Comment: According to common law...

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According to common law...

You can simply just start calling yourself whatever you want. Don't have the references off hand but I would refer you to the 9th amendment as far as the proof of your lawful ability to do so.

http://marriage.about.com/od/namechange/g/commonlawrule.htm

I try to refrain from saying "change my name" as referenced in the comment below.