Equation 1 · Part 6 · Reactor Phylogenetics: The Family Tree of Fission Power

Symbol b

P(\text{next adopter} = A \mid n_A, n_B) = \frac{n_A + a}{n_A + n_B + a + b}

b

What this part means

b occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.

Its job in the formula

b occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.

Full expressionSymbol bArticle meaning

The passage around this formula

…of competing technologies under increasing returns describes exactly this dynamic as a generalized Pólya urn: two technologies accumulate adopters, and the probability the next adopter chooses technology A over B is proportional to how many adopters A already has, so that $P(\text{next adopter} = A \mid n_A, n_B) = \frac{n_A + a}{n_A + n_B + a + b}$ . where $n_A$ and $n_B$ are cumulative past adoptions and a, b are small initial weights representing early, largely arbitrary advantages [ 2 ] . Once $n_A$ pulls ahead by chance or by an unrelated advantage — a submarine…

Read this part in the article →

Learn the underlying idea

A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

Open the illustrated variables: a letter stands for a value guide →

See this notation across published equations →

Sources cited in the surrounding passage

These citations provide research context; check each source for the exact claim it supports.