I am currently out of academia but I would like to return to university and start as a postdoc.
It is more than 5 years ago when I finished my PhD in mathematics (algebraic geometry) at a very weak British university. Despite my efforts, I was not able to find a postdoc position. From the beginning of my PhD, I did not like my research. Furthermore, the area my PhD thesis belongs to is quite isolated. I made one publication in a journal which is rather at a medium level.
Now I have a very interesting research topic I can work on together with another professor, but in a completely different field. It lies in the area of mathematical physics. I must add that there is no financial support for this project, so I have to invest a lot of my personal time into it. My questions are: Does it make sense to start working on my research topic and later at some point (for example, when I have enough results with one publication) start to apply for a postdoc position? Is it reallistic to get a postdoc position a few years after the PhD but with a research topic different from the PhD thesis?
I am concerned because of the folllowing things: my main concern is my age. I am nearly 40 years old. There are universities which take this issue into consideration although officially they would never admit it. In particular, German universities do so. Secondly, my PhD degree from a weak university does not favor an application for postdoc positions not to mention a permanent position. Thirdly, I expect that universities will reject postdocs who have such a big gap in their CV.
Here is some background: I did my undergraduate degree in Germany with an excellent grade. Unfortunately, I could not find a PhD position in Germany, so I applied to some British universities. At that time, I did not know that the British university system is completely different from the German one. So it happened, that I arrived at a weak university. I was not able to leave it because I could not get any recommendation letters to start new applications. Although my PhD advisor knew that I do not fit into this university he did not warn me. Moreover, he was telling me a lot of lies to make me stay there. It was unbearable. I would have left this university if I could.
After my PhD, he did not help me to find a postdoc position. The only thing that he did was telling me that there are no postdoc positions and that students who graduated from strong universities like Cambridge have better chances on the academic market. This was very frustrating.
I applied to many universities, even outside Europe but not a single application was successful. Even my applications for different kinds of fellowships failed. It was very difficult (and still is) for me to figure out what are the important things for a succesfull application for someone who is in my situation.
Any advice is welcome.