My university requires me to write my Bachelor thesis in my mother language. How detrimental and devastating is it to have your Bachelor thesis in non-English when it comes to applying for PhD positions and language requirements in other countries?
My thesis is on p-adics and my wish is to pursue a career in mathematical physics, so I'd be particularly interested in how mathematics faculty rank their candidates in this regard.
It should have no effect, whatever on your future. You can fulfill all of the requirements of your university, but also, when you have the time, provide a translation of your thesis for others to peruse. You can, in theory, produce an English language publication based on the thesis in another language.
You need to demonstrate some English proficiency for study in some countries, but it needn't be through your official thesis. There are many other ways. In fact, a translation, done by yourself, might be an especially good way.
Yes, my doctorate is in mathematics, though I worked mostly in CS. Your mathematics will be much more important than whether the thesis is in one language or another.
It is very unlikely that someone will want to read your bachelor thesis as is. But if you think it may contain interesting results, you can try to publish these results in a paper in English. That will actually strengthen your cv. Talk to your thesis supervisor and mention that you want to do a PhD in another country. They may be able to help you with that.
My university requires me to write my Bachelor thesis in my mother language.
You might be able to circumvent this requirement simply by asking (which avoids any detriment of the thesis not being in English).
