Jameel-Un Nabi

WEAK INTERACTION RATES OF sd-SHELL NUCLEI IN STELLAR ENVIRONMENTS CALCULATED IN THE PROTON–NEUTRON QUASIPARTICLE RANDOM-PHASE APPROXIMATION☆☆☆

Abstract Allowed weak interaction rates for sd-shell nuclei in stellar environment are calculated using a generalized form of proton–neutron quasi-particle RPA model with separable Gamow–Teller forces. The calculated capture and decay rates take into consideration the latest experimental energy levels and ft-value compilations. Weak rates calculated are tabulated at the same points of density and temperature as those of Oda et al. [ Atomic Data and Nuclear Data Tables 56, 231 (1994)]. The results are also compared with earlier works. Particle emission processes from excited states, previously ignored, are taken into account and are found to significantly affect some β decay rates.

Microscopic calculations of weak interaction rates of nuclei in stellar environment for A = 18 to 100

Abstract: We report here the microscopic calculation of weak interaction rates in stellar matter for 709 nuclei with A = 18 to 100 using a generalized form of proton-neutron quasiparticle RPA model with separable Gamow-Teller forces. This is the first ever extensive microscopic calculation of weak rates calculated over a wide temperature-density grid which includes 107≤ T(K) ≤ 30 × 109 and 10 ≤ρ Ye (gcm−3) ≤ 1011, and over a larger mass range. Particle emission processes from excited states, previously ignored, are taken into account, and are found to significantly affect some β decay rates. The calculated capture and decay rates take into consideration the latest experimental energy levels and ft value compilations. Our calculation of electron capture and β-decay rates, in the fp-shell, show considerable differences with a recently reported shell model diagonalization approach calculation.

Gamow–Teller strength distributions and electron capture rates for 55Co and 56Ni

Abstract The Gamow–Teller strength (GT) distributions and electron capture rates on 55 Co and 56 Ni have been calculated using the proton–neutron quasiparticle random phase approximation theory. We calculate these weak interaction mediated rates over a wide temperature ( 0.01 × 10 9 – 30 × 10 9 K ) and density ( 10 – 10 11 g cm −3 ) domain. Electron capture process is one of the essential ingredients involved in the complex dynamics of supernova explosion. Our calculations of electron capture rates show differences with the reported shell model diagonalization approach calculations and are comparatively enhanced at presupernova temperatures. We note that the GT strength is fragmented over many final states.

Neutrino energy loss rates and positron capture rates on {sup 55}Co for presupernova and supernova physics

Proton-neutron quasiparticle random phase approximation (pn-QRPA) theory has recently been used for the calculation of stellar weak interaction rates of the fp-shell nuclide with success. Neutrino losses from protoneutron stars play a pivotal role in deciding if these stars would be crushed into black holes or explode as supernovas. The product of abundance and positron capture rates on

Nickel isotopes in stellar matter

^{55}\mathrm{Co}

Ground and excited states Gamow-Teller strength distributions of iron isotopes and associated capture rates for core-collapse simulations

is substantial and as such can play a role in the fine tuning of input parameters of simulation codes especially in the presupernova evolution. Recently we introduced our calculation of capture rates on

Comparison of Gamow-Teller strengths in the random phase approximation

^{55}\mathrm{Co}

Stellar β±-decay rates of iron isotopes and its implications in astrophysics

, in a luxurious model space of

Quantum Gravity effect on the Quark-Gluon Plasma

7\ensuremath{\hbar} \ensuremath{\omega}

Expanded calculation of weak-interaction-mediated neutrino cooling rates due to 56Ni in stellar matter

, employing the pn-QRPA theory with a separable interaction. Simulators, however, may require these rates on a fine scale. Here we present for the first time an expanded calculation of the neutrino energy loss rates and positron capture rates on