Equation 8 · Part 18 · The Valley of Stability Is a Fitness Landscape
Numerator: (A-2Z)^2
What this part means
The complete quantity above the fraction bar.
Its job in the formula
(A-2Z)^2 occurs above the fraction bar. The numerator is divided by the entire denominator below it.
Full expression→Numerator: (A-2Z)^2→Article meaning
The passage around this formula
The quantity that plays fitness’s role has a name in nuclear physics already: binding energy per nucleon, B(A,Z)/A , where A = N + Z is the mass number. It is the energy that would have to be supplied to disassemble a nucleus into Z free protons and N free neutrons, divided by the number of nucleons, and a higher value means a more tightly bound, lower-energy configuration — precisely the sense in which a fitness function assigns a scalar payoff to a state. The theoretical account of how that payoff varies across the chart is the semi-empirical mass formula, first written down by Carl Friedrich von Weizsäcker in 1935 as a liquid-drop model of the nucleus [ 11 ] . In one common form, the…
Learn the underlying idea
A fraction a/b means a divided by b. The top number is the numerator; the bottom number is the denominator, and it cannot be zero.
Open the illustrated fractions: division written vertically guide →
Sources cited in the surrounding passage
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