The entire concept of the Accelerated World is based upon the Fluctlight theory originally introduced in Sword Art Online’s Alicization arc.
In short, this theory states that human souls are essentially a collection of photons trapped within the microtubules of brain cells. This group of lights is known collectively as an individual’s Fluctlight.
Fluctlights can be read, edited, and even copied. When an individual first enters the Accelerated World, the program creates a copy of their Fluctlight. This Fluctlight copy is stored within a Lightcube in the Accelerated World’s Lightcube Cluster – a feature that also exists in Sword Art Online’s Underworld. In all subsequent dives into the games, the Linker uses this Fluctlight copy to play.
This is also the mechanism behind Kuroyukihime as a machine child in Volume 23.
One of the most important features of the Fluctlight theory is its concept of Fluctlight Acceleration, which the Accelerated World takes its name from. By accelerating the functioning of a Fluctlight, the consciousness of the user can be accelerated to an almost infinite amount. The amount the Fluctlight is accelerated is called the “FLA Rate”. Normal activities in the Accelerated World run under a constant FLA Rate of x1000.