Line Defects Research Articles

Conformal line defects at finite temperature

We study conformal field theories at finite temperature in the presence of a temporal conformal line defect, wrapping the thermal circle, akin to a Polyakov loop in gauge theories. Although several symmetries of the conformal group are broken, the model can still be highly constrained from its features at zero temperature. In this work we show that the defect and bulk one and two-point correlators can be written as functions of zero-temperature data and thermal one-point functions (defect and bulk). The defect one-point functions are new data and they are induced by thermal effects of the bulk. For this new set of data we derive novel sum rules and establish a bootstrap problem for the thermal defect one-point functions from the KMS condition. We also comment on the behaviour of operators with large scaling dimensions. Additionally, we relate the free energy and entropy density to the OPE data through the one-point function of the stress-energy tensor. Our formalism is validated through analytical computations in generalized free scalar field theory, and we present new predictions for the O(N)O(N) model with a magnetic impurity in the \varepsilonε-expansion and the large NN limit.

R-matrices and Miura operators in 5d Chern-Simons theory

We derive Miura operators for WW- and YY-algebras from first principles as the expectation value of the intersection between a topological line defect and a holomorphic surface defect in 5-dimensional non-commutative \mathfrak{gl}(1)𝔤𝔩(1) Chern-Simons theory. The expectation value, viewed as the transition amplitude for states in the defect theories forming representations of the affine Yangian of \mathfrak{gl}(1)𝔤𝔩(1), satisfies the Yang-Baxter equation and is thus interpreted as an R-matrix. To achieve this, we identify the representations associated with the line and surface defects by calculating the operator product expansions (OPEs) of local operators on the defects, as conditions that anomalous Feynman diagrams cancel each other. We then evaluate the expectation value of the defect intersection using Feynman diagrams. When the line and surface defects are specified, we demonstrate that the expectation value precisely matches the Miura operators and their products.

Effect of Autogenous Auricular Cartilage Composite Skin Graft for Bilateral Cleft Lip Nose Deformity Repair.

Bilateral cleft lip nose deformity often involves nasal alar retraction. The use of autogenous auricular cartilage for correction further aggravated nasal alar retraction caused by nasal lining defects after the operation. A novel graft was developed to address bilateral cleft lip nose deformity. This graft effectively addresses the lining defect and avoids nasal alar retraction following surgical intervention. Seventeen patients (7 males and 10 females) with bilateral cleft lip nose deformity were treated at the authors' institution. All patients underwent repair with an auricular cartilage-composite skin graft. The surgical effect was evaluated from 4 aspects: nasal flange position, postoperative appearance satisfaction, nasal aesthetic subunit index, and three-dimensional difference. Postoperatively, 17 patients with bilateral cleft lip nose deformity were followed up from 3 months to 1 year, none of them had any obvious inward collapse or recession of the nasal margin (P > 0.05), and all of them showed satisfactory results. The satisfaction rate was above 90% (P < 0.01). The nasal tip angle and nasolabial angle were significantly smaller postoperatively than those preoperatively (P < 0.01). The nostril height and nasal columellar height were greater postoperatively than those preoperatively (P < 0.01). A comparison of the three-dimensional spatial differences revealed that the appearance of the nasal deformity was noticeably better after surgery (P < 0.01). Auricular cartilage-composite skin graft repair is highly effective for enhancing nasal support, correcting nasal tip shape, effectively resolving nasal flange recession, and preventing nasal flange retraction in the postoperative period. Level IV.

VACStent closure of oesophageal defects by covered stent and endoscopic vacuum therapy: initial use and clinical outcomes

Abstract Endoscopic management of transmural oesophageal defects following esophagectomy or spontaneous perforations, such as Boerhaave’s syndrome, is often complicated by stent migration and luminal occlusion [1]. The Vacuum-Assisted Closure (VAC) stent, which integrates a covered stent with endoscopic vacuum therapy, aims to address these issues by providing functional drainage and promoting wound healing [2]. This case series presents our initial experience with VACStent therapy in four patients treated between February 2023 and April 2024. Two patients had staple line defects post-esophagectomy, and two had Boerhaave’s syndrome. Treatment involved stent placement under general anaesthesia, followed by evaluations and scheduled stent exchanges every 6 days. All patients achieved successful defect closure, with no procedural complications noted. Three patients required one stent application, while one needed two applications. VACStent therapy appears to be a safe and effective treatment for transmural oesophageal defects, potentially establishing a new standard of care.

Imaging of dark line defect growth in high-power diode laser cavities using broadband near infrared light emission from the laser cavity

An in situ and nondestructive technique is developed to image the formation and evolution of dark line defects in the cavity of a high-power diode laser. The technique uses broadband near infrared emission that originates in the laser's core layers and enables defects to be imaged with high spatial resolution through the substrate. In particular, it enables defect imaging through the substrate of shorter wavelength lasers, even when the substrate is opaque near the lasing wavelength. The evolution of dark line defects during aging is studied in several devices, with correlations established between the observed characteristics of defect growth and changes in device parameters such as optical power, operating wavelength, threshold current, and slope efficiency. Gradual degradation is found to be associated with dark line defects that slowly propagate from dark spots that are present in the device interior in its fresh (unaged) condition, rather than propagating from spots that are formed during aging, suggesting a strategy to screen fresh devices for expected reliability. This defect growth phenomenon is found to be particularly evident in the dark spots near the output facet.

Multiscalar critical models with localised cubic interactions

Interface localised interactions are studied for multiscalar universality classes accessible with the perturbative ε expansion in 4 – ε dimensions. The associated beta functions at one loop and partially at two loops are derived, and a wide variety of interface conformal field theories (CFTs) is found, even in cases where the bulk universality class is free or as simple as the Wilson-Fisher description of the O(N) model. For up to three scalar fields in the bulk, interface fixed points are classified for all bulk universality classes encountered in this case. Numerical results are obtained for interface CFTs that exist for larger numbers of multiscalar fields. Our analytic and numerical results indicate the existence of a vast space of interface CFTs, much larger than the space of defect CFTs found for line and surface defect deformations of multiscalar models in 4 − ε dimensions. In this vast space, stable interfaces found for free and O(N) bulks belong to the F4 family, with global symmetries SO(3), SU(3), Sp(6) and F4, realised with N = 5, 8, 16, 24 scalar fields, respectively.

GPU-Accelerated Solution of the Bethe-Salpeter Equation for Large and Heterogeneous Systems.

We present a massively parallel GPU-accelerated implementation of the Bethe-Salpeter equation (BSE) for the calculation of the vertical excitation energies (VEEs) and optical absorption spectra of condensed and molecular systems, starting from single-particle eigenvalues and eigenvectors obtained with density functional theory. The algorithms adopted here circumvent the slowly converging sums over empty and occupied states and the inversion of large dielectric matrices through a density matrix perturbation theory approach and a low-rank decomposition of the screened Coulomb interaction, respectively. Further computational savings are achieved by exploiting the nearsightedness of the density matrix of semiconductors and insulators to reduce the number of screened Coulomb integrals. We scale our calculations to thousands of GPUs with a hierarchical loop and data distribution strategy. The efficacy of our method is demonstrated by computing the VEEs of several spin defects in wide-band-gap materials, showing that supercells with up to 1000 atoms are necessary to obtain converged results. We discuss the validity of the common approximation that solves the BSE with truncated sums over empty and occupied states. We then apply our GW-BSE implementation to a diamond lattice with 1727 atoms to study the symmetry breaking of triplet states caused by the interaction of a point defect with an extended line defect.

Research on Detection of Icing Cover Transmission Lines Under Different Weather Conditions Based on Wide-Field Dynamic Convolutional Network LDKA-NET

The safety of transmission lines is a crucial guarantee for the operation of the power grid. To address the issue of low detection accuracy for icing transmission line defects with existing models, this paper proposes a defect detection algorithm for icing transmission line defects under different weather conditions based on a Large Dynamic Kernel Aggregation Net (LDKA-NET). First, a wide field of view convolutional network (WFVC Net) is introduced to enhance the network’s perception and generalization capabilities, enabling better adaptation to complex scene targets. Secondly, a full-dimensional dynamic convolutional feature fusion network is proposed, which strengthens the model’s feature extraction ability by learning linear combinations of multiple convolution kernels and their weighted input-related attention. Finally, an Expectation Maximization Dynamic Convolutional Attention (EM-DCA) mechanism is introduced, which focuses on and utilizes important information in the input data to help the model better allocate attention, thereby improving its generalization and robustness. Experimental results show that on the dataset proposed in this paper, the average accuracy of the improved algorithm (mAP@0.5) reaches 99.01%. The model parameters decreased by 47.7 M compared with the baseline model and 91.26 M compared with the Faster region with CNN feature (Faster R-CNN) model. The accuracy is 4.81% and 3.11% higher than the SSD model and YOLOv5-L model, respectively. Compared with the existing models, our model is smaller and has higher detection accuracy. It can accurately detect ice-covered wires and complete the task of the ice-covered detection of transmission lines.

Combining Machine Learning Algorithms with Traditional Methods for Resolving the Atomic-Scale Dynamic Structure Reconstruction of Monolayer MoS2 in High-Resolution Transmission Electron Microscopy

Abstract High-resolution transmission electron microscopy promises rapid atomic-scale dynamic structure imaging. Yet, the precision limitations of aberration parameters and the challenge of eliminating aberrations in Cs-corrected transmission electron microscopy constrain resolution. A machine learning algorithm is developed to determine the aberration parameters with higher precision from small, lattice-periodic crystal images. The proposed algorithm is then validated with simulated HRTEM images of graphene and applied to the experimental images of a molybdenum disulfide (MoS2) monolayer with 25 variables (14 aberrations) resolved in wide ranges. Using these measured parameters, the phases of the exit-wave functions are reconstructed for each image in a focal series of MoS2 monolayers. The images were acquired due to the unexpected movement of the specimen holder. Four-dimensional data extraction reveals time-varying atomic structures and ripple. In particular, the atomic evolution of the sulfur-vacancy point and line defects, as well as the edge structure near the amorphous, are visualized as the resolution has been improved from about 1.75 Å to 0.90 Å. This method can help salvage important transmission electron microscope images and is beneficial for the images obtained from electron microscopes with average stability.

Line and surface defects in 5D N=2 SCFT from matter-coupled F(4) gauged supergravity

We study supersymmetric solutions of matter-coupled F(4) gauged supergravity in the forms of AdS2×S3- and AdS3×S2-sliced domain walls with a non-vanishing two-form field from the supergravity multiplet. These two types of solutions holographically describe conformal line and surface defects within five-dimensional N=2 SCFTs, respectively. In the case of SO(3)×SO(3) gauge group obtained by coupling F(4) supergravity to three vector multiplets, we find charged domain wall solutions describing holographic RG flows between two supersymmetric AdS6 vacua with a running two-form field supporting the line and surface defects. For a particular case of one vector multiplet with SO(3)×U(1) gauge group, we find solutions describing RG flows from an AdS6 vacuum to physically acceptable singular geometries in the presence of defects. This class of solutions can be uplifted to type IIB theory using a consistent truncation obtained from SO(5, 5) exceptional field theory with half-maximal structures.

New dimer integrable systems and defects in five dimensional gauge theory

We study the relation between the quantum integrable systems derived from the dimer graphs and five dimensional N = 1 supersymmetric gauge theories on S1 × ℝ4. We construct integrable systems based on new dimer graphs obtained from modification of hexagon dimer diagram. We study the gauge theories in correspondence to the newly proposed integrable systems. By examining three types of defects — a line defect, a canonical co-dimensional two defect and a monodromy defect — in five-dimensional gauge theory with N = 1 supersymmetry and Ωε1,ε2-background. We identify, in the ε2 → 0 limit, the canonical co-dimensional two defect satisfying the Baxter T-Q equation of the generalized A-type dimer integrable system, and the monodromy defect as its common eigenstate of the commuting Hamiltonians, with the eigenvalues being the expectation value of the BPS Wilson loop in the anti-symmetric representation of the bulk gauge group.

Direct simulation and machine learning structure identification unravel soft martensitic transformation and twinning dynamics

Phase transition between ordered phases has garnered attention from the viewpoint of materials science as well as statistical physics. One interesting example is martensitic transformation and the resulting formation of twin structures, in which atoms or molecules that form one crystalline phase move in a concerted and diffusionless manner toward another crystalline phase. Recently martensitic transformation has been observed experimentally also in various soft materials. However, the complex internal structures involving many molecules have eluded direct investigation of the dynamical processes of martensitic transformation. Here, we carry out a direct simulation of mesoscale structural transition of a liquid crystalline blue phase (BP) of cubic symmetry, known as BP II. The dynamics is simulated by a Langevin-type equation for the orientational order parameter with thermal fluctuations. We demonstrate that machine-learning-aided analysis of local structures successfully unravels the transformation process from a perfect lattice of BP II to a twinned lattice of another BP (BP I). The nucleation of BP I is initiated by the breakup of junctions of line defects (disclinations), followed by the deformation of disclination network. We further show that twinned BP I is reversibly transformed to a perfect lattice of BP II by temperature variation. Order-parameter-based simulations with machine-learning-aided local structure identification provide valuable insights into not only the martensitic transformation of soft materials but also a wider class of complex structural transitions between ordered phases.

Aerial infrared thermal imaging transmission line defect detection methods incorporating explicit visual center structures

Aerial infrared thermal imaging transmission line defect detection methods incorporating explicit visual center structures

Effect of incomplete line defect size on energy localization and harvesting in phononic crystals.

The high electrical output performance of the phononic crystal (PnC)-based piezoelectric energy harvesting (PEH) system is of great research value in self-powered applications. This work presents the effect of incomplete line defect size on elastic wave energy localization and harvesting. The results show that for a given 7 × 5 supercell when the incomplete line defect reaches the second to sixth layer, the energy localization and harvesting performance show a changing trend of first increasing and then decreasing; when the incomplete line defect reaches the 4th, 5th, 3rd, 2nd, and 6th layers of the supercell, respectively, the performance of PEH systems shows a trend from large to small. Among them, when the incomplete line defect reaches the fourth layer of the supercell, the performance of the PEH system is optimal, and the maximum output voltage and the maximum output electric power are 22.54 V and 12.78 mW, respectively. This work provides valuable insights for improving the performance of PEH devices by using the PnC with incomplete line defects.

Acoustic Tunnel Lining Void Detection: Modeling and Instrument System Development

The detachment of railway tunnel lining constitutes a grave danger to train operation safety and drastically curtails the tunnel’s service life. This study endeavors to efficiently detect the void defects in railway tunnel lining by creating a finite element model of tunnel lining structures. Utilizing this model, the study simulates the nonlinear acoustic wave propagation cloud maps for three representative tunnel lining structures: void-free, air void, and water void. This facilitates a thorough examination of the acoustic signal characteristics in the wavefield, time domain, and frequency domain. To satisfy the precision and efficiency demands of tunnel lining void detection, this study has devised and developed a portable acoustic detector that incorporates automatic analysis and processing capabilities and is furnished with a high-performance rare-earth magneto-strictive acoustic excitation device. This detection system can swiftly detect and assess typical void defects in tunnel lining. To further validate the effectiveness of this system, this study conducted lining defect detection in the Pingdao Railway Tunnel in the eastern Qinling Mountains. The test results show that the detection rate of this system for both air-filled and water-filled voids with a width of 1 m reached 100%, demonstrating its extremely high application value.

Line Defects as Valley Filters in Graphene

Hexagonal two‐dimensional crystals typically feature two identical but inequivalent conduction band minima—so‐called valleys—at the corners of the Brillouin zone. Exploiting this additional quantum number to process information—the goal of the field of valleytronics—requires directly manipulating the valley quantum number. Line defects emerging at grain boundaries between regions of pristine graphene could potentially act as valley filters. Quantum transport is quantitatively simulated through two such typical defects in a fully ab initio parameterized tight‐binding model to assess the validity of such a strategy. Pronounced valley polarization effects are found in transport through the line defect, that sensitively depend on the type and electronic structure of the line defect. In particular, a 5‐8‐5 defect features several strongly localized states breaking the valley symmetry, and, accordingly, leads to pronounced valley filtering effects. By contrast, a comparatively similar 5‐7 defect does not feature localized states, instead showing pronounced valley filtering at large angles of incidence. A much weaker energy dependence can still be exploited to select a specific valley. These results highlight the potential of defect engineering for building valleytronic devices, yet also the importance of realistic, quantitative models for judging the properties of tailored defects.

Modulation of Surface Elastic Waves and Surface Acoustic Waves by Acoustic–Elastic Metamaterials

Metamaterials enable the modulation of elastic waves or acoustic waves in unprecedented ways and have a wide range of potential applications. This paper achieves the simultaneous manipulation of surface elastic waves (SEWs) and surface acoustic waves (SAWs) using two-dimensional acousto-elastic metamaterials (AEMMs). The proposed AEMMs are composed of periodic hollow cylinders on the surface of a semi-infinite substrate. The band diagrams and the frequency responses of the AEMMs are numerically calculated through the finite element approach. The band diagrams exhibit simultaneous bandgaps for the SEWs and SAWs, which can also be effectively tuned by the modification of AEMM geometry. Furthermore, we construct the AEMM waveguide by the introduction of a line defect and hence demonstrate its ability to guide the SEWs and SAWs simultaneously. We expect that the proposed AEMMs will contribute to the development of multi-functional wave devices, such as filters for dual waves in microelectronics or liquid sensors that detect more than one physical property.

Euclidean wormholes in holographic RG flows

We describe a one-parameter family of Euclidean wormhole solutions with the topology of a compact hyperbolic space times an interval in Einstein gravity minimally coupled to a massless scalar field in AdSd+1 commonly referred to as Einstein-dilaton gravity. These solutions are locally described by the same metric and dilaton profile as the single-boundary Janus domain wall solutions in the same theory which are usually studied in the context of holographic RG flows. The wormholes compute the averaged product of partition functions of CFTs on either boundary deformed by different marginal couplings to the scalar operator dual to the dilaton. We observe that the renormalised volumes of these wormholes increase monotonically with the difference in the marginal couplings on the boundary thereby showing that the pair of CFTs on the boundaries get increasingly decorrelated as the difference in the marginal couplings increases. We use the partition functions of the three-dimensional wormhole solutions to determine the variance of the OPE data of local operators between the marginally deformed 2d CFTs and quantify how the variance decays with the difference in marginal couplings. In addition, a family of wormholes sourced by a thin shell of dust determine how the variance of the matrix elements of the dual line defect decays with the difference in marginal couplings. Applying the GKPW dictionary to wormholes, we compute averages of integrated dilaton correlators treating the wormhole amplitude as a functional of the dilaton sources. We observe that the crossed two-point correlators with a dilaton insertion on either boundary decay monotonically with the difference in marginal couplings consistent with the observation that the CFTs increasingly decorrelate as the difference in marginal couplings grows.

Statistics of three-dimensional black holes from Liouville line defects

Black holes and wormholes in the gravitational path integral can be used to calculate the statistics of heavy operators. An explicit example in higher dimensions is provided by thin shells of matter. We study these solutions in 3D gravity, and reproduce the behavior of black holes and wormholes from the dual CFT using the large-c conformal bootstrap. The CFT operator that creates a thin shell black hole is a line defect, so we begin by using the bootstrap to study the statistics of line defects, both at finite c and in the holographic large-c limit. The crossing equation leads to a universal formula for the average high-energy matrix elements of the line defect in any compact, unitary 2d CFT with c > 1. The asymptotics are controlled by a line defect in Liouville CFT at the same value of the central charge. At large c, three distinct quantities are related: the statistics of line defects in holographic CFTs, the individual matrix elements of a line defect in Liouville CFT, and the on-shell action of black holes and wormholes in 3D gravity. The three calculations match for black holes, and if the statistics of the line defects are assumed to be approximately Gaussian, then a class of wormholes is also reproduced by the dual CFT.

Electromagnetic duality for line defect correlators in N = 4 super Yang-Mills theory

We study particular integrated correlation functions of two superconformal primary operators of the stress tensor multiplet in the presence of a half-BPS line defect labelled by electromagnetic charges (p, q) in N = 4 supersymmetric Yang-Mills theory (SYM) with gauge group SU(N). An important consequence of SL(2, ℤ) electromagnetic duality in N = 4 SYM is that correlators of line defect operators with different charges (p, q) must be related in a non-trivial manner when the complex coupling τ = θ/(2π) + 4πi/gYM2 is transformed appropriately. In this work we introduce a novel class of real-analytic functions whose automorphic properties with respect to SL(2, ℤ) match the expected transformations of line defect operators in N = 4 SYM under electromagnetic duality. At large N and fixed τ, the correlation functions we consider are related to scattering amplitudes of two gravitons from extended (p, q)-strings in the holographic dual type IIB superstring theory. We show that the large-N expansion coefficients of the integrated two-point line defect correlators are given by finite linear combinations with rational coefficients of elements belonging to this class of automorphic functions. On the other hand, for any fixed value of N we conjecture that the line defect integrated correlators can be expressed as formal infinite series over such automorphic functions. The resummation of this series produces a simple lattice sum representation for the integrated line defect correlator that manifests its automorphic properties. We explicitly demonstrate this construction for the cases with gauge group SU(2) and SU(3). Our results give direct access to non-perturbative integrated correlators in the presence of an ’t Hooft-line defect, observables otherwise very difficult to compute by other means.