Equation 95 · Part 2 · No Particle Without a Cosigner
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
Nothing about 's definition requires flat spacetime; the response functional is written in terms of the Wightman function and proper time, both of which are perfectly well defined along a stationary worldline in a curved, static exterior. What changes in curved spacetime is that the field state is no longer unique even after the geometry is fixed: a Schwarzschild exterior supports the Boulware vacuum (empty at infinity, singular at the horizon), the Hartle-Hawking state (thermal everywhere, matching a black hole in equilibrium with its own radiation), and the Unruh state (matching outgoing Hawking flux with no incoming radiation), and a detector’s response depends on which of the…
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 article section
These citations provide research context; check each source for the exact claim it supports.