Querying field with parenthesis

[Tim Terlegård]

I have created my own field type. I have indexed "Stephen King" and
get no hit when searching
author:(stephen king)
I get a hit when searching like this
author:(stephen* AND *king)

I also get a hit when searching like this
author:"stephen king"

So it seems like when querying with (...) it actually splits the
words. This is the type of the author field

    <fieldType name="string_lowercase" class="solr.TextField">
      <analyzer>
        <tokenizer class="solr.KeywordTokenizerFactory"/>
        <filter class="solr.LowerCaseFilterFactory"/>
      </analyzer>
    </fieldType>

I expected that author:(stephen king) would do the same thing as
author:"stephen king". Why is this not the case?

Thanks,
Tim