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SCP-1 Brownian Motion

Brownian motion

Think of Brownian motion as a cloud of paths.
notion image
There are two kinds of properties: path properties, distributional properties
Path properties
  • for “almost every”
  • is a continuous function of for “almost every”
Distributional properties
  • For
    • taking , we have
      i.e. increments over non-overlapping intervals of time are independent.

Geometric Brownian motion

  • is a martingale
Proof for being a martingale
Let be given
This argument works even if is negative.

Practice

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