Time-inverted Wiener process limiting property

Discussion in 'CM2' started by Thabo Motaung, Jan 12, 2024.

  1. Thabo Motaung

    Thabo Motaung Member

    How does one get to this result in the Course notes:
    For a Wiener process Wt:
    lim t-> inf [Wt/t] = lim t-> inf [W_{1/t}]
     
  2. John Potter

    John Potter ActEd Tutor Staff Member

    We can verify that W*(t) = t W(1/t) is a standard Brownian motion by showing it has:
    - 0 mean
    - normally distributed increments
    - cov(W*(t),W*(s)) = min(t,s)
    and therefore W(1/t) is the same as W*(t)/t

    These 3 bullet points are an alternative definition of standard Brownian motion and you should have a go at showing the last one - it's 3 lines of algebra and quite good fun!

    Good luck!
    John
     

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