E. Lipparini

Longitudinal modes of quantum dots in magnetic fields

Abstract.The far infrared longitudinal spin and density responses of two-dimensional quantum dots are discussed within local spin-density functional theory. The influence of a partial spin polarization, induced by a perpendicular static magnetic field, is taken into account in the coupling of spin and density channels. As an illustrative application, the case of a dot made of 5 electrons in parabolic confinement is discussed.We show that in the presence of massive particles such as nucleons, the standard low energy expansion in powers of meson momenta and light quark masses in general only converges in part of the low energy region. The expansion of the scalar form factor

Sum rules and giant resonances in nuclei

\sigma(t)

Isovector M1 rotational states in deformed nuclei

, for instance, breaks down in the vicinity of

Diffusion Monte Carlo study of circular quantum dots

t=4M_\pi^2

Orbital current mode in elliptical quantum dots

. In the language of heavy baryon chiral perturbation theory, the proper behaviour in the threshold region only results if the multiple internal line insertions generated by relativistic kinematics are summed up to all orders. We propose a method that yields a coherent representation throughout the low energy region while keeping Lorentz and chiral invariance explicit at all stages. The method is illustrated with a calculation of the nucleon mass and of the scalar form factor to order

Volume and surface symmetry energy coefficients from photoabsorption cross sections

p^4

Sum rules in extended RPA theories

.

Density-functional calculations of magnetoplasmons in quantum rings

Abstract The formalism of sum rules is developed and employed to investigate various giant resonances in nuclei. Particular emphasis is given to the role of surface effects which are shown to play a crucial role in the propagation of isoscalar as well as isovector collective modes. Sum rules for non-Hermitian operators, in particular for charge exchange reactions, are derived using the formalism of the dynamic polarizability. Several sum rules for investigating magnetic excitations, the structure of the transition density and the role of the nuclear deformation and of temperature on giant resonance are also presented and discussed.

Time-dependent Hartree-Fock polarizability and random phase approximation sum rules: (II). Application to isovector monopole, quadrupole and dipole excitations

Abstract Isovector M1 rotational states are investigated in the framework of a sum rule approach. It is shown that, due to the nuclear deformation, the rotational isovector state couples to the k = 1+ component of the isovector giant quadrupole resonance. The effect of the coupling on the energy and on the M1 strength of the low-lying state as well as the comparison with previous macroscopic and microscopic models are discussed in details. The analysis suggests the existence of a highly collective M1 state occurring at the energy ω M 1 = 56 δ A −1 3 MeV

Spin-orbit effects in GaAs quantum wells: Interplay between Rashba, Dresselhaus, and Zeeman interactions

Dipartimento di Fisica and INFM, Universit`a di Trento, I-38050 Povo,Trento, Italy(February 1, 2008)We present ground and excited state energies obtained from Diffusion Monte Carlo (DMC)calculations, using accurate multiconfiguration wave functions, for N electrons (N ≤ 13) confinedto a circular quantum dot. We compare the density and correlation energies to the predictionsof local spin density approximation theory (LSDA), and Hartree-Fock theory (HF), and analyzethe electron-electron pair-correlation functions. The DMC estimated change in electrochemicalpotential as a function of the number of electrons in the dot is compared to that from LSDA andHF calculations. Hund’s first rule is found to be satisfied for all dots except N = 4 for which thereis a near degeneracy.85.30.Vw,73.61.-rI. INTRODUCTION