Let $C_1,C_2\subset \mathbb{P}^2(\mathbb{R})$ be real algebraic curves each of degree $d$. By Bezout's Theorem these curves have at most $d^2$ points of intercestion. Since we are in the real case, each of the two curves may be a union of connected components. (By Harnack's theorem each of the curve may be decomposed into $\frac{(d-1)(d-2)}{2}+1$ may connected components.) Now I wonder, what can be said about the number of intersections of the various connected components. For example, suppose that $C_1$ has only one connected component but $C_2$ has two of them. Is it then possible that $C_1$ has $d^2$ many intersections wit onlyh one of the connected components of $C_2$?
2025-01-13 05:35:36.1736746536
Intersections of connected components of real curves
230 Views Asked by Alina https://math.techqa.club/user/alina/detail At
1
There are 1 best solutions below
Related Questions in ALGEBRAIC-GEOMETRY
- Relations among these polynomials
- Completion of a flat morphism
- Is every sheaf a subsheaf of a flasque sheaf?
- Intersection of curves on surfaces and the sheaf $\mathcal O_{C\cap C'}$
- Does intersection of smooth divisors satisfy Serre $S_2$ criterion?
- Application of GRR in number theory
- Generic point and pull back
- Every point lies on a unique secant through $C$
- Projective transformation in $\mathbb{P}^1$
- Equality $H^i(K,\mathcal{F}_{|K})=\varinjlim_{U\supset K}H^i(U,\mathcal{F}_{|U})$ for a constructible sheaf
Related Questions in REAL-ALGEBRAIC-GEOMETRY
- how to prove that a set is not semi-algebraic
- Algebraic geometry book with numerical examples
- Unbounded, closed, star-shaped set contains ray
- Intersections of connected components of real curves
- What is the perimeter of the rectangle formed by 7 separate squares with different sides? Explain how you arrived at your conclusion?
- Zariski type topology in real algebraic geometry
- Can we always find homotopy of two paths which lies "between" the paths?
- Can the zeroes of a multivariate $p$-adic polynomial be bounded?
- Are algorithms for elimination of quantifiers over the reals practical?
- what is the difference between quadratic module and preprime?
Trending Questions
- Induction on the number of equations
- How to convince a math teacher of this simple and obvious fact?
- Refuting the Anti-Cantor Cranks
- Find $E[XY|Y+Z=1 ]$
- Determine the adjoint of $\tilde Q(x)$ for $\tilde Q(x)u:=(Qu)(x)$ where $Q:U→L^2(Ω,ℝ^d$ is a Hilbert-Schmidt operator and $U$ is a Hilbert space
- Why does this innovative method of subtraction from a third grader always work?
- What are the Implications of having VΩ as a model for a theory?
- How do we know that the number $1$ is not equal to the number $-1$?
- Defining a Galois Field based on primitive element versus polynomial?
- Is computer science a branch of mathematics?
- Can't find the relationship between two columns of numbers. Please Help
- Is there a bijection of $\mathbb{R}^n$ with itself such that the forward map is connected but the inverse is not?
- Identification of a quadrilateral as a trapezoid, rectangle, or square
- A community project: prove (or disprove) that $\sum_{n\geq 1}\frac{\sin(2^n)}{n}$ is convergent
- Alternative way of expressing a quantied statement with "Some"
Popular # Hahtags
real-analysis
calculus
linear-algebra
probability
abstract-algebra
integration
sequences-and-series
combinatorics
general-topology
matrices
functional-analysis
complex-analysis
geometry
group-theory
algebra-precalculus
probability-theory
ordinary-differential-equations
limits
analysis
number-theory
measure-theory
elementary-number-theory
statistics
multivariable-calculus
functions
derivatives
discrete-mathematics
differential-geometry
inequality
trigonometry
Popular Questions
- How many squares actually ARE in this picture? Is this a trick question with no right answer?
- What is the difference between independent and mutually exclusive events?
- Visually stunning math concepts which are easy to explain
- taylor series of $\ln(1+x)$?
- Determine if vectors are linearly independent
- What does it mean to have a determinant equal to zero?
- How to find mean and median from histogram
- Difference between "≈", "≃", and "≅"
- Easy way of memorizing values of sine, cosine, and tangent
- How to calculate the intersection of two planes?
- What does "∈" mean?
- If you roll a fair six sided die twice, what's the probability that you get the same number both times?
- Probability of getting exactly 2 heads in 3 coins tossed with order not important?
- Fourier transform for dummies
- Limit of $(1+ x/n)^n$ when $n$ tends to infinity
This makes me think of Harnack's construction (cf. Bochnak, Coste, Roy: Real algebraic geometry, Proposition 11.6.3): $C_2$ is an $M$-curve of any degree $d$, i.e., having the maximal number of connected components in degree $d$, such that there is a real projective line $L$ intersecting one connected component of $C_2$ in $d$ real points. Now take generic real projective lines $L_1,\ldots,L_d$ sufficiently close to $L$ and let $C_1$ be a suitable perturbation of their union. Then $C_1$ intersects $C_2$ in $d^2$ real points, all of them on one connected component of $C_2$.