Disciplines / Research questions

Mathematics

247 research topics · 1651 questions

Transcendence of the Riemann ζ\zeta function at odd positive integers10 questions
  1. Determining the Q\mathbb{Q}-dimension of the span of 1,ζ(3),ζ(5),…,ζ(s)1,\zeta(3),\zeta(5),\ldots,\zeta(s): linear independence of odd zeta values

    Open for about 48 years
  2. Is Apéry's constant ζ(3)\zeta(3) transcendental, and are ζ(3)\zeta(3) and π\pi algebraically independent?

    Open for about 47 years
  3. Irrationality of odd zeta values: is ζ(5) irrational, and how many of ζ(3), ζ(5), …, ζ(s) are irrational?

    Open for about 47 years
  4. The Sondow–Zlobin conjecture on triangle integrals: prove that InI_n is never a rational multiple of ζ(n+2)\zeta(n+2) for any integer n>2n>2

    Open for about 19 years
  5. Irrationality of ζ(5)\zeta(5)

    Open for about 47 years
  6. Irrationality of the Riemann zeta values at odd integers: is ζ(s) irrational for any fixed odd s ≥ 5?

    Open for about 48 years
  7. Arithmetic nature of the odd Riemann zeta values: irrationality of ζ(2m+1)\zeta(2m+1) for m≥2m\geq 2

    Open for about 47 years
  8. Closed forms for odd zeta values: whether ζ(2n+1)\zeta(2n+1) is a rational multiple of π2n+1\pi^{2n+1}

    Open for about 47 years
  9. Improving the lower bound for the number of irrational odd zeta values

    Open for about 24 years
  10. Irrationality of individual odd zeta values: is ζ(5) irrational?

    Open for about 48 years
Riemann Conjecture6 questions
  1. Open analytical questions for Voros's discretized Keiper–Li sequence: transseries asymptotics, all-nn positivity, and remainder bounds

    Open for about 9 years
  2. The zeta spiral on the critical line: denseness of the values of ζ(1/2+it)\zeta(1/2+it) in C\mathbb{C} and the unconditional curvature sign

    Open for about 16 years
  3. The Alternative Hypothesis for zeta-zero pairs: determinacy of the limiting densities p_{k/2} under AH-Pairs alone

    Open for about 30 years
  4. The missing direction of the Soundararajan and Radziwiłł equivalence between small gaps of zeros of the Riemann zeta-function and the horizontal distribution of zeros of ζ′(s), and the conjectured small-v asymptotics of m(v) and m′(v)

    Open for about 28 years
  5. Denseness of the values of log⁡ζ(1/2+it)\log\zeta(1/2+it) on the critical line: the remaining case of the Bohr–Courant value-distribution problem

    Open for about 112 years
  6. Unconditional discrete second moments of the Riemann zeta-function along polynomial shifts: closing the abscissa gap to the line σ=1/2\sigma=1/2

    Open for about 6 years
Lie algebras and their classification of nilpotent elements in dual spaces7 questions
  1. The normal-form map f↦wff\mapsto w_f versus the Kazhdan–Lusztig map, and the even-depth analogue of the minimal reducing subalgebra theorem for nilpotent elements

    Open for about 5 years
  2. Canonical forms for coadjoint orbits of maximal unipotent subgroups: Surkov's Conjecture 3.8 for root systems beyond G_2 and F_4

    Open for about 1 year
  3. General classification of nilpotent orbits in real graded semisimple Lie algebras: completing the real carrier-algebra programme

    Open for about 12 years
  4. Classification of coadjoint orbits of maximal dimension for Borel nilradicals in types BnB_n, DnD_n and E8E_8

    Open for about 64 years
  5. Nilpotent orbit finiteness, separability, and Howe's conjecture for non-split reductive groups over local fields of positive characteristic

    Open for about 10 years
  6. Spaltenstein's conjecture: every stabiliser sheet of a reductive Lie algebra contains a unique nilpotent orbit, in arbitrary characteristic

    Open for about 44 years
  7. Coincidence of the two Springer correspondences for the dual of a classical Lie algebra in characteristic 2 (Xue's Remark 5.19 expectation)

    Open for about 16 years
Branching laws for representations of Lie groups5 questions
  1. Packet-level multiplicity-one for the branching of O(p,q)O(p,q) to O(p−1,q)O(p-1,q) beyond regular parameters, small-rank signatures, and a Gross–Prasad-type law for non-tempered packets

    Open for about 7 years
  2. Classification of the triples (G,πλG,ϕ)(G,\pi_\lambda^G,\phi) with admissible restriction of a discrete series representation to an embedded SU(2,1)SU(2,1)

    Open for about 8 years
  3. Finite multiplicity of the continuous spectrum in discrete series branching laws: a per-representation criterion and the finite-infinite boundary for symmetric pairs beyond the real-spherical class

    Open for about 13 years
  4. Kobayashi's conjecture on admissible restrictions: does G′G'-admissibility imply K′K'-admissibility?

    Open for about 26 years
  5. Blattner-type multiplicity formula for discretely decomposable restrictions of Zuckerman modules Aq(λ)A_{\mathfrak q}(\lambda) to symmetric subgroups (Ørsted–Speh conjecture)

    Open for about 18 years
Classification of unitary representations of Lie groups8 questions
  1. Positive energy versus semiboundedness for irreducible unitary representations of full hermitian Lie groups

    Open for about 15 years
  2. The unitary duals of the complex exceptional simple Lie groups F4F_4, E6E_6, E7E_7, and E8E_8

    Open for about 37 years
  3. General super imprimitivity theorem: Mackey induction and systems of imprimitivity for super homogeneous spaces with odd directions

    Open for about 21 years
  4. Unitary dual of Drinfeld doubles of q-deformations of compact semisimple Lie groups beyond the almost-real regime

    Open for about 10 years
  5. The Salamanca-Riba–Vogan unitarily-small infinitesimal-character conjecture for real reductive groups beyond U(p,q)U(p,q)

    Open for about 27 years
  6. Structural theory of the FS-scattered part of the Dirac series for real exceptional Lie groups: u-small K-types, unipotent representations, and cancellation in the Dirac index

    Open for about 6 years
  7. Making the FPP description of the unitary dual of real reductive groups algorithmically effective

    Open for about 3 years
  8. Algebraic constructions of first-reduction-point and exceptional unitary highest weight modules

    Open for about 3 years
Decoding Problems of Reed-Solomon Code7 questions
  1. Hardware realization of quasi-linear FFT-based Reed–Solomon decoders (the modular-approach MA/FDMA/FMA family)

    Open for about 4 years
  2. Low-complexity algebraic soft-decision decoding of Reed–Solomon codes: closing the performance–complexity gap of Koetter–Vardy decoding

    Open for about 22 years
  3. Combinatorial List-Size Classification of Linearized Reed–Solomon Codes Across All Sum-Rank Parameter Regimes

    Open for about 5 years
  4. Efficient decoding, list-decodability, and dual insdel distance of Reed–Solomon codes under insertion–deletion errors

    Open for about 6 years
  5. Efficient list-decoding of Reed-Solomon codes at the generalized Singleton radius, and efficient certification of optimal list-decodability

    Open for about 6 years
  6. Explicit Reed–Solomon codes achieving capacity-level list-decodability over small fields

    Open for about 5 years
  7. Proximity gaps for Reed–Solomon codes above the Johnson radius: list- and line-decodability over prime fields up to the Elias radius

    Open for about 6 years
Determining the cardinality of the continuum5 questions
  1. Consistency strength of the higher Solovay configuration at singular cardinals of countable cofinality: measurability of κ+\kappa^+ in L(P(κ))L(\mathcal{P}(\kappa)) and the ℵω\aleph_\omega-perfect set property

  2. Woodin's Ω Conjecture: completeness of Ω-logic under a proper class of Woodin cardinals

  3. Optimal large-cardinal strength for blowing up the power of a singular cardinal of uncountable cofinality that is singular in the core model

  4. Optimal hypotheses for Easton's theorem at measurable and strong cardinals

  5. The Revision Hypothesis: must every limit cardinal be a revision cardinal?

Quantum Layer Conjecture7 questions
  1. Bound states of the Dirichlet Laplacian in the Fichera layer and generalized Fichera layers: exact counts

    Open for about 8 years
  2. Geometric characterization of the discrete spectrum of quantum layers and their nonsmooth analogues: bound states, thickness uniformity, and the converse problem

    Open for about 25 years
  3. Discrete spectrum of curved quantum layers: the Lu–Rowlett open problems on uniform thin-layer existence, the positive-total-Gauss-curvature domination inequality, and the thick-layer dichotomy

    Open for about 14 years
  4. Empty discrete spectrum of generalized quantum tubes: the converse problem beyond thin layers and surfaces

    Open for about 20 years
  5. Width-uniform existence of bound states in hard-wall quantum layers over finite-total-curvature surfaces

    Open for about 19 years
  6. Curvature-induced bound states in quantum layers over non-parabolic hypersurfaces in dimensions four and higher

    Open for about 14 years
  7. The quantum layer conjecture: bound states in hard-wall layers over nonplanar asymptotically flat surfaces with finite total curvature

    Open for about 25 years
The quantum minimal model conjecture7 questions
  1. Invariance and decomposition of quantum cohomology under flips and birational maps between minimal models

    Open for about 27 years
  2. Reduction conjecture for arbitrary smooth GIT quotients and quantum D-module decomposition for arbitrary standard flips

    Open for about 3 years
  3. Effective computation of quantum cohomology across conifold transitions: a blow-up formula along Weil divisors

    Open for about 11 years
  4. Does blowing up a Fano manifold along a smooth Fano center strictly increase the spectral radius of quantum multiplication by the first Chern class (Conjecture 1.1 of Hu–Ke–Li–Song)?

    Open for about 2 years
  5. Globalizing the quantum-flips F-embedding: big quantum cohomology under general global simple (r,r′) flips

    Open for about 6 years
  6. Establish the GG-equivariant noncommutative minimal model program: quasi-convergent paths of equivariant stability conditions from the equivariant quantum differential equation

    Open for about 3 years
  7. Blow-up compatibility of reflection vectors in quantum cohomology: convergence of the quantum cohomology of Bl(X) and the reflection-vector property for pullbacks of exceptional objects

    Open for about 3 years
Quantum Yang-Mills Millennium Problem4 questions
  1. Extending the provable area-law regime for lattice Yang-Mills: the linear-in-N ('t Hooft) regime with uniform string tension, and fixed small N at large coupling

    Open for about 52 years
  2. Deconfinement for trivial-center lattice Yang–Mills in the strong-coupling regime and mass-gap criteria beyond the Bakry–Émery approach

    Open for about 47 years
  3. Deconfinement of trivial-center lattice Yang-Mills theories: uniform perimeter law for all strong-coupling beta, extensions to SO(2N+1) and general representations, the weak-coupling regime, and the large-N reconciliation

    Open for about 47 years
  4. Yang–Mills existence and mass gap: a fully quantized, background-independent four-dimensional theory with a gauge-invariant positive mass gap

    Open for about 26 years
List Coloring Conjecture9 questions
  1. The List Equitable Total Coloring Conjecture

    Open for about 8 years
  2. Enumerative chromatic-choosability of joins with complete graphs (the enumerative Ohba conjecture of Allred and Mudrock)

    Open for about 1 year
  3. The Proportional Choice Number of Complete Bipartite and Complete Multipartite Graphs: Exact Value, Classification, and Asymptotics

    Open for about 6 years
  4. Is every line graph {1⋆(χ′(G)−3), 3}\{1\star(\chi'(G)-3),\,3\}-choosable?

    Open for about 50 years
  5. Generalized Ohba conjecture for r-uniform hypergraphs: chromatic-choosability at high chromatic number

    Open for about 8 years
  6. The List Coloring Conjecture: is the list chromatic index of every multigraph equal to its chromatic index?

    Open for about 51 years
  7. List and correspondence colouring reconfiguration conjectures: optimal diameters n(G)+μ(G)n(G)+\mu(G) and n(G)+τ(G)n(G)+\tau(G)

    Open for about 4 years
  8. Paintability of balanced complete multipartite graphs with parts of size three: is χP(K3⋆n)=⌈(4n−1)/3⌉\chi_P(K_{3\star n})=\lceil(4n-1)/3\rceil for every nn, and what is χP(K3⋆7)\chi_P(K_{3\star 7})?

    Open for about 14 years
  9. Open problems on the λ-choosability of planar graph families from Zhu's refinement of choosability

    Open for about 7 years
Existence of a complex structure on the six-dimensional sphere6 questions
  1. Integrability of the Clifford-induced almost complex structure on level hypersurfaces of OT-FKM isoparametric families

    Open for about 4 years
  2. The Hopf problem in generalized geometry: existence of an integrable generalized complex structure on the six-sphere S6\mathbb{S}^6

    Open for about 2 years
  3. Hopf's problem: does the six-sphere admit a complex structure?

    Open for about 79 years
  4. Vanishing and Chern-class constraints for compact complex threefolds with b2=0b_2=0 and holomorphic algebraic reduction in full generality

    Open for about 28 years
  5. Complex-structure rigidity without the Kähler hypothesis for the two exceptional G2G_2 flag manifolds QQ and ZZ

    Open for about 6 years
  6. A necessary-and-sufficient curvature characterization of integrability of almost complex structures

    Open for about 11 years
Does the travelling salesman problem admit an approximation ratio below 1.5?7 questions
  1. Is the integrality gap of the subtour-elimination LP for the metric s-t path TSP exactly 3/2?

    Open for about 10 years
  2. A 3/2-Approximation for Prize-Collecting TSP and a Black-Box Reduction from TSP to PCTSP

    Open for about 3 years
  3. The exact integrality ratio of the Held-Karp relaxation for the metric s-t path TSP

    Open for about 14 years
  4. The 4/3 conjecture for the integrality gap of the subtour elimination relaxation of the metric traveling salesman problem

    Open for about 46 years
  5. The 4/3-Conjecture for the Integrality Gap of the Subtour (Held–Karp) Relaxation of the Metric Traveling Salesman Problem

    Open for about 36 years
  6. Schalekamp–Williamson–van Zuylen conjecture: is the integrality gap of the subtour LP attained on half-integral vertices?

  7. The integrality ratio of the standard LP relaxation for the metric s-t-path TSP

    Open for about 14 years
The travelling salesman problem7 questions
  1. The exact integrality ratio of the Held-Karp (subtour) LP relaxation for the metric s-t path TSP

    Open for about 35 years
  2. Computational Complexity of the Symmetric Circulant Traveling Salesman Problem

    Open for about 41 years
  3. The four-thirds conjecture for the subtour elimination relaxation of the metric traveling salesman problem and the existence of a 4/3-approximation algorithm

    Open for about 36 years
  4. Determining the Beardwood–Halton–Hammersley constant for the random Euclidean traveling salesman problem: improving the rigorous lower bound 0.6277 and closing the gap to the upper bound 0.90367

    Open for about 66 years
  5. Is the integrality gap of the subtour LP for metric TSP attained on half-integral vertices? (Schalekamp–Williamson–van Zuylen conjecture)

    Open for about 13 years
  6. Constant-Factor Approximability of the Traveling Salesman Problem with Line Neighborhoods in R3\mathbb{R}^3

    Open for about 13 years
  7. Complexity of the Euclidean TSP with neighborhoods: optimal tours for rays in the plane and approximation for lines in 3-dimensional space

    Open for about 14 years
The Rohlin problem8 questions
  1. Rokhlin's multiple mixing problem: does mixing imply mixing of all orders for measure-preserving automorphisms?

    Open for about 77 years
  2. Does exponential mixing imply multiple exponential mixing for smooth measure-preserving systems? (Problem 5.2 of Dolgopyat–Dong–Kanigowski–Nándori)

    Open for about 6 years
  3. Rohlin's multiple mixing problem for Z\mathbb{Z}-actions: does mixing imply mixing of all orders?

    Open for about 77 years
  4. Is the weak Ratner property an isomorphism invariant for measure-preserving flows?

    Open for about 16 years
  5. Open problems in the rigidity theory of actions with extreme deviation from multiple mixing

    Open for about 8 years
  6. The Rohlin problem: does mixing imply mixing of all orders for measure-preserving Z\mathbb{Z}-actions?

    Open for about 77 years
  7. Non-trivial pairwise-independent 3-fold self-joinings of zero-entropy mixing stationary processes

    Open for about 39 years
  8. Rohlin's problem: does strong mixing imply mixing of all orders for measure-preserving Z\mathbb{Z}-actions?

    Open for about 77 years
Several problems in Rota-Baxter algebra5 questions
  1. Realizing subgroups as images of Rota–Baxter operators on groups: the free-group instance (Kourovka Notebook Problem 20.124) and Rota–Baxter operators on free non-abelian groups

    Open for about 5 years
  2. A polarized classical Yang–Baxter equation for matching Rota–Baxter Lie algebras of weight zero

    Open for about 6 years
  3. Extended double shuffle completeness and Zagier's dimension conjecture for multiple zeta values

    Open for about 32 years
  4. Rota-Baxter indices of upper-triangular and semisimple matrix algebras and the derived-algebra nilpotency bound for Mn(F)M_n(F)

    Open for about 8 years
  5. Restricted post-Lie structures induced by tridendriform algebras in prime characteristic

    Open for less than 1 year
Is the Fitting subgroup of a solvable group satisfying the minimal condition on normal subgroups nilpotent?3 questions
  1. Minimal condition on normal subgroups of infinite rank for locally soluble groups

    Open for about 12 years
  2. Nilpotence of the Fitting subgroup of a soluble group with the minimal condition on normal subgroups

    Open for about 7 years
  3. Minimal condition on normal subgroups of infinite rank for locally soluble groups

Existence of infinitely many solutions of nonlinear elliptic equations without symmetry7 questions
  1. Geometric uniformity of minimizing tiled deformations for non-symmetric elliptic equations: extending the Bahri–Lions multiplicity theorem to arbitrary bounded smooth domains

    Open for about 37 years
  2. Infinitely many solutions of the Dirichlet pp-Laplacian with nonzero boundary data throughout the subcritical range

    Open for about 28 years
  3. Persistence of infinitely many solutions for the perturbed elliptic system −Δu=vp−1-\Delta u=v^{p-1}, −Δv=f(u)+h-\Delta v=f(u)+h in the full subcritical range (Salvatore's open problems)

    Open for about 16 years
  4. Broken-symmetry multiplicity for superlinear elliptic Dirichlet problems: the Bahri–Lions conjecture on general domains

    Open for about 37 years
  5. Sharp thresholds for infinitely many solutions of quasilinear equations perturbed from symmetry

    Open for about 12 years
  6. Extending the network-gluing construction of finite-energy solutions with trivial symmetry group to non-even nonlinearities and higher dimensions

    Open for about 12 years
  7. Infinitely many solutions for the superlinear Dirichlet problem with fixed inhomogeneous data in G-invariant domains: the full subcritical range

    Open for about 37 years
Semiprimeness of smash products of module algebras10 questions
  1. Semiprimeness transfer to smash products of weak Hopf algebra actions: beyond the involutive, PI, finite-action case

    Open for about 40 years
  2. Does H-semiprimeness imply semiprimeness for PI-algebras acted on by finite-dimensional semisimple Hopf algebras in positive characteristic?

    Open for about 19 years
  3. The Cohen–Fishman question: is the smash product of a semisimple Hopf algebra with a semiprime module algebra always semiprime?

    Open for about 40 years
  4. Prime and semiprime smash products for finite-dimensional pointed Hopf algebras beyond quantum linear spaces

    Open for about 6 years
  5. Semiprimitivity and semiprimality of partial smash products: the general partial-action analogue of the Cohen–Fishman–Linchenko–Montgomery question

    Open for about 10 years
  6. Unconditional semiprimality and semiprimitivity transfer for partial smash products of semisimple Hopf algebra actions

    Open for about 10 years
  7. Prime and semiprime smash products for finite-dimensional pointed Hopf algebra actions beyond quantum linear spaces

    Open for about 7 years
  8. Classifying finite-dimensional Hopf algebras whose actions force a nilpotent Jacobson radical on invariant rings

    Open for about 8 years
  9. Intrinsic criteria for equality of the graded and ordinary Jacobson radical of finite groupoid graded algebras beyond trace invertibility

    Open for about 7 years
  10. The Cohen–Fischman semiprime smash product question and Jacobson-radical stability for Hopf actions on PI-algebras

    Open for about 40 years
Kac-Weisfeiler Conjecture in Modular Lie Algebra Representation Theory8 questions
  1. The super Kac-Weisfeiler divisibility property for the strange classical Lie superalgebras q(n)q(n) and p~(n)\tilde p(n)

    Open for about 18 years
  2. Super Kac–Weisfeiler divisibility for arbitrary restricted Lie superalgebras: irreducible module dimensions, the maximal-locus statement, and support-variety refinements

    Open for about 18 years
  3. The first Kac–Weisfeiler conjecture for restricted Lie algebras and the index of algebras with isomorphic enveloping algebras

    Open for about 55 years
  4. Tikaradze's Kac–Weisfeiler-type conjecture for filtered algebras in positive characteristic: i(χ)≥12s(χ)i(\chi)\ge\tfrac{1}{2}s(\chi)

    Open for about 16 years
  5. The second Kac-Weisfeiler divisibility conjecture for truncated current Lie algebras

    Open for about 55 years
  6. Effective thresholds for the first Kac–Weisfeiler conjecture in large characteristics and the Frobenius-characterisation conjecture for arbitrary restricted Lie algebras

    Open for about 55 years
  7. Super first Kac–Weisfeiler conjecture for finite-dimensional restricted Lie superalgebras

    Open for about 55 years
  8. Minimal-dimensional representations of finite WW-superalgebras and attainability of the super Kac–Weisfeiler bounds (Zeng–Shu Conjecture 0.3)

    Open for about 11 years
Singularities induced by characteristic vectors in quasilinear hyperbolic systems6 questions
  1. No shock formation for totally linearly degenerate quasilinear hyperbolic systems: the C0⇒C1C^0\Rightarrow C^1 conjecture beyond block-structured classes

    Open for about 42 years
  2. Majda's no-shock conjecture for one-dimensional linearly degenerate quasilinear hyperbolic systems: ODE-type amplitude blowup versus shock formation

    Open for about 42 years
  3. Majda's conjecture: ODE-type singularity for linearly degenerate quasilinear hyperbolic systems

    Open for about 42 years
  4. Majda's conjecture: ODE-type singularity formation for one-dimensional quasilinear hyperbolic systems with linearly degenerate characteristic fields

    Open for about 42 years
  5. Global regularity versus finite-time singularity formation in linearly degenerate dissipative relativistic fluid models

    Open for about 2 years
  6. Spectral-data regularity and normalized coordinates for quasilinear hyperbolic systems with non-constant characteristic multiplicity

    Open for about 19 years
Computation and additivity of knot crossing numbers7 questions
  1. Additivity of the crossing number of knots under connected sum (Tait's problem; Kirby Problem 1.65)

    Open for about 149 years
  2. The satellite crossing number conjecture

    Open for about 30 years
  3. Additivity of the triple-crossing number under connected sum and sharpness of the genus lower bound

    Open for about 6 years
  4. Constancy of the quadratic Jones-slope coefficient functions in the colored Jones degree quasipolynomials of a knot

    Open for about 5 years
  5. Monotonicity of the crossing spectrum of knots and the additivity threshold for multi-crossing numbers

    Open for about 12 years
  6. Additivity of the crossing number under connected sum of knots

    Open for about 31 years
  7. Completing the restricted-Reidemeister-move route to crossing-number additivity: robust diagram invariants and a topological interpretation of the restricted move set (Weinstein 2025, Questions 1-2)

    Open for less than 1 year
Computation and additivity of unknotting numbers6 questions
  1. The band-unknotting number of the double twist knots C(22+8k,62+8k)C(22+8k,62+8k)

    Open for less than 1 year
  2. The unknotting number of the knot 10610_6: deciding between 22 and 33

    Open for less than 1 year
  3. Does the unknotting number of a connected sum of knots grow with the number of summands?

    Open for about 49 years
  4. Exact unknotting numbers of the connected sums T(2,k) # T(2,−k)T(2,k)\,\#\,T(2,-k) of two-strand torus knots with their mirrors, and exact Reidemeister move counts for unlinking

    Open for about 15 years
  5. Quasi-additivity of the Delta-unknotting number, a strand-independent braid-knot constant, and primality of knots with Delta-unknotting number one

    Open for less than 1 year
  6. How badly unknotting number fails to be additive under connected sum: the max bound, universally additive knots, and the exact value of u(71#71‾)u(7_1\#\overline{7_1})

    Open for about 1 year
Transcendence of Euler's constant10 questions
  1. Apéry-type rational approximations to Euler's constant: a second-order homogeneous recurrence construction, or integer linear forms in 1 and γ of better-than-sub-exponential quality

    Open for about 47 years
  2. Is Euler's constant a value of an arithmetic Gevrey series? Membership of γ\gamma in the rings E\mathbf{E}, G\mathbf{G} and D\mathbf{D}

    Open for about 3 years
  3. The arithmetic nature of the Euler–Gompertz constant: irrationality and transcendence of δ=eE1(1)\delta=eE_1(1)

    Open for about 58 years
  4. Irrationality and arithmetic nature of the Euler–Mascheroni constant

    Open for about 126 years
  5. Arithmetic nature of the linear combinations γ+αδ\gamma+\alpha\delta of the Euler–Mascheroni and Euler–Gompertz constants for α≠1/e\alpha\neq 1/e

    Open for about 292 years
  6. Arithmetic nature of the non-trivial zeros of the Riemann zeta function and of their power sums f(x)=∑ρxρ/ρf(x)=\sum_\rho x^\rho/\rho at algebraic arguments

    Open for about 8 years
  7. Unconditional algebraic independence of the logarithmic parts of generalized Euler–Briggs constants (removing the Weak Schanuel hypothesis in Gun–Murty–Saha)

    Open for about 10 years
  8. Occurrence of the exceptional algebraic generalized Euler–Briggs constant γ(Ω,a,q)\gamma(\Omega,a,q) in the families of Gun–Saha–Sinha

    Open for about 16 years
  9. Erdős's conjecture on the non-vanishing of L(1,f)L(1,f) for ±1\pm1-valued periodic functions (Erdősian functions)

    Open for about 61 years
  10. Determine the arithmetic nature of generalized Euler–Kronecker constants of number fields (algebraic or transcendental)

    Open for about 295 years
Well-posedness of global L∞L^{\infty} weak solutions of the Euler equations8 questions
  1. Beyond the Yudovich class for the 2D Euler equations: propagating localized instability to full non-uniqueness of unforced LpL^p weak solutions, Gevrey-type well-posedness, and the self-similar structure of the algebraic singularity

    Open for about 39 years
  2. Existence of global energy-admissible weak solutions of the incompressible Euler equations for arbitrary initial data in the energy space

    Open for about 15 years
  3. Uniqueness versus non-uniqueness for the 2D incompressible Euler equations with vorticity in LpL^p, p<∞p<\infty (the Yudovich gap)

    Open for about 39 years
  4. Well-posedness of the 2D Euler equations with bounded, non-decaying planar vorticity: uniqueness of Yudovich-type limits beyond symmetry and far-field prescriptions

    Open for about 9 years
  5. Existence of energy-admissible global weak solutions to the incompressible Euler equations for arbitrary L2L^2 initial data

    Open for about 15 years
  6. Existence of invariant measures for the 2D stochastic Euler equations driven by linear multiplicative noise on a bounded domain

    Open for about 3 years
  7. Well-posedness of the two-dimensional Euler equations with merely bounded vorticity in wide planar sectors and general unbounded domains (the Caprino–Marchioro one-point Green-function conjecture)

    Open for about 17 years
  8. Uniqueness for the two-dimensional incompressible Euler equations with unbounded LpL^p vorticity

    Open for about 63 years
Schoen's conjecture on harmonic maps of the Poincaré disk4 questions
  1. Finite non-transversality of positive maps into flag varieties for general Guichard–Wienhard positive structures

    Open for less than 1 year
  2. Harmonic diffeomorphisms between Euclidean and hyperbolic model spaces: the open non-symmetric and higher-dimensional cases of Schoen's problem

    Open for about 33 years
  3. Nonvanishing of the Jacobian for harmonic quasiconformal mappings in dimensions n≥4n\ge4 (Problem 7.3 of Todorčević, 2019)

    Open for about 11 years
  4. Nonexistence of harmonic diffeomorphisms from the disk onto a complete parabolic plane (Mazet–Rodríguez–Rosenberg conjecture)

    Open for about 10 years
Penrose's Conjecture6 questions
  1. The Penrose inequality for general (non-time-symmetric) asymptotically flat initial data sets

    Open for about 52 years
  2. The sharp Penrose inequality for asymptotically (locally) hyperbolic initial data

    Open for about 27 years
  3. Penrose inequality and positive mass theorem under averaged dominant energy conditions beyond spherical symmetry

    Open for about 1 year
  4. Extremal Reissner–Nordström–Tangherlini rigidity at equality in the charged positive mass inequality for higher-dimensional black-hole initial data

    Open for about 12 years
  5. The Penrose inequality for general asymptotically flat initial data sets beyond the 2-convexity condition

    Open for about 53 years
  6. Lower bounds for black hole area in terms of mass, charge, and angular momentum: minimal enclosing area, multiple black holes, and rigidity

    Open for about 13 years
Poincaré's problem on degrees of invariant curves of planar vector fields5 questions
  1. Divergent separatrices of holomorphic foliations on the complex projective plane with a unique singular point: an explicit saddle-node example and rigorous divergence for the Alcántara–Mozo-Fernández nilpotent family

    Open for about 3 years
  2. Characterizing when the index–Diophantine strategy bounds the degrees of algebraic solutions of non-degenerate polynomial differential equations

    Open for about 8 years
  3. Realizability of the pure algebraic multiplicity and topological invariance of the algebraic multiplicity for dicritical foliation germs (Genzmer–Mol's open questions)

    Open for about 10 years
  4. The algebraic-critical case of the Poincaré problem: which local algebraic solutions extend to global invariant algebraic curves

    Open for about 21 years
  5. Genus-one rational first integrals and intrinsic dicritical bounds in the effective Poincaré problem for foliations of the projective plane

    Open for about 14 years
Homogeneous Einstein manifolds8 questions
  1. Splitting of complete negative Einstein manifolds with cocompact connected Lie group symmetry: Conjecture 1.1 of Böhm–Lafuente without unimodularity

    Open for about 3 years
  2. The Böhm–Lafuente splitting conjecture for negative Einstein manifolds with cocompact isometric symmetry

    Open for about 3 years
  3. Which compact homogeneous spaces admit an invariant Einstein metric: completing the topological existence criteria of Wang–Ziller, Böhm, and Graev

    Open for about 40 years
  4. Globke–Nikolayevsky conjecture: every compact pseudo-Riemannian Einstein solvmanifold is a nilmanifold

    Open for about 9 years
  5. The dynamical Alekseevskii conjecture in dimensions six and above

    Open for about 9 years
  6. Which nilpotent Lie algebras are Einstein nilradicals? (Lauret–Will Problem 3 and the positive-graph question)

    Open for about 20 years
  7. The Böhm–Wang–Ziller Finiteness Conjecture: finiteness of invariant Einstein metrics on compact homogeneous spaces

    Open for about 22 years
  8. Finiteness of the moduli space of invariant Einstein metrics on a compact homogeneous space

    Open for about 22 years
Resolution of singularities7 questions
  1. Extension of the idealistic filtration resolution algorithm to ambient dimension 4 and above in positive characteristic (Kawanoue–Matsuki)

    Open for about 14 years
  2. Resolution of the monomial case of the Idealistic Filtration Program in positive characteristic in dimension four and higher

    Open for about 11 years
  3. Gluing local resolutions into a global resolution over perfect fields, and geometric resolution of singular moduli spaces (open problems from Hu's 'Grassmannians and Singularities')

    Open for about 62 years
  4. Canonical resolution of singularities in positive and mixed characteristic via cobordant blow-ups at weighted centers

    Open for about 4 years
  5. Embedded resolution of singularities in positive characteristic: stability of the residual order under permissible blowups and the existence of a terminating resolution invariant

    Open for about 62 years
  6. Forced point centers and the residual-order cycle obstruction to resolution of singularities in positive characteristic

    Open for about 8 years
  7. Canonical functorial resolution of singularities in positive characteristic: extending McQuillan's characteristic-zero invariant beyond equicharacteristic zero

    Open for about 61 years
Problem of singular cardinals4 questions
  1. Consistency strength of Ord-long strictly increasing iterates of Shelah's pcf operator

  2. Class-many strong limit singular cardinals with 2ℵδ<ℵ(∣δ∣+3)2^{\aleph_\delta}<\aleph_{(|\delta|^{+3})} in ZFC (Garti's Conjecture 3.4 on weak diamond and pcf theory)

  3. Stationary reflection with the failure of SCH at a singular cardinal of uncountable cofinality without supercompactness

  4. The residual program for Shelah's approachability ideal at successors of singular cardinals: uniform non-approachability, global failure of SCH and approachability, Woodin's AP-versus-SCH question, and the Tree Property at every successor of a singular (Jakob-Poveda, Questions 5.1-5.4)

Embedding conjecture9 questions
  1. An explicit counterexample to Connes' embedding conjecture: a concretely presented type II1_1 factor not embedding into an ultrapower of the hyperfinite factor

    Open for about 6 years
  2. The GNRS conjecture for minor-excluding graph families: the planar embedding and kk-sum conjectures

    Open for about 27 years
  3. Strong embeddings of 3-connected cubic planar graphs on surfaces of negative Euler characteristic

    Open for about 2 years
  4. The Dèbes–Deschamps conjecture: regular Galois solvability of finite split embedding problems over k(T)k(T) for an arbitrary field kk

    Open for about 29 years
  5. Abhyankar–Sathaye embedding conjecture for hypersurfaces in affine space

    Open for about 52 years
  6. The planar embedding conjecture: constant-distortion embeddings of planar graph metrics into L1L_1

    Open for about 26 years
  7. Regularity of the left-Garside category LD+ and the Embedding Conjecture for free left-self-distributive systems

    Open for about 17 years
  8. The convex greedy embedding conjecture for 3-connected planar graphs and the Tutte spring-weight question

    Open for about 22 years
  9. Existence of the enforceable II1_1 factor

    Open for about 9 years
Artificial boundary method for solving nonlinear partial differential equations in unbounded domains7 questions
  1. Explicit time-step bounds and Padé artificial-boundary-condition modeling error for the nonlinear time-fractional Burgers equation on unbounded domains

    Open for about 5 years
  2. Higher-order, multi-dimensional fast discretizations with exact fractional artificial boundary conditions for the time-fractional Schrödinger equation on unbounded domains

    Open for about 9 years
  3. Pressure-type artificial boundary conditions for steady Navier-Stokes flows in pipe systems beyond the small-data regime

    Open for about 19 years
  4. Higher-order diagonal Padé nonlinear absorbing boundary conditions for nonlinear time-fractional parabolic problems on unbounded domains

    Open for about 10 years
  5. Efficient and provably stable numerical realization of exact artificial boundary conditions for heat equations with nonlinear boundary conditions on unbounded domains

    Open for about 19 years
  6. Stability, error, and convergence analysis of the artificial boundary method for the two-dimensional Burgers equation on unbounded domains

    Open for about 18 years
  7. Discrete H1H^1 error estimates and higher-order-in-time boundary discretizations for the artificial-boundary finite difference scheme for nonlinear Schrödinger equations on unbounded domains

    Open for about 8 years
Optimal methods for solving linear algebraic systems6 questions
  1. Convergence of AdaRBFGS: adaptive randomized BFGS matrix inversion with iterate-dependent sketching

    Open for about 10 years
  2. Truly linear working space and the bit-time frontier for rational linear-system solvers with entrywise multiplicative guarantees

    Open for about 1 year
  3. Certified construction of Lagrange-principle optimal recovery methods for finite-dimensional linear systems: the general mixed-constraint case

    Open for about 19 years
  4. The Time Complexity of Solving Dense Linear Systems with k Large Singular Values: Logarithmic Factors, Matrix-Multiplication Dependence, and Derandomization

    Open for about 2 years
  5. Parameter selection for the HSS preconditioner: transfer of condition-number-balancing estimates from the HSS iteration and matrix-free parameter estimation

    Open for about 10 years
  6. Stochastic preconditioning: designing the reformulation parameters (B, D) to minimize the condition number zeta(A, B, D) in stochastic reformulations of linear systems

    Open for about 9 years
Rigidity of spheres and algebraic domains6 questions
  1. Sharp degree bounds for rational proper holomorphic maps between balls: the D'Angelo conjecture and the classification of valid quadruples (n, r, d, k)

    Open for about 37 years
  2. Sharp degree bounds for rational proper maps between balls of maximal geometric rank: sharpness at minimal target dimension and the above-minimal regime (Problem (D))

    Open for about 33 years
  3. Rigidity of proper holomorphic maps between unit balls with non-compact symmetry at low Hölder boundary regularity

    Open for about 25 years
  4. D'Angelo's degree conjecture for rational proper holomorphic maps between complex unit balls: unresolved regimes beyond the third gap interval

    Open for about 33 years
  5. Group data versus map data for rational proper maps of balls: detection of map invariants from the associated symmetry groups

    Open for about 9 years
  6. Classifying local orthogonal pairs and generalized Huang equations between hyperquadrics at the borderline dimension n′=2(r+s)−2n'=2(r+s)-2

    Open for about 2 years
Raising Pieri-type formulas for zonal functions7 questions
  1. Affine Pieri rule for periodic Macdonald spherical functions of the excluded twisted type BC^n=A2n(2)\widehat{BC}_n=A^{(2)}_{2n}, and identification of the deformed fusion ring with deformed Verlinde algebras

    Open for about 4 years
  2. Schur positivity of the 1,n1,n-Macdonald polynomials and the positive GLl\mathrm{GL}_l-character expansion of the Macdonald series Hμ\mathbf{H}_\mu

    Open for about 3 years
  3. Mixed-type twisted Pieri formulas for Jack polynomials

    Open for about 5 years
  4. Explicit Pieri formulas for Macdonald spherical functions and polynomials beyond small dominant weights

    Open for about 23 years
  5. Twisted Pieri formulas beyond type AA: extensions to BCBC-type root systems, (q,t)(q,t)-Macdonald polynomials, and elliptic analogues

    Open for about 6 years
  6. Factorized product forms for the Pieri-type coefficients of nonsymmetric Macdonald polynomials and the effective choice of the reduction index

    Open for about 16 years
  7. A Pieri-type multiplication rule for spherical functions: Bravi–Gandini Conjecture 1.1 for spherical pairs of type A (including F4/Spin(9)) and the Hermitian symmetric cases of types B, C, BC

    Open for about 5 years

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