## Sorting it Out

- According to Wikipedia, a
**quiver**is a container for arrows, bolts, or darts that is attached in various positions on an archer’s body, to his bow, or to the ground, depending on the type of shooting and the archer’s personal preferences. Quivers were once made of leather, wood, furs, and other natural materials, but are now more often made of metal or plastic. - What a quiver means in mathematics is obscure to me even after reading this definition. However, I include it here for its eloquence:

In mathematics, a quiver is a directed graph where loops and multiple arrows between two vertices are allowed, that is, a multidigraph. They’re commonly used in representation theory: a representation V of a quiver assigns a vector space V(x) to each vertex x of the quiver and a linear map V(a) to each arrow a. In category theory, a quiver can be understood to be an underlying structure of a category, but without identity morphisms and composition. That is, there is a forgetful functor from Cat to Quiv. Its left adjoint is a free functor which, from a quiver, makes the corresponding free category.

A quiver diagram isn’t an aid to making better quivers. It’s a graph representing the matter content of a gauge theory that describes D-branes on orbifolds. While string theorists use the words quiver diagram, many of their colleagues in particle physics have taken to calling these diagrams mooses.

- A
**quiver tree**(or kokerboom),*Aloe dichotoma,*is indigenous to Southern Africa, specifically in the Northern Cape region, and Namibia. Known as Choje to the indigenous San people, the quiver tree gets its name from their practice of hollowing out the tubular branches to form quivers for arrows. (This is*not*what I was expecting.) - A group of cobras is called a quiver. Cobras are the only snake in the world that can spit their venom; they’re accurate up to about half their own length. King Cobras are the longest venomous snake in the world — the average male grows 18 feet long, and some have grown to more than 20 feet. In the wild, they live for 20 years, maybe more. Cobras aren’t
*poisonous,*they’re*venomous.*This means that even though they possess sacs of deadly venom, they’re otherwise edible to predators. Cobras don’t always inject venom when they bite — they can “dry bite” if they wish. (Is their decision based on something I can influence should I need to? I’m guessing I should try to look neither threatening nor tasty.) Cobras vary in weight from a few ounces to 35 pounds.