect of three parameters, activity, elastic constant and rotational diffusion…

Soft Condensed Matter · Physics 2015-06-18 Sumesh P. Thampi , Ramin Golestanian , Julia M. Yeomans

The stability of the fundamental defects of an unstretchable flat sheet is examined. This involves expanding the bending energy to second order in deformations about the defect. The modes of deformation occur as eigenstates of a…

Soft Condensed Matter · Physics 2011-12-06 Jemal Guven , Martin Michael Mueller , Pablo Vázquez-Montejo

Using agent-based simulations of self-propelled particles subject to short-range repulsion and nematic alignment we explore the dynamical phases of a dense active material confined to the surface of a sphere. We map the dynamical phase…

Soft Condensed Matter · Physics 2018-04-25 Silke Henkes , M. Cristina Marchetti , Rastko Sknepnek

Theoretical study of dynamical phenomena induced by a linearly polarized plane wave incident perpendicularly on a planar aligned nematic layer with the light intensity as the control parameter is reported. We find the threshold of the…

Soft Condensed Matter · Physics 2010-01-29 Dmitry O. Krimer

The Tayler instability of an azimuthal magnetic field with one or two ``rings'' along the radius is studied for an axially unbounded Taylor-Couette flow. The rotation law of the conducting fluid is a quasi-Keplerian one. Without rotation…

Solar and Stellar Astrophysics · Physics 2025-03-18 Günther Rüdiger , Manfred Schultz

We investigate two-dimensional neural fields as a model of the dynamics of macroscopic activations in a cortex-like neural system. While the one-dimensional case has been treated comprehensively by Amari 30 years ago, two-dimensional neural…

Adaptation and Self-Organizing Systems · Physics 2007-06-07 K. Doubrovinski , M. Herrmann

We investigate a disordered multi-dimensional linear system in which the interaction parameters vary stochastically in time with defined temporal correlations. We refer to this type of disorder as "annealed", in contrast to quenched…

Disordered Systems and Neural Networks · Physics 2025-02-07 Francesco Ferraro , Christian Grilletta , Amos Maritan , Samir Suweis , Sandro Azaele

We study a continuum model of an extensile active nematic to show that mesoscale turbulence develops in two stages: (i) ordered regions undergo an intrinsic hydrodynamic instability generating walls, lines of stong bend deformations, (ii)…

Soft Condensed Matter · Physics 2015-06-18 Sumesh P. Thampi , Ramin Golestanian , Julia M. Yeomans

Various director configurations of a nematic liquid crystal, confined in a toroidal volume and subject to an external magnetic field, were evaluated numerically by performing finite element calculations in three dimensions. The equilibrium…

Soft Condensed Matter · Physics 2007-05-23 Joachim Stelzer , Ralf Bernhard

We study the necking of a filament of complex fluid or soft solid subject to uniaxial tensile stretching, under conditions of constant imposed stress and force, by means of linear stability analysis and nonlinear simulations. We demonstrate…

Soft Condensed Matter · Physics 2016-11-22 David M. Hoyle , Suzanne M. Fielding

The solid nematic equivalent of the Fredericks transition is found to depend on a critical field rather than a critical voltage as in the classical case. This arises because director anchoring is principally to the solid rubbery matrix of…

Soft Condensed Matter · Physics 2009-10-31 E. M. Terentjev , M. Warner , R. B. Meyer , J. Yamamoto

The non-linear Hall term present in the induction equation in the electron-magneto-hydrodynamics limit is responsible for the Hall drift of the magnetic field and, in some cases, for the so-called Hall instability. We investigate whether or…

Solar and Stellar Astrophysics · Physics 2012-03-28 Jose A. Pons , Ulrich Geppert

We numerically model a two-dimensional active nematic confined by a periodic array of fixed obstacles. Even in the passive nematic, the appearance of topological defects is unavoidable due to planar anchoring by the obstacle surfaces. We…

Soft Condensed Matter · Physics 2024-01-25 Cody D. Schimming , C. J. O. Reichhardt , C. Reichhardt