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δ(A)\delta(A)

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where α\alpha , β\beta , and γ\gamma collect the volume, surface, Coulomb, and asymmetry contributions and the pairing term δ(A)\delta(A) shifts the curve up or down depending on whether N and Z are both even or both odd. For odd A , exactly one of N , Z is even and the pairing term vanishes, giving a single parabola with one minimum: one value of Z at that mass number is the most tightly bound, and every other isobar decays toward it by beta-minus emission (if it sits to the neutron-rich side) or by positron emission or electron capture (if it sits to the proton-rich side). For even A , the pairing term splits the curve into two parabolas — one for even-even nuclei sitting lower in mass (more…

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δ\delta

Symbol delta

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AA

Symbol A

A is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

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δ(A)\delta(A)

Equation 28 · Evolutionary Nuclear Physics

The Valley of Stability Is a Fitness Landscape

This mathematical expression combines the displayed quantities; its precise role follows from the surrounding article text.

where α\alpha , β\beta , and γ\gamma collect the volume, surface, Coulomb, and asymmetry contributions and the pairing term δ(A)\delta(A) shifts the curve up or down depending on whether N and Z are both even or both odd. For odd A , exactly one of N , Z is even and the pairing term vanishes, giving a single parabola with one minimum: one value of Z at that mass number is the most tightly bound, and every other isobar decays toward it by beta-minus emission (if it sits to the neutron-rich side) or by positron emission or electron capture (if it sits to the proton-rich side). For even A , the pairing term splits the curve into two parabolas — one for even-even nuclei sitting lower in mass (more…

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