We present a Monte Carlo simulation study of chiral nematic liquid crystals confined in torus-shaped and cylindrical cavities. For an achiral nematic with planar degenerate anchoring confined to a toroidal or cylindrical cavity, the ground state is defect free, with an untwisted director field. As chirality is introduced, the ground state remains defect free but the director field becomes twisted within the cavity. For homeotropic anchoring, the ground state for an achiral nematic within a toroidal cavity consists of two disclination rings, one large and one small, that follow the major circumference of the torus. As chirality is introduced and increased, this ground state becomes unstable with respect to twisted configurations. The closed nature of the toroidal cavity requires that only a half integer number of twists can be formed and this leads to the ground state being either a single disclination line that encircles the torus twice or a pair of intertwined disclination rings forming stable, knotted defect structures.
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http://dx.doi.org/10.1103/PhysRevE.100.052702 | DOI Listing |
Structure
January 2025
Biochemistry Center Heidelberg, Heidelberg University, 69120 Heidelberg, Germany. Electronic address:
The data presented at the 9 International Murnau Conference on September 18-21, 2024, the largest recurring structural biology meeting in Central Europe, illustrated the thriving state of the structural biology community. This is largely attributed to the ground-breaking developments over the last decade, which were intensely discussed during the meeting.
View Article and Find Full Text PDFGait Posture
December 2024
Marquette University, 1250 W. Wisconsin Ave, Milwaukee, WI 53233, United States; Shriners Children's Chicago, 2211 N. Oak Park Ave, Chicago, IL 60707, United States.
Background: Understanding midfoot joint kinetics is valuable for improved treatment of foot pathologies. Segmental foot kinetics cannot currently be obtained in a standard gait lab without the use of multiple force plates or a pedobarographic plate overlaid with a force plate due to the single ground reaction force (GRF) vector.
Research Question: Can an algorithm be created to distribute the GRF into multiple segmental vectors that will allow for calculation of accurate midfoot and ankle moments?
Methods: 20 pediatric subjects (10 typically developing, 10 with foot pathology) underwent multi-segment foot gait analysis using the Milwaukee Foot Model.
Phys Rev Lett
December 2024
Departament de Física Aplicada, Universitat d'Alacant, 03690 Alicante, Spain.
The existence of light QCD axions, whose mass depends on an additional free parameter, can lead to a new ground state of matter, where the sourced axion field reduces the nucleon effective mass. The presence of the axion field has structural consequences, in particular, it results in a thinner (or even prevents its existence) heat-blanketing envelope, significantly altering the cooling patterns of neutron stars. We exploit the anomalous cooling behavior to constrain previously uncharted regions of the axion parameter space by comparing model predictions with existing data from isolated neutron stars.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Kadanoff Center for Theoretical Physics, University of Chicago, Chicago, Illinois 60637, USA.
Recently, it was proposed that the chiral central charge of a gapped, two-dimensional quantum many-body system is proportional to a bulk ground state entanglement measure known as the modular commutator. While there is significant evidence to support this relation, we show in this Letter that it is not universal. We give examples of lattice systems that have vanishing chiral central charge, which nevertheless give nonzero "spurious" values for the modular commutator for arbitrarily large system sizes, in both one and two dimensions.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Department of Physics, Durham University, South Road, Durham DH1 3LE, United Kingdom.
Many experimental platforms for quantum science depend on state control via laser fields. Frequently, however, the control fidelity is limited by optical phase noise. This is exacerbated in stabilized laser systems where high-frequency phase noise is an unavoidable consequence of feedback.
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