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Equation 60 · Part 3 · The Atlas That Refuses to Close

=

[XNWi,XNWj]=0[X_{\mathrm{NW}}^i, X_{\mathrm{NW}}^j] = 0
=

What this part means

The expressions on both sides represent the same quantity under the stated assumptions.

Its job in the formula

The equals sign connects the complete expression on the left with the complete expression on the right. Both sides must have compatible units.

The passage around this formula

The first, the covariant centre of energy, transforms simply as the spatial part of a four-vector under a change of Lorentz frame — exactly the property Xμ(u,Σ)X^\mu(u,\Sigma) was built with above — but its three spatial components fail to commute with each other once spin is present, by an amount proportional to the spin itself. The second, constructed by Newton and Wigner for exactly this purpose and reproduced in Pryce’s classification as a distinct case, has strictly commuting components, [XNWiX_{\mathrm{NW}}^i, XNWjX_{\mathrm{NW}}^j] = 0 , the property any operator called “position” ought to have if it is to support ordinary probability densities and wavefunction localization at all, at the price of…

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Learn the underlying idea

An equals sign says that the expression on its left and the expression on its right have the same value under the stated definitions and assumptions.

Open the illustrated equality: what the equals sign claims guide →

Sources cited in the surrounding passage

These citations provide research context; check each source for the exact claim it supports.