As suggested by Marcus, I have read the whole paper and decided to start a discussion of Kober's paper by asking a few questions.(adsbygoogle = window.adsbygoogle || []).push({});

The paper certaintly presents a very interesting view. Part of it is an extension of Heisenberg's work on unified QFT, that the mass originates from self-interaction of spinor fields. However, this theory has chosen the Minkowski metric as a priori, so that it takes the view that the structure of spacetime is more fundamental than the matter fields. Therefore, the thoeory is background dependent.

While Kober in the paper takes the view that mass are generated through self-interaction, he differes from Heisenberg in that the spinor fields are the most fundamental in nature. He does this by constructing the spacetime metric tensor [tex]g_{\mu\nu}[/tex] from tetrads. And the tetrad are constructed from two two-component spinors [tex]\varphi[/tex] and [tex]\chi[/tex] so that, [tex]g_{\mu\nu}=g_{\mu\nu}(\varphi,\chi)[/tex].

Using the constructed metric tensor, he then writes down the action for both matter and gravity. Since my knowledge on gravity is limited, I do not have much to say about it.

One interesting thing arises here is that, because the spinor fields [tex]\varphi[/tex] and [tex]\chi[/tex] are more fundamental than the metric tensor [tex]g_{\mu\nu}[/tex]. So to quantise [tex]g_{\mu\nu}[/tex] one only needs to impose the canonical anticommutation relations on [tex]\varphi[/tex] and [tex]\chi[/tex].

In my opinion, the essence of this paper is the proposed construction of the metric tensor [tex]g_{\mu\nu}[/tex] from spinors, and the view that the spacetime is a consequence of the matter field. This is essentially a "relationalistic" view of spacetime, and I think it is also the view adocated by Julian Barbour in his book the "End of Time".

Another thing that interested me is that the following statements

1. Tetrads can be constructed from spinors

2. The metric tensor can be written in terms of the tetrads

seems to be text-book stuff for knowlegeable people in the field (not me). If so, why hasn't anyone thought of this, or is there some previous objections to this formulation?

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# Martin Kober: The relation of a unified QFT of spinors to the structure of GR

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