I am currently at the end of my Master's program in Theoretical Physics. I am now looking for PhD positions. My problem is as follows.
I have mostly chosen courses on the high energy physics (Cosmology, particle physics String etc.) and when applying for PhD, although most of the research groups focus on few problems, this is still a lot of literature (past 50-60 years worth of work), only a part of which is humanly possible to cover in a program that lasts 2 years. However, I have done my project/thesis in Beyond Standard Model Physics and this narrows it down a bit. So even when I see research positions where the groups are working in this particular field and look up their research/publications, it is still a lot of literature to cover. So when it comes to understanding what to work on during my PhD, I am still not sure if I have some original ideas as of yet in this field/sub-field. So I am not sure what exactly should I tell my future employers in my application. Is it necessary to mention what exactly I want to work on? I would like some perspective here. There are some PhD positions where it is already laid out what I will be working on.
Also, my question would be how would one go through a plethora of literature before starting to work on something by themselves. My usual approach is to read the publications/research by the concerned professors and then contemplate on whether I can extend their work in some way. TIA.