What is the Gaussian Curvature of a Cone at its Vertex?

In summary, the Gaussian curvature of a cone tends to infinity at the vertex, but the curvature is zero anywhere else on the cone. This is possible because the curvature approaches infinity at the vertex due to the flatness of the cone's geometry, which can be approximated by a sphere of decreasing radius. At z=0, the curvature is undefined and can be defined as either of the two principal curvatures.
  • #1
lavenderblue
19
0
Hi,

I know that you can determine that the Gaussian curvature of a cone tends to infinity at the vertex, but seeing as the curvature anywhere else on the cone is zero, how is this possible?
 
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  • #2
lavenderblue said:
Hi,

I know that you can determine that the Gaussian curvature of a cone tends to infinity at the vertex

Where do you know it from?
 
  • #3
I was told this by a GR lecturer. But I'm not sure of the mathematics!
 
  • #4
Did you look at the definition in, say Wikipedia? What is the behavior of the two principal curvatures for the cone as you approach the apex? What do you think?
 
  • #5
lavenderblue said:
Hi,

I know that you can determine that the Gaussian curvature of a cone tends to infinity at the vertex, but seeing as the curvature anywhere else on the cone is zero, how is this possible?

Since the Gauss curvature of a cone is zero away from its vertex it does not tend to infinity.
But .. one could imagine a parabaloid like surface that deforms smoothly into a cone with the Gauss curvature of the tip increasing without limit.
 
  • #6
I was told that geometry of the cone is flat with K=0 everywhere except z=0. Do I use the expression for Gaussian curvature for a parabaloid?
 
  • #7
lavenderblue said:
I was told that geometry of the cone is flat with K=0 everywhere except z=0. Do I use the expression for Gaussian curvature for a parabaloid?

You don not need to do a computation in my opinion. As the surface flattens into a cone the tip is approximated by a sphere of decreasing radius.
 
  • #8
lavenderblue said:
I was told that geometry of the cone is flat with K=0 everywhere except z=0.

At z=0 it is just undefined. Depending on how you want to define it there - you will get any number you want. I think your teacher had in mid one of the two principal curvatures.
 

What is the definition of Gaussian curvature of a cone?

The Gaussian curvature of a cone is a measure of the curvature at any point on the surface of a cone. It is the product of the principal curvatures at that point and represents the amount of bending or twisting in the surface.

How is the Gaussian curvature of a cone calculated?

The Gaussian curvature of a cone can be calculated using the formula K = (-1/R1) * (-1/R2), where R1 and R2 are the principal curvatures at a given point on the surface. This formula can also be simplified as K = 1/r^2, where r is the radius of the cone at that point.

What is the relationship between the Gaussian curvature and the shape of a cone?

The Gaussian curvature of a cone is constant and equal to zero at all points, except at the apex where it is undefined. This means that the cone has zero curvature along its entire surface, except at the pointy top. This results in a conical shape with a pointy tip.

Can a cone have negative Gaussian curvature?

No, a cone cannot have negative Gaussian curvature. This is because the Gaussian curvature of a surface is related to the sign of the determinant of the surface's second fundamental form. Since a cone has a positive determinant, its Gaussian curvature must also be positive or zero.

What is the significance of Gaussian curvature of a cone in real-world applications?

The Gaussian curvature of a cone has various applications in fields such as geometry, physics, and engineering. For example, it is used in the design of structures such as bridges and buildings to ensure their stability and strength. It is also used in optics to determine the shape of lenses and in computer graphics for creating 3D shapes and surfaces.

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