Search results for "ASIP"
showing 10 items of 322 documents
KAM Techniques for Time Dependent Quantum Systems
1995
We consider a spin 1/2 in constant magnetic field perturbed by a quasiperiodic time dependent magnetic field. We discuss its stability properties in terms of the spectrum of the corresponding quasienergy operator. Since the spectrum of the unperturbed problem is dense, there appear small denominators in the perturbation theory, corresponding to resonances. They are treated with a technique developped by L.H. Eliasson, based on a KAM iteration.
Quasiparticle alignments and α-decay fine structure of 175Pt
2014
Excited states and decay properties of 175Pt have been investigated using the 92Mo(86Sr,2pn) fusion-evaporation reaction. The JUROGAM I γ -ray spectrometer and the GREAT spectrometer were used in conjunction with the gas-filled recoil separator RITU for the measurement of the radiation at the target and focal plane positions, respectively. Two new band structures, assigned to be based on the I π = (7/2 −) ground state in 175Pt, have been established and the known yrast band has been extended up to I π = (49/2 +). Rotational properties of the excited states in 175Pt have been investigated within the cranked shell-model formalism. The low-frequency changes in the alignments of the positive- a…
Extended shell model calculation for even N = 82 isotones with a realistic effective interaction
1996
The shell model within the $2s1d0g_{7/2}0h_{11/2}$ shell is applied to calculate nuclear structure properties of the even Z=52 - 62, N=82 isotones. The results are compared with experimental data and with the results of a quasiparticle random-phase approximation (QRPA) calculation. The interaction used in these calculations is a realistic two-body G-matrix interaction derived from modern meson-exchange potential models for the nucleon-nucleon interaction. For the shell model all the two-body matrix elements are renormalized by the $\hat{Q}$-box method whereas for the QRPA the effective interaction is defined by the G-matrix.
Plasmon mass scale in classical nonequilibrium gauge theory
2017
Classical lattice Yang-Mills calculations provide a good way to understand different nonequilibrium phenomena in nonperturbatively overoccupied systems. Above the Debye scale the classical theory can be matched smoothly to kinetic theory. The aim of this work is to study the limits of this quasiparticle picture by determining the plasmon mass in classical real time Yang-Mills theory on a lattice in 3 spatial dimensions. We compare three methods to determine the plasmon mass: a hard thermal loop expression in terms of the particle distribution, an effective dispersion relation constructed from fields and their time derivatives, and by measuring oscillations between electric and magnetic fiel…
Broad excitations in a 2+1D overoccupied gluon plasma
2021
Motivated by the initial stages of high-energy heavy-ion collisions, we study excitations of far-from-equilibrium 2+1 dimensional gauge theories using classical-statistical lattice simulations. We evolve field perturbations over a strongly overoccupied background undergoing self-similar evolution. While in 3+1D the excitations are described by hard-thermal loop theory, their structure in 2+1D is nontrivial and nonperturbative. These nonperturbative interactions lead to broad excitation peaks in spectral and statistical correlation functions. Their width is comparable to the frequency of soft excitations, demonstrating the absence of soft quasiparticles in these theories. Our results also su…
Pinning down the strength function for ordinary muon capture on 100Mo
2019
Ordinary muon capture (OMC) on 100Mo is studied both experimentally and theoretically in order to access the weak responses in wide energy and momentum regions. The OMC populates states in 100Nb up to some 50 MeV in excitation energy. For the first time the associated OMC strength function has been computed and compared with the obtained data. The present computations are performed using the Morita-Fujii formalism of OMC by extending the original formalism beyond the leading order. The participant nuclear wave functions are obtained in extended no-core single-particle model space using the spherical version of proton-neutron quasiparticle random-phase approximation (pnQRPA) with two-nucleon…
First observation of high-K isomeric states in $$^{249}$$Md and $$^{251}$$Md
2021
Decay spectroscopy of the odd-proton nuclei $^{249}$Md and $^{251}$Md has been performed. High-K isomeric states were identified for the first time in these two nuclei through the measurement of their electromagnetic decay. An isomeric state with a half-life of 2.8(5) ms and an excitation energy $\ge 910$ keV was found in $^{249}$Md. In $^{251}$Md, an isomeric state with a half-life of 1.4(3) s and an excitation energy $\ge 844$ keV was found. Similarly to the neighbouring $^{255}$Lr, these two isomeric states are interpreted as 3 quasi-particle high-K states and compared to new theoretical calculations. Excited nuclear configurations were calculated within two scenarios: via blocking nucle…
Analysis of the Intermediate-State Contributions to Neutrinoless Double β− Decays
2016
A comprehensive analysis of the structure of the nuclear matrix elements (NMEs) of neutrinoless double beta-minus (0νβ-β-) decays to the0+ground and first excited states is performed in terms of the contributing multipole states in the intermediate nuclei of0νβ-β-transitions. We concentrate on the transitions mediated by the light (l-NMEs) Majorana neutrinos. As nuclear model we use the proton-neutron quasiparticle random-phase approximation (pnQRPA) with a realistic two-nucleon interaction based on the Bonn one-boson-exchangeGmatrix. In the computations we include the appropriate short-range correlations, nucleon form factors, and higher-order nucleonic weak currents and restore the isospi…
Properties of nuclei in the nobelium region studied within the covariant, Skyrme, and Gogny energy density functionals
2015
We calculate properties of the ground and excited states of nuclei in the nobelium region for proton and neutron numbers of 92 <= Z <= 104 and 144 <= N <= 156, respectively. We use three different energy-density-functional (EDF) approaches, based on covariant, Skyrme, and Gogny functionals, each within two different parameter sets. A comparative analysis of the results obtained for odd-even mass staggerings, quasiparticle spectra, and moments of inertia allows us to identify single-particle and shell effects that are characteristic to these different models and to illustrate possible systematic uncertainties related to using the EDF modelling
Nuclear structure of97Y in the interacting boson-fermion model
1988
Unique-parity states of97Y are studied in the framework of the interacting boson-fermion model (IBFM). Spin assignments for the levels of the unique-parity yrast band are proposed on the basis of nuclear systematics and the IBFM band pattern associated with coupling of a particle-type quasiparticle (g9/2) to the SU(5) core3896Sr58. The good fit of the experimental data with the IBFM calculations confirms the single particle character of this immediate neighbour of the doubly sub-magic nucleus96Zr.