Novelty as recombination of knowledge

Recombination of knowledge is commonly identified as the source of novelty in patents and in scientific articles. We introduce a new indicator of novelty as recombination of concepts in documents based on Latent Dirichlet Allocation and Hellinger distance and discuss its properties. In comparison with the measures adopted in literature, our indicator has several desirable properties: it is a continuous measure - i.e. it allows to identify breakthrough and to rank articles and patents,- it is robust to the number of topics and to the introduction of neologisms.