NegativeDept said:
Wow, really? I thought Ito SDEs were still a huge deal - but I'm not working in finance, so my information is probably out of date.
All of the important results in SDE's were worked out a decade ago, and there is no new work in them. One thing about current models is that for the most part they are "phenomenological". In the late-1980's, it was believed that you could take some basic economic principles and calculated prices and SDE's were involved in that. People for the most part don't believe that, so most of the new models are merely to quantify how the market behaves. Data mining and statistics.
What kind of problems are quants working on now? Binomial models? Risk measures?
Regulatory compliance and counterparty risk.
You have a government regulator that wants to know how your portfolios will behave in a crisis situation. "I don't know" is not an acceptable answer. "It will take us three months to figure out" is also not acceptable. "I'll have those numbers for you in an hour" is what they want to hear.
Also, if you want to do anything new, it will have to go through *tons* of signoffs and permissions. Trying to streamline processes so that you can get the necessary data to make sure that you aren't going to blow up the world (again) in a matter of days rather than weeks is where the game is at right now.
The "cowboy era" of Wall Street is over, and now if you want to do anything, you have a dozen people looking over your shoulder. This may not be a bad thing since it means lots of jobs for physics Ph.D.
As far as counterparty risk goes. There was a time in which one bank could lend money to each other without worrying that the bank they are lending to would go under. For some reason, people aren't assuming that any more so there is a lot of work trying to figure out exactly what happens if the bank you let to defaults, and what the pricing aspects are.
Example situation: I borrow $1M from a bank and then I put up $800K in collateral. The bank goes under. No problem! I'm borrowing money from the bank so I don't have to worry about anything. Oh wait, I gave them $800K in collateral, well since it's my money, I can head over to the bank and get that money back, right? (At that point you have a lawyer nervously looking at the loan agreement and shaking their head). Oh, but if I can't get that collateral, I can just subtract it from the the amount of money that I owe the dead bank (and then you have another lawyer looking over the fine print of the loan agreement and then shaking their head.)
Well, I guess I'm screwed...
Fast forward a few years. You have two loan agreements with different collateral conditions. The bank is offering different interest rates for the different conditions (suppose one condition is that you can take back your money, and one that says you have to want in line at the bankruptcy court). The lawyers tell you the conditions, and you ask them what the difference in value of those contracts are. The lawyers then say "we're lawyers, we don't know how to numerically model stuff, you need a numerical modelling expert". Hmmm...
Here are some recent papers
http://arxiv.org/pdf/1111.1331.pdfhttp://arxiv.org/pdf/1112.1607.pdf