What is Xi?
Xi is the 14th letter of the Greek alphabet.
It is pronounced ksi in modern greek and zai in English.
The lower case letter xi, ξ, is used to represent the damping ratio in dynamics. When any structure is knocked and begins to vibrate the rate that vibration decreases is controlled by the damping ratio; by increasing ξ you reduce how long a structure vibrates.
The engineers, mathematicians and physicists that make up our team come across ξ every day, be it as the damping ratio in the vibration equation or as a representation of the eigenvectors in the computer models we solve. Xi was seen as a natural name for us, as the key to providing vibration solutions is the understanding and application of ξ. It also doesn’t hurt that ξ looks a lot like a spring, which is a symbol of oscillating systems and appeals to both our technical and non-technical staff.
You may also be interest to know that ξ is used to represent the Killing vector in general relativity; though the vector does not have a murderous derivation, rather it is named for the mathematician Wilhelm Killing.