RSS Few-Body Systems
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Isospin Symmetry of $$\omega $$ Meson at Finite Temperature in the Soft-Wall Model of Holographic QCD
Abstract
The coupling constants of \(\rho \) meson-nucleon and \(\omega \) meson-nucleon are connected through the isospin relation. Using the soft-wall model of holographic QCD, the current work aims to examine the violation (if any) of isospin symmetry of the \(\omega \) -meson as well as the temperature dependency of the \(\omega \) -meson- \(\Delta \) and \(\omega \) -meson-nucleon- \(\Delta \) baryon coupling constants. Applying the temperature-dependent profile functions of the vector and fermion fields to the expression of the coupling constants in the model yields the temperature dependence of the coupling constants. The minimum and magnetic type interactions between vector and fermion fields in 5-dimensional AdS space-time are included in the written interaction Lagrangian terms. The temperature dependence of the coupling constants \(g_{\omega N N}(T)\) , \(g_{\omega \Delta \Delta }(T)\) , and \(g_{\omega N \Delta }(T)\) has been investigated. Comparing \(g_{\omega NN}(T)\) with the coupling constant \(g_{\rho NN}(T)\) , it is found that the isospin symmetry of the \(\omega \) and \(\rho \) mesons is not violated at the finite temperature. It is also observed that the coupling constant of the \(\omega \) meson with baryons decreases as the temperature increases, and this coupling constant becomes zero near the confinement-deconfinement phase transition temperature.
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Cross Section Calculation of H–He Collisions using Three-Electron Close-Coupling Method
Abstract
The three-electron atomic-orbital close-coupling method is applied to H–He collision. The cross sections are calculated for projectile excitations to H(2 s) and H(2p), ionizations of projectile H, single ionization of target He, and electron capture for incident energy of 0.5–30 keV. Some basis sets are adopted to see the convergence behavior of the cross section for each process. The electron-exchange effect is essential to obtain reasonable results. Although the results have not yet reached convergence, the agreement with the experimental data is as good as previous calculations or better.
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Folding Procedure for $$\Omega $$ - $$\alpha $$ Potential
Abstract
Using the folding procedure, we investigate the bound state of the \(\Omega \) + \(\alpha \) system. Previous theoretical analyses have indicated the existence of a deeply bound ground state, which is attributed to the strong \(\Omega \) -nucleon interaction. By employing well-established parameterizations of nucleon density within the alpha particle, we performed numerical calculations for the folding \(\Omega \) - \(\alpha \) potential. Our results show that the \(V_{\Omega \alpha }(r)\) potential can be accurately fitted using a Woods-Saxon function, with a phenomenological parameter \(R = 1.1A^{1/3} \approx 1.74\) fm ( \(A=4\) ) in the asymptotic region where \(2< r < 3\) fm. We provide a thorough description of the corresponding numerical procedure. Our evaluation of the binding energy of the \(\Omega \) + \(\alpha \) system within the cluster model is consistent with both previous and recent reported findings. To further validate the folding procedure, we also calculated the \(\Xi \) - \(\alpha \) folding potential based on a simulation of the ESC08c Y-N Nijmegen model. A comprehensive comparison between the \(\Xi \) - \(\alpha \) folding and \(\Xi \) - \( \alpha \) phenomenological potentials is presented and discussed.
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An Experimental Platform for Studying the Heteronuclear Efimov Effect with an Ultracold Mixture of $$^\textbf{6}$$ Li and $$^\textbf{133}$$ Cs Atoms
Abstract
We present the experimental apparatus enabling the observation of the heteronuclear Efimov effect in an optically trapped ultracold mixture of \(^6\) Li- \(^{133}\) Cs with high-resolution control of the interactions. A compact double-species Zeeman slower consisting of four interleaving helical coils allows for a fast-switching between two optimized configurations for either Li or Cs and provides an efficient sequential loading into their respective MOTs. By means of a bichromatic optical trapping scheme based on species-selective trapping we prepare mixtures down to 100 nK of \({1\times 10^{4}}\) Cs atoms and \({7\times 10^{3}}\) Li atoms. Highly stable magnetic fields allow high-resolution atom-loss spectroscopy and enable to resolve splitting in the loss feature of a few tens of milligauss. These features allowed for a detailed study of the Efimov effect.
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The Steepest Slope toward a Quantum Few-Body Solution: Gradient Variational Methods for the Quantum Few-Body Problem
Abstract
Quantum few-body systems are deceptively simple. Indeed, with the notable exception of a few special cases, their associated Schrödinger equation cannot be solved analytically for more than two particles. One has to resort to approximation methods to tackle quantum few-body problems. In particular, variational methods have been proposed to ease numerical calculations and obtain precise solutions. One such method is the Stochastic Variational Method, which employs a stochastic search to determine the number and parameters of correlated Gaussian basis functions used to construct an ansatz of the wave function. Stochastic methods, however, face numerical and optimization challenges as the number of particles increases.We introduce a family of gradient variational methods that replace stochastic search with gradient optimization. We comparatively and empirically evaluate the performance of the baseline Stochastic Variational Method, several instances of the gradient variational method family, and some hybrid methods for selected few-body problems. We show that gradient and hybrid methods can be more efficient and effective than the Stochastic Variational Method. We discuss the role of singularities, oscillations, and gradient optimization strategies in the performance of the respective methods.