Properties and Elements of SO(4) Group in 4 Dimensions

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Discussion Overview

The discussion centers on the properties and elements of the SO(4) group in four dimensions, exploring its role as a rotator and the nature of its rotation matrices. Participants raise questions about the structure of rotations in four dimensions and the generators associated with these rotations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • The original poster inquires about the properties of the SO(4) group and how it functions as a rotator in four dimensions, specifically asking about the elements of the rotation matrix.
  • One participant suggests that in four dimensions, the concept of an axis of rotation may be replaced by a two-dimensional subspace, questioning whether this analogy holds true.
  • Another participant reiterates the idea that SO(4) can be expressed as the exponential of the Lie algebra so(4), noting that the antisymmetric matrices in so(4) depend on six real variables, which raises questions about the representation of the "axis space."
  • A further contribution discusses the generators of rotation in SO(4), proposing that they include components of angular momentum and the Laplace Runge Lenz vector, and questions whether this understanding is correct.

Areas of Agreement / Disagreement

Participants express various hypotheses and questions regarding the structure and properties of SO(4), but no consensus is reached on the nature of its generators or the analogy with lower-dimensional groups.

Contextual Notes

Participants highlight potential limitations in understanding the relationship between the number of variables in the antisymmetric matrices and the dimensionality of the rotation space, but these issues remain unresolved.

jobinjosen
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What are the properties of SO(4) group? , How this acts as a rotator in 4 dimensions?, What are the elements of Rotation matrix in a specific dimension among four dimensions?
 
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I've been waiting for some kind of answer for this post too. I cannot answer the OP, but I'll throw more questions :smile:

When a rotation is carried out in three dimensions, there is an axis of rotation, that is a one dimensional subspace of the three dimensional space, and the rotation is in fact just a two dimensional rotation in the orthogonal complement of this axis. In analogy with this I might guess, that in four dimensions the one dimensional axis is replaced by a two dimensional subspace, that is then some kind of "axis" of rotation. Is this correct?

In analogy with SO(3), I might guess that SO(4)=\textrm{exp}(\mathfrak{so}(4)), where \mathfrak{so}(4) consists of those 4x4 matrices that are antisymmetric (satisty X^T=-X). However, these matrices depend only on 6 real variables, which is not enough to define two four dimensional vectors that would span the "axis space", so it seems I'm guessing something wrong.
 
jostpuur said:
In analogy with SO(3), I might guess that SO(4)=\textrm{exp}(\mathfrak{so}(4)), where \mathfrak{so}(4) consists of those 4x4 matrices that are antisymmetric (satisty X^T=-X).

This is true of SO(n) and so(n).

However, these matrices depend only on 6 real variables, which is not enough to define two four dimensional vectors that would span the "axis space", so it seems I'm guessing something wrong.

https://www.physicsforums.com/showpost.php?p=1110359&postcount=20 may be of interest to both you and jobinjosen.
 
Here are some more points regarding SO(4) group.

In SO(3) rotations, generator of rotation are components of Angular momentum (Lx, Ly, Lz) for rotation w.r.t corresponding axis.

Now, In SO(4), what are the generators of rotation?

They are components of Angular momentum (Lx, Ly, Lz) and components of Laplace Runge Lenz (LRL) vector (Ax, Ay, Az). Constancy of this LRL vector creates aditional symmetry. Am I correct?
 

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