Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2004/iii/paper-28/5/c/solution

Condition on the number of stars. The independence assumptions give , with the inverse-square one-star characteristic function from part (a). Averaging over the Poisson distribution therefore gives the compound Poisson distribution formula directly:
Since , the Lévy continuity theorem gives exactly the same weak convergence of random variables as in part (a):
The random number of stars introduces no additional limiting term: its effect is already contained in the exact exponential formula. This is the symmetric inverse-power Poisson field on a line at spatial intensity and exponent .

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