Equation 12 · Part 9 · The Physical Plant: Power, Cooling, and Networks in an AI Datacenter
subscript
subscript
What this part means
The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.
Its job in the formula
A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.
Full expression→subscript→Article meaning
The passage around this formula
Power usage effectiveness is the industry’s one universally reported number: . Uptime Institute, which has collected the metric since its introduction by The Green Grid in 2007, reported a weighted average annual PUE of 1.54 across its 2025 respondent sample, “marking the sixth consecutive year that this headline figure has virtually stood still.” Beneath that flat average the sample separates: facilities commissioned within five years of the survey averaged 1.48, facilities of 20 MW and above averaged 1.44 globally, and 15% of respondents reported 1.3 or better [ 3 ] . Google, disclosing its own fleet, states that “in 2025, the average annual power usage effectiveness for…
Learn the underlying idea
A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.
Open the illustrated subscripts: which member of a family? guide →
Sources cited in the surrounding passage
These citations provide research context; check each source for the exact claim it supports.