Talk:Heston model

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[edit] Merge Proposal

Given the paucity of information here, can we merge this page with Stochastic volatility and replace this page with a redirect for now? Ronnotel 16:44, 2 May 2007 (UTC)

Agreed - frankly, there's absolutely nothing here of any practical value. I was thinking of putting in a description of Heston stochastic vol (along with some of the extensions, so as to differentiate it from the existing information at stochastic volatility which seems more introductory than explanatory) but if you think that it'd be better to expand that instead ... Chiinners 18:00, 2 May 2007 (UTC)

If there's enough info available to support it's own page, then by all means let's expand it. Go ahead and add what you want here. Ronnotel 17:37, 2 May 2007 (UTC)

So far, I've added some basic (not much more than on the stochastic volatility page, but hopefully better explained). Bear in mind though that this is only a start, I'll continue expanding it once I have a bit more time ... Chiinners 00:22, 3 May 2007 (UTC)

[edit] Risk Neutral Measure Unclear

I find this section extraordinarily difficult to follow. I think there are good ideas here, but it needs to be tied back to real world terms through better illustrated examples. Here are some specific criticisms:

• It's claimed that in the Heston model, the market is no longer assumed to be complete. In what way is the market incomplete? Of what relevance is this to the practitioner attempting to use the model?
• The terms martingale and equivalent martingale measure are used without any explanation as to what they are. If these terms are going to be used, it should be made clear what they are and why they are relevant.
• What does identify the risk-free measure which is compatible with the market mean in practice? Completely unintelligible to the non-PhD I'm afraid.
• Why is it important to observe the contingent claim on the underlying asset?
• A concrete example, using real-world instruments such as pricing an exchange-trade equity option, should be provided to illustrate this entire paragraph.

Ronnotel 14:59, 5 May 2007 (UTC)

Thanks very much for your constructive criticisms! (sorry for the confusion - forgot to sign in when writing this bit) I'm currently torn between two approaches: (1) Rewriting the whole of this paragraph as a more theoretical (and, alas, inevitably technical) summary of the whole arbitrage-free valuation business, and then using that to explain why we can't simply change μ to ρ in the asset SDE, and (2) replacing this paragraph with one on practical use of the Heston model for options with exposure to the vol skew, and then noting calibration of the Heston parameters to call/put prices (amongst others). In retrospect, I'm not sure Wikipedia is really designed as an academic reference, so perhaps the latter would be preferable, but I'll see how the writing goes ... Chiinners 17:54, 5 May 2007 (UTC)

First, let me say that I was too negative above. I do think the material you have added is very useful. Thanks for not getting offended. I believe there's no reason not include themes of interest to both academic and practical users. In fact, WP is an ideal medium to help span the two audiences - something I personally find frustrating in the vast majority of financial literature. Whatever you can add that would help tie it back to practice would be much appreciated. Ronnotel 18:00, 5 May 2007 (UTC)

No apology necessary, and certainly no reason to take offence - comments were fair, suggestions useful and criticisms free of personal attacks :-) I've revised this paragraph to try to explain the theoretical viewpoint as clearly as possible (or rather, my interpretation thereof - here I should admit that I was never a mathematical finance academic, and would appreciate corrections from any who read this!) and will extend it tomorrow to link these points with practical issues (hedging and calibration, though again I'm not an expert) Chiinners 03:09, 7 May 2007 (UTC)

I just went through part of the article and (hopefully) clarified a few things for the typical reader. One thing that strikes me is the use of acronyms. For instance, "SDE" should be spelled out as "stochastic differential equation" (or even stochastic difference equation – why is everyone hung up on continuous time?) before it's used as an acronym.

It's an interesting article. I'll check back in a few days to see what else has been added. DavidCBryant 17:40, 7 May 2007 (UTC)

[edit] measure

physical measure & risk nutral measure, the difference is on kappa, & theta, and their relation to lamada (the risk premium). kappaQ=kappa+lamada, kappa*theta=kappaQ*thetaQ. 67.55.18.159 Jackzhp (talk) 18:54, 15 April 2008 (UTC)