The Role of Topological Defects in Subcritical Bifurcations

1989 ◽  
pp. 189-205 ◽  
Author(s):  
P. Coullet ◽  
L. Gil ◽  
D. Repaux
Keyword(s):  
Topological Defects

scholarly journals VORTEX NUCLEATION IN ROTATING BOSE–EINSTEIN CONDENSATE: THE ROLE OF THE BOUNDARY CONDITION FOR THE ORDER PARAMETER

2006 ◽  
Vol 20 (15) ◽  
pp. 2147-2158
Author(s):  
W. V. POGOSOV ◽  
K. MACHIDA
Keyword(s):  
Boundary Condition ◽  
Order Parameter ◽  
Topological Defects ◽  
Einstein Condensate ◽  
Two Dimensional ◽  
Surface Modes ◽  
Bose Einstein Condensate ◽  
Bose Einstein ◽  
Vortex Nucleation

We study the problem of vortex nucleation in rotating two-dimensional Bose–Einstein condensate confined in a harmonic trap. We show that, within the Gross–Pitaevskii theory with the boundary condition of vanishing of the order parameter at infinity, topological defects nucleation occurs via the creation of vortex-antivortex pairs far from the cloud center, where the modulus of the order parameter is small. Then vortices move toward the center of the cloud and antivortices move in the opposite direction but never disappear. We also discuss the role of surface modes.

MODELS OF FREE COOLING GRANULAR GASES

2001 ◽  
Vol 04 (04) ◽  
pp. 321-331 ◽  
Author(s):  
UMBERTO MARINI BETTOLO MARCONI ◽  
ANDREA BALDASSARRI ◽  
ANDREA PUGLISI
Keyword(s):  
Kinetic Energy ◽  
Lattice Model ◽  
Topological Defects ◽  
Total Momentum ◽  
Granular Gases ◽  
Two Dimensional ◽  
Spatial Structures ◽  
Free Evolution ◽  
Free Cooling

We consider the free evolution of systems of granular particles whose dynamics is characterized by a collision rule which preserves the total momentum, but dissipates the kinetic energy. Starting from an inelastic version of a minimal model proposed by Ulam for a gas of Maxwell molecules, we introduce a new lattice model aimed at investigating the role of dynamical correlations and the onset of spatial order induced by the inelasticity of the interactions. We study, in one- and two-dimensional cases, the velocity distribution, the decay of the energy, the formation of spatial structures and topological defects. Finally, we relate our findings to other models known in other fields.

scholarly journals Axial-Compressive Behavior, Including Kink-Band Formation and Propagation, of Singlep-Phenylene Terephthalamide (PPTA) Fibers

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
M. Grujicic ◽  
S. Ramaswami ◽  
J. S. Snipes ◽  
R. Yavari ◽  
C.-F. Yen ◽  
...  
Keyword(s):  
Detrimental Effect ◽  
Mechanical Response ◽  
Topological Defects ◽  
Kink Band ◽  
Coarse Grained ◽  
Computational Investigation ◽  
Band Formation ◽  
Longitudinal Tensile Strength ◽  
Kink Bands

The mechanical response ofp-phenylene terephthalamide (PPTA) single fibers when subjected to uniaxial compression is investigated computationally using coarse-grained molecular statics/dynamics methods. In order to construct the coarse-grained PPTA model (specifically, in order to define the nature of the coarse-grained particles/beads and to parameterize various components of the bead/bead force-field functions), the results of an all-atom molecular-level computational investigation are used. In addition, the microstructure/topology of the fiber core, consisting of a number of coaxial crystalline fibrils, is taken into account. Also, following our prior work, various PPTA crystallographic/topological defects are introduced into the model (at concentrations consistent with the prototypical PPTA synthesis/processing conditions). The analysis carried out clearly revealed (a) formation of the kink bands during axial compression; (b) the role of defects in promoting the formation of kink bands; (c) the stimulating effects of some defects on the fiber-fibrillation process; and (d) the detrimental effect of the prior compression, associated with fiber fibrillation, on the residual longitudinal-tensile strength of the PPTA fibers.

scholarly journals Introduction to Colloidal and Microfluidic Nematic Microstructures

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 956
Author(s):  
Simon Čopar ◽  
Miha Ravnik ◽  
Slobodan Žumer
Keyword(s):  
Soft Matter ◽  
Liquid Crystalline ◽  
Colloidal Particles ◽  
Topological Defects ◽  
Crystalline Materials ◽  
Inherent Anisotropy ◽  
Metastable Structures ◽  
Liquid Crystalline Materials ◽  
Mesoscopic Theory

In this brief review, we give an introduction to selected colloidal and microfluidic nematic microstructures, as enabled by the inherent anisotropy and microscopic orientational ordering in complex liquid crystalline materials. We give a brief overview of the mesoscopic theory, for equilibrium and dynamics, of nematic fluids, that provides the framework for understanding, characterization, and even prediction of such microstructures, with particular comment also on the role of topology and topological defects. Three types of nematic microstructures are highlighted: stable or metastable structures in nematic colloids based on spherical colloidal particles, stationary nematic microfluidic structures, and ferromagnetic liquid crystal structures based on magnetic colloidal particles. Finally, this paper is in honor of Noel A. Clark, as one of the world pioneers that helped to shape this field of complex and functional soft matter, contributing at different levels to works of various groups worldwide, including ours.

scholarly journals Skeletal Rearrangements of the C240 Fullerene: Efficient Topological Descriptors for Monitoring Stone–Wales Transformations

Mathematics ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 968 ◽  
Author(s):  
Denis Sh. Sabirov ◽  
Ottorino Ori
Keyword(s):  
Long Range ◽  
Chemical Reactivity ◽  
Topological Defects ◽  
Theoretical Chemistry ◽  
Topological Descriptors ◽  
Complex Chemical ◽  
Chemical Mechanisms ◽  
Skeletal Rearrangements ◽  
Icosahedral Fullerene

Stone–Wales rearrangements of the fullerene surface are an uncharted field in theoretical chemistry. Here, we study them on the example of the giant icosahedral fullerene C240 to demonstrate the complex chemical mechanisms emerging on its carbon skeleton. The Stone–Wales transformations of C240 can produce the defected isomers containing heptagons, extra pentagons and other unordinary rings. Their formations have been described in terms of (i) quantum-chemically calculated energetic, molecular, and geometric parameters; and (ii) topological indices. We have found the correlations between the quantities from the two sets that point out the role of long-range topological defects in governing the formation and the chemical reactivity of fullerene molecules.

Sign in / Sign up

Export Citation Format

Share Document