I am trying to rewrite http://www.domain to http://domain in a wordpress installation, but it looks like it\'s making the url loop from http://www to http:// and back to http://
It looks like you made changes to your .htaccess file that aren't necessary. To fix this problem change your .htaccess file back to default wordpress value which is:
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress
Now that your .htaccess file is back to normal, login to your wordpress dashboard and click on Setting -> General. You'll see two text boxes labeled "WordPress address (URL)" and "Site address (URL)". Change the URL in both of these fields and you can remove the www part if you don't want that in your site URL. Save the changes and you're good to go! Here's a screenshot of the settings page so you can see the exact fields:
Hope this answers your question!
WordPress can do this for you. Remove the .htaccess stuff you've added, and go to Options -> General and change your site's URL.