Question about Lucene's search algorithm

[inge santoso]

    Hi  all,
  I’m still new to Lucene. I'm in the last year of my bachelor degree in
  Computer Science. My final thesis is about indexing and searching in Lucene  
1.4.3. I've read about “Space Optimizations for Total Ranking” paper. My main  
question is : 
          1.    What  search algorithm Lucene implements? Would it implement 
inverted index search on  the ‘Space Optimizations for Total Ranking’ paper? 
  
          2.  Which class in  Lucene that uses this search algorithm? 
  
      3. About Lucene scoring :
           score_d =  sum_t(tf_q * idf_t/ norm_q*tf_d* idf_t/ norm_d_t)
          What is the role  of norm_d_t? Is it equal to normalization for 
document(norm_d)?
               Does lengthNorm  affect lucene ranking? 
  
      It's confusing for me, so I'm hoping you can give us
  the answer so there wouldn't be any wrong perception about this search  
algorithm in the future.
      Thank  you for reading my letter. I'm very thankful for your attention.
      Inge 
                
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