Neutron Boson Research Articles

Quantum entanglement of SO(6)-U(5) transitional nuclei in the interacting boson model-2 (IBM-2)

The quantum shape phase transition between the spherical and deformed γ-unstable (U(5)−O(6)) even-even nuclei within the frameworks of Interacting Boson Model-1 and 2 (IBM-1,2) for low-lying states, using the “entanglement entropy” (S) has been studied. In both frameworks, the theoretical results showed that there exist minimum and maximum entanglement values between s bosons in the U(5) and O(6) limits, respectively. In order to confirmation of the theoretical results, we have calculated and analyzed the entanglement entropy of s−d bosons and proton (π) - neutron (ν) bosons in Cerium (C58122−136e) isotopes. The results indicate that the entanglement entropy correctly describes the transition from U(5) to O(6), for ground state (01+), but it cannot accurately determine the transitional nucleus.

Tidal Love numbers of novel and admixed celestial objects

A sub-fraction of dark matter or new particles trapped inside celestial objects can significantly alter their macroscopic properties. We investigate the new physics imprint on celestial objects by using a generic framework to solve the Tolman-Oppenheimer-Volkoff (TOV) equations for up to two fluids. We test the impact of populations of new particles on celestial objects, including the sensitivity to self-interaction sizes, new particle mass, and net population mass. Applying our setup to neutron stars and boson stars, we find rich phenomenology for a range of these parameters, including the creation of extended atmospheres. These atmospheres are detectable by their impact on the tidal love number, which can be measured at upcoming gravitational wave experiments such as Advanced LIGO, the Einstein Telescope, and LISA. We release our calculation framework as a publicly available code, allowing the TOV equations to be generically solved for arbitrary new physics models in novel and admixed celestial objects.

Can fermion-boson stars reconcile multimessenger observations of compact stars?

Mixed fermion-boson stars are stable, horizonless, everywhere regular solutions of the coupled Einstein-(complex, massive) Klein-Gordon-Euler system. While isolated neutron stars and boson stars are uniquely determined by their central energy density, mixed configurations conform an extended parameter space that depends on the combination of the number of fermions and (ultra-light) bosons. The wider possibilities offered by fermion-boson stars could help explain the tension in the measurements of neutron star masses and radii reported in recent multi-messenger observations and nuclear-physics experiments. In this work we construct equilibrium configurations of mixed fermion-boson stars with realistic equations of state for the fermionic component and different percentages of bosonic matter. We show that our solutions are in excellent agreement with multi-messenger data, including gravitational-wave events GW170817 and GW190814 and X-ray pulsars PSR J0030+0451 and PSR J0740+6620, as well as with nuclear physics constraints from the PREX-2 experiment.

Stability analysis of the spin evolution fixed points in inspiraling compact binaries with black hole, neutron star, gravastar, or boson star components

Based on the secular spin evolution of black holes, neutron stars, gravastars, or boson stars in precessing compact binaries on eccentric orbit, we identify the aligned and more generic coplanar configurations of the spins and orbital angular momentum as fix points. Through a dynamical system analysis, we investigate their linear stability as function of the mass quadrupole parameter. Marginal stability holds for the binary configurations with both spins antialigned to the orbital angular momentum, for both spins aligned to the orbital angular momentum (with the exception of certain quadrupolar parameter ranges of neutron stars and boson stars), and for the extremal mass ratio. For equal masses, the configurations of one of the spins aligned and the other antialigned is stable for gravastar binaries, for neutron star binaries in the high quadrupolar parameter range, and for boson star binaries. For some unequal mass gravastar binaries, black hole binaries or neutron star binaries, a transition from stability to instability can occur during the inspiral, when one of the spins is aligned, while the other is antialigned to the orbital angular momentum. We discover a transitional instability regime during the inspiral of certain gravastar, neutron star, or boson star binaries with opposing spins. For coplanar configurations we find instabilities only for the gravastar - gravastar, boson star - boson star and black hole - boson star binaries. For a given spin configuration, marginal stability strongly depends on the value of the quadrupolar parameters. The stability region is larger for neutron star binaries than for black hole binaries, while the mixed systems have a restricted stability parameter region.

Electric Monopole Transitions in Nd Nuclei within IBM-2

The monopole transitions of 144-154Nd isotopes have been investigated in this work within the interacting boson model-2 (IBM-2) framework. The low-lying energy levels, electric quadrupole transition probability rates B(E2), electric quadrupole moments for first excited states monopole transition matrix elements and the intensity ratio were calculated in this work. The results of IBM-2 have been compared with the available experimental data; we have obtained a reasonable agreement. Unfortunately, the experimental data available on E0 transitions are very rare.The electric transition probability rates of beta and gamma bands to ground state band were calculated are fairly good agreement with available experimental values. Concerning the electric transition rates properties in IBM-2, we find that all calculations trends is reproduced well reasonably. The effective charges for neutron bosons and proton bosons calculated within IBM-2 are depending on the IBM-2 symmetries, we get suitable values for which is a constant for all 144-154Nd isotopes because the number of proton bosons is constant. The effective charge for neutron bosons varies from isotope to another

A unified description of shape coexistence and mixed-symmetry states in 98Mo using IBM-2**Supported by the National Natural Science Foundation of China under Grant Nos. 11947410, 11147148 and U1832139 and the Natural Science Foundation of Zhejiang Province under grant No. LY19A050002.

Level structure and electromagnetic transitions in 98Mo have been investigated on the basis of the proton-neutron interacting boson model (IBM-2) by considering the energy difference between neutron boson εν and proton boson επ. The results are compared with the recent experimental data and it is observed that they are in good agreement. In particular, the strongest M1 transition from state to can be well reproduced, from which one can determine the as an mixed-symmetry (MS) state. We have calculated the electric monopole strength , and our result agrees with the experimental one. The calculation indicates that shape coexistence and MS states are simultaneously well described using IBM-2.

Description of Shape Coexistence and Mixed-Symmetry States in 96Mo Using IBM-2**Supported by the National Natural Science Foundation of China under Grant Nos 11475062, 11575059, 11747312 and 11147148.

We investigate the level structure and E2, M1 electromagnetic transition properties in an even–even 96Mo nucleus within the framework of the proton–neutron interacting boson model (IBM-2). The calculated results of the IBM-2 can reproduce the recent new experimental data on 96Mo both qualitatively and quantitatively. It is found that both shape coexistence and mixed-symmetry states in 96Mo can be simultaneously described very well with the IBM-2 by taking into account that the relative energy of d neutron bosons is different from that of proton bosons.

Shape coexistence close to N = 50 in the neutron-rich isotope 80Ge investigated by IBM-2**Supported by National Natural Science Foundation of China (11475062, 11647306, 11147148)

The properties of the low-lying states, especially the relevant shape coexistence in 80Ge, close to one of most neutron-rich doubly magic nuclei at N = 50 and Z = 28, have been investigated within the framework of the proton-neutron interacting model (IBM-2). Based on the fact that the relative energy of the d neutron boson is different from that of the proton boson, the calculated energy levels of low-lying states and E2 transition strengths can reproduce the experimental data very well. Particularly, the first excited state , which is intimately related to the shape coexistence phenomenon, is reproduced quite nicely. The transition strength is also predicted. The experimental data and theoretical results indicate that both collective spherical and γ-soft vibration structures coexist in 80Ge.

Nuclear structure of 76Ge from proton-neutron interacting boson model calculations

The properties of low-lying states in $^{76}$Ge, especially the characteristics of themixed-symmetry states, have been investigated within the neutron-proton interactingboson model (IBM-2). By considering the relative energy of $d$ proton boson to bedifferent from that of neutron boson, the low-lying positive parity levels and $M1$, $E2$transition strengths have been calculated. The IBM-2 calculated results are in goodagreement with the experimental data. Particularly, the mixed-symmetry states have beenreproduced quite well. The calculation and systematic analysis demonstrated that thecollective character of $^{76}$Ge lies closest to the $\textrm{SU}^{\ast}_{\pi\nu}(3)$, with some possible $\textrm{O}_{\pi\nu}(6)$ dynamic symmetry in IBM-2 viewpoint.

Description of spectrum and electromagnetic transitions in 94Mo through the proton-neutron interacting boson model

We investigated the properties of low-lying states in 94Mo within the framework of the proton-neutron interacting boson model (IBM-2), with special focus on the characteristics of mixed-symmetry states. We calculated level energies and M1 and E2 transition strengths. The IBM-2 results agree with the available quantitative and qualitative experimental data on 94Mo. The properties of mixed-symmetry states can be well described by IBM-2 given that the energy of the d proton boson is different from that of the neutron boson, especially for the transition of B(M1; 4 2 + → 4 1 + ).

Alternative description of chiral properties in 138Nd

The phenomenological generalized coherent-state model Hamiltonian is amended with a many-body term describing a set of nucleons moving in a spherical shell-model mean field and interacting among themselves with pairing, as well as with a particle–core interaction involving a harmonic quadrupole–quadrupole, an anharmonic hexdecapole–hexdecapole and a spin–spin interaction. The model Hamiltonian is treated in a restricted space consisting of the core projected states associated to the bands ground, and and two proton-aligned quasiparticles coupled with the states of the ground band to a total angular momentum. The chirally transformed particle–core states are also included. The Hamiltonian contains two terms which are not invariant to the chiral transformations relating the right-handed trihedral and the left-handed ones , , where are the angular momenta carried by fermions, proton and neutron bosons, respectively. The energies defined with the particle–core states form four chiral bands, two of them being degenerate. The electromagnetic properties of the chiral bands are investigated and the results are compared with the experimental data of 138Nd.

Description of mixed symmetry states in 96Ru using IBM-2

We have investigated the properties of low-lying states in 96Ru within the framework of the neutron-proton interacting boson model (IBM-2), with special attention paid to the characteristics of the mixed symmetry states. By considering the relative energy of d proton boson to be different from that of neutron boson, the level energies and M1, E2 transition strengths have been calculated. The IBM-2 calculation is consistent with the experimental data of 96Ru both quantitatively and qualitatively. Particularly, the strong M1 transition between the 42+ and 41+ states has been reproduced nicely. The calculated results show that the M1 transition strength of B(M1; 42+ → 41+) in 96Ru can be described successfully by the IBM-2.

Radial stability of anisotropic strange quark stars

The influence of the anisotropy in the equilibrium and stability of strange stars is investigated through the numerical solution of the hydrostatic equilibrium equation and the radial oscillation equation, both modified from their original version to include this effect. The strange matter inside the quark stars is described by the MIT bag model equation of state. For the anisotropy two different kinds of local anisotropic σ = pt−pr are considered, where pt and pr are respectively the tangential and the radial pressure: one that is null at the star's surface defined by pr(R) = 0, and one that is nonnull at the surface, namely, σs = 0 and σs ≠ 0. In the case σs = 0, the maximum mass value and the zero frequency of oscillation are found at the same central energy density, indicating that the maximum mass marks the onset of the instability. For the case σs ≠ 0, we show that the maximum mass point and the zero frequency of oscillation coincide in the same central energy density value only in a sequence of equilibrium configurations with the same value of σs. Thus, the stability star regions are determined always by the condition dM/dρc > 0 only when the tangential pressure is maintained fixed at the star surface's pt(R). These results are also quite important to analyze the stability of other anisotropic compact objects such as neutron stars, boson stars and gravastars.

Coexistence of Prolate and Oblate Shapes in 98Sr Nuclei Using IBM2**Supported by the National Natural Science Foundation of China under Grant Nos 11475062, 11547312 and 11147148.

The properties of the low-lying states and the shape coexistence in 98Sr are investigated within the framework of the proton—neutron interacting boson model (IBM2). By considering the relative energy of the d proton boson to be different from that of the neutron boson, it is found that the calculated energy levels and the B(E2) transition strengths agree with the experimental data perfectly. Particularly, the second 0+ state, which is associated with the shape coexistence phenomenon and has the lowest energy E(02+) among all known even—even nuclei, is reproduced very well. The behavior of the calculated quadrupole shape invariants is consistent with the experimental results.

New type of chiral motion in even–even nuclei: the 138Nd case

The phenomenological generalized coherent state model Hamiltonian is amended with a many body term describing a set of nucleons moving in a shell model mean-field and interacting among themselves with pairing, as well as with a particle–core interaction of spin–spin type. The model Hamiltonian is treated in a restricted space consisting of the core projected states associated to the band ground, and and two proton aligned quasiparticles coupled to the states of the collective dipole band. The chirally transformed particle–core states are also included. The Hamiltonian contains two terms which are not invariant to the chiral transformations relating the right-handed frame and the left-handed ones , , where are the angular momenta carried by fermions, proton and neutron bosons, respectively. The energies defined with the particle–core states form four bands, two of them being degenerate in the present formalism, while the other two exhibit chiral properties reflected by energies, electromagnetic properties and the energy staggering function. A numerical application for 138Nd shows a good agreement between results and the corresponding experimental data.

Description of the shape coexistence in neutron-deficient 74,76Kr with IBM2

The shape deformation and shape coexistence in $^{74,76}$Kr isotopes are investigated within the framework of the proton-neutron interacting boson model (IBM2). By considering the relative energy of the $d$ proton boson to be different from that of the neutron boson, the low-lying energy spectrum is in good agreement with experimental results both qualitatively and quantitatively. In particular, the low-lying 0$^+_2$ states associated with the shape-coexistence phenomenon are reproduced quite well. The calculated key sensitive quantities of$B(E2)$ transition branch ratios are fairly consistent with the experimental data except for $R_4$. The predicated deformation parameter is very similar for the ground states in $^{74}$Kr and $^{76}$Kr, showing good agreement with the experimental result, and the calculated deformation parameter for the second 0$^+$ state in $^{74}$Kr is close to the experimental data. The calculated results of the triaxiality parameter indicated an almost purely prolate shape for the ground state of $^{76}$Kr and a mostly prolate shape with a little triaxiality for the ground state of$^{74}$Kr. The calculations also show an oblate triaxial shape for the second 0$^+$ state in $^{76}$Kr and maximum triaxiality for the second 0$^+$ state in $^{74}$Kr. These results confirm the importance of the triaxial deformation for the description of such shape coexistence.

Description of the Shape Coexistence in 98Mo with IBM2**Supported by the National Natural Science Foundation of China under Grant No 11475062, and the Natural Science Foundation of Zhejiang Province under Grant No Y6100135.

We investigate the properties of the low-lying states and the relevant shape dynamics of 98Mo within the framework of the proton-neutron interacting boson model (IBM2). By considering the relative energy of the d proton boson to be different from that of the neutron bosons, the low-lying levels and the key observable B(E2) transition branching ratios are calculated. The characteristic feature of the energy spectrum and the most crucial available structure indicator indicate that the substantial mixing between the spherical-vibrational and γ-unstable shapes in 98Mo. The calculation results of the overall deformation in 98Mo are almost the same for both the ground and the first excited 0+ states, showing a weak deformation. While the triaxiality parameter indicates that the mostly triaxial shape with some oblate for the ground state, and the triaxial shape with some prolate for the excited 0+2 state, being equilibrium shapes of spherical-vibrational and γ-unstable in 98Mo.

Description of the properties of the low-lying energy states in 100Mo with IBM2

The properties of the low-lying energy states for the 100Mo isotope is investigated within the framework of the proton-neutron interacting model IBM2. By considering the relative energy of the d proton boson to be different from that of the neutron boson and taking into account the dipole interacting among like-boson \(\hat L_\pi \cdot \hat L_\pi \) and \(\hat L_\nu \cdot \hat L_\nu \), the low-lying energy spectrum is reproduced well. Particularly, the relative position of the energies for 21+, 02+, 22+ and 41+ states shifted correctly fit the experimental data. The electromagnetic properties, including the key observable B(E2) reduced transition branching ratios and the E2 reduced matrix elements of the experimental data, are well described. Our calculations show possible shape coexistence in the 100Mo nucleus.

A proton–neutron nuclear vibron model

We have developed a new phenomenological approach to clustering in the atomic nucleus. It is an extension of the nuclear vibron model of Daley and Iachello, where we take into account the distinction between proton and neutron bosons. We discuss in detail the SU(3) limit of this model and show that it predicts new mixed symmetry negative parity states.

Recent advances in the application of dynamical supersymmetry to describe atomic nuclei

In recent years we have investigated further the use of supersymmetry in the Au-Pt regio. In the extended supersymmetry which takes account of the neutron-proton degree of freedom, the even-even Hg isotopes 196,198Hg could be described as two proton fermions coupled to a neutron boson core. We have performed experiments on 193Au at the 10 MV Tandem accelerator in Cologne using the HORUS and Double ORANGE spectrometers and fast LaBr3(Ce) scintillators to perform γ − γ, γ − e− and e− − e− coincidences and on 196Hg at the Yale accelerator using YRAST Ball. Both level schemes could be considerably extended and corrected. This allowed a detailed comparison with the predictions of the U(6/4) supersymmetry for the positive parity states in 193Au and 196Hg.