|1.|| Non-singular Disclinations,
J. de Physique
33, 591 (1972) (with M. Kléman).
First demonstration that a non-linear ordinary differential equation had solutions that broke the symmetry of the boundary conditions. This equation has an infinite number of solutions but the minimum energy one is called “escape into the third dimension”. The other solutions can be accessed by systems out of equilibrium. The immediate consequence of this result was the discovery of point defects (hedgehog-antihedgehog) in the bulk of liquid crystals in
Non-singular S = +1 Disclinations, Phys. Rev. Lett. 29, 90 (1972) (with C. Williams and P. Pieranski). See also: Hedgehog-antihedgehog pair annihilation to a static soliton, Physica A326, 322 (2003), (with H. R. Brand).
|2.||New Liquid Crystal Phase Diagram,
Phys. Rev. Lett. 35, 48 (1975).
Discovery of the Reentrant Nematic Phase where a higher symmetry phase occurs at a lower temperature than one of lower symmetry.
|3.|| The Reentrant Nematic
Transition in Cyanooctyloxybiphenyl (8OCB), Phys.
Rev. A23, 2594 (1981) (with D. Guillon, F. R. Bouchet and P. L.
Microscopic interpretation of the reentrant nematic phenomena that has been theoretically framed by Nihat Berker as a “spin gas” in analogy to a spin glass. Because the two phases are liquids, they escape non-ergodicity by “reentering”.
|4.||"Soliton" Switch in Chiral
Smectics, Phys. Rev. A28Rap. Comm., 512 (1983) (with H. R. Brand
and P. L. Finn).
First interpretation of switching phenomena in chiral smectic C’s as a thresholdless, non-linear effect.
|5.||Kossel Diagrams Show Electric
Field Induced Cubic-Tetragonal Structural Transition in Frustrated Liquid
Crystal Blue Phases (with T. Garel and P. Pieranski) Phys. Rev. Lett
Nice observations with potential applications in photonics.
|6.||Phase Winding and Flow Alignment
in Freely Suspended Films of Smectic C Liquid Crystals, (with Y. Couder
and H. R. Brand) Phys. Rev. Lett. 55, 2945 (1985).
First “flow experiment” in freely suspended smectic liquid crystal films and observation of "phase winding".
|7.||Dynamical Test of Phase Transition
Order, (with Wim van Saarloos, David A. Huse, J. S. Patel, J. W. Goodby
and P. L. Finn) Phys. Rev. Lett. 62, 1764 (1989).
The first test of the order of a thermodynamic liquid crystal phase transition by front propagation. With this test, we clarified a 20 year old mystery as to the nature of the nematic-smectic A phase transition accounting for the non-universality of its exponent and leading to the following:
|8.||Experimental Test of a Fluctuation Induced First Order Transition: the Nematic - Smectic A transition (with A. Anisimov, E. E. Gorodetskii, D. A. Huse, V. G. Taratuta, W. van Saarloos and V. P. Voronov), Phys. Rev. A41, 6749 (1990). We give an estimate of the magnitude of the gap in the fluctuation spectrum that results from the coupling between orientational fluctuations and the 1-d density fluctuations from a lower temperature smectic A phase making the nematic-smectic A transition intrinsically first order.|
|9.|| Breathing Mode in a
Pattern Forming System with Two Competing Lengths (with J. T. Gleeson,
P. L. Finn and H. R. Brand) Phys. Rev. Lett. 67, 3239 (1991).
We show that the traveling liquid crystal phase boundary with the minimal broken symmetries of life: broken mirror symmetry (chiral), broken time reversal symmetry (non-equilibrium) and broken continuous rotational symmetry (liquid crystal phase transition), “knows” time.
|10.||Symmetry and Defects in the
CM Phase of Polymeric Liquid Crystals (with H. R. Brand
and H. Pleiner), Macromolecules 25, 7223 (1992).
We point out that the symmetry of an anticlinic stacking of smectic C-type layers introduces a 2-fold axis without mirror symmetry. The importance of this observation includes: 1. the prediction that banana-shaped liquid crystal molecules without any asymmetric carbons can have a spontaneous polarization (now observed and intensely studied) and 2. Antiferroelectric liquid crystals are not a surface induced artefact of ferroelectric liquid crystals.