3x3 Invertible transformations

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SUMMARY

The discussion centers on the concept of invertible transformations in projective geometry, specifically within the context of the projective plane \(\mathbb{P}^{2}\). A user attempts to apply transformations A and B to a vector in the affine plane, leading to confusion regarding the nature of these transformations. It is clarified that the projective plane involves equivalence relations among coordinates, meaning that transformations yield proportional results rather than identical coordinates. This distinction is crucial for understanding the properties of projective transformations.

PREREQUISITES
  • Understanding of projective geometry concepts, particularly \(\mathbb{P}^{2}\)
  • Familiarity with affine transformations and their properties
  • Knowledge of vector representation in homogeneous coordinates
  • Basic grasp of linear algebra and invertible matrices
NEXT STEPS
  • Study the properties of projective transformations in \(\mathbb{P}^{2}\)
  • Learn about homogeneous coordinates and their applications in projective geometry
  • Explore the relationship between affine and projective spaces
  • Investigate invertible matrices and their role in transformations
USEFUL FOR

Mathematicians, geometry enthusiasts, students studying projective geometry, and anyone interested in the applications of transformations in higher-dimensional spaces.

Aleoa
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Homework Statement



Schermata 2018-04-23 15:00:46.png


\mathbb{P}^{2} is an affine plane of 2 dimensions

The Attempt at a Solution



Take for example the affine plane with z=1. Then I take a general vector v= [x,y,1] and i apply the transformation B and then the transformation A.
So i get Bv=f(v) and Av=cf(v).

To me this doesn't seems the same transformation in the affine plane.
Where am i wrong ?
 

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Aleoa said:
So i get Bv=f(v) and Av=cf(v).

To me this doesn't seems the same transformation in the affine plane.
Where am i wrong ?
You're not, but we have the projective plane here, not the affine.
Let ##f(v)=(f_1:f_2:f_3)##, then projective means ##(f_1:f_2:f_3) = (c \cdot f_1:c \cdot f_2:c \cdot f_3)##. This is exactly what projective means: the relations between the coordinates are equal, not the coordinates themselves.
 
Aleoa said:

Homework Statement



View attachment 224549

\mathbb{P}^{2} is an affine plane of 2 dimensions

The Attempt at a Solution



Take for example the affine plane with z=1. Then I take a general vector v= [x,y,1] and i apply the transformation B and then the transformation A.
So i get Bv=f(v) and Av=cf(v).

To me this doesn't seems the same transformation in the affine plane.
Where am i wrong ?

Please take the trouble to actually type out the problem statement; your attached image is unreadable on my devices. Read the post "Guidelines for students and helpers" for more about this issue!
 

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