Search results for "ansat"
showing 10 items of 224 documents
Perturbative treatment of triple excitations in coupled‐cluster calculations of nuclear magnetic shielding constants
1996
A theory for the calculation of nuclear magnetic shielding constants at the coupled‐cluster singles and doubles level augmented by a perturbative correction for connected triple excitations (CCSD(T)) has been developed and implemented. The approach, which is based on the gauge‐including atomic orbital (GIAO) ansatz, is illustrated by several numerical examples. These include a comparison of CCSD(T) and other highly correlated methods with full configuration interaction for the BH molecule, and a systematic comparison with experiment for HF, H2O,NH3, CH4, N2, CO, HCN, and F2. The results demonstrate the importance of triple excitations in establishing quantitative accuracy. Finally, the abil…
Dark spatial solitary waves in a cubic-quintic-septimal nonlinear medium
2017
We consider the evolution of light beams in nonlinear media exhibiting nonlinearities up to the seventh order wherein the beam propagation is governed by the cubic-quintic-septimal nonlinear Schr\"odinger equation. An exact analytic solution that describes dark solitary wave propagation is obtained, based on a special ansatz. Unlike the well-known $\text{tanh}$-profile dark soliton in Kerr media, the present one has a functional form given in terms of ``${\text{sech}}^{2/3}$''. The requirements concerning the optical material parameters for the existence of this localized structure are discussed. This propagating solitary wave exists due to a balance among diffraction, cubic, quintic, and s…
Thin bases of order h
2003
Abstract A subset A⊆ N 0 is called a basis of order h if every positive integer can be represented as a sum of h members of A . Thin bases of order h will be constructed in this paper, for each h ⩾2, where the value of lim sup A(n)/ n h is smaller than that of thin bases known so far. In the most important case h =2 it is shown that for the considered class of bases (which generalizes an ansatz of Stohr) the result is best possible up to an e >0.
Regular and singular pulse and front solutions and possible isochronous behavior in the short-pulse equation: Phase-plane, multi-infinite series and …
2014
In this paper we employ three recent analytical approaches to investigate the possible classes of traveling wave solutions of some members of a family of so-called short-pulse equations (SPE). A recent, novel application of phase-plane analysis is first employed to show the existence of breaking kink wave solutions in certain parameter regimes. Secondly, smooth traveling waves are derived using a recent technique to derive convergent multi-infinite series solutions for the homoclinic (heteroclinic) orbits of the traveling-wave equations for the SPE equation, as well as for its generalized version with arbitrary coefficients. These correspond to pulse (kink or shock) solutions respectively o…
Eurosceptic Attitudes Towards the Transatlantic Trade and Investment Partnership: Who are the Trendsetters and Followers?
2020
Since the Hooghe et al.(2002) publication about party positions on European integration, a comparison of radical right and radical left Eurosceptic parties is not often conducted. In literature about Euroscepticism, the image of the horseshoe or “inverted U” illustrates the orientation of Euroscepticism among parties without any deeper analysis. This paper tries fill the research gap by investigating whether these two Eurosceptic groups are distinct from each other in the area of EU trade policy by analyzing the debate surrounding the Transatlantic Trade and Investment Partnership (TTIP). Using European Parliament debates about this EU-US partnership, the author tries give answers to the fo…
Un ponte ancora aperto? Alcune note sull’emigrazione siciliana verso gli Stati Uniti durante il fascismo
2018
During the 1920s, after the promulgation by US government of the Quota Acts, and after the new fascist policies about emigration in Italy (1926), we register a dramatic decrease of the transatlantic migration flows from Italy to the US. Focusing on the case of Sicily, one of the region which had sent more emigrants to the US during the Great Migration, this essay analyses the issue of migratory waves from Southern Italy to the US during the Fascism. In fact, despite of the reshaping of migration policies, some traditional networks between Sicily and America are still working. For example, some new researches about transnational Mafia reveal the existence of dynamic Sicilian-American network…
Kaikki aistit käyttöön – kongressikokemuksia Lissabonista
2011
People make places - ways of feeling the world The 10th congress of the International Society of Ethnology and Folklore (SIEF) Lissabon, Portugali, 17.-21.4.2011.
Dimensión socio-laboral de las relaciones comerciales trasatlánticas: algunas lecciones del pasado.
2022
En la cumbre UE-EE.UU. del pasado 15 de junio de 2021, la Unión Europea y los Estados Unidos realizaron una declaración conjunta en la que anunciaron una asociación transatlántica renovada para la era posterior a la pandemia. De manera que en el momento en el que se refuerzan las negociaciones comerciales entre la UE y EE.UU. vale la pena analizar hasta dónde se llegó en las negociaciones del Acuerdo Transatlántico sobre Comercio e Inversión en el marco de la OMC, en particular en relación a los aspectos más controvertidos desde la perspectiva social. Lo que incluye un análisis comparado específicamente enfocado al tratamiento del desplazamiento de trabajadores en el AGCS y en la Directiva …
Kondo Resonance in a Mesoscopic Ring Coupled to a Quantum Dot: Exact Results for the Aharonov-Bohm/Casher Effects
2000
We study the persistent currents induced by both the Aharonov-Bohm and Aharonov-Casher effects in a one-dimensional mesoscopic ring coupled to a side-branch quantum dot at Kondo resonance. For privileged values of the Aharonov-Bohm-Casher fluxes, the problem can be mapped onto an integrable model, exactly solvable by a Bethe ansatz. In the case of a pure magnetic Aharonov-Bohm flux, we find that the presence of the quantum dot has no effect on the persistent current. In contrast, the Kondo resonance interferes with the spin-dependent Aharonov-Casher effect to induce a current which, in the strong-coupling limit, is independent of the number of electrons in the ring.
The discretized harmonic oscillator: Mathieu functions and a new class of generalized Hermite polynomials
2003
We present a general, asymptotical solution for the discretised harmonic oscillator. The corresponding Schr\"odinger equation is canonically conjugate to the Mathieu differential equation, the Schr\"odinger equation of the quantum pendulum. Thus, in addition to giving an explicit solution for the Hamiltonian of an isolated Josephon junction or a superconducting single-electron transistor (SSET), we obtain an asymptotical representation of Mathieu functions. We solve the discretised harmonic oscillator by transforming the infinite-dimensional matrix-eigenvalue problem into an infinite set of algebraic equations which are later shown to be satisfied by the obtained solution. The proposed ansa…