after remove zeitgeist, there is no unity in Ubuntu

Use this to Remove/Uninstall Compiz Unity:

sudo apt-get remove compizconfig-settings-manager

sudo apt-get remove compiz-fusion-plugins-extra

sudo apt-get remove compiz-plugins-extra

sudo apt-get purge compiz*

Then to Re-install Compiz Unity use:

sudo apt-get install unity-2d

sudo apt-get install ubuntu-desktop

sudo apt-get install ubuntu-desktop-2d

sudo apt-get install compizconfig-settings-manager

sudo apt-get install xserver-xgl

sudo apt-get install emerald

sudo apt-get install compiz-fusion-plugins-extra

sudo apt-get install git compiz-plugins-extra

sudo apt-get install compiz-plugins-extra

sudo apt-get install unity