Questions tagged [conformal-geometry]
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3
votes
1answer
144 views
Hodge theory, conformal manifolds and Fredholm modules-understanding the proof of one Lemma
I would like to understand the proof of Lemma 1, page 339 in this book. Very briefly, the context is as follows: we have even dimensional oriented conformal manifold with the Hodge star operator ...
3
votes
0answers
35 views
An integral estimate in conformal geometry
Let $g_0$ be a Riemannian metric of positive scalar curvature $R_0$ on a closed 4-manifold, and for some fixed constant $C$, define the set
\begin{equation}
\mathcal{S} = \{u\in C^\infty(M): ||u||_{W^{...
15
votes
3answers
655 views
How to find a conformal map of the unit disk on a given simply-connected domain
By the classical Riemann Theorem, each bounded simply-connected domain in the complex plane is the image of the unit disk under a conformal transformation, which can be illustrated drawing images of ...
11
votes
2answers
498 views
Are conformal maps between Riemannian manifolds real-analytic?
This is a cross-post.
Let $M,N$ be oriented smooth ($C^{\infty}$) $n$-dimensional Riemannian manifolds, and let $f:M \to N$ be a smooth orientation-preserving weakly* conformal map.
Do there ...
4
votes
0answers
42 views
numerically approximating the conformal map between two curvilinear triangles to high precision
Here is a triangular region $T$ whose two curved edges are complicated analytic curves that I know only numerically, but can compute to any desired precision:
And here is a simpler region $H$ whose ...
2
votes
2answers
385 views
Conformal mappings that preserve angles and areas but not perimeters?
Conformal mappings from $U$ to $V$, both subsets of $\mathbb{C}$, locally preserve angles.
But, in general, such mappings neither preserve areas nor preserve perimeters.
Q. Are there examples of ...
2
votes
1answer
80 views
Is the conformal compactification of a convex-cocompact hyperbolic manifold $M$ conformally diffeomorphic to the convex core of $M$?
I am not a hyperbolic geometer, so I apologize if I get anything wrong here, and please correct me.
The conformal compactification $\overline {\mathbb{H}^n}$ of hyperbolic $n$-space $\mathbb{H}^n$ ...
1
vote
0answers
74 views
Is every “higher-order” harmonic morphism conformal?
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12
votes
3answers
495 views
A conformal map whose Jacobian vanishes at a point is constant?
Let $f:M \to N$ be a smooth weakly conformal map between connected $d$-dimensional Riemannian manifolds, i.e. $f$ satisfies $df^Tdf =(\det df)^{\frac{2}{d}} \, \text{Id}_{TM}$.
Assume $d \ge 3$ ...
8
votes
3answers
405 views
Is there a discrete lattice analogue of conformal transformations?
There is a simple discrete combinatorial analogue of manifolds and homeomorphisms: Replace manifolds by simplicial complexes and homeomorphisms by Pachner moves. Equivalence classes of manifolds under ...
1
vote
0answers
50 views
Conformal factors and light rays
Suppose $(\mathcal{M},g)$ is a $3$-dimensional Riemannian manifold and let $\gamma \in \mathcal{M}$ denote an arbitrary curve in $\mathcal{M}$. Does there exist a conformal factor $c>0$ such that $...
6
votes
0answers
148 views
Reference request: normal form of k-differentials and flat surfaces at a puncture
Let $f(z)$ be a holomorphic function defined on a punctured neighborhood of $z=0$ with non-essential singularity of degree $d$ at $0$ (namely, $f(z)=z^dh(z)$, where $h(z)$ is a holomorphic function ...
1
vote
1answer
53 views
Equality on $\partial \mathbb{H}$ of lifts for isotopy to a conformal map
Let $\mathbb{H} \subset \mathbb{C}$ be the upper half plane. First recall the following statement: if $f^* \colon \mathbb{H} \rightarrow \mathbb{H}$ is quasi-conformal (qc), then there exists an ...
4
votes
0answers
62 views
Conformal $L^p$ rigidity of Riemannian manifolds
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7
votes
1answer
419 views
Proofs that the conformal group in dimension $\ge 3$ is a Lie group
Let $M$ be a smooth manifold of dimension $\ge 3$, equipped with a conformal structure (or a Riemannian metric). Then, the group of conformal diffeomorphisms is a finite dimensional Lie group.
A ...
12
votes
2answers
460 views
Is there a conformal diffeomorphism between R3 minus a line and R2 x S1?
There exists a conformal diffeomorphism between $\mathbb{R}^3$ and $S_3$ (less a point):
$$
g = dr^2+r^2\left(d\theta^2 + \sin^2\theta\ d\phi^2\right)
$$
$$
r = R \tan \frac{\alpha}{2}
$$
$$
g = \...
2
votes
1answer
87 views
conformal mapping and rational function
Let $E$ be an infinite compact subset of the complex plane $\mathbb{C}$ such that $\overline{\mathbb{C}}\setminus E$ is simply connected. By Riemann mapping theorem, there exists a unique exterior ...
2
votes
0answers
80 views
How do conformal maps affect curvature?
Let $(\overline{M}^{n+1}, \langle \cdot, \cdot \rangle)$ be a riemannian manifold with riemannian connection $\overline{\nabla}$ and consider $M^n \subset \overline{M}$ an orientable hypersurface with ...
2
votes
1answer
139 views
Vanishing of determinant of Cotton York tensor
suppose $\Omega \subset \mathbb{R}^3$ is a Riemannian manifold with $g= dx_1^2 + dx_2^2 + c(x_1,x_2,x_3)dx_3^2$. Is it true that $det(CY)=0$?
Thanks
2
votes
0answers
52 views
Will a slightly differently shaped torus make this guess about plane sections of a torus true?
Jacobi's elliptic functions and plane sections of a torus
After Greg Egan posted an excellent answer to a question of mine, which I accepted, I posted my own answer, linked above. The question ...
2
votes
1answer
145 views
$\zeta(2n)$ and Levy processes
I am missing some steps in the final derivation of a probabilistic computation of the even values of $\zeta$. They show the Cauchy distribution is relate to a certian Levy process:
$$ |\mathbb{C}_1| \...
7
votes
1answer
183 views
Uniformisation for non simple closed curves
Given a simple closed curve in the plane, there is a homeomorphism from the unit open disk to the interior of the curve. The homeomorphism can be taken conformal, this is the uniformisation theorem.
...
3
votes
0answers
84 views
conformal mapping and its residue
Let $T$ be a closed rectifiable Jordan curve in $\mathbb{C},$ $G$ be the interior of $T,$ and $\Phi$ be a conformal map of $G$ onto the unit disk $\mathbb{D}.$
My question is the following: for $n\in ...
4
votes
0answers
72 views
Regularity of weak solutions of an equation related to conformal maps
Let $\Omega\subset R^d$ be a nice bounded domain (say, the unit ball). Consider the following equation for $f:\Omega\to R^d$,
$$
\operatorname{div}((\det \nabla f)^{1-2/d} \nabla f) = 0.
$$
Suppose ...
30
votes
7answers
3k views
Why is conformal invariance only possible for massless theories?
I'm conscious that this isn't necessarily a research level question, but I've asked this question on mathstackexchange, and received no answer. So I'm trying it here.
A usual mantra in field theories ...
13
votes
1answer
467 views
Is this expression for the Laplacian of conformal maps between Riemannian manifolds known?
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1
vote
2answers
154 views
Conformal harmonic maps in high dimensions are scaled isometries
This is a cross-post from MSE (where I got no answer).
It is well-known that conformal maps between $2$-dimensional Riemannian manifolds are harmonic.
I discovered lately that in dimension $d>2$, ...
3
votes
1answer
158 views
Circles in conformal geometry
We know that conformal transformations of the Riemann sphere (which are general Mobius transformations) transform circles to circles. A similar fact is also true in higher dimensions. So we can say ...
0
votes
0answers
51 views
Heat trace asymptotic coefficients for conformal metrics $\widetilde{g}=e^{f}g$ surfaces
As is well known $\sum e^{-\lambda_{k}t}\approx(4\pi t)^{dim(M)/2}\sum a_{j}t^{j}$, where $a_{j}$ are geometric properties of manifold M.
Moreover, the arbitrary order coefficients don't have closed ...
1
vote
0answers
60 views
The invariant of a shape which determines percolation
Suppose we have a shape bounded by a simple closed curve $\gamma \subset \mathbb{C}$, with points $A,B,C,D$ in cyclic order on the curve.
If we randomly color the interior of that shape in half red ...
3
votes
1answer
150 views
What are the scalar conformal invariants of weight -3/2 in 3 dimensions?
I am looking for all the scalar conformal invariants (diffeomorphism-invariant polynomials $P[g]$ in the metric $g_{ij}$, its inverse $g^{ij}$ and its derivatives $g_{ij,klm\dots}$ such that $P[\...
1
vote
1answer
120 views
Harmonic maps between surfaces
Suppose $M$ and $N$ are Riemannian manifolds (non compact) of dimension $2$ and $f$ is an harmonic map between $M$ and $N$. When is $f$ conformal?
-1
votes
2answers
203 views
$L^{n/2}$ norm of scalar curvature
In the Wikipedia article on scalar curvature, it is noticed that the Hölder inequality implies
$$Y(g) \geq - \left(\int_M |R(g)|^{n/2} \mathrm{d}V_g\right)^{n/2}$$
for the Yamabe functional $Y(g)$ and ...
7
votes
2answers
699 views
Jacobi's elliptic functions and plane sections of a torus
In $\mathbb R^3$ with Cartesian coordinates $(x,y,z),$ revolve the circle $(x-\sqrt 2)^2+z^2 =1,\ y=0$ about the $z$-axis.
This yields a torus embedded in $3$-space that is conformally equivalent to ...
7
votes
1answer
191 views
Uniqueness theorem for conformal maping
Let $f$ and $g$ be analytic functions in the unit disk $D$, continuous in the closed disk and locally univalent, $f'(z)\neq 0,\; g'(z)\neq 0,\; z\in D$.
Assume that each has only finitely many ...
2
votes
0answers
133 views
Paneitz-Branson operator and Q-curvature
Let $(M,g)$ a n-dimensional Riemannian manifold, $n\neq 4$, and $h=u^{\frac{4}{n-4}}g$. Then the formula that connect the Panitz-Branson opertator $P_g$ and the Q-curvature $Q_{h}$ is
$Q_h=\frac{2}{...
0
votes
1answer
177 views
Conformal equivalence of square and upper-plane, including part of the boundary
I was reading the book "Conformal Invariants" of L. Ahlfors, and seen (P.74) he says that "It is in fact obvious that the part of the teichmuller annulus (for R=1) in the upper plane is conformally ...
0
votes
1answer
53 views
quasi-conformal embedding of Carnot group into euclidean space
By Pansu's theorem, there are no bi-Lipschitz embeddings of Carnot groups (with exception of the Euclidean space itself) into Euclidean space.
Do there exist quasi-conformal embeddings (into Eucl. sp.)...
1
vote
0answers
170 views
Schwarz–Ahlfors–Pick theorem for hyperbolic pair of pants
Let $\mathcal{P}$ be a hyperbolic pair of pants with geodesic boundary and $\Sigma_3$ be the hyperbolic thrice punctures sphere. I want to construct a conformal map $f:\mathcal{P}\rightarrow \Sigma_3$ ...
5
votes
1answer
312 views
Geometric quantization of Teichmuller space
The quantizations of Teichmuller space I have seen are via special coordinates (e.g. the paper of Chekhov and Fock) or conformal blocks. Does one get an equivalent quantization by geometric ...
6
votes
0answers
97 views
Does the Hodge *-operator act on the tangent space at 0 to the space of integral (n-1)-cycles in a conformal manifold of dimension d=2n?
Suppose $M$ is a compact, oriented conformal manifold of even dimension $d=2n$.
Write ${\cal D}^{\mathit{int}}_{k}(M)$ for the space of integral
$k$-currents in $M$
and write ${\cal D}^{\mathit{int}}...
1
vote
1answer
281 views
Can a conformal map be turned into an isometry? [closed]
Let $f: (M, g) \to (M, g)$ be a conformal diffeomorphism of the riemannian manifold $(M, g)$, with
$$ g(f(p))(Df(p) \cdot v_1, Df(p) \cdot v_2) = \mu^2(p) g(p)(v_1, v_2), \quad \forall p \in M, \, \...
0
votes
0answers
84 views
Weak $H^1$-limit of “almost conformal” maps
Let us consider a sequence of maps $\phi_n : (M, g) \to \mathbb{R}^k$, where $M$ is a surface. Let $\phi_n \to \phi$ weakly in the sense of $H^1$-norm, and let $\phi$ be non-trivial. Let $\mathcal{H}$ ...
8
votes
1answer
188 views
Does $S^n\times H^k$ have non-isometric conformal transformations?
Question: Consider the product Riemannian manifold $(M,g)=(S^n\times H^k,g_{round}\oplus g_{hyp})$ of a round sphere $(S^n,g_{round})$ of curvature $1$ and hyperbolic space $(H^k,g_{hyp})$ of ...
7
votes
0answers
212 views
$2-$conformal vector fields on Riemannian manifolds
A vector field $\zeta$ is conformal on a Riemannian manifold $(M,g)$ if $$\mathcal L_\zeta g=\rho g$$These vector fields have a well known geometrical interpretation. The flow of a conformal vector ...
2
votes
3answers
280 views
Classification of open subset of $\mathbb{R}^{3}$ [closed]
There is a theorem which gives a classification of connected open sets of $\mathbb{R}^{2}$. Unfortunately, I don't remember the correct statement, but it looks like this
Theorem ? Let $U\subset\...
0
votes
0answers
82 views
conformal deformation with fixed boundaries
For a flat plane with certain boundary, e.g., a rectangular patch, is it possible to conformally displace or deform such patch to a curved bump with exact same boundary? In this thesis, Dr. Keenan ...
4
votes
0answers
102 views
A conformal mapping onto a region bounded by convex contours (Ahlfors)
I want to solve the following exercise (from Ahlfors' text, page 261). I've tried posting it on MSE, and placed a generous bounty, but I couldn't get any answers there.
*3. Using Ex. 2, show that $...
6
votes
1answer
241 views
Factorization of conformal maps between annuli
Consider two doubly-connected open subsets $A$ and $A'$ of the Riemann sphere. We assume these two domains to be of same modulus (the moduli space being one real parameter), i.e. we assume that there ...
3
votes
3answers
566 views
Equivalence of Harmonic Maps and Conformal Maps on Genus-0 closed surfaces
By the uniformization theorem, for every genus-0 closed surface $\mathcal{M}\subset\mathbb{R}^3$, there is a conformal map $f:\mathcal{M}\rightarrow \mathbb{S}^2$. Furthermore consider the Dirichlet ...
