scholarly journals Creating synthetic spaces for higher-order topological sound transport

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hui Chen ◽  
Hongkuan Zhang ◽  
Qian Wu ◽  
Yu Huang ◽  
Huy Nguyen ◽  
...  
Keyword(s):  
Higher Order ◽  
Atomic Gases ◽  
Strongly Coupled ◽  
Technological Advances ◽  
Weakly Coupled ◽  
Hall Effects ◽  
Topological States ◽  
Wave Guides ◽  
Geometrical Imperfections ◽  
Acoustic Cavities

AbstractModern technological advances allow for the study of systems with additional synthetic dimensions. Higher-order topological insulators in topological states of matters have been pursued in lower physical dimensions by exploiting synthetic dimensions with phase transitions. While synthetic dimensions can be rendered in the photonics and cold atomic gases, little to no work has been succeeded in acoustics because acoustic wave-guides cannot be weakly coupled in a continuous fashion. Here, we formulate the theoretical principles and manufacture acoustic crystals composed of arrays of acoustic cavities strongly coupled through modulated channels to evidence one-dimensional (1D) and two-dimensional (2D) dynamic topological pumpings. In particular, the higher-order topological edge-bulk-edge and corner-bulk-corner transport are physically illustrated in finite-sized acoustic structures. We delineate the generated 2D and four-dimensional (4D) quantum Hall effects by calculating first and second Chern numbers and physically demonstrate robustness against the geometrical imperfections. Synthetic dimensions could provide a powerful way for acoustic topological wave steering and open up a platform to explore any continuous orbit in higher-order topological matter in dimensions four and higher.

scholarly journals Acoustic cavities in 2D heterostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Maxim K. Zalalutdinov ◽  
Jeremy T. Robinson ◽  
Jose J. Fonseca ◽  
Samuel W. LaGasse ◽  
Tribhuwan Pandey ◽  
...  
Keyword(s):  
Sound Propagation ◽  
Phonon Scattering ◽  
Frequency Comb ◽  
Material Interfaces ◽  
Low Frequencies ◽  
Strongly Coupled ◽  
Propagation Analysis ◽  
Acoustic Cavities ◽  
Ab Initio Approach ◽  
Spatiotemporal Response

AbstractTwo-dimensional (2D) materials offer unique opportunities in engineering the ultrafast spatiotemporal response of composite nanomechanical structures. In this work, we report on high frequency, high quality factor (Q) 2D acoustic cavities operating in the 50–600 GHz frequency (f) range with f × Q up to 1 × 1014. Monolayer steps and material interfaces expand cavity functionality, as demonstrated by building adjacent cavities that are isolated or strongly-coupled, as well as a frequency comb generator in MoS2/h-BN systems. Energy dissipation measurements in 2D cavities are compared with attenuation derived from phonon-phonon scattering rates calculated using a fully microscopic ab initio approach. Phonon lifetime calculations extended to low frequencies (<1 THz) and combined with sound propagation analysis in ultrathin plates provide a framework for designing acoustic cavities that approach their fundamental performance limit. These results provide a pathway for developing platforms employing phonon-based signal processing and for exploring the quantum nature of phonons.

scholarly journals CFT unitarity and the AdS Cutkosky rules

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
David Meltzer ◽  
Allic Sivaramakrishnan
Keyword(s):  
Flat Space ◽  
Tree Level ◽  
Optical Theorem ◽  
Conformal Field Theories ◽  
Strongly Coupled ◽  
Conformal Field ◽  
Weakly Coupled ◽  
S Matrix ◽  
Space Limit ◽  
Diagrammatic Method

Abstract We derive the Cutkosky rules for conformal field theories (CFTs) at weak and strong coupling. These rules give a simple, diagrammatic method to compute the double-commutator that appears in the Lorentzian inversion formula. We first revisit weakly-coupled CFTs in flat space, where the cuts are performed on Feynman diagrams. We then generalize these rules to strongly-coupled holographic CFTs, where the cuts are performed on the Witten diagrams of the dual theory. In both cases, Cutkosky rules factorize loop diagrams into on-shell sub-diagrams and generalize the standard S-matrix cutting rules. These rules are naturally formulated and derived in Lorentzian momentum space, where the double-commutator is manifestly related to the CFT optical theorem. Finally, we study the AdS cutting rules in explicit examples at tree level and one loop. In these examples, we confirm that the rules are consistent with the OPE limit and that we recover the S-matrix optical theorem in the flat space limit. The AdS cutting rules and the CFT dispersion formula together form a holographic unitarity method to reconstruct Witten diagrams from their cuts.

scholarly journals Prandtl Number in Classical Hard-Sphere and One-Component Plasma Fluids

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 821
Author(s):  
Sergey Khrapak ◽  
Alexey Khrapak
Keyword(s):  
Prandtl Number ◽  
Hard Sphere ◽  
Solid Phase ◽  
Freezing Point ◽  
Three Dimensional ◽  
Order Unity ◽  
Strongly Coupled ◽  
Dielectric Fluids ◽  
Weakly Coupled ◽  
Component Plasma

The Prandtl number is evaluated for the three-dimensional hard-sphere and one-component plasma fluids, from the dilute weakly coupled regime up to a dense strongly coupled regime near the fluid-solid phase transition. In both cases, numerical values of order unity are obtained. The Prandtl number increases on approaching the freezing point, where it reaches a quasi-universal value for simple dielectric fluids of about ≃1.7. Relations to two-dimensional fluids are briefly discussed.

Article

1999 ◽  
Vol 77 (11) ◽  
pp. 1810-1812 ◽  
Author(s):  
Alex D Bain
Keyword(s):  
Spin System ◽  
Coupled System ◽  
Coupled Systems ◽  
Physical Reason ◽  
Strongly Coupled ◽  
System Combination ◽  
First Order ◽  
Weakly Coupled ◽  
Quantum Transitions ◽  
Weakly Coupled Systems

Strongly coupled spin systems provide many curious and interesting effects in NMR spectra, one of which is the presence of unexpected (from a first-order viewpoint) lines. A physical reason is given for the presence of these combination lines. The X part of the spectrum of an ABX spin system is analysed as an example. For an ABX system, it is well known that the AB nuclei give a spectrum consisting of two AB-type spectra, corresponding to the two orientations of the X nucleus. It can also be shown that the X part of the spectrum corresponds to the X nucleus undergoing a transition in the presence of an AB-like spin system. For weakly coupled systems, the four observed lines correspond to the four different orientations of the A and B nuclei. For a strongly coupled system, two additional lines may appear, the combination lines. The resulting six lines correspond to the four spin orientations, plus the two zero-quantum transitions. It is shown that these six lines are such that there is no net excitation of the AB-like spin system associated with the X transitions. There is no AB coherence created directly by a pulse applied to X. AB coherence is created as the system evolves, and this is responsible for many of the curious effects. This is shown to be true for all spin sub-systems, which are weakly coupled to a strongly coupled sub-system.Key words: NMR, strong coupling, second-order spectra, ABX spin system, combination lines, spectral analysis.

A New Method for Displacement Analysis of Multi-Loop Spatial Linkages Based on Ordered Simple-Opened-Chains

1996 ◽  
Author(s):  
Xian-Wen Kong ◽  
Ting-Li Yang
Keyword(s):  
Continuation Method ◽  
The Other ◽  
New Method ◽  
New Approach ◽  
Strongly Coupled ◽  
Displacement Analysis ◽  
Cpu Time ◽  
Base Points ◽  
Weakly Coupled ◽  
Spatial Linkages

Abstract This paper presents systematically a new method for the displacement analysis (DA) of multi-loop spatial linkages (MLSLs) based on ordered simple-opened-chains (SOCs). In performing DA, a MLSL is converted into not a set of base points, a set of isolated links or a tree with/without isolated links in common use, but a weakly coupled MLSL in this paper. The characteristics of the proposed method are: (a) The number of unknowns in the set of equations for displacement analysis (EDA) of a MLSL is reduced to the minimum; (b) All the possible configurations corresponding to a given set of inputs of a weakly coupled MLSL or a strongly coupled MLSL with the coupled degree k = 1 can be obtained quickly. As compared with the other two methods available to find all the solutions to the DA in the case of MLSL with k = 1, the proposed method is superior to the resultant method in that it is applicable to more complex MLSLs and superior to the continuation method in that it takes much less CPU time to find all the solutions; (c) The set of EDA can be formulated and solved automatically; and (d) The new approach makes it possible to perform the kinematic and kineto-static analyses in a unified and simplified way.

Square-root-like higher-order topological states in three-dimensional sonic crystals

2021 ◽  
Author(s):  
Zhiguo Geng ◽  
Huanzhao Lv ◽  
Zhan Xiong ◽  
Yu-Gui Peng ◽  
Zhaojiang Chen ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Surface States ◽  
Higher Order ◽  
Square Root ◽  
Root Lattice ◽  
Third Order ◽  
Topological Materials ◽  
Topological States ◽  
Sonic Crystal ◽  
Sonic Crystals

Abstract The square-root descendants of higher-order topological insulators were proposed recently, whose topological property is inherited from the squared Hamiltonian. Here we present a three-dimensional (3D) square-root-like sonic crystal by stacking the 2D square-root lattice in the normal (z) direction. With the nontrivial intralayer couplings, the opened degeneracy at the K-H direction induces the emergence of multiple acoustic localized modes, i.e., the extended 2D surface states and 1D hinge states, which originate from the square-root nature of the system. The square-root-like higher order topological states can be tunable and designed by optionally removing the cavities at the boundaries. We further propose a third-order topological corner state in the 3D sonic crystal by introducing the staggered interlayer couplings on each square-root layer, which leads to a nontrivial bulk polarization in the z direction. Our work sheds light on the high-dimensional square-root topological materials, and have the potentials in designing advanced functional devices with sound trapping and acoustic sensing.

A Reusable 3D Printed Cavity Resonator for Liquid Sample Characterization

2018 ◽  
Vol 2018 (1) ◽  
pp. 000389-000392
Author(s):  
Saranraj Karuppuswami ◽  
Saikat Mondal ◽  
Mohd Ifwat Mohd Ghazali ◽  
Premjeet Chahal
Keyword(s):  
Dielectric Constant ◽  
Cavity Resonator ◽  
Dielectric Constants ◽  
Sample Holder ◽  
Strongly Coupled ◽  
Weakly Coupled ◽  
Sample Characterization ◽  
3D Printed ◽  
Standard Values ◽  
High Dielectric

Abstract In this paper, additive manufacturing (3D printing) is used to fabricate and demonstrate a reusable microfluidic coupled rectangular cavity resonator for characterizing liquids in small volumes. The designed cavity operates in the fundamental TE101 mode and resonates at 4.12 GHz. The resonance of the cavity is perturbed by the sample placed in a small volume sample holder through a slot in the top cover. Two different perturbation configurations are investigated: i) strongly coupled (liquids with low to medium dielectric constants), and ii) weakly coupled (liquids with medium to high dielectric constant). The sample holder is loaded with different solvents and the shift in the resonance frequency is monitored. Based on these changes, the dielectric constant of the solvent is theoretically estimated and compared to standard values. The reusable liquid sensor holds significant potential in identifying and quantifying unknown liquid samples in the supply chain.

scholarly journals Higher‐Order Topological States in Surface‐Wave Photonic Crystals

2020 ◽  
Vol 7 (6) ◽  
pp. 1902724 ◽  
Author(s):  
Li Zhang ◽  
Yihao Yang ◽  
Zhi‐Kang Lin ◽  
Pengfei Qin ◽  
Qiaolu Chen ◽  
...  
Keyword(s):  
Surface Wave ◽  
Photonic Crystals ◽  
Higher Order ◽  
Topological States

scholarly journals Nonlinear matter terms in general scalar–tensor braneworld cosmology

2019 ◽  
Vol 28 (11) ◽  
pp. 1950138
Author(s):  
Kevin F. S. Pardede ◽  
Agus Suroso ◽  
Freddy P. Zen
Keyword(s):  
Big Bang ◽  
Accelerated Expansion ◽  
Big Bang Nucleosynthesis ◽  
Braneworld Cosmology ◽  
Strongly Coupled ◽  
Weakly Coupled ◽  
General Scalar ◽  
Bulk Scalar Field ◽  
The Big Bang ◽  
Correction Terms

A five-dimensional braneworld cosmological model in general scalar–tensor action that is comprised of various Horndeski Lagrangians is considered. The Friedmann equations in the case of strongly and weakly coupled [Formula: see text] Horndeski Lagrangians have been obtained. The strongly coupled [Formula: see text] model produces the Cardassian term [Formula: see text] with [Formula: see text], which can serve as an alternative explanation for the accelerated expansion phase of the universe. Furthermore, the latest combined observational facts from BAO, CMB, SNIa, [Formula: see text] and [Formula: see text] value observation suggest that the [Formula: see text] term lies quite close to the constrained value. On the other hand, the weakly coupled [Formula: see text] case has several new correction terms which are omitted in the braneworld Einstein–Hilbert model, e.g. the cubic [Formula: see text] and the dark radiation–matter interaction term [Formula: see text]. Furthermore, this model provides a cosmological constant constructed from the bulk scalar field, requires no brane tension and supports the big bang nucleosynthesis (BBN) constraint naturally.

Rhythmic patterns evoked in locust leg motor neurons by the muscarinic agonist pilocarpine

1993 ◽  
Vol 69 (5) ◽  
pp. 1583-1595 ◽  
Author(s):  
S. Ryckebusch ◽  
G. Laurent
Keyword(s):  
Motor Neurons ◽  
Rhythmic Activity ◽  
Cycle Period ◽  
Muscarinic Agonist ◽  
Strongly Coupled ◽  
Weakly Coupled ◽  
Metathoracic Ganglion ◽  
Common Drive ◽  
Muscarinic Cholinergic

1. When an isolated metathoracic ganglion of the locust was superfused with the muscarinic cholinergic agonist pilocarpine, rhythmic activity was induced in leg motor neurons. The frequency of this induced rhythm increased approximately linearly from 0 to 0.2 Hz with concentrations of pilocarpine from 10(-5) to 10(-4) M. Rhythmic activity evoked by pilocarpine could be completely and reversibly blocked by 3 x 10(-5) M atropine, but was unaffected by 10(-4) M d-tubocurarine. 2. For each hemiganglion, the observed rhythm was characterized by two main phases: a levator phase, during which the anterior coxal rotator, levators of the trochanter, flexors of the tibia, and common inhibitory motor neurons were active; and a depressor phase, during which depressors of the trochanter, extensors of the tibia, and depressors of the tarsus were active. Activity in depressors of the trochanter followed the activity of the levators of the trochanter with a short, constant interburst latency. Activity in the levator of the tarsus spanned both phases. 3. The levator phase was short compared with the period (0.5-2 s, or 10-20% of the period) and did not depend on the period. The interval between the end of a levator burst and the beginning of the following one thus increased with cycle period. The depressor phase was more variable, and was usually shorter than the interval between successive levator bursts. 4. Motor neurons in a same pool often received common discrete synaptic potentials (e.g., levators of trochanter or extensors of tibia), suggesting common drive during the rhythm. Coactive motor neurons on opposite sides (such as left trochanteral depressors and right trochanteral levators), however, did not share obvious common postsynaptic potentials. Depolarization of a pool of motor neurons during its phase of activity was generally accompanied by hyperpolarization of its antagonist(s) on the same side. 5. Rhythmic activity was generally evoked in both hemiganglia of the metathoracic ganglion, but the intrinsic frequencies of the rhythms on the left and right were usually different. The activity of the levators of the trochanter on one side, however, was strongly coupled to that of the depressors of the trochanter on the other side. 6. The locomotory rhythm was weakly coupled to the ventilatory rhythm such that trochanteral levator activity on either side never occurred during the phase of spiracle opener activity corresponding to inspiration. 7. The rhythmic activity observed in vitro bears many similarities to patterns of neural and myographic activity recorded during walking. The similarities and differences are discussed.

Sign in / Sign up

Export Citation Format

Share Document