Search results for "Strong coupling"
showing 10 items of 53 documents
A coupled lossy local-mode theory description of a plasmonic tip
2012
International audience; We investigate power propagation in a metal-coated tapered optical fiber. We analyze in detail the conversion from the fiber core guided mode to a surface plasmon polariton (SPP) confined at the tip apex. To this aim, we adapt coupled local-mode theory to include lossy modes. Two distinct regimes are identified. In the case of thin metal coating, a strong coupling regime occurs between a core guided mode and a SPP with good conversion efficiency. In the case of thick metal coating, a very weak coupling occurs. Finally, energy confinement and the role of Joule losses are discussed in the near-infrared and visible ranges. Moreover, the coupled equations derived for loc…
Engineering light emission of two-dimensional materials in both the weak and strong coupling regimes
2017
Abstract Two-dimensional (2D) materials have promising applications in optoelectronics, photonics, and quantum technologies. However, their intrinsically low light absorption limits their performance, and potential devices must be accurately engineered for optimal operation. Here, we apply a transfer matrix-based source-term method to optimize light absorption and emission in 2D materials and related devices in weak and strong coupling regimes. The implemented analytical model accurately accounts for experimental results reported for representative 2D materials such as graphene and MoS2. The model has been extended to propose structures to optimize light emission by exciton recombination in…
From kinks to compactonlike kinks
1998
We show that, in the continuum limit, the generalized \ensuremath{\Phi}-four or double-well model with nonlinear coupling can exhibit compactonlike kink solutions for some specific velocity regimes and when the nonlinear coupling between pendulums is dominant. Our numerical simulations point out that the static compacton is stable and the dynamic compacton is unstable. Our study is extended to other topological systems where compacton solutions can also be found. A nice feature is that a mechanical analog of the double-well system can be constructed in the form of an experimental lattice of coupled pendulums, which, in the strong coupling limit, allows the observation of these entities.
Sensitivity of Measurement-Based Purification Processes to Inner Interactions
2017
The sensitivity of a repeated measurement-based purification scheme to additional undesired couplings is analyzed, focusing on the very simple and archetypical system consisting of two two-level systems interacting with a repeatedly measured one. Several regimes are considered and in the strong coupling (i.e., when the coupling constant of the undesired interaction is very large) the occurrence of a quantum Zeno effect is proven to dramatically jeopardize the efficiency of the purification process.
Convergent Strong-Coupling Expansions from Divergent Weak-Coupling Perturbation Theory
1995
Divergent weak-coupling perturbation expansions for physical quantities can be converted into sequences of uniformly and exponentially fast converging approximations. This is possible with the help of an additional variational parameter to be optimized order by order. The uniformity of the convergence for any coupling strength allows us to take all expressions directly to the strong-coupling limit, yielding a simple calculation scheme for the coefficients of convergent strong-coupling expansions. As an example, we determine these coefficients for the ground state energy of the anharmonic oscillator up to 22nd order with a precision of about 20 digits.
The spiked harmonic oscillatorV(r)=r 2+λr −4 as a challenge to perturbation theory
1991
The standard weak- and strong-coupling perturbation series are interpreted as extreme special cases of expansions obtainable within the framework of Rayleigh-Schroedinger perturbation theory with non-diagonal propagators and unspecified zero-order energies. The formalism of the latter type is then tested by our strongly singular example. It proves suitable for applications in the domain of virtually arbitrary couplings. A few related technicalities and especially the quadruple problem of convergence are also discussed.
Nonperturbative effective model for the Higgs sector of the standard model
2010
A nonperturbative effective model is derived for the Higgs sector of the Standard Model which is described by a simple scalar theory. The renormalized couplings are determined by the derivatives of the Gaussian effective potential that are known to be the sum of infinite bubble graphs contributing to the vertex functions. A good agreement has been found with strong coupling lattice simulations when a comparison can be made.
Charmed baryon strong coupling constants in a light-front quark model
1998
Light-Front quark model spin wave functions are employed to calculate the three independent couplings g_{\Sigma_c \Lambda_c \pi}, f_{\Lambda_{c1} \Sigma_c \pi} and f_{\Lambda^{*}_{c1} \Sigma_c \pi} of S-wave to S-wave and P-wave to S-wave one-pion transitions. It is found that g_{\Sigma_c \Lambda_c \pi}=6.81 MeV^{-1}, f_{\Lambda_{c1} \Sigma_c \pi}=1.16 and f_{\Lambda^{*}_{c1} \Sigma_c \pi}=0.96 . 10^{-4} MeV^{-2}. We also predict decay rates for specific strong transitions of charmed baryons.
Precision thrust cumulant moments atN3LL
2012
We consider cumulant moments (cumulants) of the thrust distribution using predictions of the full spectrum for thrust including O(alpha_s^3) fixed order results, resummation of singular N^3LL logarithmic contributions, and a class of leading power corrections in a renormalon-free scheme. From a global fit to the first thrust moment we extract the strong coupling and the leading power correction matrix element Omega_1. We obtain alpha_s(m_Z) = 0.1141 \pm (0.0004)_exp \pm (0.0014)_hadr \pm (0.0007)_pert, where the 1-sigma uncertainties are experimental, from hadronization (related to Omega_1) and perturbative, respectively, and Omega_1 = 0.372 \pm (0.044)_exp \pm (0.039)_pert GeV. The n-th th…
Generalized parton distributions of the pion in a Bethe Salpeter approach
2004
We calculate generalized parton distribution functions in a field theoretic formalism using a covariant Bethe-Salpeter approach for the determination of the bound-state wave function. We describe the procedure in an exact calculation in scalar Electrodynamics proving that the relevant corrections outside our scheme vanish. We extend the formalism to the Nambu--Jona-Lasinio model, a realistic theory of the pion. We go in both cases beyond all previous calculations and discover that all important features required by general physical considerations, like symmetry properties, sum rules and the polynomiality condition, are explicitly verified. We perform a numerical study of their behavior in t…