Hi Dieter,
this is working for me:
<%= link_to 'Search', {:action => 'show_activity', :name => 'Dieter' } %>
Note: Check how to pass arguments to "link_to" in http://api.rubyonrails.org/ In your case it's take name as the html_options so it will rendered as an attribute of <a> tag like this <a href="http://example.com/controller/some_action" name="dieter"/>
I guess this answers your question.