Strong Coupling Behavior Research Articles

Toward Exact Critical Exponents from the low-order loop expansion of the Effective Potential in Quantum Field Theory

The asymptotic strong-coupling behavior as well as the exact critical exponents from scalar field theory even for the simplest case of 1+1 dimensions have not been obtained yet. Hagen Kleinert has linked both critical exponents and strong coupling parameters to each other. He used a variational technique ( back to kleinert and Feynman) to extract accurate values for the strong coupling parameters from which he was able to extract precise critical exponents. In this work, we suggest a simple method of using the effective potential ( low order) to obtain exact values for the strong-coupling parameters for the ϕ4 scalar field theory in 0+1 and 1+1 space–time dimensions. For the 0+1 case, our results coincide with the well-known exact values already known from literature while for the 1+1 case we test the results by obtaining the corresponding exact critical exponent. As the effective potential is a well-established tool in quantum field theory, we expect that the results can be easily extended to the most important three dimensional case and then the dream of getting exact critical exponents is made possible.

Strong coupling of double excitons with guided mode resonances and quasi-bound states in the continuum in heterogeneous metamaterials.

Heterogeneous metamaterials containing excitonic materials provide an ideal platform for strong exciton-photon coupling. In this Letter, we theoretically demonstrate four strong couplings in a heterogeneous metamaterial consisting of a TiO2 grating standing on a perovskite-WS2-perovskite waveguide layer by tuning the structural sizes. The quasi-bound state in the continuum (qBIC) and the guided mode resonance (GMR) both strongly coupled with the excitons of both perovskite and WS2 under oblique incident illumination, resulting in four large Rabi splittings of 177.32, 187.53, 406.25, and 435.09 meV via a reasonable combination of oscillator strengths of perovskite and WS2. Double strong coupling behaviors are also achieved when the grating period equals 222 nm with an incident light angle of 19.3°. Moreover, double ultrastrong coupling can even be realized by the GMR and qBIC respectively interacting with the exciton of WS2 when its oscillator strength reaches a certain value. Our work paves an effective avenue to realizing strong coupling and even ultrastrong coupling between multiple excitons and multiple optical modes.

Strong-coupling critical behavior in three-dimensional lattice Abelian gauge models with charged N-component scalar fields and SO(N) symmetry.

We consider a three-dimensional lattice Abelian Higgs gauge model for a charged N-component scalar field ϕ, which is invariant under SO(N) global transformations for generic values of the parameters. We focus on the strong-coupling regime, in which the kinetic Hamiltonian term for the gauge field is a small perturbation, which is irrelevant for the critical behavior. The Hamiltonian depends on a parameter v, which determines the global symmetry of the model and the symmetry of the low-temperature phases. We present renormalization-group predictions, based on a Landau-Ginzburg-Wilson effective description that relies on the identification of the appropriate order parameter and on the symmetry-breaking patterns that occur at the strong-coupling phase transitions. For v=0, the global symmetry group of the model is SU(N); the corresponding model may undergo continuous transitions only for N=2. For v≠0, i.e., in the SO(N) symmetric case, continuous transitions (in the Heisenberg universality class) are possible also for N=3 and 4. We perform Monte Carlo simulations for N=2,3,4,6, to verify the renormalization-group predictions. Finite-size scaling analyses of the numerical data are in full agreement.

Strong-coupling limits induced by weak-coupling expansions

A method is described for the extrapolation of perturbative expansions in powers of asymptotically small coupling parameters or other variables onto the region of finite variables and even to the variables tending to infinity. The method involves the combination of ideas from renormalization group theory, approximation theory, dynamical theory, and optimal control theory. The extrapolation is realized by means of self-similar factor approximants, whose control parameters can be uniquely defined. The method allows to find the large-variable behavior of sought functions knowing only their small-variable expansions. Convergence and accuracy of the method are illustrated by explicit examples, including the so-called zero-dimensional field theory and anharmonic oscillator. Strong-coupling behavior of Gell-Mann–Low functions in multicomponent field theory, quantum electrodynamics, and quantum chromodynamics is found, being based on their weak-coupling perturbative expansions.

Sensors Layout Optimization Design of Rocket Sled Test System.

The rocket sled, as a ground dynamic test system, combines the characteristics of the wind tunnel test and the flight test. However, some practical factors, such as shock wave interference, ground effect, and high-intensity aerodynamic noise will cause serious interference and even failure of the uniformly distributed sensors during horizontal sliding in a wide speed range. The AGARD HB-2 standard model is employed as the payload to simulate the aerodynamic and aeroacoustic characteristics during the variable acceleration period, aiming to optimize the test sensors layout. It is observed that in the high Mach number flow fields, strong coupling behaviors among complex waves will occur. The peak of wake vortex strength will appear at 1.5 s and gradually diminish over time. In addition, when the vortex between the load and the booster is monitored, its position shifts forward in the subsonic stage, then gradually moves backward and expands in the supersonic stage. Acoustic directivity is pronounced at subsonic and transonic speeds, pointing towards 75° and 135° relative to the sliding speed, respectively. These results can provide technical support for sensor layout and high-precision testing in rocket sled tests.

Self-consistent dynamical maps for open quantum systems

In several cases, open quantum systems can be successfully described using master equations relying on Born-Markov approximations, but going beyond these approaches has become often necessary. In this work, we introduce the NCA and NCA-Markov dynamical maps for open quantum systems, which go beyond these master equations replacing the Born approximation with a self-consistent approximation, known as non-crossing approximation (NCA). These maps are formally similar to master equations, but allow to capture non-perturbative effects of the environment at a moderate extra numerical cost. To demonstrate their capabilities, we apply them to the spin-boson model at zero temperature for both a Ohmic and a sub-Ohmic environment, showing that they can both qualitatively capture its strong-coupling behaviour, and be quantitatively correct beyond standard master equations.

Wilson loop correlators at strong coupling in N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 2 quiver gauge theories

We consider 4-dimensional N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 2 superconformal quiver theories with SU(N)M gauge group and bi-fundamental matter and we evaluate correlation functions of n coincident Wilson loops in the planar limit of the theory. Exploiting specific untwisted/twisted combinations of these operators and using supersymmetric localization, we are able to resum the whole perturbative expansion and find exact expressions for these correlators that are valid for all values of the ’t Hooft coupling. Moreover, we analytically derive the leading strong coupling behaviour of the correlators, showing that they obey a remarkable simple rule. Our analysis is complemented by numerical checks based on a Padé resummation of the perturbative series.

Continuation of the Stieltjes series to the large regime by finite-part integration

We devise a prescription to use a novel convergent expansion in the strong-asymptotic regime for the Stieltjes integral and its generalizations (Galapon EA. 2017 Proc. R. Soc A 473 , 20160567) to sum the associated divergent series of Stieltjes across all asymptotic regimes. The novel expansion makes use of the divergent negative-power moments, which we treated as Hadamard’s finite part integrals. The result allowed us to compute the ground state energy of the quartic, sextic anharmonic oscillators as well as the P T symmetric cubic oscillator, and the funnel potential across all perturbation regimes from a single expansion that is built from the divergent weak-coupling perturbation series and incorporates the known leading-order strong-coupling behaviour of the spectra.

Study of Strong Electromagnetic-thermal Coupling Behavior in Induction Motor

In this paper after recalling the electromagnetic and thermal formulations in time harmonic of a three-phase asynchronous motor, we propose to study its electromagnetic-thermal behavior in the event that the motor is healthy and in the event that there is a fault. Therefore, it is quite natural to focus on the intervention of the coupling of the two physical phenomena in question. We used the direct coupling model (strong coupling), especially take into account the variation of physical properties (electric conductivity) in respect of temperature also the heat source in respect of electric filed and electric conductivity using the finite element method.

Observation of ultra-large Rabi splitting in the plasmon-exciton polaritons at room temperature

Abstract Modifying the light–matter interactions in the plasmonic structures and the two-dimensional (2D) materials not only advances the deeper understanding of the fundamental studies of many-body physics but also provides the opportunities for exploration of novel 2D plasmonic polaritonic devices. Here, we report the plasmon-exciton coupling in the hybrid system with a plasmonic metasurface which can confine the electric field in an extremely compact mode volume. Because of the 2D feature of the designed and fabricated Al plasmonic metasurface, the confined electronic field is distributed in the plane with the same orientation as that of the exciton dipole moment in the transition metal dichalcogenides monolayers. By finely tuning the geometric size of the plasmonic nanostructures, we can significantly modify the dispersion relation of the coupled plasmon and the exciton. Our system shows a strong coupling behavior with an achieved Rabi splitting up to ∼200 meV at room temperature, in ambient conditions. The effective tailoring of the plasmon-exciton coupling with the plasmonic metasurfaces provides the testing platform for studying the quantum electromagnetics at the subwavelength scale as well as exploring plasmonic polariton Bose–Einstein condensation at room temperature.

High-order parametrization of the hypergeometric-Meijer approximants

In this work, we introduce an extension to the hypergeometric algorithm we developed before for the resummation of divergent series. The extension overcome the time-consuming problem we face in the parametrization process of the hypergeometric approximants. In the previous version, the parametrization process results in a set of non-linear equations which is hard to solve (might be impossible) for relatively high orders (greater than six) using normal PCs with Mathematica software for instance. To solve this problem, we formulate an equivalent (order by order) linear set of equations which is easy to solve in an appropriate time using normal PCs. We also show that such extension of the hypergeometric resummation algorithm is able to employ non-perturbative information like strong-coupling and large-order asymptotic data which are always used to accelerate the convergence. We applied the algorithm for different orders (up to O(29)) of the ground state energy of the x4 anharmonic oscillator with and without the non-perturbative information. We also considered the available 20 orders for the ground state energy of the PT−symmetric ix3 anharmonic oscillator as well as the given 20 orders of its strong-coupling expansion or equivalently the Yang–Lee model. For high order weak-coupling parametrization, accurate results have been obtained for the ground state energy and the non-perturbative parameters describing strong-coupling and large-order asymptotic behaviors. The employment of the non-perturbative data accelerated the convergence very clearly. The High temperature expansion for the susceptibility within the SQ lattice has been also considered and led to accurate prediction for the critical exponent and critical temperature.

Strong-Coupling Behavior of the Critical Temperature of Pb/Ag, Pb/Cu and Pb/Al Nanocomposites Explained by Proximity Eliashberg Theory

The experimental critical temperature of the systems of superconducting (Pb) and normal (Ag, Cu and Al) nanoparticles, with a random distribution and sizes less than their respective coherence lengths, is governed by the proximity effect, as shown by the experimental data. At first glance, the behavior of the variation in the critical temperature in function of the ratio of volume fractions of the superconducting and the normal metal components seems to suggest a weak coupling behavior for the superconductor. In reality, upon a more careful analysis, using Eliashberg’s theory for the proximity effect, the system instead shows a strong coupling nature. The most interesting thing is that the theory has no free parameters and perfectly explains the behavior of the experimental data just with the assumption in the case of the nanoparticles Ag and Cu, that the value of the density of states at the Fermi level of silver and copper is equal to the value of lead.

Photochromic engineering of radiative decay rate in plasmon–emitter coupling

The development of advanced plasmonic applications is centered on the achievement of active devices. Active plasmonic nanostructures exhibiting tunable resonances have the potential to provide smart materials with a wide range of applications in optoelectronics, including sensing and logic operations. Here, we use finite-difference time-domain simulations to compare the optical properties of nanocones and nanocylinders embedded in two different states of a photochromic medium, first considering a plane wave illumination and then a point dipole one. We show that the photochromic transition induces strong coupling behavior for both illuminations, and it allows a nanocone to effectively enhance one emitter’s emission at one wavelength and quench another emitter at a different wavelength.

Collective Coupling of 3D Confined Optical Modes in Monolithic Twin Microtube Cavities Formed by Nanomembrane Origami.

We report the monolithic fabrication of twin microtube cavities by a nanomembrane origami method for achieving collective coupling of 3D confined optical modes. Owing to the well-aligned twin geometries, two sets of 3D confined optical modes in twin microtubes are spectrally and spatially matched, by which both the fundamental and higher-order axial modes are respectively coupled with each other. Multiple groups of the coupling modes provide multiple effective channels for energy exchange between coupled microcavities illustrated by the measured spatial optical field distributions. The spectral anticrossing and changing-over features of each group of coupled modes are revealed in experiments and calculations, indicating the occurrence of strong coupling. In addition, the simulated 3D mode profiles of twin microcavities confirm the collective strong coupling behavior, which shows good agreement with experiments. The collective coupling of 3D confined resonant modes promises broad applications in multichannel optical signal processing, nanophotonics, and 3D non-Hermitian systems.

Mie Exciton-Polariton in a Perovskite Metasurface

Exciton-polariton arising from strong light-matter interaction between exciton and optical cavity has attracted considerable attention due to its potential applications in Bose-Einstein condensation, low-threshold lasing, and slow light. In recent years, two-dimensional lead halide perovskite has emerged as an ideal candidate for realizing exciton polariton at room temperature because it has large exciton binding energy and quantum yield. Here, we demonstrate that strong coupling could be enabled with a perovskite metasurface that supports multipolar Mie resonance, including magnetic quadrupole dominant, anapole, and toroidal resonances. For an array of perovskite nanodisks, the strong coupling behavior between these resonances and exciton is confirmed by the anticrossing features in absorption spectra mapping, while the Rabi splitting is increased from 230.7 meV in magnetic quadrupole-exciton strong coupling to 253 meV in both anapole-exciton and toroidal-exciton strong coupling. The enhanced Rabi splitting is attributed to the stronger field localization within the perovskite instead of within the air gap. In addition, we find that the Rabi splitting depends on the oscillatory strength of the exciton mode and can then be boosted to 362 meV in anapole-exciton strong coupling. Our results provide promising ways to improve the performance of optoelectronic devices such as low-threshold lasers and slow-light devices.

Structure Constants in N=2 Superconformal Quiver Theories at Strong Coupling and Holography.

In a four-dimensional N=2 superconformal quiver theory with gauge group SU(N)×SU(N) and bifundamental matter, we analytically obtain the exact strong-coupling behavior of the normalized 3-point correlators of single-trace scalar operators in the large-N limit using localization techniques. We then obtain the same strong-coupling behavior from the holographic dual using the AdS/CFT correspondence at the supergravity level. This agreement confirms the validity of the analytic strong-coupling results and of the holographic correspondence in a nonmaximally supersymmetric setup in four dimensions.

Renormalization group study of the dynamics of active membranes: Universality classes and scaling laws.

Motivated by experimental observations of patterning at the leading edge of motile eukaryotic cells, we introduce a general model for the dynamics of nearly-flat fluid membranes driven from within by an ensemble of activators. We include, in particular, a kinematic coupling between activator density and membrane slope which generically arises whenever the membrane has a nonvanishing normal speed. We unveil the phase diagram of the model by means of a perturbative field-theoretical renormalization group analysis. Due to the aforementioned kinematic coupling the natural early-time dynamical scaling is acoustic, that is the dynamical critical exponent is 1. However, as soon as the the normal velocity of the membrane is tuned to zero, the system crosses over to diffusive dynamic scaling in mean field. Distinct critical points can be reached depending on how the limit of vanishing velocity is realized: in each of them corrections to scaling due to nonlinear coupling terms must be taken into account. The detailed analysis of these critical points reveals novel scaling regimes which can be accessed with perturbative methods, together with signs of strong coupling behavior, which establishes a promising ground for further nonperturbative calculations. Our results unify several previous studies on the dynamics of active membrane, while also identifying nontrivial scaling regimes which cannot be captured by passive theories of fluctuating interfaces and are relevant for the physics of living membranes.

Universal properties of active membranes.

We put forward a general field theory for nearly flat fluid membranes with embedded activators and analyze their critical properties using renormalization group techniques. Depending on the membrane-activator coupling, we find a crossover between acoustic and diffusive scaling regimes, with mean-field dynamical critical exponents z=1 and 2, respectively. We argue that the acoustic scaling, which is exact in all spatial dimensions, leads to an early-time behavior, which is representative of the spatiotemporal patterns observed at the leading edge of motile cells, such as oscillations superposed on the growth of the membrane width. In the case of mean-field diffusive scaling, one-loop corrections to the mean-field exponents reveal universal behavior distinct from the Kardar-Parisi-Zhang scaling of passive interfaces and signs of strong-coupling behavior.

Thermo-mechanical coupling shock waves propagation with phase transition under impact loading

In the present study, a thermo-mechanical coupling model including constitutive relation and kinetics for phase transformation is developed to study stress wave propagation in shape memory TiNi rods. The front tracking/capturing method is adopted for numerical analysis and impact experiments are performed to verify theoretical model. It is demonstrated that, a phase transition shock wave will be induced during loading due to the mixed phase hardening effect originating from the temperature dependence of transformation stress, and for unloading, double wave profile (an elastic wave and a shock wave with reverse phase transition) will be excited since the change of unloading path caused by the transient temperature rise during loading. Furthermore, shock wave propagation speeds are increased with loading stress, while driving force acting on the shock wave is supplied by shock dissipation energy, in which the temperature gradient across the shock front plays an important role. SHPB experiments show that the phase change wavefront is also a moving temperature interface, which will have an important influence on the stress wave structure. Taylor impact experiments show that the proposed kinetic relation in this paper is in good agreement with the experimental results, which reflects the intrinsic characteristic of materials with strong nonlinear thermo-mechanical coupling behavior.

Heavy quark spin partners of the Y(4260) in coupled-channel formalism

The charmoniumlike state $Y(4260)$ is described as predominantly a $D_1 \bar{D}$ molecule in a coupled-channel quark model [Phys.\,Rev.\,D\,\textbf{96},\,114022\,(2017)]. The heavy quark spin symmetry (HQSS) thus implies the possible emergence of its heavy quark spin partners with molecular configuration as $D_1 \bar{D}^*$ and $D_2^* \bar{D}^*$ below these charmed mesons' thresholds. We analyze the probabilities of various intermediate charmed meson loops for $J^{PC}=1^{--}$ exotic state $Y(4360)$ and find that the channel $D_1 \bar{D}^*$ couples more strongly around its mass regime, and the coupling behavior remains the same even if the mass of $Y(4360)$ is pushed closer to $D_1 \bar{D}^*$ threshold. This enlightens that the most favorable molecular scenario for the $Y(4360)$ could be $D_1 \bar{D}^*$, and hence it can be interpreted as HQSS partner of the $Y(4260)$. We also find the strong coupling behavior of $D_2^* \bar{D}^*$ channel with the $\psi(4415)$, which makes it a good candidate for a dominant $D_2^* \bar{D}^*$ molecule. We discuss the important decay patterns of these resonances to disentangle their long- and short-distance structures.