Interacting Boson Model Research Articles

Preponderance of triaxial shapes in atomic nuclei predicted by the proxy-SU(3) symmetry

Abstract The proxy-SU(3) symmetry predicts, in a parameter-free way, based only on the Pauli principle and the short-range nature of the nucleon-nucleon interaction, non-vanishing values of the collective variable gamma almost everywhere across the nuclear chart. Substantial triaxiality with gamma between 15 and 45 degrees is proved to be expected along horizontal and vertical stripes on the nuclear chart, covering the nucleon numbers 22-26, 34-48, 74-80, 116-124, 172-182. Empirical support for these stripes is found by collecting all even-even nuclei for which the first two excited 2+ states are known, along with the B(E2)s connecting them, as well as the second 2+ state to the ground state. The stripes are related to regions in which oblate SU(3) irreducible representations appear, bearing similarity to the appearance of triaxiality within the SU(3)* dynamical symmetry of the interacting boson model-2. Detailed comparisons of the proxy-SU(3) predictions to the data and to predictions by state-of-the-art Monte Carlo shell model calculations for deformed N=94, 96, 98 isotones in the rare earth region show good overall agreement, with the exception of Z=70 and N=94, which correspond to fully symmetric proxy-SU(3) irreps, suggesting that the latter are an artifact of the method which can be amended by considering the influence of the neighboring irreps.

Study of the properties of Ru-isotopes using the proton-neutron interacting boson model (IBM-2)

The proton-neutron interacting boson model (IBM-2) has been used to make a schematic study of the Ruthenium ( ) isotopes of mass region around with and . For each isotope of the values of the IBM-2 Hamiltonian parameters, which yield an acceptable results for excitation energies in comparison with those of experimental data, have been determined. Fixed values of the effective charges ( ) and of the proton and neutron g factors ( and ) have been chosen for all isotopes under study. The calculated electric quadrupole moments of state, transitions, the magnetic dipole moments transitions and mixing ratios are in reasonable agreement with the experimental data.

Entanglement entropy approach for examining quantum phase transition in the framework of semiclassical approximation: Testing its validity in Casten triangle

The entanglement entropy of s and d bosons in the framework of Interacting Boson Model -1 (IBM-1) has been obtained using consistent-Q formalism and semiclassical approximation. This has been possible by using Schmidt decomposition and expressing s and d bosons entanglement entropy in terms of Schmidt numbers. In this research, a simple method in the framework of IBM-1 has been presented for deriving the entanglement entropy in the Casten triangle. The results indicated that the entanglement entropy is sensitive to the shape-phase transition in the various regions of the Casten triangle. It was demonstrated that the entanglement entropy of s and d bosons in the semiclassical approximation depends only on the values of the deformation parameter (β) and is independent of the angular parameter (γ). Also, the entanglement entropy between s and d bosons reaches its maximum value in the O(6) limit, while it decreases in the SU(3) limit, and reaches zero in the U(5) limit. Based on the results obtained via Schmidt decomposition, it is shown that the probability distribution functions of the number of s bosons in IBM-1 are the binomial distributions. For NB≫1, it was proved that the distribution function in the SU(3), O(6) and SU(3)‾ limits is the Gaussian, and in the U(5) limit is the Poissonian.

An Investigation into Properties for (_66^156)Dy Isotope Using IBM-1 and IVBM Model

Abstract: The (_66^156)Dy isotopes in the O (6) region were investigated. The positive ground-state band of (_66^156)Dy nuclei was calculated using the interacting boson model ‎(IBM-1) and the interacting vector boson model (IVBM). The negative parity band energies of the above isotope were calculated using (IVBM) only. We plotted the ratios ((E(I+2))/(〖E(2〗_1^+)), (E(I+2))/(E(I)),r(((I+2))/I)) and the E-GOS curve as a function of the spin (I) to investigate the properties of the yrast band. Accordingly, the best-fit values of the parameters were used to construct the Hamiltonian, and the electromagnetic transition probability B(E2) of this nucleus was determined. Theoretical energy levels of dysprosium-156 isotope with a neutron number N = 90 and spin parity up to 〖30〗_1^+ were obtained using the MATLAB-20 simulation program. A comparison of these calculated energy levels with the corresponding experimentally measured ones shows a good agreement. The results also ‎draw our attention to the fact that the nucleus of interest deforms and exhibits gamma-instability ‎properties. Keywords: Dysprosium Isotopes, Even-even nuclei, Interacting Boson Model-1, Interacting Vector Boson Model, Negative parity, Yrast band. Abbreviations and Acronyms, IBM: Interacting Boson Model, IVBM: Interacting Vector Boson Model, U(5): Spherical limit, SU(3): Axially deformed shape limit O(6): γ-unstable limit, SP(12; R): the non-compact symplectic group.

IBFFM Low-Lying States and Their Spin- Dependent Level Densities For Even-A Nuclei Associated with SU(6) Approximation and It’s O(6) Dynamical Symmetry of IBM

Objective: in this paper spin dependent level density dependence from dynamical, exchange particle-quasiparticle interactions and residual proton-neutron interactions are investigated. Theoretical framework: in the interacting boson-fermion-fermion model(IBFFM) for odd-odd nuclei 196Au the low-lying states and their densities are calculated for π d 3/2 , π d 5/2 , π s ½ , π h11/2 proton quasiparticles and ν p1/2, ν f5/2, ν p3/2, ν f7/2, ν i13/2 neutron quasiparticles and ν p1/2, ν f5/2, ν p3/2, ν f7/2, ν i13/2 neutron quasiparticles states, coupled to the IBM core in Su(6) approximation and it's O(6) dynamical symetry of interacting boson model (IBM). Method: we also applied cutting bosons and fermions space and investigated their impacts on spin dependent level density. The results are shown graphically and compared to the previous combinatorial, thermodynamic and spectral distribution approaches for 132Pr, 244 am and 114 Cd. Results and discussion: the IBFFM low-lying states up to 2 MeV are exactely in acordance with experimentala data. The IBFFM spin–dependent level densities can be well accounted by bethe and modified spin distribution formula. For small changes of dynamical, exchange and residual interactions we have a small changes in the spin-dependent level density of states. Research implications: the complex collective features and interplay between collective and quasiparticle degrees of freedom do not influence sizeable the IBFFM spin-dependent level density distribution. Originality/value: this study contributes to the literature of IBFFM low-lying states and their spin- dependent level densities for even-A nuclei.

Collectivity at the prolate-oblate transition: The [formula omitted] lifetime of 190W

The neutron-rich rare isotope 190W is discussed as a candidate for a prolate-oblate transitional nucleus with maximum γ-softness. The collectivity of this isotope is assessed for the first time by the measurement of the reduced E2 transition probability of its first 2+ state to the ground state. The experiment employed the FAst TIming Array (FATIMA), comprised of 36 LaBr3(Ce) scintillators, which was part of the DESPEC setup at GSI, Darmstadt. The 41+ and 21+ states of 190W were populated subsequently to the decay of its 127(12) μs isomeric Jπ=10− state. The mean lifetime of the 21+ state was determined to be τ=274(28) ps, which corresponds to a B(E2;21+→01+) value of 95(10) W.u. The results motivated a revision of previous calculations within an energy-density functional-based interacting boson model-2 approach, yielding E2 transition properties and spectroscopic quadrupole moments for tungsten isotopes. From comparison to theory, the new data suggest that 190W is at the transition from prolate to oblate structure along the W isotopic chain, which had previously been discussed as a nuclear shape-phase transition.

Re-examination of nuclear structure properties and shape co-existence of nuclei around A ∼ 70

We re-examine the nuclear structure properties of waiting point nuclei around A ∼ 70 using the interacting boson model-1 (IBM-1) and the relativistic mean field (RMF) model. Effective density-dependent meson-exchange functional (DD-ME2) and density-dependent point-coupling functional (DD-PC1) were used for the RMF calculations. We calculated the energy levels, the geometric shapes, binding and separation energies of nucleons and quadrupole deformation parameters (β2). The shape co-existence phenomena in A ∼ 70 nuclei (68Se, 70Se, 70Br, 70Kr, 72Kr, 74Kr, 74Rb and 74Sr) was later investigated. Spherical and deformed shapes of the selected waiting point nuclei were computed using the IBM-1 and RMF models, respectively. The proton-neutron quasiparticle random phase approximation (pn-QRPA) model was used to calculate β-decay properties (Gamow-Teller strength distributions, β-decay half-lives and branching ratios) of selected nuclei as a function of β2. The results revealed a significant variation in calculated half-lives and Gamow-Teller strength distributions as the shape parameter was changed. The β2 computed via DD-ME2 functional resulted in half-lives in best agreement with the measured data.

A study of the nuclear structure of even-even Te isotopes in the Interacting Boson Model framework

A study of the nuclear structure of even-even Te isotopes in the Interacting Boson Model framework

Weakening of N = 28 shell gap and the nature of 02+ states

The work reports a novel application of the interacting boson model in light-mass region around 48Ca, that takes into account intruder states and configuration mixing. The model is shown to provide a reasonable description of the observed low-lying yrast and yrare states of the N = 28 even–even isotones from Si to Fe, and even–even Ca isotopes. The nature of 02+ states is addressed in terms of the competition between spherical and deformed intruder configurations, and the rigidity of the N = 28 shell gap is tested, particularly for 44S. The 02+ isomer in 44S is shown to arise from a weak mixing between the two configurations and called as shape isomer. The unresolved low-lying spectra in 46Ar is also approached using the core-excitations across N = 28 shell. The SU(3) structure in 42Si is supported by the present calculation. The nearly spherical nature of 50Ti, 52Cr, 54Fe and 42,44,46Ca isotopes is found, while the core excitations are found to be essential for the description of yrare states. Shell model calculation is also performed for comparison.

Dynamical Symmetry and B(E2) Transitions of (_42^94)Mo by Utilizing (IBM-1)

Background:In this study, we utilize the IBM-1 model to theoretically investigate the structural characteristics of , with a specific emphasis on a nucleus consisting of 5 bosons. Employing the IBM-1, an innovative interacting boson model, we analyze the nuclear structure. Materials and Methods: In our theoretical exploration, we delved into the nuclear architecture of Molybdenum. Employing the Interacting Boson Model (IBM-1), we identified the pertinent Hamiltonian to scrutinize the isotope in this research endeavor. Results: Our investigation delved into the symmetry limit of the proposed nucleus, unveiling its stable nature within the SU(5) dynamical symmetry domain. To optimize alignment with observed energy states in experiments, we meticulously determined the parameters in the IBM-1 Hamiltonian equation. Furthermore, our research extends to the computation of B(E2) transitions, quadrupole moments, and energy levels across all bands for the examined nucleus. Conclusions: Our investigation reveals the stability of the nucleus in the isotope, showcasing the presence of SU(5) dynamical symmetry. These findings offer fresh perspectives by suggesting additional electric quadrupole moments.

Intertwined quantum phase transitions in the zirconium and niobium isotopes

Nuclei in the A ≈ 100 region exhibit intricate shape-evolution and configuration crossing signatures. Exploring both even–even and their adjacent odd-mass nuclei gives further insight on the emergence of deformation and shape-phase transitions. We employ the algebraic frameworks of the interacting boson model with configuration mixing and the new interacting boson-fermion model with configuration mixing in order to investigate the even–even zirconium with neutron number 52–70 (40Zr) and odd-mass niobium (41Nb) isotopes with 52–62. We compare between the evolution in energy levels, configuration and symmetry content of the wave functions, two neutron separation energies and E2 transition rates, alongside comparison with the experimental data. The comparisons between the two chains of isotopes denote the occurrence of two types of QPTs, a crossing of normal and intruder configurations (named Type II QPT), and a shape-evolution of the intruder configuration (named Type I QPT). The latter QPT begins from spherical shape to axially deformed rotor in the Zr isotopes and from weak to strong coupling scenario in the Nb isotopes. This occurrence, named intertwined quantum phase transitions (IQPTs), in the even–even Zr chain is thus demonstrated to persists when coupling a proton to the boson core for the odd-mass Nb chain, even as deformation increases.

Description of moment of inertia and the interplay between anti-pairing and pairing correlations in 244Pu and 248Cm* *Xiao-Tao He Supported by the the National Key R and D Program of China (2023YFA1606503)

A variable moment of inertia (VMI) inspired interacting boson model (IBM), which includes many-body interactions and a perturbation possessing (5) (or (5)) symmetry, is used to investigate the rotational bands of the mass region. A novel modification is introduced, extending the Arima coefficient to the third order. This study is dedicated to the quantitative analysis of evolving trends in intraband γ-transition energy as well as the kinematic and dynamic moments of inertia (MoIs) within the rotational bands of Pu and Cm. The computed outcomes exhibit an exceptional degree of agreement with experimental observations across various conditions. The significance of including a higher-order Arima coefficient is further examined by contrasting it with the previously proposed model. The calculated results demonstrate the significance of both the anti-pairing and pairing effects in the evolution of the dynamic MoI. Additionally, these insights reveal the importance of a newly introduced parameter in accurately depicting complex nuclear behaviors, such as back-bending, up-bending, and downturn in the MoI.

Origin of regularity in different nuclei from the viewpoint of the effective quadrupole deformation and triaxiality

This paper presents a theoretical investigation of the possible relation between the regularity of nuclei and the quadrupole deformation of different levels (and also triaxiality). The present paper aims to uncover the underlying physical reasons for this regularity. To this aim, we calculated the effective quadrupole deformation of different levels using the interacting boson model. Also, different ratios between the quadrupole deformations of the energy levels in the ground, beta, and gamma bands are defined. The results for the energy levels confirm the correctness of labeling these states by the quantum numbers of U(5) and SU(3) dynamical symmetry limits (and also the extraction processes). Also, we observed a repetition pattern for these ratios for regular nuclei. Of course, the regularity and sameness of repetition patterns for the levels of the rotational bands are more than the levels of the ground band. For further study, we analyzed the effective quadrupole deformation values of different levels of regular nuclei using random matrix theory. The results show a strong statistical correlation for these quantities and confirm the observed repetition pattern. Also, the results of our studies showed that regular nuclei have triaxial properties.

Nuclear structure properties and weak interaction rates of even–even Fe isotopes

Nuclear structure properties and weak interaction rates of neutron-rich even–even iron (Fe) isotopes (A = 50 – 70) are investigated using the Interacting Boson Model-1 (IBM-1) and the proton–neutron Quasiparticle Random Phase Approximation (pn-QRPA) model. The IBM-1 is used for the calculation of energy levels and the B(E2) values of neutron-rich Fe isotopes. Later their geometry was predicted within the potential energy formalism of the IBM-1 model. Weak interaction rates on neutron-rich nuclei are needed for the modeling and simulation of presupernova evolution of massive stars. In the current study, we investigate the possible effect of nuclear deformation on stellar rates of even–even Fe isotopes. The pn-QRPA model is applied to calculate the weak interaction rates of selected Fe isotopes using three different values of deformation parameter. It is noted that, in general, bigger deformation values led to smaller total strength and larger centroid values of the resulting Gamow–Teller distributions. This later translated to smaller computed weak interaction rates. The current finding warrants further investigation before it may be generalized. The reported stellar rates are up to 4 orders of magnitude smaller than previous calculations and may bear astrophysical significance.

Study of Octupole Transitions in Xe, Ba, Ce and Nd Nuclei within Interacting Boson Model

For nuclei with 54≤Z≤60 and 86≤N≤94, the results regarding the excitation spectra at low energies, both in positive and negative parity, as well as the transition probabilities for electric dipole (B(E1)), quadrupole (B(E2)), and octupole transitions (B(E(3)), indicate the emergence of significant octupole behavior. These observations have been made using the Interacting Boson Model-1 (IBM-1). The study examines the onset of octupole deformation and its impact on the spectroscopic characteristics in even-even neutron-rich lanthanide isotopes, specifically in the Ba and Nd nuclei. The investigation compares the results obtained from the Interacting Boson Model-1 (IBM-1) with the existing experimental data. The focus is on understanding how the addition of neutrons influences the development of octupole deformation and its manifestation in the observed spectroscopic features. The onset of strong octupolarity for Z≈ 56 and N ≈ 88 nuclei is indicated by the results obtained for the electric dipole, quadrupole, and octupole transition probabilities, as well as the low-energy positive and negative-parity excitation spectra. Conversely, discrepancies between the spectroscopic data and the IBM results suggest that the mapping quality needs to be evaluated in order to determine if the mapped boson Hamiltonian or the fermionic calculations are the source of the issues.

Prolate-oblate shape transitions and O(6) symmetry in even-even nuclei: A theoretical overview

Abstract Prolate to oblate shape transitions have been predicted in an analytic way in the framework of the Interacting Boson Model (IBM), determining O(6) as the symmetry at the critical point. Parameter-independent predictions for prolate to oblate transitions in various regions on the nuclear chart have been made in the framework of the proxy-SU(3) and pseudo-SU(3) symmetries, corroborated by recent non-relativistic and relativistic mean field calculations along series of nuclear isotopes, with parameters fixed throughout, as well as by shell model calculations taking advantage of the quasi-SU(3) symmetry. Experimental evidence for regions of prolate to oblate shape transitions is in agreement with regions in which nuclei bearing the O(6) dynamical symmetry of the IBM have been identified, lying below major shell closures. In addition, gradual oblate to prolate transitions are seen when crossing major nuclear shell closures, in analogy to experimental observations in alkali clusters.

The Evolution of 174Yb, 176Hf, 178W and 180Os Isotones

The characteristics of 174Yb, 176Hf, 178W, and 180Os isotones are determined, followed by the calculation of their energy states. The first energy states 𝐸21+ and the ratios of the second excited energy states to the first excited energy states𝑅4/2 = 𝐸41 +/𝐸21+ provide primary information regarding the characteristics of the nuclei at low levels. To know the properties of high-energy states of nuclei, the behavior of the ground states band (GSB) studied by determine the back-bending curves which may occur and determine the change in the moment of inertia 2𝜗/ℏ2 and the rotation energy of gamma emitted at different states 2𝜔2, the E-GOS curve which study the gamma energy emitted from each state 𝐸𝐵🁡nd the behavior of the successive energy states in comparison with those states close to them 𝑟 (𝐼+2🀩 are drawn and studied. The relationship between GSB and NPB (the negative parity band) which give the odd staggering ∆𝐼 = 1 curve of each nucleus have been studied and determine the probability of change of the property of 174Yb, 176Hf, 178W, 180Os isotones. We used all of the information from the previous study to calculate the energy states of GSB using the appropriate equations for the different limits of the interacting boson model IBM-1. The interacting vector boson model IVBM was also utilized to compute the GSB and NPB of the isotones 174Yb, 176Hf, 178W, 180Os. A modification of IVBM was introduced to improve the results of calculations.

Algebraic cluster model calculations for shape phase transitions of boson-fermion systems

The Algebraic Cluster Model (ACM) is an interacting boson model that gives the relative motion of the cluster configurations in which all vibrational and rotational degrees of freedom are present from the outset. We schemed a solvable extended transitional Hamiltonian based on affine [Formula: see text] Lie algebra within the framework for two-, three- and four-body algebraic cluster models that explains both regions [Formula: see text], [Formula: see text] and [Formula: see text], respectively. We offer that this method can be used to study [Formula: see text] nucleon structures with [Formula: see text] and [Formula: see text] in specific [Formula: see text] such as structures [Formula: see text], [Formula: see text], [Formula: see text]; [Formula: see text], [Formula: see text], [Formula: see text]; [Formula: see text], [Formula: see text]. Numerical extraction to the energy levels, the expectation value of the boson number operator, and the behavior of the overlap of the ground state wave function within the control parameters of this evaluated Hamiltonian are presented. The effect of the coupling of the odd particle to an even–even boson core is discussed along the shape transition and, in particular, at the critical point.

Effect of general anesthesia drugs on GFAP/Iba-1 expression: a meta-analysis.

Glial fibrillary acidic protein (GFAP) is a marker associated with astrocyte activation and plays a role in various pathologic processes, including traumatic brain injury, stroke, and neurodegenerative diseases. Interacting boson approximation (Iba-1) is a marker protein for microglia, which are important in neuroinflammatory responses. This meta-analysis aimed to investigate the impact of general anesthetics on the expression of GFAP and Iba-1 in animal models. A meta-analysis was conducted using databases such as PubMed, EMBASE, Springer, and Web of Science. The quality of the selected publications was estimated using the SYRCLE guidelines to ensure credibility and consistency of the research. Continuous variables were measured using mean difference or standardized mean difference (SMD), with a 95% confidence interval (CI) calculated. Ten randomized controlled animal experiments were included in this analysis, utilizing different general anesthetics such as sevoflurane and propofol compared to untreated control groups. The results consistently demonstrated a significant increase in GFAP (SMD = 0.41, 95% CI: 0.09, 0.72, P = 0.01) and Iba-1 (SMD = 0.43, 95% CI: 0.04, 0.83, P = 0.03) expression in the general anesthetic-treated groups, suggesting a neuroinflammatory response induced by these agents. Assessment of publication bias revealed no significant bias in the included studies. This meta-analysis highlights the impact of general anesthetics on GFAP expression in animal models, emphasizing the importance of understanding the neuroinflammatory response associated with anesthesia administration. Further research is warranted to elucidate the underlying molecular pathways and explore possible therapeutic interventions to mitigate adverse effects associated with anesthesia administration.

New Interacting Boson Fermion-Fermion Model results

We present a new application of the Interacting Boson Model (IBM) and its extensions for describing double charge exchange reactions. The study of double charge exchange reactions induced by heavy ions involving candidate nuclei for neutrinoless double beta decay is a complex task carried out by the NUMEN collaboration. This investigation faces the intricacies of complex oddodd intermediate nuclei in sequential double charge exchange processes. We will offer a comprehensive description of heavy odd-odd nuclei using the Interacting Boson Fermion-Fermion Model (IBFFM). Additionally, we will outline the methodology for describing transfer operators within this framework. Finally, we will explore the potential applications of our results for describing double charge exchange reactions.