Leaving the unit neighbourhood on a triangular lattice
Question
A walker sits at a vertex of the infinite triangular lattice made of unit equilateral triangles, so each vertex has neighbours. On every move the walker steps along one of the edges at its current vertex, chosen uniformly and independently of the past. What is the probability that at some point during the first moves the walker is at distance strictly greater than from where it began?
Short answer
. Compute the complement: staying within distance 1 means being at the start or at one of its 6 neighbours. From a neighbour, edge leads back, lead to other neighbours and lead outside. Tracking the probabilities of being at the start or on the ring gives a total of of staying inside after 5 moves, so the answer is .
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Open the worked solutionLessons behind this question
- Random Variables and Probability Mass Functions
- Independence
- Continuous Random Variables and Probability Density Functions
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