Changing the main topic of research I started my PhD about a year and a half ago in an area that I will call A, which is quite applied. I've been doing a lot of programming and coding, and although I've learnt a lot and we've been doing some progress recently, I strongly feel that I haven't got any important result worth of appearing in a doctoral thesis. Even when we complete our current project (something that, I hope, is going to happen already in the near future), I won't feel like I've done any truly significant/original work. It is a nice work, but we've spent way too much time in a problem and we just don't have many results or important conclusions. I've been working on developing methodologies and improving little things, but I haven't got any concrete scientific result yet.

However, in the last 4/5 months we started thinking about a different problem (in collaboration with another professor) in a different area, B. B is a more theoretical area, and although A and B are loosely related (and ideally our work in B would be at some point applied to our work in A), they are very different topics. The thing is that I'm very happy with our progress with B, where recently I finally managed to do some hard computations and reach some interesting results with which I'm quite satisfied. Now, I feel that continuing our work in B could be really fruitful and -since we already have several ideas and plans- could soon yield some very interesting stuff. In combination with what I have already achieved, I definitely deem this work worthy of a doctoral thesis.

The problem is that B was, at least initially, a side topic, and my grant and my initial doctoral project was clearly associated to A, but not B. Working in A I feel like I'm stuck: yes, I write code and I do stuff which is sort of important, but I am spending a lot of time in something that it is not yielding very relevant results and that I don't think is going to give enough material for a thesis. However, A is like my main topic and I can only spend bits of time working on B once in a while.

That's why I've been thinking about the idea of discussing with my thesis advisor the possibility of changing my main research topic and start focusing on B, while keeping A as a side topic. He is a very nice person and has always been helpful and supporting, but I fear he is not going to take it well, since he clearly has more interest in A and has always thought of B as something nice but that "shouldn't distract me too much".

Maybe I should just accept things they way they are, or does it make sense for you to talk freely about my concerns?  I don't intend to fight or anything, but having at least a conversation about the whole thing would be nice. 

Any similar experiences to be shared?  Ideas?
There's only one thing to do here, and it is having a talk with your thesis director. He's most likely the best qualified to :


answer your worries with A being not valuable enough and if it's worth pursuing
assess the scope of the grant and the leeway you have with this


Doing a thesis on a subject is a commitment. Don't give up because you 'feel' it's going no where, prove it's not going there first. Also, finding similar results in different initial conditions, while not exciting regarding finding the next innovative thing, is not necessarily worthless. It's good to have results doubled checked/confirmed, found by other methods, or  if another result is expected, the work also serves as excluding things that don't give this expected result. Which is a result by itself.