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Search Results: 1 - 10 of 325372 matches for " S. Frauendorf "
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Cross-over between different symmetries
S. Frauendorf
Physics , 2013,
Abstract: The yrast states of even even vibrational and transitional nuclei are interpreted as a rotating condensate of interacting d-bosons. The corresponding semi-classical tidal wave concept is used for microscopic calculations of energies and E2 transition probabilities. The strong octupole correlations in the light rare earth and actinide nuclides are interpreted as rotation-induced condensation of interacting f-bosons.
Description of Multi Quasi Particle Bands by the Tilted Axis Cranking Model
S. Frauendorf
Physics , 2000, DOI: 10.1016/S0375-9474(00)00308-0
Abstract: The selfconsistent cranking approach is extended to the case of rotation about an axis which is tilted with respect to the principal axes of the deformed potential (Tilted Axis Cranking). Expressions for the energies and the intra bands electromagnetic transition probabilities are given. The mean field solutions are interpreted in terms of quantal rotational states. The construction of the quasiparticle configurations and the elimination of spurious states is discussed. The application of the theory to high spin data is demonstrated by analyzing the multi quasiparticle bands in the nuclide-s with $N=102,103$ and $Z=71,72,73$.
Heart - Shaped Nuclei: Condensation of Rotational Aligned Octupole Phonons
S. Frauendorf
Physics , 2007, DOI: 10.1103/PhysRevC.77.021304
Abstract: The strong octupole correlations in the mass region $A\approx 226$ are interpreted as rotation-induced condensation of octupole phonons having their angular momentum aligned with the rotational axis. Discrete phonon energy and parity conservation generate oscillations of the energy difference between the lowest rotational bands with positive and negative parity. Anharmonicities tend to synchronize the the rotation of the condensate and the quadrupole shape of the nucleus forming a rotating heart shape.
The Low-Energy Quadrupole Mode of Nuclei
S. Frauendorf
Physics , 2015, DOI: 10.1142/S0218301315410013
Abstract: The phenomenological classification of collective quadrupole excitations by means of the Bohr Hamiltonian is reviewed with focus on signatures for triaxility. The variants of the microscopic Bohr Hamiltonian derived by means of the Adiabatic Time Dependent Mean Field theory from the Pairing plus Quadrupole-Quadrupole interaction, the Shell Correction Method, the Skyrme Energy Density Functional, the Relativistic Mean Field Theory, and the Gogny interaction are discussed and applications to concrete nuclides reviewed. The Generator Coordinate Method for the five dimensional quadrupole deformation space and first applications to triaxial nuclei are presented. The phenomenological classification in the framework of the Interacting Boson Model is discussed with a critical view on the boson number counting rule. The recent success in calculating the model parameters by mapping the mean field deformation energy surface on the bosonic one is discussed and the applications listed. A critical assessment of the models is given with focus on the limitations due to the adiabatic approximation. The Tidal Wave approach and the Triaxial Projected Shell Model are presented as practical approaches to calculate spectral properties outside the adiabatic region.
Pairing at High Spin
S. Frauendorf
Physics , 2012,
Abstract: Pair correlations are described in the framework of the HFB approximation applied to a uniformly rotating system (Cranking model). The reduction of the moments of inertia, the classification of rotational bands as multi quasiparticle configurations, and the signatures of the rotation induced transition to the unpaired state are discussed.
Transverse wobbling-a collective mode in odd-A triaxial nuclei
S. Frauendorf,F. Doenau
Physics , 2013, DOI: 10.1103/PhysRevC.89.014322
Abstract: The wobbling motion of a triaxial rotor coupled to a high-j quasiparticle is treated semiclassi- cally. Longitudinal and transverse coupling regimes can be distinguished depending on, respectively, whether the quasiparticle angular momentum is oriented parallel or perpendicular to the rotor axis with the largest moment of inertia. Simple analytical expressions for the wobbling frequency and the electromagnetic E2 and M1 transition probabilities are derived assuming rigid alignment of the quasiparticle with one of the rotor axes and harmonic oscillations (HFA). Transverse wobbling is characterized by a decrease of the wobbling frequency with increasing angular momentum. Two examples for transverse wobbling, 163Lu and 135Pr, are studied in the framework of the full triax- ial particle-rotor model and the HFA. The signature of transverse wobbling, decreasing wobbling frequency and enhanced E2 inter-band transitions, is found in agreement with experiment.
Microscopic Calculation of IBM Parameters by Potential Energy Surface Mapping
I. Bentley,S. Frauendorf
Physics , 2011, DOI: 10.1103/PhysRevC.83.064322
Abstract: A coherent state technique is used to generate an Interacting Boson Model (IBM) Hamiltonian energy surface that simulates a mean field energy surface. The method presented here has some significant advantages over previous work. Specifically, that this can be a completely predictive requiring no a priori knowledge of the IBM parameters. The technique allows for the prediction of the low lying energy spectra and electromagnetic transition rates which are of astrophysical interest. Results and comparison with experiment are included for krypton, molybdenum, palladium, cadmium, gadolinium, dysprosium and erbium nuclei.
Comment on "Interaction induced deformation of the momentum distribution of spin polarized nuclear matter" by Frick, Muether, and Sedrakian
S. Frauendorf,K. Neergard
Physics , 2002, DOI: 10.1103/PhysRevC.69.049801
Abstract: The paper does not take into account previous work where the effect they discuss is explored in detail. It is known from this previous work that the approach is incomplete.
Relation between Wigner energy and proton-neutron pairing
I. Bentley,S. Frauendorf
Physics , 2012, DOI: 10.1103/PhysRevC.88.014322
Abstract: The linear term proportional to $|N-Z|$ in the nuclear symmetry energy (Wigner energy)is obtained in a model that uses isovector pairing on single particle levels from a deformed potential combined with a $\vec T^2$ interaction. The pairing correlations are calculated by numerical diagonalization of the pairing Hamiltonian acting on the six or seven levels nearest the $N=Z$ Fermi surface. The experimental binding energies of nuclei with $N\approx Z$ are well reproduced. The Wigner energy emerges as a consequence of restoring isospin symmetry. We have found the Wigner energy to be insensitive to the presence of moderate isoscalar pair correlations.
QRPA treatment of the transverse wobbling mode reconsidered
S. Frauendorf,F. Doenau
Physics , 2015, DOI: 10.1103/PhysRevC.92.064306
Abstract: The quasiparticle random phase approximation is used to study the properties of the wobbling bands in $^{163}$Lu. Assuming that the wobbling mode represents pure isoscalar orientation oscillations results in too low wobbling frequencies and too strong M1 transitions between the one- and zero-phonon wobbling bands. The inclusion of an LL interaction, which couples the wobbling mode to the scissors mode, generates the right upshift of the wobbling frequencies and the right suppression of the B(M1)$_{out}$ values toward the experimental values. In analogy to the quenching of low-energy E1 transition by coupling to the Isovector Giant Dipole Resonance, a general reduction of the M1 transitions between quasiparticle configurations caused by coupling to the scissors mode is suggested.
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