Disclinations, first observed in mesomorphic phases, are relevant to a number of ill-ordered condensed matter media, with continuous symmetries or frustrated order. They also appear polycrystals at the edges grain boundaries. limited interest solid single crystals, where, owing their large elastic stresses, they mostly close pairs opposite signs. The relaxation mechanisms associated disclination its creation, motion, change shape, involve an interplay quantized dislocations and/or...

Defects are local breakings of symmetry in an ordered medium. The physics defects has long been reduced to the study dislocations solids, and main physical phenomena they responsible for, like plastic deformation. Dislocations break translational symmetries. Disclinations rotational symmetries basic media with continuous symmetries, liquid crystals. In this review, it is stressed how their contributed a renewal defects. Static dynamic properties nematic, cholesteric, blue, smectic columnar...

Abstract Point defects in nematics, also called hedgehogs, are topological entities that have no equivalent ordered atomic solids, despite the homonymy. They been subject of intense experimental and, above all, theoretical (analytical and computational) investigations last thirty years. present bulk specimens at specimen boundaries. This review article stresses importance core structure defect, possibility it splitting into a disclination loop, boundary conditions, as well taking stock...

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation M. Kléman, N. David Mermin; Points, Lines, Walls in Liquid Crystals, Magnetic Systems, Various Ordered Media. Am. J. Phys. 1 February 1984; 52 (2): 188–189. https://doi.org/10.1119/1.13723 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar...

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Abstract Observation of the nucleation surface disclination lines in nematics shows their correspondence to emergences walls at boundary sample; these have no core discontinuity and width gives an estimate anchoring energy molecules surface.

Abstract In order to verify experimentally some recent calculations on screw disclination lines in nematics we have observed with a polarizing microscope, meridian section, nematic filled capillary tubes homeotropic boundary conditions, or without inserted fibers. the simple case no fiber observe non-singular S = + 1 and point singularities associated them. The of force directors are visualized by flickering fluctuations molecules correspond well shape predicted theoretically. When glass...

Abstract The structure of media whose short-range order cannot be extended crystallographically in flat space (disordered metallic and covalent systems, Frank-Kasper phases, quasicrystals, blue phases various molecular phases) is describable terms distributions defects a crystal situated constant curvature. This paper reviews the geometrical topological properties curved crystals their defects, relations between mapping on space, how certain universal generally attributed to disordered...

Effet d'un desordre deterministe sur la densite d'etats de vibration et les modes d'une chaine elastique a une dimension. Pour cette etude on utilise des sequences automatiques engendrees par substitution operant un alphabet deux lettres

Observations with the polarizing microscope of defects in lyotropic L α (SmA) phase quasi-ternary system cetylpiridinium chloride/hexanol/brine give evidence that oily streaks are chains focal conic domains. The stable vicinity -L 3 transition. Such a model was suggested long ago by G. Friedel but its existence not confirmed unquestionably. We discuss geometrical, topological and energetics properties these structures show their stability depends on material constants, particular,...

Observations are reported of the behaviour a smectic-A liquid crystal, 4-n-octyl-4’-cyanobiphenyl (8CB), as it is sheared in two geometries. In first an initially-homeo-tropic sample planar shear flow cell, and observed that creates textures which resemble those caused by dilating smectic. The same seen second geometry, where placed transparent cone-and-plate rheometer. apparent viscosity smectic material measured this geometry found to increase with fraction contains certain disordered...

A red thread marks the history of liquid crystals from start; it is concept focal conic domains in smectic phases. Discovered by G. Friedel and F. Grandjean early beginning 20th century, still attract attention researchers field. The presence a touchstone layered media. They rightly excited interest P.-G. de Gennes seminal paper about Apollonius tiling toric domains. In this we shall review development notion over last one hundred years, firstly emphasising its importance appearance...

The notion of quasi dislocations is used to describe the sources internal stresses in a nonuniformly magnetized body which otherwise perfect. Energy densities and interaction energies with other defects are derived same formalism. distortion tensor (strains rotations) calculated case plane infinite wall; difference between elastically stable unstable walls emphasized. junction also studied, an approach calculation they produce proposed, using disclinations. As illustration, physics 90°...

We show how many mesomorphic states illustrate the following general scheme: The symmetry group of an equilibrium state Euclidean-invariant quantum statistical mechanics is a subgroup $H$ Euclidean $E$ such that orbit $\frac{E}{H}$ compact. Moreover, homotopy groups yield classification topologically stable defects and configurations these ordered media. This suggests predictive value this scheme for yet unobserved media defects.

Les domaines focaux des phases lamellaires types Sm C et C* sont toujours accompagnes de lignes singulieres (du type disinclinaison) qui n'existent pas dans la phase A. Dans cet article nous observons au microscope polarisant interpretons les soit plonges masse, attaches en surface, C*. se formes A nos echantillons ont tous subi une transition → ou Le modele toriques masse (Ref. [3]) est etendu cas plus generaux, par analyse topologique amene a approfondir notion disinclinaison imparfaite...

Usual Penrose tilings are defined by a set of five phases gamma j which add up to an integer. The authors study the general case where any number and show that these generalised can be obtained with four tiles (two thick rhombi two thin rhombi) different colourings edges. consideration is relevant for phase distortions, local structural transitions, therefore various defects usual things.

2014 On montre que, dans un cristal liquide nématique, les disinclinaisons attachées aux limites de l'échantillon peuvent être traitées par modèle du type Peierls-Nabarro connu la théorie des dislocations cristaux.Mathématiquement, avec c0153ur plan et sur surface sont complètement analogues si on considère approximations l'élasticité isotrope distribution planaire directeur.Les solutions données d'abord pour demi-cylindre grand rayon; puis discute possibilité d'une asymétrie directeur...

Observations, by means of X-ray topography and stroboscopy combined, moving domain walls wall junctions in Fe–Si single crystals are reported. Instabilities, surface effects interactions 90° {110} with dislocations have been observed.

Abstract It is possible to define a local frame of reference at each point distorted liquid crystal, transformed from fixed in the perfect crystal by pure rotation. In director n has constant components. A curvature tensor Kij used describe rotations between neighbouring frames; it obeys compatibility condition θ = Rot K − M 0, where formed minors K. takes into account non-commutativity small rotations. The deformation can therefore be described three types defect densities. αij δij ii ji...

The distortions of a smectic phase with respect to planar state reference are described either by displacement u the layers (and conjugated stresses σij), or rotation ω director torques). In principle, choice as an independent variable is justified for study disclinations, and dislocations translation. this latter case, restricting theory small distortions, one extends various results in dislocation solids case smectics. With help stress field due unit point force (Green's function), able...

Abstract K 1, 2, 3 and [mgrave]1 have been measured for the first time in a typical main-chain polymer belonging to polyester series. 1 is very large compared conventional nematics, while 2 more values. by two methods, one of them consisting measurement characteristic rise regular striped domains.