I recently completed my Masters in a particular domain from a university in India. Typically for most masters in India (as far as I know), research experience is hard to get by. I graduated in a field that is only taught in one or two universities here in Eastern India, and most professors aren't keen on letting post-graduate students do substantial research. However, after I majored in Physics, I chose to specialize in this field during my Masters, as I found my niche in this area of research and it provided me a way to pursue my career as a researcher. I worked on two independent studies during the first year of my master which I presented at two national conferences only. My final year proved to be much more favorable when I had the opportunity to work with a guest professor from a reputed research institute for my master's thesis. After my thesis, I am working under him unofficially for a few more projects, two of which have churned out two papers still in preparation, but it is on its way. The problem is, I still don't know which area I should do my Ph.D. in, but I have a few areas in mind. The research experience that I am currently gathering is not what I surely wanted to work on, but what I could get my hands on. I hope I am making the point clear.
I have made a draft of my statement of purpose (SOP) for foreign universities (especially the US) describing the research studies that I have worked and am working on, but is it possible that I indicate in some way that I am willing to work in any of the research interests that I have, not necessarily the ones I am currently working in or did my dissertation in. I don't consider the experiences I have gained to be stellar compared to the ones by top students who get admitted, but it is what I could get my hands on to the best of my ability. The education system here is not that great, so I had to teach programming and statistical analysis myself which I have used in the dissertation.
P.S. I apologize for having one more question. Should I archive my master's thesis in the likes of arXiv?