Particle-Number Reprojection in the Shell Model Monte Carlo Method: Application to Nuclear Level Densities

Alhassid, Y.; Liu, S.; Nakada, H.

doi:10.1103/physrevlett.83.4265

Cited by 97 publications

(92 citation statements)

References 18 publications

(32 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The shell model Monte Carlo (SMMC) method has proven to be quite accurate for calculating the nuclear level density in the range of excitation energies up to several tens of MeV [1,2,3]. The advantage of the SMMC method is that it can be used to calculate thermal observables in model spaces that are orders of magnitude larger than can be treated by conventional diagonalization methods.…”

Section: Introductionmentioning

confidence: 99%

Nuclear moment of inertia and spin distribution of nuclear levels

et al. 2005

Self Cite

View full text Add to dashboard Cite

We introduce a simple model to calculate the nuclear moment of inertia at finite temperature. This moment of inertia describes the spin distribution of nuclear levels in the framework of the spincutoff model. Our model is based on a deformed single-particle Hamiltonian with pairing interaction and takes into account fluctuations in the pairing gap. We derive a formula for the moment of inertia at finite temperature that generalizes the Belyaev formula for zero temperature. We show that a number-parity projection explains the strong odd-even effects observed in shell model Monte Carlo studies of the nuclear moment of inertia in the iron region.

show abstract

Section: Introductionmentioning

confidence: 99%

Nuclear moment of inertia and spin distribution of nuclear levels

et al. 2005

Self Cite

View full text Add to dashboard Cite

show abstract

“…This limitation can be overcome in part by using the shell model Monte Carlo (SMMC) method [1][2][3][4][5]. The SMMC method enables the calculation of statistical nuclear properties, and in particular of level densities, in very large model spaces [6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Nuclear state densities of odd-mass heavy nuclei in the shell model Monte Carlo approach

2015

Self Cite

View full text Add to dashboard Cite

The shell model Monte Carlo (SMMC) approach enables the microscopic calculation of nuclear state densities in model spaces that are many orders of magnitude larger than those that can be treated by conventional diagonalization techniques. However, it has been difficult to calculate accurate state densities of odd-mass heavy nuclei as a function of excitation energy. This is because of a sign problem that arises from the projection on an odd number of particles at low temperatures, making it difficult to calculate accurate ground-state energies of odd-mass nuclei in direct Monte Carlo calculations. Here we extract the ground-state energy from a one-parameter fit of the SMMC thermal energy to the thermal energy that is determined from experimental data. This enables us to calculate the state densities of the odd-even isotopes 149−155 Sm and 143−149 Nd as a function of excitation energy. We find close agreement with state densities extracted from experimental data. Our results demonstrate that the state densities of the odd-mass samarium and neodymium isotopes can be consistently reproduced using the same Hamiltonian of the neighboring even-mass isotopes within the configuration-interaction shell model approach.

show abstract

“…The NLD can be described quite well within the finite-temperature shell model quantum Monte-Carlo method [9], but this method is time consuming when it is applied to heavy nuclei. Regarding the γ-strength functions, which involve giant resonances and the related RSF, they are beyond the scope of this method.…”

mentioning

confidence: 99%

Simultaneous Microscopic Description of Nuclear Level Density and Radiative Strength Function

2017

View full text Add to dashboard Cite

Nuclear level density (NLD) and radiative strength function (RSF) are described simultaneously within a microscopic approach, which takes into account the thermal effects of the exact pairing as well as the giant resonances within the phonon-damping model. The good agreement between the results of calculations and experimental data extracted by the Oslo group for 170,171,172 Yb isotopes shows the importance of exact thermal pairing in the description of NLD at low and intermediate excitation energies and invalidates the assumption based on the Brink-Axel hypothesis in the description of the RSF. The rapid decrease in level spacing between the excited states as the excitation energy increases to several MeV leads to an exponential increase in the level densities and transition probabilities between the excited levels in the medium and heavy nuclei. In this condition it is impractical to deal with an individual state. Instead, it is meaningful and convenient to consider the average properties of nuclear excitations. Two main quantities, which are often employed to describe these properties, are the nuclear level density (NLD) and radiative γ-ray strength function (RSF). The NLD is defined as the number of excited levels per unit of excitation energy E * , whereas the RSF is the average transition probability per γ-ray energy E γ . The NLD provides the information on several properties of an atomic nucleus, namely the pairing correlations and nuclear thermodynamic properties such as temperature, entropy, heat capacity, etc. [1]. The RSF reveals the characteristics of average nuclear electromagnetic properties [2]. These two quantities have important contributions in the study of low-energy nuclear reactions and nuclear astrophysics such as the calculation of the stellar reaction rates and the description of nucleosynthesis in stars [3,4]. The study of NLD and RSF has therefore been one of the most important topics in nuclear structure physics. It became particularly attractive after the recent developments of the experimental technique proposed by Oslo's group (the Oslo method), which is able to extract simultaneously both NLD and RSF from the primary γ-decay spectrum of the residual compound nucleus created in the transfer and/or inelastic scattering reactions [5][6][7]. These experimental data also serve as a good testing ground for all the present theoretical approaches to NLD and RSF.Although the concepts of NLD and RSF are rather old [2,8], a unified theory, which can describe simultaneously and microscopically both the NLD and RSF is still absent so far. The NLD can be described quite well within the finite-temperature shell model quantum Monte-Carlo method [9], but this method is time consuming when it is applied to heavy nuclei. Regarding the γ-strength functions, which involve giant resonances and the related RSF, they are beyond the scope of this method. The Hartree-Fock BCS [10] and Hartree-FockBogolyubov plus combinatorial method (HFBC) [11] have provided a global description of NLD and might be consid...

show abstract

Particle-Number Reprojection in the Shell Model Monte Carlo Method: Application to Nuclear Level Densities

Cited by 97 publications

References 18 publications

Nuclear moment of inertia and spin distribution of nuclear levels

Nuclear moment of inertia and spin distribution of nuclear levels

Nuclear state densities of odd-mass heavy nuclei in the shell model Monte Carlo approach

Simultaneous Microscopic Description of Nuclear Level Density and Radiative Strength Function

Contact Info

Product

Resources

About