Assuming one submits a sitemap for a website in Google Webmaster, does Google reprocess it from time to time? If yes, at which rate?
Edit: Google will recrawl it (see comment by John Mueller from Google below).
However, if you want your sitemap reprocessed more quickly by Google, the recommended practice is to resubmit it.
You can resubmit using Webmaster Tools or using an HTTP request.
Using Webmaster Tools:
The linked source also describes the slightly more complex alternative method where you use an HTTP request.