The Structure of Free Gauge Fields over Minkowski Space
It is shown that the physical states of a source free gauge field form pre-Hilbert spaces already on the classical level. These spaces may be closed in such a way that the determining characteristics remain. One type of free fields has a continuous mass spectrum with no mass gap. One type is massless. Dark matter may consist of (otherwise) free gauge fields. Second quantisation of free gauge fields yield Gårding-Wightman fields identifying the massless and the massive fields as different manifestations of the same field.
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