Let \(\{B(t),\, t\ge 0\}\) be a standard Brownian motion. Prove directly, using \[ V_n=\sum _{i=1}^{2^n}\left |B(i/2^n)-B((i-1)/2^n)\right |, \] that \(B(\cdot ,\omega )\) is of unbounded variation on \([0,1]\) for a.e. \(\omega \).
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1996 • Question 5
Let \(\{B(t),\, t\ge 0\}\) be a standard Brownian motion. Prove directly, using \[ V_n=\sum _{i=1}^{2^n}\left |B(i/2^n)-B((i-1)/2^n)\right |, \] that \(B(\cdot ,\omega )\) is of unbounded variation on \([0,1]\) for a.e. \(\omega \).
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