Functions homo/isomorphic to change in scale

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
2 replies · 2K views
LogicalTime
Messages
114
Reaction score
0
I would like to find out which functions retain the same structure when they are scaled. Particularly I am interested in projections.

For example, a parabola 3d space viewed at another angle can still be represented by at^2 + bt+c. A circle however can not (ellipse)

I am guessing conic sections have this property? Are there any other functions that have this property, and what terms are associated with this property?
 

Attachments

  • straight.jpg
    straight.jpg
    7.4 KB · Views: 457
  • at angle.jpg
    at angle.jpg
    6.2 KB · Views: 452
Physics news on Phys.org
I think it would help looking at projective surfaces, with homogeneous coordinates.
 
LogicalTime said:
I would like to find out which functions retain the same structure when they are scaled. Particularly I am interested in projections.

For example, a parabola 3d space viewed at another angle can still be represented by at^2 + bt+c. A circle however can not (ellipse)

I am guessing conic sections have this property? Are there any other functions that have this property, and what terms are associated with this property?
Have what property? You assert that a parabola, projected onto any plane, is still a parabola (which is not quite true- it can project to a ray) while that is not true for a circle. But parabola and circle are both conic sections.