Equation 14 · Part 2 · Every Crystal Has Its Own Speed of Light
Symbol j
What this part means
j is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.
Its job in the formula
j is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.
Full expression→Symbol j→Article meaning
The passage around this formula
Trapped-ion chains make that material-dependence concrete, because they let experimenters dial the range of the interaction and watch the cone respond. Philip Jurcevic and collaborators encoded a tunable-range Ising model on chains of trapped calcium-40 ions, with couplings falling off as 1/|i-j|^{} for an adjustable exponent , and extracted the fastest magnon velocity the resulting dispersion supports. At short range the measured velocity agrees with the ordinary nearest-neighbour prediction; as is pushed toward zero, toward an interaction that barely decays with distance at all, the velocity is consistent with growing without bound, and the light-cone picture stops…
Learn the underlying idea
A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.
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Sources cited in the surrounding passage
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