Magnetic Thomas-Fermi-Weizs\"acker model for quantum dots: a comparison with Kohn-Sham ground states

The magnetic extension of the Thomas-Fermi-Weizs\"acker kinetic energy is used within density-functional-theory to numerically obtain the ground state densities and energies of two-dimensional quantum dots. The results are thoroughly compared with the microscopic Kohn-Sham ones in order to assess the validity of the semiclassical method. Circular as well as deformed systems are considered.Comment: EPJ LateX, revised EPJ-

Magnetic dipole and electric quadrupole responses of elliptic quantum dots in magnetic fields

The magnetic dipole (M1) and electric quadupole (E2) responses of two-dimensional quantum dots with an elliptic shape are theoretically investigated as a function of the dot deformation and applied static magnetic field. Neglecting the electron-electron interaction we obtain analytical results which indicate the existence of four characteristic modes, with different $B$-dispersion of their energies and associated strengths. Interaction effects are numerically studied within the time-dependent local-spin-density theory, assessing the validity of the non-interacting picture.Comment: 11 pages, 3 GIF figure

Electron spin precession in semiconductor quantum wires with Rashba spin-orbit coupling

The influence of the Rashba spin-orbit coupling on the electron spin dynamics is investigated for a ballistic semiconductor quantum wire with a finite width. We monitor the spin evolution using the time-dependent Schr\"odinger equation. The pure spin precession characteristic of the 1D limit is lost in a 2D wire with a finite lateral width. In general, the time evolution in the latter case is characterized by several frequencies and a nonrigid spin motion.Comment: 7 pages, 9 figure

Collective oscillations in quantum rings: a broken symmetry case

We present calculations within density functional theory of the ground state and collective electronic oscillations in small two-dimensional quantum rings. No spatial symmetries are imposed to the solutions and, as in a recent contribution, a transition to a broken symmetry solution in the intrinsic reference frame for an increasingly narrow ring is found. The oscillations are addressed by using real-time simulation. Conspicuous effects of the broken symmetry solution on the spectra are pointed out.Comment: ReVTeX, 5 embedded eps, two gifs. Accepted in EPJ

Exploring efficient neural architectures for linguistic-acoustic mapping in text-to-speech

Conversion from text to speech relies on the accurate mapping from linguistic to acoustic symbol sequences, for which current practice employs recurrent statistical models such as recurrent neural networks. Despite the good performance of such models (in terms of low distortion in the generated speech), their recursive structure with intermediate affine transformations tends to make them slow to train and to sample from. In this work, we explore two different mechanisms that enhance the operational efficiency of recurrent neural networks, and study their performance–speed trade-off. The first mechanism is based on the quasi-recurrent neural network, where expensive affine transformations are removed from temporal connections and placed only on feed-forward computational directions. The second mechanism includes a module based on the transformer decoder network, designed without recurrent connections but emulating them with attention and positioning codes. Our results show that the proposed decoder networks are competitive in terms of distortion when compared to a recurrent baseline, whilst being significantly faster in terms of CPU and GPU inference time. The best performing model is the one based on the quasi-recurrent mechanism, reaching the same level of naturalness as the recurrent neural network based model with a speedup of 11.2 on CPU and 3.3 on GPU.Peer ReviewedPostprint (published version