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Derivatives -- the View from the Trenches

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Theorem 1 and Trading<br />

If you're gamma long, VSS<br />

0, and realised volatility is higher<br />

than pricing volatility you make money.<br />

The option trader's job is really about balancing realised<br />

against implied (or pricing) volatility.<br />

realised vol > implied vol => go long gamma<br />

realised vol < implied vol => go short gamma<br />

In essence this is what all trading is about: buy low -- sell<br />

high.<br />

In practice it is of course not that easy to predict how realised<br />

and implied volatility are going to relate to each o<strong>the</strong>r over a<br />

given period.<br />

In <strong>the</strong> context of <strong>the</strong> derivation of <strong>the</strong> Black-Scholes' formula,<br />

one can see Theorem 1 as an investigation of <strong>the</strong> selffinancing<br />

condition.<br />

6

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