Changing research area and ArXiv As an undergrad I posted an undergrad research paper on the arXiv. It was not very interesting at all and I did not try to get it published (I essentially only used it for grad school applications).

Since entering grad school I have completely changed my research area and I am now ready to publish a paper in my new field (that will be interesting to some experts). I have also changed how my first name is spelled (and I'm affiliated to a completely different university).

But I'm not sure how best to proceed here: 


I can make a new arXiv account and post the paper under my new name, without linking to my past account at all. The only problem with that is if people search for me using the older spelling of my name, they might see the older account 
I can post this under the older account, updating my name and affiliation there. The older paper will be there and frankly I am slightly embarrassed by it. I also haven't worked in that area in many years so it doesn't make sense to have it listed together with the new paper.


I was wondering if the people here would know what's best. My field is pure math if that's important. Thanks!
I'd recommend your second option. As for being embarrassed by your old paper, you could alleviate the problem by adding, either to the arXiv's comment field  or to the paper itself, something like "This paper is a report on an undergraduate research project and there is no plan to publish it."  (You might also point out explicitly the  change in the spelling of your name, so that people aren't confused by it.)