Riemann-Tensor have in n- dimensional space?

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Discussion Overview

The discussion revolves around the number of independent components of the Riemann tensor in n-dimensional space. Participants explore the relationship between the components of the Riemann tensor and the dimensionality of the space, touching on related concepts in differential geometry and general relativity.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions how many independent components the Riemann tensor has in n-dimensional space, suggesting a connection to the number of components in mixed tensors.
  • Another participant emphasizes the importance of understanding algebraically independent components and mentions the Bianchi identity's role in the context of the Einstein field equation.
  • A participant provides an example involving a mixed tensor with 5 components in 4-dimensional space, leading to a calculation of 1024 components, but notes the contraction of equations.
  • There is a correction regarding the historical context of Einstein's studies, clarifying the distinction between Hermann Grassmann and Marcel Grossmann.
  • Another participant points out that the example given overlooks algebraic symmetries that reduce the number of independent components, specifically referencing the antisymmetry of the Riemann tensor.

Areas of Agreement / Disagreement

Participants express differing views on the number of independent components and the implications of algebraic symmetries, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Limitations include the potential oversight of algebraic symmetries in the calculations of independent components and the dependence on definitions of tensor components in various contexts.

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How many independent components does the Riemann-Tensor have in n- dimensional space?
 
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Thaakisfox said:
How many independent components does the Riemann-Tensor have in n- dimensional space?

this is related to the number of components related to riemanian tensor and the space that contains it
as a simple example if u have a mixed tensor of 5 components 3 contarvariant and 2 covariant in 4 dimensional space so u have 4^5 compnents i.e 1024
u see how many equations are contracted to single one that's why einstein begin his general relativity by studying tensors with his friend Grassmann

my name is mina, i study QFT
 
Thaakisfox said:
How many independent components does the Riemann-Tensor have in n- dimensional space?

for more information see Shaum vector analysis chap8
 
Independent components?

Thaakisfox said:
How many independent components does the Riemann-Tensor have in n- dimensional space?

Just thought I'd stress that you are probably asking about the number of algebraically independent components. To understand the physical significance of a "geometric" field equation such as the Einstein field equation, you also need to appreciate a crucial differential relation, the (differential) Bianchi identity, which is crucial to understanding, for example, how it can happen in gtr that fluid motion inside some fluid filled region can give rise to gravitational radiation which propagatges as a wave across a vacuum region.
 
mina26 said:
this is related to the number of components related to riemanian tensor and the space that contains it
as a simple example if u have a mixed tensor of 5 components 3 contarvariant and 2 covariant in 4 dimensional space so u have 4^5 compnents i.e 1024
u see how many equations are contracted to single one that's why einstein begin his general relativity by studying tensors with his friend Grassmann

my name is mina, i study QFT

Hi, Mina, I think you are confusing Marcel Grossmann with Hermann Grassmann here! The latter was a fellow graduate student with Einstein at ETH (but Grossmann studied math not physics); the former was the completely different mathematician who introduced what is now called Grassmann or exterior algebra, later adopted by Cartan to give exterior calculus, aka the study of differential forms.

Also, the example you gave overlooks the possibility of algebraic symmetries which will in general reduce the number of algebraically independent components. For example the Riemann tensor (more or less by definition) satisfies R_{abcd} = -R_{bacd}.
 
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