Questions in Geometric Group Theory — Q 1.10
v1.3 research notes(Canary) Let $G$ be word-hyperbolic and $H$ a finitely presented subgroup of $G$. Suppose that for every $g\in G$ there is $n>0$ such that $g^n\in H$....
Questions in Geometric Group Theory — Q 8.8
v1.3 research notesCompute the asymptotic dimension of CAT(0) groups, Out(Fn), mapping class groups, nonuniform lattices, Thompson’s group. Is there a group of finite ty...
Questions in Geometric Group Theory — Q 11.5
v1.3 research notes(Bridson) Classify the mapping tori of automorphisms $\mathbb{Z}^n\to\mathbb{Z}^n$ up to quasi-isometry....
Some Questions — Question 41
v1.3 research notesDoes every countable group have fixed price; that is, do all its free probability-measure-preserving actions have the same cost?...
Algebraic Stories — Hilbert functions of fat points.
v1.3 research notesGiven a scheme of generic fat points $X \subset \mathbb{P}^{n_1-1}\times\ldots\times \mathbb{P}^{n_t-1}$, what is the multi-graded Hilbert function $\...
Green's conjecture
v1.3 research notesFor a non-hyperelliptic algebraic curve, is its Clifford index determined by the extent to which its canonical embedding has linear syzygies?...
Some Open Problems in Elasticity — Lavrentiev phenomena
v1.3 research notesCan the Lavrentiev phenomenon occur for elastostatics under growth conditions ensuring that all finite-energy deformations are continuous?...
Some Open Problems in Elasticity — Global dynamics
v1.3 research notesProve global existence and uniqueness for suitable initial-boundary-value problems in dynamic nonlinear elasticity....
Research Problems in Function Theory — Problem 2.78
v1.3 research notes(Fatou's conjecture) Show that the subset $U$ of functions $g$ in $R_d$, such that all the critical points of $g$ are in the basins of attraction of p...
Research Problems in Function Theory — Problem 2.88
v1.3 research notesLet $B$ denote the boundary of the Mandelbrot set (or, equivalently, the topological bifurcation set of the family $z\mapsto z^2+c$, $c\in\mathbb{C}$....
Fuglede's conjecture in dimensions one and two
v1.3 research notesFor nonconvex subsets of $\mathbb{R}$ and $\mathbb{R}^2$, is a set spectral if and only if it tiles by translations?...
Pompeiu problem
v1.3 research notesCharacterize the domains for which there exists a nonzero function whose integral vanishes over every congruent copy of the domain....
Vlasov–Maxwell regularity
v1.3 research notesEstablish global regularity, or exhibit breakdown, for solutions of the Vlasov–Maxwell equations from appropriate smooth initial data....
Five Open Problems — Global Cauchy theory for one-dimensional Euler–Fourier flow
v1.3 research notesDevelop a global-in-time theory of the Cauchy problem for the one-dimensional Euler–Fourier system for initial data constrained only by finite energy ...
Five Open Problems — Compensated compactness for symmetric matrices
v1.3 research notesDevelop a compensated-compactness calculus for symmetric matrices when compensated compactness yields only inequalities. As a first application, prove...
Five Open Problems — Compressible Navier–Stokes near vacuum
v1.3 research notesFor compressible Navier–Stokes equations with constant viscosities near vacuum, does the unphysical one-dimensional consequence identified by Hoff and...
Five Open Problems — Eternal finite-energy compressible Euler flow
v1.3 research notesDoes the compressible Euler system in odd spatial dimension admit a nontrivial smooth eternal solution having finite nonzero mass and energy?...
Five Open Problems — Regular reflection without irrotationality
v1.3 research notesProve existence of a regular reflection for compressible flow against a wedge without assuming that the flow is irrotational....
10 Lectures and 42 Open Problems — Open Problem 3.3
v1.3 research notesLet ${G=(V,E,W)}$ be a graph and ${k}$ a positive integer, is the following true? $\rho_G(k) \leq \mathrm{polylog}(k) \sqrt{\lambda_k}. \ \ \ \ \ (2)$...
10 Lectures and 42 Open Problems — Deterministic Restricted Isometry Property matrices
v1.3 research notesConstruct deterministic matrices $A\in\mathbb{C}^{M\times N}$ (or $A\in\mathbb{R}^{M\times N}$ ) satisfying the $(s,\frac13)$ -RIP for $s\approx\frac{...
10 Lectures and 42 Open Problems — Constructive Kadison-Singer
v1.3 research notesGive a (polynomial time) construction of the tight frame partition satisfying the properties required in the Kadison-Singer problem (or the related We...
Goddyn's conjecture on thin spanning trees
v1.3 research notesA spanning tree of a graph G is called $\epsilon$-thin if it contains at most an $\epsilon$ fraction of the edges of each cut. Is there a function $f:...
Rota's conjecture on disjoint bases
v1.3 research notesLet $M$ be a matroid of rank n whose ground set S can be partitioned into n disjoint bases $B_1,\dots,B_n$. Is it true that $B_1,\dots,B_n$ always hav...
Suppose I have a sequence of positive integers whose reciprocals sum to infinity
v1.3 research notesErdős: Suppose I have a sequence of positive integers whose reciprocals sum to infinity. Must that sequence contain arbitrarily long arithmetic progre...
How quickly do the gaps between successive primes grow
v1.3 research notesHow quickly do the gaps between successive primes grow? Is it slower than n^(ľ) for every ľ > 0? See this....
Is there a prime between n^(2)and (n+1)^(2 )for every n > 0
v1.3 research notesErdős: Is there a prime between n^(2)and (n+1)^(2 )for every n > 0?...
Is the least quadratic residue modulo p at most p^(ľ)^( )for any ľ > 0
v1.3 research notesIs the least quadratic residue modulo p at most p^(ľ)^( )for any ľ > 0?...
Rudin's conjecture on squares in progressions
v1.3 research notesFor positive integers $N,q,a$, let $Q(N;q,a)$ be the number of perfect squares among $a,a+q,\ldots,a+(N-1)q$, and let $Q(N)=\max_{q,a\geq1}Q(N;q,a)$. ...
Littlewood constants $lpha$ and $eta$
v1.3 research notesFor $\phi(n)=\sup_{\deg p=n}\int_{|z|<1}|p'|/(1+|p|^2)\,dm$, let $\alpha=\limsup\log\phi(n)/\log n$. For a regular compact set $E$, define $\beta_E$ f...
Unfolding convex polytopes
v1.3 research notesDoes every three-dimensional convex polytope have a non-self-intersecting edge unfolding? Does a minimum spanning tree of the dual edge graph, with a ...
Antipodes of symmetric convex bodies
v1.3 research notesOn a centrally symmetric convex body, must every pair of points at maximum intrinsic surface distance be antipodal? Resolve this even for rectangular ...
Triangulating a hypercube
v1.3 research notesDetermine the minimum number of $d$-simplices needed to triangulate the $d$-dimensional cube, and its asymptotic growth with $d$....
Embedding the hyperbolic plane
v1.3 research notesDoes the hyperbolic plane admit a smooth isometric immersion into $\mathbb R^4$? More generally, determine the least Euclidean dimension for such an i...
Rationality of Hermite constants
v1.3 research notesAre the Hermite constants associated with densest lattice sphere packings always rational? Determine their arithmetic nature in dimensions where the e...
Prince Rupert ratio for tetrahedra
v1.3 research notesWhat is the largest possible ratio between the sum of edge lengths of a tetrahedron that can pass through or fit inside another tetrahedron and the su...
Perfect rational triangles
v1.3 research notesDoes there exist a nondegenerate triangle whose side lengths, three medians, three altitudes, and area are all rational?...
Conjugacy
v1.3 research notesIf two Birkhoff billiard maps $T_1$ and $T_2$ satisfy $T_1=ST_2S^{-1}$ for a homeomorphism $S$, must their tables be similar? Relatedly, can one hear ...
Periodic orbits
v1.3 research notes(a) Is the set of $n$-periodic orbits of a smooth strictly convex Birkhoff billiard nowhere dense for every $n$? (b) Does every polygonal Birkhoff bil...
Mañé's last theorem
v1.3 research notesIn the space of area-preserving $C^1$ diffeomorphisms of a compact manifold, is it generic that the dynamics is either hyperbolic or has zero Lyapunov...
Calogero–Moser–Vlasov
v1.3 research notesFor the infinite-dimensional Calogero–Moser system, in which particles on the real line interact through the inverse-square potential, does the dynami...
Order of mixing
v1.3 research notesLet $p$ be a prime for which $$f(u_1,u_2)=1+u_1u_2+u_1^2u_2+u_1^3u_2+u_1^4+u_2^2+u_1^4u_2^2$$ is irreducible, and consider the algebraic $\mathbb{Z}^2...
Typical group automorphisms
v1.3 research notesChoose a random subset $Q$ of the primes by independently retaining each prime with probability $1/2$. Is it almost surely true that $$\limsup_{n\to\i...
Entropy values and Lehmer's problem
v1.3 research notesGiven $\varepsilon>0$, does there exist a polynomial $f(x)=\prod_{i=1}^d(x-\alpha_i)\in\mathbb{Z}[x]$ whose logarithmic Mahler measure $$m(f)=\sum_{i:...
Entropy and Deligne periods
v1.3 research notesLet $\log_p:\mathbb{C}_p^*\to\mathbb{C}_p$ be the branch of the $p$-adic logarithm with $\log_p(p)=0$, and let $T_\lambda:x\mapsto\lambda x$ on $\math...
Pingree open problems — Ledrappier problem 1
v1.3 research notesLet $M$ be a compact Riemannian manifold of constant negative curvature and $(g_t)_{t\in\mathbb{R}}$ its geodesic flow. Does there exist a probability...
Factor maps between sofic shifts
v1.3 research notesFor sofic shifts $S,T$ with $h(S)\ge h(T)$, give necessary and sufficient conditions for a factor map from $S$ onto $T$. The most fundamental unequal-...
Beta functions
v1.3 research notesCharacterize the functions that occur as beta functions of mixing Markov shifts....
Expansive directions of two-dimensional SFTs
v1.3 research notesFor a $\mathbb Z^2$ shift of finite type $\alpha$, characterize the possible sets $E_1(\alpha)$ of expansive directions, especially under the assumpti...
Furstenberg times-p-times-q problem
v1.3 research notesFor multiplicatively independent integers $p,q>1$, can there exist a nonatomic Borel probability measure on the circle, other than Haar measure, that ...
Full-support invariant measures
v1.3 research notesFor the symbolic system $X$ constructed in Section 14 of the source from a commuting pair of full-shift endomorphisms, is Haar measure its only invari...