A ?Gravity in 3D: Computing Degree of Freedom

shereen1
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Dear all
can anyone help me to understand why gravity in 3 dim doesn't have local degree of freedom. How can i compute the degree of freedoms for gravity in and dimension D.
If i consider massless gravity in 3d is the graviton propagating
 
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See e.g.Carlip's book on 2+1 quantum gravity. In three dimensions, the Riemann tensor is completely determined by the Ricci tensor and the metric. Hence the vacuum einstein eqns state the Riemann tensor vanishes. Hence no gravitational waves.
 
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haushofer said:
See e.g.Carlip's book on 2+1 quantum gravity. In three dimensions, the Riemann tensor is completely determined by the Ricci tensor and the metric. Hence the vacuum einstein eqns state the Riemann tensor vanishes. Hence no gravitational waves.
Thank you haushofer i will download the book and have a look on it.
 
Zwiebach's book onstring theory has a nice exposition of the counting of degrees of freedom in phase space. This amount is proportional to (D-3). So no graviton propagation for D=3.
 
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haushofer said:
Zwiebach's book onstring theory has a nice exposition of the counting of degrees of freedom in phase space. This amount is proportional to (D-3). So no graviton propagation for D=3.
I will download it to, i also find the book of Steven Carlip interesting too!
Thank you for your time.
 
haushofer said:
Zwiebach's book onstring theory has a nice exposition of the counting of degrees of freedom in phase space. This amount is proportional to (D-3). So no graviton propagation for D=3.
Ther is also a book for John David Brown. It is interesting too.
 
https://arxiv.org/pdf/2503.09804 From the abstract: ... Our derivation uses both EE and the Newtonian approximation of EE in Part I, to describe semi-classically in Part II the advection of DM, created at the level of the universe, into galaxies and clusters thereof. This advection happens proportional with their own classically generated gravitational field g, due to self-interaction of the gravitational field. It is based on the universal formula ρD =λgg′2 for the densityρ D of DM...
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