The effect of PhD topic on postdoc

[MathematicalPhysicist]

I wonder how does the topic you choose to specalise in during your PhD affect what you'll research later on in your postdoc years?

I mean assuming you specalise in number theory and decide you want to change to geometry or analysis in postdoc who would even give you a job if your'e not specilaised enough in the field, I mean you would have people with a suitable PhDs competing on the same spot as you do, and why should they appoint you, if you'll need anyway to learn an equivalent of a Phd of 3-5 years in something like less than a month, for a postdoc job which spans usually 1-2 years.

So I don't get how there are some people that change direction in their postdoc.

Anyone care to elaborate?

Thanks.

 

[Choppy]

People change directions for a lot of reasons.

Over the 5 years or so that it takes to earn a PhD a lot can change. People can develop new personal interests. Or, sometimes people realize they don't like the field they are in, but want to try something different. Also, the problems that the academic community (or industry for that matter) are interested in will have changed.

There is also a question of opportunity. Because you do a PhD in a particular subfield does not mean that there will be a post doc position doing the same thing in that area when you finish. When you factor in issues such as where people want to live, and the fact that they will want to earn a paycheque, the choice will usually come down to what is available at the time.

You're right in that it can be an uphill battle to change fields. And yes, you likely won't be as competative for a given position if you don't have the background in that field, but people looking for post docs also have to select the best candidate they can out of the pool of applicants that apply.

 

[Gokul43201]

I mean you would have people with a suitable PhDs competing on the same spot as you do, and why should they appoint you, if you'll need anyway to learn an equivalent of a Phd of 3-5 years in something like less than a month, for a postdoc job which spans usually 1-2 years.

They wouldn't! Not if the jump is to a field far enough from your specialization that it takes years to catch up. Smaller jumps to more closely related fields (I don't know ... maybe from algebraic number theory into low dimensional topology?) happen more frequently (I know this for a fact in other fields - I imagine mathematics is not uniquely different), depending on the overlap in the tools used.