Mathematics Problem Archive
Multiple ergodic averages — Problem 27
v1.3 research notesLet $c$ be a positive non-integer. Show that the sequence $([p_n^c])$ is good for multiple recurrence and convergence of powers....
Multiple ergodic averages — Problem 28
v1.3 research notesShow that the sequence $([n \sin n])$ is good for multiple recurrence and convergence of powers....
Multiple ergodic averages — Problem 29
v1.3 research notesShow that if $c>1$ is not an integer, then the sequence $([n^c])$ is good for multiple recurrence and convergence of commuting transformations. Moreov...
Multiple ergodic averages — Problem 30
v1.3 research notesLet $\ell \in \mathbb N$ and $c,c_1,\ldots, c_\ell$ be positive real numbers. Show that the prime numbers contain patterns of the form $$ \{m,m+[n^{c}...
Multiple ergodic averages — Problem 31
v1.3 research notesSuppose that $n\sigma_n\to\infty$. Show that almost surely the sequence $(a_n(\omega))$ is good for multiple recurrence and convergence of commuting t...
Multiple ergodic averages — Problem 32
v1.3 research notesSuppose that $n\sigma_n\to\infty$. Show that almost surely the following holds: For every system $(X,\mathcal X,\mu, T,S)$ and functions $f, g \in L^\...
Multiple ergodic averages — Problem 33
v1.3 research notesSuppose that $a,b\in(0,1)$ and $a\neq b$. Show that almost surely the following holds: For every system $(X,\mathcal X,\mu,T,S)$ and functions $f, g \...
Multiple ergodic averages — Problem 34
v1.3 research notesLet $(X,\mathcal X,\mu, T_n)$ be a measure preserving system with multiplicative structure and $A\in \mathcal X$ with $\mu(A)>0$. Is it true that ther...
Multiple ergodic averages — Problem 35
v1.3 research notesLet $(X,\mathcal X,\mu, T_n)$ be a measure preserving system with multiplicative structure and $A\in \mathcal X$ with $\mu(A)>0$. Is it true that ther...
Arnold and Arnold–Givental conjectures
v1.3 research notesFor a Hamiltonian diffeomorphism of a closed symplectic manifold, prove the Arnold lower bound on its number of fixed points in terms of Morse-theoret...
Berry–Tabor conjecture
v1.3 research notesFor a generic quantum system whose classical counterpart is integrable, prove that the unfolded high-energy level spacings have Poisson statistics....
Banach's simple Lebesgue spectrum problem
v1.3 research notesDoes there exist an ergodic measure-preserving transformation whose Koopman operator has simple Lebesgue spectrum?...
Eden's conjecture on local Lyapunov dimension
v1.3 research notesFor a smooth dissipative dynamical system with a global attractor, is the supremum of the local Lyapunov dimension on the attractor attained at an equ...
Kaplan–Yorke dimension conjecture
v1.3 research notesUnder the hypotheses in which the Lyapunov (Kaplan–Yorke) dimension is defined from the ordered Lyapunov exponents, prove that it equals the appropria...
Margulis measure-classification conjecture
v1.3 research notesClassify invariant ergodic probability measures for higher-rank diagonalizable group actions on homogeneous spaces; in particular, prove that the meas...
Unbounded outer-billiard orbits for almost every polygon
v1.3 research notesProve that the outer billiard about almost every convex polygon has an unbounded orbit....
Quantum unique ergodicity
v1.3 research notesLet $M$ be a compact negatively curved Riemannian manifold. Do the probability measures $|\varphi_j|^2\,d\operatorname{vol}$ associated with every ort...
Rokhlin multiple-mixing problem
v1.3 research notesIs every strongly mixing measure-preserving transformation strongly mixing of order three?...
Termination of juggler sequences
v1.3 research notesStarting from a positive integer $a_0$, define $a_{n+1}=\lfloor a_n^{1/2}\rfloor$ when $a_n$ is even and $a_{n+1}=\lfloor a_n^{3/2}\rfloor$ when $a_n$...
Completeness of Lyapunov's second method
v1.3 research notesFor which classes of ordinary differential equations do the classical and canonically generalized forms of Lyapunov's second method give necessary as ...
Local reversibility of reversible cellular automata
v1.3 research notesIn every dimension at least three, is each reversible cellular automaton locally reversible?...
Closed-versus-preclosed trajectory lengths
v1.3 research notesIn a regular $n$-gon, call a trajectory preclosed when its endpoints divide their boundary edges into equal-length parts and meet those oriented edges...
Types of vertices of reachable polygons
v1.3 research notesUnfold a billiard trajectory in a regular $n$-gon by reflecting the polygon across each encountered side. A short trajectory joins two vertices and me...
Reachable points lie on reachable polygons
v1.3 research notesUnfold a billiard trajectory in a regular $n$-gon by reflecting the polygon across each encountered side. A short trajectory joins two vertices and me...
Reachable points on lines through a unitary pair
v1.3 research notesUnfold a billiard trajectory in a regular $n$-gon by reflecting the polygon across each encountered side. A short trajectory joins two vertices and me...
Types of parallel short trajectories
v1.3 research notesUnfold a billiard trajectory in a regular $n$-gon by reflecting the polygon across each encountered side. A short trajectory joins two vertices and me...
Length ratios of parallel short trajectories
v1.3 research notesUnfold a billiard trajectory in a regular $n$-gon by reflecting the polygon across each encountered side. A short trajectory joins two vertices and me...
Short geodesics on the regular dodecahedron
v1.3 research notesOn a regular dodecahedron, unfold a geodesic beginning at a vertex $v$ through successive faces. Call it short if it ends at a vertex and meets no ver...
Elliptic-billiard invariant k_{107}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{108}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{109}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{110}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{111}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{114}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{115}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{117}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{118}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{120}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{203,a}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{203,b}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{204}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{303,a}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{303,b}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{304}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{307}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{401}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{402}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{403,a}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{403,b}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...
Elliptic-billiard invariant k_{404}
v1.3 research notesFix an ellipse with center $O$ and foci $f_1,f_2$, and let $P=(P_i)_{i=1}^N$ range over its Poncelet family of $N$-periodic billiard orbits tangent to...