Can a Continuous Curve Only Intersect a Differentiable Curve at the Origin?

  • Context: MHB 
  • Thread starter Thread starter caffeinemachine
  • Start date Start date
  • Tags Tags
    Conjecture Curve
Click For Summary
SUMMARY

The discussion centers on the conjecture that for a differentiable function \( f:[0,1]\to\mathbb{R}^2 \) with \( f(0)=(0,0) \), there exists a continuous function \( g:[0,1]\to\mathbb{R}^2 \) that intersects \( f \) only at the origin. The participants explore the implications of defining \( g(x) = f(x) + (x^2, x^2) \) and the challenges in ensuring that \( g \) remains distinct from \( f \) except at the origin. A specific example is provided with \( f(t) = t^3 \sin(1/t) e^{i\pi/t} \), illustrating the difficulty in constructing such a \( g \) without intersection.

PREREQUISITES
  • Understanding of differentiable functions in \( \mathbb{R}^2 \)
  • Knowledge of continuous functions and their properties
  • Familiarity with intersection properties of curves
  • Basic concepts of limits and continuity in calculus
NEXT STEPS
  • Research the properties of differentiable functions in \( \mathbb{R}^2 \)
  • Explore the concept of continuous functions and their intersections
  • Study examples of curves that do not intersect except at specific points
  • Investigate advanced topics in topology related to curve intersections
USEFUL FOR

Mathematicians, calculus students, and anyone interested in the properties of curves in higher dimensions, particularly those studying differentiable and continuous functions.

caffeinemachine
Gold Member
MHB
Messages
799
Reaction score
15
Hello MHB,

I have the following conjecture which I cannot seem to settle either way:

Let $f:[0,1]\to\mathbb R^2$ be a differentiable function such that $f(0)=(0,0)$.
Then there exists a continuous function $g:[0,1]\to\mathbb R^2$ such that:
1) $g(0)=(0,0)$
2) $g([0,1])\cap f([0,1])=\{(0,0)\}$.
3) $g$ is not a constant function. (Forgot to add this earlier.)

Basically what I am trying to prove is that if we have a differentiable curve in $\mathbb R^2$ whic passes through origin then we can find a continuous curve in $\mathbb R^2$ which intersects the gives curve only at origin.
 
Last edited:
Physics news on Phys.org
What's wrong with defining, say, g(x)= f(x)+ (x2, x2)?
 
HallsofIvy said:
What's wrong with defining, say, g(x)= f(x)+ (x2, x2)?
It might so happen that $g(x_1)=f(x_1)+(x_1^2,x_1^2)=f(x_2)\neq (0,0)$.
 
[From my phone by Tapatalk, so this has to be short. ]

Suppose $ f (t)=t^3 \sin (1/t) e^{i\pi/t} $, with $ f (0) =0$. This is differentiable, and I don't see how a function $ g $ can get away from the origin without crossing the graph of $ f $.
 
Last edited:

Similar threads

  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
11
Views
2K
  • · Replies 24 ·
Replies
24
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
21
Views
2K
  • · Replies 27 ·
Replies
27
Views
4K
  • · Replies 21 ·
Replies
21
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 38 ·
2
Replies
38
Views
5K