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Articles de revues sur le sujet « Quasiparticle Random Phase Approximation (QRPA) »

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Publié le 25 janvier 2025

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1

Raduta, A. A., et C. M. Raduta. « A new renormalization procedure of the quasiparticle random phase approximation ». International Journal of Modern Physics E 25, no 03 (mars 2016) : 1650017. http://dx.doi.org/10.1142/s0218301316500178.

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The ground state of a many body Hamiltonian considered in the quasiparticle representation is redefined by accounting for the quasiparticle quadrupole pairing interaction. The residual interaction of the newly defined quasiparticles is treated by the quasiparticle random phase approximation (QRPA). Solutions of the resulting equations exhibit specific features. In particular, there is no interaction strength where the first root is vanishing. A comparison with other renormalization methods is presented. Application to a single [Formula: see text]-shell allows for the results interpretation by comparing them with those obtained by exact calculations.
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MARIANO, A. « THE NUMBER SELF-CONSISTENT RENORMALIZED RANDOM PHASE APPROXIMATION ». International Journal of Modern Physics B 20, no 30n31 (20 décembre 2006) : 5334–37. http://dx.doi.org/10.1142/s0217979206036442.

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RPA and its quasiparticle generalization (QRPA) have been widely used to study electromagnetic transitions and beta decays in medium and heavy nuclei, being the pn-QRPA charge exchange mode extensively employed in the description of single and double beta decays in vibrational nuclei. However develops a collapse, i.e. it presents imaginary eigen-values for strengths beyond a critical value of the force. Extensions called renormalized QRPA (RQRPA) do not develop any collapse going beyond the simplest quasiboson approximation, however they present several drawbacks which will be analyzed.
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González-Miret Zaragoza, Luis, Jean-Paul Ebran, Stéphane Hilaire, Sophie Péru, Mikael Frosini et Thomas Duguet. « Towards systematic large scale Quasiparticle Random-Phase Approximation calculations with covariant and chiral interactions ». EPJ Web of Conferences 294 (2024) : 03003. http://dx.doi.org/10.1051/epjconf/202429403003.

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One of the main methods used to microscopically describe collective states in atomic nuclei is the quasiparticle random-phase approximation (QRPA). However, due to its high computational cost, systematic studies covering the full nuclear chart are rare. In this work we show the first results of our systematic large-scale QRPA calculations. We do this by means of the quasiparticle finite-amplitude method (QFAM), which significantly reduces computation times. We use two kinds of interactions, the covariant DD-PC1 and a novel chiral interaction.
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Civitarese, O. « Fundamental nuclear structure symmetries in double beta decay processes ». HNPS Proceedings 9 (11 février 2020) : 211. http://dx.doi.org/10.12681/hnps.2792.

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The nuclear structure physics of double beta decay transitions is reviewed starting from the consideration of fundamental symmetries of the nuclear many body problem. The problems found in the use of the Quasiparticle Random Phase Approximation (QRPA) and related approximations, in dealing with the calculation of nuclear double beta decay observables, are understood in terms of the mixing between isospin collective and intrinsic variables.
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YOSHIDA, KENICHI. « LOW-LYING EXCITATION MODES IN DEFORMED NEUTRON-RICH NUCLEI ». International Journal of Modern Physics E 17, supp01 (décembre 2008) : 272–85. http://dx.doi.org/10.1142/s0218301308011914.

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Low-frequency modes of excitation in deformed neutron-rich nuclei are studied by the use of the deformed quasiparticle-random-phase approximation (QRPA) based on the coordinate-space Hartree–Fock–Bogoliubov formalism. We investigate the microscopic structure of the low-lying Kπ = 0+ modes in neutron-rich Mg , Cr and Fe isotopes. It is found that the spatially extended structure of neutron quasiparticle wave functions around the Fermi level brings about a striking enhancement of the transition strengths. It is also found that the fluctuation of the pairing field plays an important role in generating coherence among two-quasiparticle excitations of neutron. Recent progress towards the self-consistent deformed QRPA calculation using the Skyrme density functional is also presented.
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Nesterenko, V. O. « Dual nature of low-energy isoscalar monopole and dipole states in light nuclei ». Journal of Physics : Conference Series 2586, no 1 (1 septembre 2023) : 012074. http://dx.doi.org/10.1088/1742-6596/2586/1/012074.

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Abstract Isoscalar monopole (IS0) and dipole (IS1) states located below and around the alpha-particle threshold Sα in prolate 24Mg are investigated within fully self-consistent Skyrme Quasiparticle Random-Phase Approximation (QRPA) approach. It is shown that these states demonstrate strong mean-field (MF) effects: dipole vorticity, deformation-induced monopole-quadrupole (IS0/IS2) and dipole-octupole (IS1/IS3) coupling. At the same time, the density distributions show precursors of a cluster structure. So we get a cluster/MF duality with a strong dominance of MF impact. IS0 QRPA results are compared with iThemba Lab and RCNP (α, α′) data.
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Quliyev, H., N. Demirci Saygı, E. Guliyev et A. A. Kuliev. « The electric dipole response of even-even 154–164Dy isotopes ». Physica Scripta 97, no 2 (17 janvier 2022) : 025302. http://dx.doi.org/10.1088/1402-4896/ac4863.

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Abstract The excitation of pygmy dipole resonance (PDR) and giant dipole resonance (GDR) in even–even 154–164Dy isotopes is examined through quasiparticle random-phase approximation (QRPA) with the effective interactions that restore the broken translational and Galilean invariances. In each isotope, an electric response emerges by showing ample distribution at energies below and above 10 MeV. We, therefore, study the transition cross-sections and probabilities, photon strength functions, transition strengths, isospin character, and collectivity of the predicted E1 responses.
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YUKSEL, ESRA, et KUTSAL BOZKURT. « TENSOR EFFECTS IN PYGMY DIPOLE EXCITATION ». International Journal of Modern Physics E 20, no 10 (octobre 2011) : 2143–51. http://dx.doi.org/10.1142/s0218301311020216.

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We investigate tensor effects in pygmy dipole excitations for the case of neutron-rich nuclei 68 Ni and 124 Sn using effective nucleon–nucleon Skyrme interaction. We use the Hartree–Fock–Bogoliubov (HFB) theory and employ the quasiparticle random phase approximation (QRPA). We calculate and compare the PDR and also GDR strength in the PDR–GDR energy region for QRPA calculations with and without tensor correlations. The most obvious results for the dipole excitations calculations are strongly dependent on the tensor terms. We see that the tensor correlations are more active at around 14–20 MeV , especially for the neutron-rich nuclei 68 Ni . We also compare the PDR calculations with their experimental results for the different proton–neutron tensor coupling constants.
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Pirinen, P., J. Suhonen et E. Ydrefors. « Neutral-Current Neutrino-Nucleus Scattering off Xe Isotopes ». Advances in High Energy Physics 2018 (4 octobre 2018) : 1–11. http://dx.doi.org/10.1155/2018/9163586.

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Large liquid xenon detectors aiming for dark matter direct detection will soon become viable tools also for investigating neutrino physics. Information on the effects of nuclear structure in neutrino-nucleus scattering can be important in distinguishing neutrino backgrounds in such detectors. We perform calculations for differential and total cross sections of neutral-current neutrino scattering off the most abundant xenon isotopes. The nuclear-structure calculations are made in the nuclear shell model for elastic scattering and also in the quasiparticle random-phase approximation (QRPA) and microscopic quasiparticle-phonon model (MQPM) for both elastic and inelastic scattering. Using suitable neutrino energy distributions, we compute estimates of total averaged cross sections for ​8B solar neutrinos and supernova neutrinos.
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Ren, Zhongzhu, A. Faessler et T. S. Kosmas. « Study of the exotic μ-e conversion in nuclei using RQRPA ». HNPS Proceedings 9 (11 février 2020) : 1. http://dx.doi.org/10.12681/hnps.2772.

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The neutrinoless muon-to-electron conversion in nuclei is studied by using the renormalized quasiparticle random-phase approximation (RQRPA). This generalization of RPA is more reliable for the extremely small (μ-,e-) transition matrix elements than the ordinary QRPA because it restores the Pauli principle to a large extent. We apply the method to a set of nuclei throughout the periodic table, but we specifically investigate the 48Ti and 208Pb nuclei which are currently used as stopping targets at the PSI μ-e conversion experiments with the SINDRUM II spectrometer.
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NABI, JAMEEL-UN, et IRGAZIEV BAKHADIR. « β-DECAY OF KEY TITANIUM ISOTOPES IN STELLAR ENVIRONMENT ». International Journal of Modern Physics E 20, no 03 (mars 2011) : 705–19. http://dx.doi.org/10.1142/s0218301311018174.

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Amongst iron regime nuclei, β-decay rates on titanium isotopes are considered to be important during the late phases of evolution of massive stars. The key β-decay isotopes during presupernova evolution were searched from available literature and a microscopic calculation of the decay rates were performed using the proton–neutron quasiparticle random phase approximation (pn-QRPA) theory. As per earlier simulation results, electron capture and β-decay on certain isotopes of titanium are considered to be important for the presupernova evolution of massive stars. Earlier the stellar electron capture rates and neutrino energy loss rates due to relevant titanium isotopes were presented. In this paper we finally present the β-decay rates of key titanium isotopes in stellar environment. The results are also compared against previous calculations. The pn-QRPA β-decay rates are bigger at high stellar temperatures and smaller at high stellar densities compared to the large scale shell model results. This study can prove useful for the core-collapse simulators.
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Goriely, Stephane, Stephane Hilaire et Sophie Péru. « The Gogny-HFB+QRPA dipole strength function and its application to radiative neutron capture cross section ». EPJ Web of Conferences 178 (2018) : 04001. http://dx.doi.org/10.1051/epjconf/201817804001.

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Valuable theoretical predictions of nuclear dipole excitations in the whole chart are of great interest for different nuclear applications, including in particular nuclear astrophysics. Here we extend our large-scale calculations of the E1 and M1 absorption γ-ray strength function obtained in the framework of the axially-symmetric deformed quasiparticle random phase approximation (QRPA) based on the finite-range D1M Gogny force to the determination of the de-excitation strength function. To do so, shell-model calculations of the de-excitation dipole strength function as well as experimental data are considered to provide insight in the low-energy limit and to complement the QRPA estimate phenomenologically. We compare our final prediction of the E1 and M1 strengths with available experimental data at low energies and show that a relatively good agreement can be obtained. Its impact on the average radiative width as well as radiative neutron capture cross section is discussed.
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13

Taqi, A. H., et W. A. Mansour. « Isoscalar giant quadrupole resonance of even-even 112-124Sn isotopes using BCS-QRPA ». Nuclear Physics and Atomic Energy 25, no 1 (25 mars 2024) : 26–35. http://dx.doi.org/10.15407/jnpae2024.01.026.

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Using self-consistent Bardeen - Cooper - Schriffer + Hartree - Fock and quasiparticle random phase approximation, the isoscalar giant quadrupole resonance in the isotopes of 112,114,116,118,120,122,124Sn has been studied in this work. Five sets of Skyrme-type interactions of different values of the nuclear matter incompressibility coefficient KNM and effective mass m*/m are used in the calculations. Additionally, the impact of different types of pairing forces (i.e., volume, surface, and mixed) is examined. Comparisons are made between the computed strength distributions, centroid energies Ecen, scaled energies Es, and constrained energies Econ of the isoscalar giant quadrupole resonance and the available experimental data. Analysis is done on the relationships between KNM and m*/m, and the estimated properties.
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RING, P. « COVARIANT DENSITY FUNCTIONAL THEORY FOR COLLECTIVE EXCITATIONS IN NUCLEI FAR FROM STABILITY ». International Journal of Modern Physics E 15, no 02 (mars 2006) : 520–28. http://dx.doi.org/10.1142/s0218301306004478.

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Modern methods for the description of the nuclear many-body system use the concepts of density functional theory (DFT) and of effective field theory (EFT). Relativistic Hartree Bogoliubov (RHB) theory is a covariant version of this method, which takes into account Lorentz symmetry and pairing correlations in a fully self-consistent way. This theory has been used in the past for a very successful phenomenological description of ground state properties of nuclei all over the periodic table. Recently is also has been extended for the investigation of excited states. We discuss the calculation of rotational bands within cranked RHB-theory and recent investigations of vibrational excitations within the framework of relativistic Quasiparticle Random Phase Approximation (QRPA).
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Chimanski, Emanuel V., Eun Jin In, Jutta E. Escher, Sophie Péru et Walid Younes. « Towards a Predictive HFB+QRPA Framework for Deformed Nuclei : Selected Tools and Techniques ». Journal of Physics : Conference Series 2340, no 1 (1 septembre 2022) : 012033. http://dx.doi.org/10.1088/1742-6596/2340/1/012033.

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Abstract Reliable predictions of the static and dynamic properties of a nucleus require a fully microscopic description of both ground and excited states of this complicated many-body quantum system. Predictive calculations are key to understanding such systems and are important ingredients for simulating stellar environments and for enabling a variety of contemporary nuclear applications. Challenges that theory has to address include accounting for nuclear deformation and the ability to describe medium-mass and heavy nuclei. Here, we perform a study of nuclear states in an Hartree-Fock-Bogoliubov (HFB) and Quasiparticle Random Phase Approximation (QRPA) framework that utilizes an axially-symmetric deformed basis. We present some useful techniques for testing the consistency of such calculations and for interpreting the results.
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BOZKURT, KUTSAL. « ISOVECTOR PYGMY DIPOLE EXCITATION IN NEUTRON-RICH NUCLEI ». Modern Physics Letters A 25, no 34 (10 novembre 2010) : 2905–13. http://dx.doi.org/10.1142/s021773231003389x.

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We investigate isovector pygmy dipole resonance (IVPDR) for the case of neutron-rich nuclei 68 Ni , 130 Sn and 134 Sn using effective nucleon–nucleon Skyrme interaction. We use the Hartree–Fock–Bogoliubov (HFB) theory and employ the (quasiparticle) random phase approximation (Q)RPA. We calculate and compare the PDR strength in the PDR energy region for the case of density dependent central and full interaction modes for RPA and QRPA calculations. We observe that the results for the pygmy dipole resonance for neutron-rich soft nuclei 68 Ni that we consider are in reasonable agreement with their experimental results in both interactions and calculations. We also study the PDR for highly neutron-rich heavy nuclei, such as 130 Sn and 134 Sn . We see that only the QRPA calculation with full interaction is in good agreement with the experimental results for these nuclei and with a recent study in the literature. We find that the PDR strength distribution sensitively depends on the chosen interaction modes, especially for the neutron-rich heavy nuclei 134 Sn .
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Nabi, Jameel-Un, Muhammad Riaz et Arslan Mehmood. « Re-Examination of the Effect of Pairing Gaps on Gamow–Teller Strength Distributions and β-Decay Rates ». Universe 10, no 3 (6 mars 2024) : 128. http://dx.doi.org/10.3390/universe10030128.

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β-decay is one of the key factors for understanding the r-process and evolution of massive stars. The Gamow–Teller (GT) transitions drive the β-decay process. We employ the proton–neutron quasiparticle random phase approximation (pn-QRPA) model to calculate terrestrial and stellar β-decay rates for 50 top-ranked nuclei possessing astrophysical significance according to a recent survey. The model parameters of the pn-QRPA model affect the predicted results of β-decay. The current study investigates the effect of nucleon–nucleon pairing gaps on charge-changing transitions and the associated β decay rates. Three different values of pairing gaps, namely TF, 3TF, and 5TF, were used in our investigation. It was concluded that both GT strength distributions and half-lives are sensitive to pairing gap values. The 3TF pairing gap scheme, in our chosen nuclear model, resulted in the best prediction with around 80% of the calculated half-lives within a factor 10 of the measured ones. The 3TF pairing scheme also led to the calculation of the biggest β-decay rates in stellar matter.
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Nesterenko, Valentin, Jan Kvasil, Anton Repko et Paul-Gerhard Reinhard. « Individual low-energy E1 toroidal and compression states in light nuclei : deformation effect, spectroscopy and interpretation ». EPJ Web of Conferences 194 (2018) : 03005. http://dx.doi.org/10.1051/epjconf/201819403005.

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The existence of individual low-energy E1 toroidal and compression states (TS and CS) in 24Mg was predicted recently in the framework of quasiparticle random phase approximation (QRPA) model with Skyrme forces. It was shown that the strong axial deformation of 24Mg is crucial to downshift the toroidal strength to the low-energy region and thus make the TS the lowest E1(K=1) dipole state. In this study, we explain this result by simple mean-field arguments. Comparing TS in two strongly axial nuclei, 24Mg and 20Ne, we show that the lowest TS is not a universal phenomenon but rather a peculiarity of 24Mg. The spectroscopy of TS and CS is analyzed and some additional interpretation of these states is suggested.
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Giannaka, P. G., et T. S. Kosmas. « Electron Capture Cross Sections for Stellar Nucleosynthesis ». Advances in High Energy Physics 2015 (2015) : 1–11. http://dx.doi.org/10.1155/2015/398796.

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In the first stage of this work, we perform detailed calculations for the cross sections of the electron capture on nuclei under laboratory conditions. Towards this aim we exploit the advantages of a refined version of the proton-neutron quasiparticle random-phase approximation (pn-QRPA) and carry out state-by-state evaluations of the rates of exclusive processes that lead to any of the accessible transitions within the chosen model space. In the second stage of our present study, we translate the abovementionede--capture cross sections to the stellar environment ones by inserting the temperature dependence through a Maxwell-Boltzmann distribution describing the stellar electron gas. As a concrete nuclear target we use the66Zn isotope, which belongs to the iron group nuclei and plays prominent role in stellar nucleosynthesis at core collapse supernovae environment.
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Demirci Saygı, Nilufer, Filiz Ertuğral Yamaç et Ali Kuliev. « Theoretical investigation of giant dipole resonance in 146−152Nd isotopes with QRPA ». International Journal of Modern Physics E 29, no 07 (juillet 2020) : 2050040. http://dx.doi.org/10.1142/s0218301320500408.

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We investigate the electric dipole ([Formula: see text]) structure properties of the deformed [Formula: see text]Nd nuclei in the giant dipole resonance (GDR) region within the framework of the quasiparticle random-phase approximation (QRPA). Translational and Galilean invariance (TGI) QRPA with separable isovector dipole–dipole residual interaction have been employed for the calculations. We have computed the photoabsorption cross-section and then we have compared with the experimental data. Our calculations revealed that while the photoabsorption cross-section shows a Lorentzian line in the neighborhood of spherical geometry, it starts to shift to an asymmetric shape by increasing deformation in [Formula: see text]Nd isotopes by increasing neutron number. In addition to this, we have also observed that the splitting of the [Formula: see text] strength distribution and the separation between [Formula: see text] and [Formula: see text] branches are increasing. We have calculated the contribution of the electric and magnetic parts of total dipole strength up to 20[Formula: see text]MeV for the nuclei of interest. This calculation shows that the electric part dominates the total dipole strength and [Formula: see text] excitation dominates the electric part.
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Tsakstara, Vaitsa. « Convolutedν-Signals on114Cd Isotope from Astrophysical and Laboratory Neutrino Sources ». Advances in High Energy Physics 2015 (2015) : 1–11. http://dx.doi.org/10.1155/2015/632131.

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At first, we evaluate scattering cross sections of low, and intermediate-energy neutrinos scattered off the114Cd isotope, the most abundant Cd isotope present also in the COBRA detector (CdTe and CdZnTe materials) which aims to search for double beta decay events and neutrino observations at Gran Sasso laboratory (LNGS). The coherentν-nucleus channel addressed here is the dominant reaction channel of the neutral currentν-nucleus scattering. Ourν-nucleus cross sections (calculated with a refinement of the quasiparticle random-phase approximation, QRPA) refer to thegs→gstransitions forν-energiesεν≤100 MeV. Subsequently, simulatedν-signals on114Cd isotope are derived. Towards this purpose, the required folded cross section comes out of simulation techniques by employing several low, and intermediate-energy neutrino distributions of the astrophysicalν-sources, like the solar, supernova, and Earth neutrinos, as well as the laboratory neutrinos, the reactor neutrinos, the pion-muon stopped neutrinos, and theβ-beam neutrinos.
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NABI, JAMEEL-UN. « NEUTRINO AND ANTINEUTRINO ENERGY LOSS RATES IN MASSIVE STARS DUE TO ISOTOPES OF TITANIUM ». International Journal of Modern Physics E 19, no 01 (janvier 2010) : 63–77. http://dx.doi.org/10.1142/s0218301310014716.

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Weak interaction rates on titanium isotopes are important during the late phases of evolution of massive stars. A search was made for key titanium isotopes from available literature and a microscopic calculation of weak rates of these nuclei were performed using the proton-neutron quasiparticle random phase approximation (pn-QRPA) theory. Earlier the author presented the stellar electron capture rates on titanium isotopes. In this paper I present the neutrino and antineutrino energy loss rates due to capture and decay rates on isotopes of titanium in stellar environment. Accurate estimate of neutrino energy loss rates are needed for the study of the late stages of the stellar evolution, in particular for cooling of neutron stars and white dwarfs. The results are also compared against previous calculations. At high stellar temperatures the calculated neutrino and antineutrino energy loss rates are bigger by more than two orders of magnitude as compared to the large scale shell model results and favor stellar cores with lower entropies. This study can prove useful for core-collapse simulators.
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Tabar, E., H. Yakut et A. A. Kuliev. « Low-energy dipole strength in even–even 152–164Dy isotopes within the quasiparticle random phase approximation (QRPA) including symmetry restoring interactions ». Nuclear Physics A 979 (novembre 2018) : 143–64. http://dx.doi.org/10.1016/j.nuclphysa.2018.09.040.

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CAO, LI-GANG, et ZHONG-YU MA. « SOFT DIPOLE MODES IN NEUTRON-RICH Ni-ISOTOPES IN QRRPA ». Modern Physics Letters A 19, no 38 (14 décembre 2004) : 2845–56. http://dx.doi.org/10.1142/s0217732304015233.

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The soft dipole modes in neutron-rich even–even Ni-isotopes are investigated in the quasiparticle relativistic random phase approximation. We study the evolution of strengths distribution, centroid energies of dipole excitation in low-lying and normal GDR regions with the increase of the neutron excess. It is found in the present study that the centroid energies of the soft dipole strengths strongly depend on the thickness of neutron skin along with the neutron-rich even–even Ni-isotopes.
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Nabi, Jameel-Un, et Muhammad Majid. « Gamow-Teller strength and lepton captures rates on 66−71Ni in stellar matter ». International Journal of Modern Physics E 26, no 03 (mars 2017) : 1750005. http://dx.doi.org/10.1142/s0218301317500057.

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Charge-changing transitions play a significant role in stellar weak-decay processes. The fate of the massive stars is decided by these weak-decay rates including lepton (positron and electron) captures rates, which play a consequential role in the dynamics of core collapse. As per previous simulation results, weak interaction rates on nickel (Ni) isotopes have significant influence on the stellar core vis-à-vis controlling the lepton content of stellar matter throughout the silicon shell burning phases of high mass stars up to the presupernova stages. In this paper, we perform a microscopic calculation of Gamow–Teller (GT) charge-changing transitions, in the [Formula: see text]-decay and electron capture (EC) directions, for neutron-rich Ni isotopes ([Formula: see text]Ni). We further compute the associated weak-decay rates for these selected Ni isotopes in stellar environment. The computations are accomplished by employing the deformed proton–neutron quasiparticle random phase approximation (pn-QRPA) model. A recent study showed that the deformed pn-QRPA theory is well suited for the estimation of GT transitions. The astral weak-decay rates are determined over densities in the range of 10–10[Formula: see text][Formula: see text]g/cm3and temperatures in the range of 0.01[Formula: see text]–30[Formula: see text][Formula: see text]K. The calculated lepton capture rates are compared with the previous calculation of Pruet and Fuller (PF). The overall comparison demonstrates that, at low stellar densities and high temperatures, our EC rates are bigger by as much as two orders of magnitude. Our results show that, at higher temperatures, the lepton capture rates are the dominant mode for the stellar weak rates and the corresponding lepton emission rates may be neglected.
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Nabi, Jameel-Un, Mavra Ishfaq, Ovidiu Niţescu, Mihail Mirea et Sabin Stoica. « β−-Decay Half-Lives of Even-Even Nuclei Using the Recently Introduced Phase Space Recipe ». Universe 6, no 1 (26 décembre 2019) : 5. http://dx.doi.org/10.3390/universe6010005.

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In this paper, we present the β -decay half-lives calculation for selected even-even nuclei that decay through electron emission. The kinematical portion of the half-life calculation was performed using a recently introduced technique for computation of phase space factors (PSFs). The dynamical portion of our calculation was performed within the proton-neutron quasiparticle random phase approximation (pn-QRPA) model. Six nuclei ( 20 O, 24 Ne, 34 Si, 54 Ti, 62 Fe and 98 Zr) were selected for the present calculation. We compare the calculated PSFs for these cases against the traditionally used recipe. In our new approach, the Dirac equation was numerically solved by employing a Coulomb potential. This potential was adopted from a more realistic proton distribution of the daughter nucleus. Thus, the finite size of the nucleus and the diffuse nuclear surface corrections are taken into account. Moreover, a screened Coulomb potential was constructed to account for the effect of atomic screening. The power series technique was used for the numerical solution. The calculated values of half-lives, employing the recently developed method for computation of PSFs, were in good agreement with the experimental data.
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Tabar, E., H. Yakut et A. A. Kuliev. « Corrigendum to “Low-energy dipole strength in even–even 152–164Dy isotopes within the quasiparticle random phase approximation (QRPA) including symmetry restoring interactions” [Nucl. Phys. A 979 (2018) 143–164] ». Nuclear Physics A 1004 (décembre 2020) : 122057. http://dx.doi.org/10.1016/j.nuclphysa.2020.122057.

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AVOGADRO, PAOLO, et TAKASHI NAKATSUKASA. « THE FINITE AMPLITUDE METHOD FOR THE QRPA ». Modern Physics Letters A 25, no 21n23 (30 juillet 2010) : 1999–2000. http://dx.doi.org/10.1142/s0217732310000848.

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We present the finite amplitude method (FAM) for the Quasi Particle Random Phase Approximation (QRPA). This method allows to extract a QRPA code starting from a Hartree-Fock-Bogoliubov (HFB) code. The code obtained is fully self consistent, moreover since the FAM is not restricted to spherical symmetry it can be used to obtain deformed QRPA codes.
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29

Mariano, A., et J. G. Hirsch. « Particle number fluctuations in the quasiparticle random-phase approximation and renormalized quasiparticle random-phase approximation ». Physical Review C 57, no 6 (1 juin 1998) : 3015–19. http://dx.doi.org/10.1103/physrevc.57.3015.

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30

PERU, S., G. GOSSELIN, M. DUPUIS, S. HILAIRE, M. MARTINI et J. C. DEVAUX. « QRPA CALCULATIONS FOR SPHERICAL AND DEFORMED NUCLEI WITH THE GOGNY FORCE ». Modern Physics Letters A 25, no 21n23 (30 juillet 2010) : 1775–78. http://dx.doi.org/10.1142/s0217732310000307.

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Fully consistent axially-symmetric-deformed Quasi-particle Random Phase Approximation (QRPA) calculations have been performed with the D1S Gogny force. Impact of the deformation in giant multipole resonances is discussed. QRPA and 5 Dimensional Collective Hamiltonian results are compared for low lying 2+ states in N = 16 isotones and Ni isotopes. Multipole resonances are also obtained for the heavy nucleus 238 U .
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31

MARTINI, M., et S. PÉRU. « LOW-ENERGY DIPOLE EXCITATIONS IN NEON ISOTOPES AND N = 6 ISOTONES ». Modern Physics Letters A 25, no 21n23 (30 juillet 2010) : 2010–11. http://dx.doi.org/10.1142/s0217732310000897.

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Low-energy dipole excitations in Neon isotopes and N = 16 isotones are calculated with a fully consistent axially-symmetric-deformed Quasi-particle Random Phase Approximation (QRPA) approach based on Hartree-Fock-Bogolyubov (HFB) states. The same Gogny D1S effective force has been used both in HFB and QRPA calculations. The behavior of proton and neutron transition densities is presented in order to determine the isoscalar or isovector nature of the excitations.
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32

Akbar, Maryam A., et Ali H. Taqi. « Isoscalar Giant Octupole Resonance ISGOR of 116Cd using Self-Consistent Skyrme QRPA ». East European Journal of Physics, no 2 (2 juin 2023) : 324–28. http://dx.doi.org/10.26565/2312-4334-2023-2-37.

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Collective models based on the random phase approximation (RPA) are widely used to accurately depict collective modes of response. They can quickly calculate the strength function for the entire nuclear mass range. The quasi-particle random phase approximation (QRPA), which considers the pairing effect, is an enhanced RPA model. It is anticipated that this effect will be significant for open-shell nuclei. In this work, the self-consistent Skyrme Hartree-Fock-Bardeen, Cooper, and Schrieffer (HF-BCS) and QRPA models have been used to study the isoscalar giant octupole resonance (ISGOR) in the 116Cd isotope. Ten Skyrme-type parameters are utilized in the computations since they may be identified by different values of the incompressibility modulus KMN in nuclear matter. The calculated strength distributions and centroid energy are compared with available experimental data. We saw that the strength distributions varied depending on the type of Skyrme-interaction, and we also observed a definite impact of the KNM values on the centroid energy.
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33

Arteaga, D. Peña, et P. Ring. « Relativistic quasiparticle random phase approximation in deformed nuclei ». Progress in Particle and Nuclear Physics 59, no 1 (juillet 2007) : 314–16. http://dx.doi.org/10.1016/j.ppnp.2006.12.033.

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Balasi, K. G., T. S. Kosmas, P. C. Divari et V. C. Chasioti. « Cross sections for the neutral current νe - 116Cd scattering reaction ». HNPS Proceedings 16 (1 janvier 2020) : 97. http://dx.doi.org/10.12681/hnps.2586.

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The cross sections for neutrino scattering off the 116Cd nucleus have been computed by utilizing the Quasi-particle Random Phase Approximation (QRPA). An- gular and initial energy dependence of the neutrino-nucleus cross sections have been calculated at low and intermediate electron neutrino energies up to 100 MeV. By solving the QRPA equations and fixing the appropriate parameters the lowest lying excitation energies spectrum was reproduced. The contributions from multipole ex- citations was examined. The obtained results could be used for studying the nuclear response of this isotope to supernova neutrino spectra.
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35

Simkovic, F., M. Smotlák et A. A. Raduta. « Quasiparticle random-phase approximation with an optimal ground state ». Journal of Physics G : Nuclear and Particle Physics 27, no 8 (2 juillet 2001) : 1757–65. http://dx.doi.org/10.1088/0954-3899/27/8/305.

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36

Kamerdzhiev, S., R. J. Liotta, E. Litvinova et V. Tselyaev. « Continuum quasiparticle random-phase approximation description of isovectorE1giant resonances ». Physical Review C 58, no 1 (1 juillet 1998) : 172–78. http://dx.doi.org/10.1103/physrevc.58.172.

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Kamiński, Wiesław A., et Amand Faessler. « Quasiparticle random phase approximation and pion double charge exchange ». Physics Letters B 244, no 2 (juillet 1990) : 155–60. http://dx.doi.org/10.1016/0370-2693(90)90046-9.

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38

SHIMOYAMA, HIROTAKA, et MASAYUKI MATSUO. « PAIR VIBRATION 0+ STATE IN NEUTRON-RICH Sn ISOTOPE : CONTINUUM QRPA ANALYSIS OF NEUTRON PAIR TRANSFER STRENGTH ». Modern Physics Letters A 25, no 21n23 (30 juillet 2010) : 2024–25. http://dx.doi.org/10.1142/s0217732310000964.

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We discuss the pair transfer mode populating pair vibration [Formula: see text] state in neutron-rich Sn isotopes by means of the continuum quasi particle random phase approximation (continuum QRPA). It is seen that the strength of the two-neutron addition transfer from the ground state to the [Formula: see text] state is significantly enhanced beyond the N=82 shell gap.
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39

Kabir, Abdul, Jameel-Un Nabi, Wajeeha Khalid et Hamad Almujibah. « Re-examination of the β-decay properties of As isotopes ». Communications in Theoretical Physics 77, no 3 (12 décembre 2024) : 035302. https://doi.org/10.1088/1572-9494/ad8dba.

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Abstract The β-decay properties of 67−80As nuclei have been investigated within the framework of the proton–neutron quasi-particle random phase approximation (pn-QRPA) model. The nuclear deformation obtained from the finite range droplet model is used as an input parameter in the pn-QRPA model for the analysis of β-decay properties including Gamow–Teller strength distributions, log ft, β-decay half-lives and stellar β ± decay rates. The predicted log ft values were fairly consistent with the observed data. The computed β-decay half-lives matched the measured values by a factor of 10. The stellar rates were compared with the shell model outcomes. At high densities and temperatures, the β + and electron capture rates had a finite contribution. However, the β − and positron capture rates are only significant at high temperatures and low densities. The pn-QRPA rates outperformed the shell model rates by a factor of 22 or more.
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40

Kardaras, I. S., V. N. Stavrou, I. G. Tsoulos et T. S. Kosmas. « Detailed calculations for muon capture rates within the quasi-particle RPA ». HNPS Proceedings 18 (23 novembre 2019) : 175. http://dx.doi.org/10.12681/hnps.2549.

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Detailed calculations for bound muon capture in complex nuclei are performed by employing the quasi particle random phase approximation (QRPA). The required bound muon wavefunctions for the large and the small components of the Dirac muon wavefunctions are obtained by using the genetic algorithm approach. We ob- tained contributions for 2p muon orbit; that is to say wavefunctions for atomic ex- cited state of the muonic atoms in nucleus 28Si. As a byproduct the above method give the corresponding energies to these wavefunctions which are compared with those of other methods. Our goal is to use the method developed recently by Laganke, Zinner and Vogel and our advantageous numerical approach to obtain state by state calculations of the muon capture rates within the QRPA.
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41

Niu, Y. F., G. Colò et E. Vigezzi. « Gamow--Teller Response Calculated in Quasiparticle Random Phase Approximation Plus Quasiparticle Vibration Coupling Model ». Acta Physica Polonica B Proceedings Supplement 11, no 1 (2018) : 127. http://dx.doi.org/10.5506/aphyspolbsupp.11.127.

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42

Udias, J. M., R. Nojarov et Amand Faessler. « M1 excitations in30Si and31S from the quasiparticle random-phase approximation ». Journal of Physics G : Nuclear and Particle Physics 23, no 11 (1 novembre 1997) : 1673–83. http://dx.doi.org/10.1088/0954-3899/23/11/015.

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43

Yuan, Tian, Ma Zhong-Yu et Ring Peter. « Relativistic Quasiparticle Random Phase Approximation with a Separable Pairing Force ». Chinese Physics Letters 26, no 5 (mai 2009) : 052103. http://dx.doi.org/10.1088/0256-307x/26/5/052103.

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44

Giannaka, P. G., et T. S. Kosmas. « The role of e- capture in neutrino-nucleosynthesis ». HNPS Proceedings 22 (8 mars 2019) : 84. http://dx.doi.org/10.12681/hnps.1935.

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In the first stage of this paper, we perform detailed calculations of the electron capture cross sections on nuclei under laboratory conditions. We use the nuclear method known as proton-neutron quasi-particle random phase approximation (pn-QRPA). In the second stage, we translate the above mentioned e--capture cross sections to the stellar environment. As a concrete nuclear target we use the 56Fe and the 66Zn isotopes, which belong to the iron group nuclei and play prominent role in stellar nucleosynthesis: i) in pre-supernova phase and ii) in supernova phase.
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45

Riemelmoser, Stefan, Merzuk Kaltak et Georg Kresse. « Optimized effective potentials from the random-phase approximation : Accuracy of the quasiparticle approximation ». Journal of Chemical Physics 154, no 15 (21 avril 2021) : 154103. http://dx.doi.org/10.1063/5.0045400.

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46

Suhonen, J., et O. Civitarese. « Calculation of the beta decay of . Quasiparticle random phase approximation results ». Physics Letters B 280, no 3-4 (avril 1992) : 191–97. http://dx.doi.org/10.1016/0370-2693(92)90054-8.

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47

Balasi, K. G., et T. S. Kosmas. « Neutral current neutrino-94Mo scattering in the context of the QRPA method ». HNPS Proceedings 18 (23 novembre 2019) : 31. http://dx.doi.org/10.12681/hnps.2535.

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A systematic investigation of neutrino-nucleus reaction rates at low and intermediate energies of the stable 94Mo isotope is performed. Differential and integrated cross sections for neutrino inelastic scattering off the aforementioned target are calculated for neutrino energies εi ≼ 100 MeV. The nuclear wave functions for the initial and final nuclear states are constructed in the context of the quasi-particle random phase approximation (QRPA). The reliability of our method is tested by checking the reproducibility of the low-lying energy spectrum of the isotope under investigation.
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48

Tsakstara, V., T. S. Kosmas et J. Sinatkas. « Nuclear response to supernova neutrino spectra ». HNPS Proceedings 18 (23 novembre 2019) : 187. http://dx.doi.org/10.12681/hnps.2551.

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In current probes searching for rare event processes, appropriate nuclear targets are employed (in the COBRA double-beta decay detector the CdZnTe semiconductor is used). In this work the response of such detectors to various low-energy neutrino spectra is explored starting from state-by-state calculations of the neutrino-nucleus reactions cross sections obtained by using the quasi particle random phase approximation (QRPA) based on realistic two-body residual interactions. As a concrete example, we examine the response of 64Zn isotope to low energy supernova neutrinos.
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49

Mohammed, Gullala A., et Ali H. Taqi. « ISOSCALAR DIPOLE RESPONSE IN 92Mo AND 100Mo ISOTOPES ». MOMENTO, no 67 (4 juillet 2023) : 101–16. http://dx.doi.org/10.15446/mo.n67.107907.

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In this work, the Isoscalar (IS) Giant Dipole Resonance (GDR) and Pygmy Dipole Resonance (PDR) of 92Mo and 100Mo Isotopes were calculated in the farmwork of the self-consistent quasi-particle random phase approximation (QRPA) based on the results of Hartree-Fock-Bardeen, Cooper and Schrieffer (HF-BCS) using 10 Skyrme-type interactions: KDE0v1, eMSL08, SKX, SGOI, v080, SKP, SIV, SIII, SKIII, and SGI. The strength distributions of isoscalar dipole response were compared with the available experimental data. Also, we discussed the statistical relation between the centroid energy and the nuclear matter incompressibility KNM.
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Giannaka, P. G., et T. S. Kosmas. « Electron-capture modes with realistic nuclear structure calculations ». HNPS Proceedings 21 (8 mars 2019) : 4. http://dx.doi.org/10.12681/hnps.1997.

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Nuclear electron capture posses prominent position among other weak interaction processes occuring in explosive nucleosynthesis. In particular, this process plays important role in the core-colapse of massive stars by modifying the electron to baryon ratio Ye. From a nuclear theory point of view, such processes may be studied by using the same nuclear methods (e.g. the quasi-particle random phase approximation, QRPA), employed in the present work with these used for the one-body charge changing nuclear reactions (β-decay modes, charged-current electron-neutrino absorption by nuclei, etc). In this work we calculate e−-capture cross sections on 56Fe using two different approaches. At first, original cross section calculations are perfored by using the pn-QRPA method considering all the accessible transitions of the final nucleus 56Mn. Secondly, we evaluate the Gamow-Teller strength distributions and obtain the cross sections at the limit of zero-momentum transfer. The agreement between the two methods is very good.
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