How is a "small-world" defined formally?

Question

I would like to work with "small-worlds" in communication networks...

Answer 1

You're refering to Milgram's Small world phenomenon.

"A social network exhibits the small-world phenomenon if, roughly speaking, any two individuals in the network are likely to be connected through a short sequence of intermediate acquaintances. "

Follow the link:

http://www.cs.cornell.edu/home/kleinber/...

Answer 2

I think the term "small world" you are referring to is the general effective of common, cross-cultural experientiality. Cultures, no matter how varying, will in the course of their tenure have common experiences, practices and beliefs. This is probably owing to our most basic similarity, humanity. Owing to our being as homo sapiens we are bound to have commonalities with other cultural groups.

Another reason for the "small-world" effect is globalization or the spread of cultures through national and continental boundaries. Globalization is shared culture thanks to a numbers of factors including immigration, diaspora and technological advancements.