*“Knowledge that is nice to have but not essential.”* –Wikipedia

### § On Information Retrieval

From the movie Brazil (1985):

**
Sam Lowry**:

*My name’s Lowry. Sam Lowry. I’ve been told to report to Mr. Warrenn.*

**:**

Porter

Porter

*Thirtieth floor, sir. You’re expected.*

**:**

Sam Lowry

Sam Lowry

*Um… don’t you want to search me?*

**:**

Porter

Porter

*No sir.*

**:**

Sam Lowry

Sam Lowry

*Do you want to see my ID?*

**:**

Porter

Porter

*No need, sir.*

**:**

Sam Lowry

Sam Lowry

*But I could be anybody.*

**:**

Porter

Porter

*No, you couldn’t sir. This is Information Retrieval.*

**§ On Erdős numbers**

** **The **Erdős number** describes the “collaborative distance” between a person and mathematician Paul Erdős, as measured by authorship of mathematical papers. It was created by friends as a humorous tribute to the enormous output of Erdős, one of the most prolific modern writers of mathematical papers, and has become well-known in scientific circles as a tongue-in-cheek measurement of mathematical prominence.

To be assigned an Erdős number, an author must co-write a mathematical paper with an author with a finite Erdős number. Paul Erdős is the one person having an Erdős number of zero. For any author other than Erdős, if the lowest Erdős number of all of his co-authors is *k*, then the author’s Erdős number is *k* + 1.

* *

Publishing with Avi Arampatzis will get you a decent Erdös number of 4 . The median Erdös number is 5; the mean is 4.65, and the standard deviation is 1.21.