We know that the volatility is lower when the sampling period is longer, for example $\sigma_{7days} < \sigma_{1day}$, Then I came across this strategy that I cannot quite understand how to exploit this:
It says:
If weekly historical vol < daily historical vol:
buy strip of T options, delta hedge daily;
sell strip of T options, delta hedge weekly.
Adding up:
We do not buy nor sell any option;
play intra-week mean reversion until T;
Daily Vol / weekly Vol Arbitrage: On each leg: always keep $a invested in the index and update every Δt;
Resulting spot strategy: follow each week a mean reverting strategy;
Prove that we should keep each day the following exposure: $$ a.(\frac{1}{S_{t_{i,j}}} - \frac{1}{S_{t_{i,1}}})$$ where $t_{i,j}$ is the j-th day of the i-th week
It amounts to follow an intra-week mean reversion strategy
Could someone helps to explain a little?