It seems that most of this forum are more interested in sell side than buy side. However, I am going to join a buy side firm. What do guys with mathematics backgroud do in buy side?I knew pricing derivatives and structuring is fun, however, I have not got a chance to do it.

As a buy-side quant, it really depends on the scale of the firm.For a large asset manager or insurance co, you will probably do a lot of risk modeling and a little bit of forecasting (alpha), with the ultimate goal of portfolio construction/optimization. The downside is that there isn't always opporunity to try out your funky trading ideas because they don't fit the business model. The upside is that you have access to lots of data and resources and support.For a small boutique firm or hedge fun, you will probably do a little bit of risk modeling and a lot of forecasting, although depending on the firm you also be doing pricing and valuation. Downside is that you will probably have to wear many hats, which may distract you from what you are really interested in, and that you don't have the support of a large firm. Upside is that you can get your ideas put into trades if they are good.

Right, smaller boutiques try to get cheap brains by offering to have you sit on the desk, get into trading if you want, a share of pnl, get to see your strategy in action, etc. I woudl be sceptical of any one trying to get you on the cheap. They invariably try to keep you on the cheap. Every situation is defferent of course.

well, they can't keep you on the cheap if they are overly dependent on you - and you will have access to more of the picture than you did before, which makes you more valuable for future jobs as well. So it's not necessarily a bad trade, unless you are in a firm that is so-so. if there is anything I miss - being in JS's category #2 of small buyside fund, having worked in a big bank before - there are occasionally things that you need, which you'd prefer somebody else could deal with. I'm a credit guy and for most of what I do, riskless interest rate stuff is not that important - but every once in a while, I wish I had a toolkit of FI stuff that was calibrated to the current market... it's a bit of work to build the whole thing yourself and do it the right way, when you're only going to need it for a silly calculation here and there.

Are buy side quants with a few years experience considered for an ibank's desk quant type of role, or is there a Hadrian wall between these 2 different career paths ?

its not impossible to cross over, but the game's totally different.. depends what you are doing; if you do pure reaearch on the buy side and you're heading into a research role than the main differential is that you don not have the perk of picking up a phone and getting sell-side to be your b*tch..