Yilmaz theory of gravitation
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The Yilmaz theory of gravitation is an attempt by Huseyin Yilmaz (Turkish: Hüseyin Yılmaz) and a handful of coworkers to formulate a classical field theory of gravitation which closely mimics general relativity in weak-field conditions, but in which event horizons cannot appear.
Yilmaz's work has been sharply criticized on various grounds, including the claims that
- his proposed field equation is ill-defined,
- event horizons can occur in weak field situations according to the general theory of relativity, in the case of a supermassive black hole.
- the theory is consistent only with either a completely empty universe or a negative energy vacuum[1]
Yilmaz vigorously disputes these criticisms. Nonetheless, apart from Yilmaz's own papers, the theory has apparently received no attention in the research literature, apart from a few critical papers. Yilmaz claims that his critics have misunderstood him, but it has been suggested that his papers are too murky in crucial places to admit a single clear interpretation. Yilmaz's credibility has also been badly damaged by what appear to be serious misstatements about general relativity.[citation needed]
It is well known that naive attempts to quantize general relativity along the same lines which lead from Maxwell's classical field theory of electromagnetism to quantum electrodynamics fail, and that it has proven very difficult to construct a theory of quantum gravity which goes over to general relativity in an appropriate limit. Yilmaz has claimed that, in contrast, his theory is in some sense 'compatible with quantum mechanics'. He even suggests that it might be an alternative to superstring theory. These claims have apparently been given no credence by physicists other than Yilmaz and a handful of his coworkers.
Yilmaz has offered several descriptions of the field equation for his theory, which his critics feel are neither entirely consistent with each other nor well-defined. To understand one of the most basic criticisms of Yilmaz's work, one needs to be familiar with
- the statement of the Einstein field equation,
- the distinction between coordinate dependent and coordinate independent quantities,
- well known facts concerning integration in curved spacetimes,
- well known facts concerning gravitational energy-momentum pseudotensors in general relativity.
With this background in hand, one can say that Yilmaz apparently wishes to keep the left hand side of the Einstein field equation (namely the Einstein tensor, which is well defined for any Lorentzian manifold, independent of general relativity) but to modify the right hand side, the stress-energy tensor, by adding a kind of gravitational contribution. According to Yilmaz's critics, this additional term is not well-defined, and cannot be made well defined.
Yilmaz has apparently failed to produce a convincing proposal for an observational or experimental test of his theory, and it would appear that no astronomers have contemplated any attempts to test his ideas. On the other hand, astronomers are very interested in testing theoretically solid competitors of general relativity; see Category:Tests of general relativity.
External links
- One page in the website Relativity on the World Wide Web (archived link) lists some apparent misstatements by Yilmaz concerning the general theory of relativity, similar to those discussed by Fackerell.
References
- ^ Michael Ibison, Cosmological test of the Yilmaz theory of gravity, Class. quantum gravity 2006, vol. 23, no3, pp. 577-589
- Yilmaz, H. (1992). "Toward a field theory of gravitation". Nuovo Cimento B. 107: 941–960. doi:10.1007/BF02899296.
- Misner, Charles W. (1999). "Yilmaz Cancels Newton". Nuovo Cimento B. 114: 1079–1085. eprint version In this paper Charles Misner (an internationally recognized expert on gtr) argues that Yilmaz's field equation is ill-defined.
- C. O. Alley; P. K. Aschan; and H. Yilmaz, Refutation of C. W. Misner's claims in his article ``Yilmaz Cancels Newton
- Edward D. Fackerell, Remarks on the Yilmaz and Alley papers; in this preprint Fackerell criticizes several claims by Yilmaz concerning gtr
- Carroll O. Alley and Huseyin Yilmaz, Response to Fackerell's Article
- Misner, Charles; Thorne, Kip S. & Wheeler, John Archibald (1973). Gravitation. San Francisco: W. H. Freeman. ISBN 0-7167-0344-0.
{{cite book}}: CS1 maint: multiple names: authors list (link) See section 20.4 for nonlocal nature of gravitational field energy, and all of chapter 20 for relation between integration, Bianchi identities, and 'conservation laws' in curved spacetimes.