Kosterlitz-Thouless phase transition and reentrance in an anisotropic 3-state Potts model on the generalized Kagome lattice

The unusual reentrant phenomenon is observed in the anisotropic 3-state Potts model on a gen- eralized Kagome lattice. By employing the linearized tensor renormalization group method, we find that the reentrance can appear in the region not only under a partial ordered phase as commonly known but also a phase without a local order parameter, which is uncovered to fall into the uni- versality of the Kosterlitz-Thouless (KT) type. The region of the reentrance depends strongly on the ratios of the next nearest couplings {\alpha} = J2 /|J1 | and {\beta} = J3 /|J1 |. The phase diagrams in the plane of temperature versus {\beta} for different {\alpha} are obtained. Through massive calculations, it is also revealed that the quasi-entanglement entropy can be used to accurately detect the KT transition temperature

On Galilean conformal bootstrap

In this work, we develop conformal bootstrap for Galilean conformal field theory (GCFT). In a GCFT, the Hilbert space could be decomposed into quasiprimary states and its global descendants. Different from the usual conformal field theory, the quasi-primary states in a GCFT constitute multiplets, which are block-diagonized under the Galilean boost operator. More importantly the multiplets include the states of negative norms, indicating the theory is not unitary. We compute global blocks of the multiplets, and discuss the expansion of four-point functions in terms of the global blocks of the multiplets. Furthermore we do the harmonic analysis for the Galilean conformal symmetry and obtain an inversion formula. As the first step to apply the Galilean conformal bootstrap, we construct generalized Galilean free theory (GGFT) explicitly. We read the data of GGFT by using Taylor series expansion of four-point function and the inversion formula independently, and find exact agreement. We discuss some novel features in the Galilean conformal bootstrap, due to the non-semisimpleness of the Galilean conformal algebra and the non-unitarity of the GCFTs.Comment: 75 pages, 2 figures, 4 tables; v2: references added, typos corrected; v3: references added, typos corrected, new appendices adde

Cosmic Radio Background from Primordial Black Holes at Cosmic Dawn

The presence of an extra radio background besides the cosmic microwave background has important implications for the observation of the 21-cm signal during the cosmic Dark Ages, Cosmic Dawn, and epoch of Reionization. The strong absorption trough found in the 21-cm global spectrum measured by the EDGES experiment, which has a much greater depth than the standard model prediction, has drawn great interest to this scenario, but more generally it is still of great interest to consider such a cosmic radio background (CRB) in the early Universe. To be effective in affecting the 21-cm signal at early time, such a radio background must be produced by sources which can emit strong radio signals but modest amount of X-rays, so that the gas is not heated up too early. We investigate the scenario that such a radio background is produced by the primordial black holes (PBHs). For PBH with a single mass, we find that if the PBHs' abundance $\log(f_{\rm PBH})$ (ratio of total PBH mass density to total matter density) and mass satisfy the relation $\log(f_{\rm PBH}) \sim -1.8\log(M_\bullet/{\rm M}_{\odot})-3.5$ for $1\,{\rm M}_\odot \lesssim M_\bullet \lesssim 300 {\rm M}_\odot$, and have jet emission, they can generate a CRB required for reproducing the 21-cm absorption signal seen by the EDGES. The accretion rate can be boosted if the PBHs are surrounded by dark matter halos, which permits lower $f_{\rm PBH}$ value to satisfy the EDGES observation. In the latter scenario, since the accretion rate can evolve rapidly during the Cosmic Dawn, the frequency (redshift) and depth of the absorption trough can determine the mass and abundance of the PBHs simultaneously. For absorption trough redshift $\sim$ 17 and depth $\sim -500$ mK, it corresponds to $M_\bullet \sim 1.05\,{\rm M}_{\odot}$ and $f_{\rm PBH}\sim 1.5\times10^{-4}$.Comment: 16 pages, 13 figures, accepted for publication in PR

HyExo:A Novel Quasi-Passive Hydraulic Exoskeleton for Load-Carrying Augmentation

The development of assistive lower-limb exoskeletons gains prominence for human load-carrying augmentation. Hydraulic transmission has attractive hydrostatic features and lower inertia at the end of human limbs. However, few hydraulic lower-limb exoskeletons were developed with low energy consumption and light weight. In this article, we introduce HyExo, a quasi-passive hydraulic exoskeleton that is built on a lightweight rotary cage valve (RCV) block with a fast response and low energy consumption of 1.55&amp;#x00A0;W. Based on the RCV block, we propose an optimization-based regulator for joint energy distribution to harvest and release the hydraulic energy among joints during the stance phase. The interaction force model and control of the novel nonanthropomorphic structure are presented and evaluated. The load-supporting effect was investigated and validated through human subject experiments. The results show that with an assisting fluid pressure of 2.5&amp;#x00A0;MPa, HyExo can transfer a mean force of 237&amp;#x00A0;N to the ground. Meanwhile, the impact of wearing HyExo on gait is analyzed. The metabolic expenditure test shows that HyExo can slow the increasing rate in metabolic cost as load increases. Compared with a regular backpack, walking with HyExo to carry 30&amp;#x00A0;kg of weight reduces wearers&amp;#x0027; metabolic energy expenditure by 7.8&amp;#x0025;.</p

Structural, magnetic, and electronic transport properties of (Sr0.9Ca0.1)3Ru2O7 single crystal

We have studied the structural, magnetic, and electronic transport properties of (Sr0.9Ca0.1)3Ru2O7 using single crystals grown by a floating-zone technique. The structure analysis by Rietveld refinements reveals that the Ca substitution for Sr intensifies the structure distortion; the rotation angle of the RuO6 octahedron increases. This structure change tunes magnetic and transport properties dramatically. The magnetic ground state switches from an itinerant metamagnetic state for Sr3Ru2O7 to a nearly ferromagnetic state for (Sr0.9Ca0.1)3Ru2O7. The Fermi liquid behavior occurs in Sr3Ru2O7, but is suppressed in (Sr0.9Ca0.1)3Ru2O7. These results strongly suggest that lattice, spin, and charge degrees of freedom are strongly coupled in this system. The band width narrowing caused by the structure distortion should be responsible for the enhancement of ferromagnetic correlations and the change of transport propertie

Simulation and Experiment Analysis of Driveshaft

A driveshaft is a small spring coil less than 1mm in diameter, composed of several stainless-steel wire filaments. In intervention, the driveshaft is used to transmit force and motion to the inside body through the existing micro channels (such as arteries, veins, and gastrointestinal tract). The performance of the driveshaft determines the efficiency, stability, and accuracy of force and motion transitions, the ability to pass through tortuous microchannels, and the damage to healthy tissues. To determine the influence of fabrication parameters (filament, wire diameter, and outer diameter) on the mechanical properties (such as bending stiffness and natural frequency) of the driveshaft, a simulation was established in ABAQUS to calculate the deformation displacement under 0.0098N and first-order natural frequency. Then, the bending stiffness is calculated. The results show that the bending stiffness and the first-order natural frequency of the driveshaft increase with the increase of the filament number and wire diameter, and with the outer diameter of the driveshaft increases, the bending stiffness increases, while the first-order natural frequency decreases. Finally, the simulation model is verified by measuring the deformation displacement in the experiment. This study provides a methodology for designing and selecting the driveshaft in Interventional therapy

Structural, magnetic, and electronic transport properties of (Sr0.9Ca0.1)3Ru2O7 single crystal

We have studied the structural, magnetic, and electronic transport properties of (Sr0.9Ca0.1)3Ru2O7 using single crystals grown by a floating-zone technique. The structure analysis by Rietveld refinements reveals that the Ca substitution for Sr intensifies the structure distortion; the rotation angle of the RuO6 octahedron increases. This structure change tunes magnetic and transport properties dramatically. The magnetic ground state switches from an itinerant metamagnetic state for Sr3Ru2O7 to a nearly ferromagnetic state for (Sr0.9Ca0.1)3Ru2O7. The Fermi liquid behavior occurs in Sr3Ru2O7, but is suppressed in (Sr0.9Ca0.1)3Ru2O7. These results strongly suggest that lattice, spin, and charge degrees of freedom are strongly coupled in this system. The band width narrowing caused by the structure distortion should be responsible for the enhancement of ferromagnetic correlations and the change of transport propertie

Operando and three-dimensional visualization of anion depletion and lithium growth by stimulated Raman scattering microscopy

Visualization of ion transport in electrolytes provides fundamental understandings of electrolyte dynamics and electrolyte-electrode interactions. However, this is challenging because existing techniques are hard to capture low ionic concentrations and fast electrolyte dynamics. Here we show that stimulated Raman scattering microscopy offers required resolutions to address a long-lasting question: how does the lithium-ion concentration correlate to uneven lithium deposition? In this study, anions are used to represent lithium ions since their concentrations should not deviate for more than 0.1 mM, even near nanoelectrodes. A three-stage lithium deposition process is uncovered, corresponding to no depletion, partial depletion, and full depletion of lithium ions. Further analysis reveals a feedback mechanism between the lithium dendrite growth and heterogeneity of local ionic concentration, which can be suppressed by artificial solid electrolyte interphase. This study shows that stimulated Raman scattering microscopy is a powerful tool for the materials and energy field