The Douady-Hubbard landing theorem for periodic external rays is one of the cornerstones of the study of polynomial dynamics. It states that, for a complex polynomial f with bounded postcritical set, every periodic external ray lands at a repelling or parabolic periodic point, and conversely every repelling or parabolic point is the landing point of at least one periodic external ray. We prove an analogue

We will study metric measure spaces \((X,\mathsf{d},{\mathfrak {m}})\) beyond the scope of spaces with synthetic lower Ricci bounds. In particular, we introduce distribution-valued lower Ricci bounds \(\mathsf{BE}_1(\kappa ,\infty )\) for which we prove the equivalence with sharp gradient estimates, the class of which will be preserved under time changes with arbitrary \(\psi \in \mathrm {Lip}_b(X)\)

The classical theta correspondence establishes a relationship between automorphic representations on special orthogonal groups and automorphic representations on symplectic groups or their double covers. This correspondence is achieved by using as integral kernel a theta series on the metaplectic double cover of a symplectic group that is constructed from the Weil representation. There is also an analogous

Suppose that a binary operation \(\circ \) on a finite set X is injective in each variable separately and also associative. It is easy to prove that \((X,\circ )\) must be a group. In this paper we examine what happens if one knows only that a positive proportion of the triples \((x,y,z)\in X^3\) satisfy the equation \(x\circ (y\circ z)=(x\circ y)\circ z\). Other results in additive combinatorics would

We develop a new method, based on non-vanishing of second cohomology groups, for proving the failure of lifting properties for full C\(^*\)-algebras of countable groups with (relative) property (T). We derive that the full C\(^*\)-algebras of the groups \(\mathbb {Z}^2\times \text {SL}_2({\mathbb {Z}})\) and \(\text {SL}_n({\mathbb {Z}})\), for \(n\ge 3\), do not have the local lifting property (LLP)

We establish a first general partial regularity theorem for area minimizing currents \({\mathrm{mod}}(p)\), for every p, in any dimension and codimension. More precisely, we prove that the Hausdorff dimension of the interior singular set of an m-dimensional area minimizing current \({\mathrm{mod}}(p)\) cannot be larger than \(m-1\). Additionally, we show that, when p is odd, the interior singular set

Given an integer \(k \ge 5\), and a \(C^k\) Anosov flow \(\Phi \) on some compact connected 3-manifold preserving a smooth volume, we show that the measure of maximal entropy is the volume measure if and only if \(\Phi \) is \(C^{k-\varepsilon }\)-conjugate to an algebraic flow, for \(\varepsilon >0\) arbitrarily small. Moreover, in the case of dispersing billiards, we show that if the measure of maximal

We prove that almost all arc complexes do not admit a CAT(0) metric with finitely many shapes, in particular any finite-index subgroup of the mapping class group does not preserve such a metric on the arc complex. We also show the analogous statement for all but finitely many disc complexes of handlebodies and free splitting complexes of free groups. The obstruction is combinatorial. These complexes

The arithmetic version of Anderson localization (AL), i.e., AL with explicit arithmetic description on both the localization frequency and the localization phase, was first given by Jitomirskaya (Ann Math 150:1159–1175, 1999) for the almost Mathieu operators (AMO). Later, the result was generalized by Bourgain and Jitomirskaya (Invent Math 148:453–463, 2002) to a class of one dimensional quasi-periodic

We develop index theory on compact Riemannian spin manifolds with boundary in the case when the topological information is encoded by bundles which are supported away from the boundary. As a first application, we establish a “long neck principle” for a compact Riemannian spin n-manifold with boundary X, stating that if \({{\,\mathrm{scal}\,}}(X)\ge n(n-1)\) and there is a nonzero degree map into the

We consider the Calabi–Yau metrics on \(\mathbf {C}^n\) constructed recently by Yang Li, Conlon–Rochon, and the author, that have tangent cone \(\mathbf {C}\times A_1\) at infinity for the \((n-1)\)-dimensional Stenzel cone \(A_1\). We show that up to scaling and isometry this Calabi–Yau metric on \(\mathbf {C}^n\) is unique. We also discuss possible generalizations to other manifolds and tangent cones

The total influence of a function is a central notion in analysis of Boolean functions, and characterizing functions that have small total influence is one of the most fundamental questions associated with it. The KKL theorem and the Friedgut junta theorem give a strong characterization of such functions whenever the bound on the total influence is \(o(\log n)\). However, both results become useless

We use tools of additive combinatorics for the study of subvarieties defined by high rank families of polynomials in high dimensional \({\mathbb {F}}_q\)-vector spaces. In the first, analytic part of the paper we prove a number properties of high rank systems of polynomials. In the second, we use these properties to deduce results in Algebraic Geometry , such as an effective Stillman conjecture over

In this note, we show that sub-Riemannian manifolds can contain branching normal minimizing geodesics. This phenomenon occurs if and only if a normal geodesic has a discontinuity in its rank at a non-zero time, which in particular for a strictly normal geodesic means that it contains a non-trivial abnormal subsegment. The simplest example is obtained by gluing the three-dimensional Martinet flat structure

We develop a toolbox for proving decouplings into boxes with diameter smaller than the canonical scale. As an application of this new technique, we solve three problems for which earlier methods have failed. We start by verifying the small cap decoupling for the parabola. Then we find sharp estimates for exponential sums with small frequency separation on the moment curve in \(\mathbb {R}^3\). This

Let \(Z=G/H\) be the homogeneous space of a real reductive group and a unimodular real spherical subgroup, and consider the regular representation of G on \(L^2(Z)\). It is shown that all representations of the discrete series, that is, the irreducible subrepresentations of \(L^2(Z)\), have infinitesimal characters which are real and belong to a lattice. Moreover, let K be a maximal compact subgroup

For random d-regular graphs on N vertices with \(1 \ll d \ll N^{2/3}\), we develop a \(d^{-1/2}\) expansion of the local eigenvalue distribution about the Kesten–McKay law up to order \(d^{-3}\). This result is valid up to the edge of the spectrum. It implies that the eigenvalues of such random regular graphs are more rigid than those of Erdős–Rényi graphs of the same average degree. As a first application

We investigate conformal actions of cocompact lattices in higher-rank simple Lie groups on compact pseudo-Riemannian manifolds. Our main result gives a general bound on the real-rank of the lattice, which was already known for the action of the full Lie group by a result of Zimmer. When the real-rank is maximal, we prove that the manifold is conformally flat. This indicates that a global conclusion

Given \(n \ge 2\) and \(1

On an odd-dimensional oriented hyperbolic manifold of finite volume with strongly acyclic coefficient systems, we derive a formula relating analytic torsion with the Reidemeister torsion of the Borel–Serre compactification of the manifold. In a companion paper, this formula is used to derive exponential growth of torsion in cohomology of arithmetic groups.

The main proposition, Theorem 1.2, is the existence for excellent Deligne–Mumford champ of characteristic zero of a resolution functor independent of the resolution process itself. Received wisdom was that this was impossible, but the counterexamples overlooked the possibility of using weighted blow ups. The fundamental local calculations take place in complete local rings, and are elementary in nature

In this article we define new flows on the Hitchin components for \(\mathrm {PGL}(V)\). Special examples of these flows are associated to simple closed curves on the surface and give generalized twist flows. Other examples, so called eruption flows, are associated to pair of pants in S and capture new phenomena which are not present in the case when \(n=2\). We determine a global coordinate system

We construct a multiplicative spectral sequence converging to the symplectic cohomology ring of any affine variety X, with first page built out of topological invariants associated to strata of any fixed normal crossings compactification \((M,{\mathbf {D}})\) of X. We exhibit a broad class of pairs \((M,{\mathbf {D}})\) (characterized by the absence of relative holomorphic spheres or vanishing of certain

Manifold submetries of the round sphere are a class of partitions of the round sphere that generalizes both singular Riemannian foliations, and the orbit decompositions by the orthogonal representations of compact groups. We exhibit a one-to-one correspondence between such manifold submetries and maximal Laplacian algebras, thus solving the Inverse Invariant Theory problem for this class of partitions

Singular vectors are those for which the quality of rational approximations provided by Dirichlet’s Theorem can be improved by arbitrarily small multiplicative constants. We provide an upper bound on the Hausdorff dimension of singular vectors lying on self-similar fractals in \({\mathbb {R}}^d\) satisfying the open set condition. The bound is in terms of quantities which are closely tied to Frostman

We establish Anderson localization for general analytic k-frequency quasi-periodic operators on \({\mathbb {Z}}^d\) for arbitraryk, d.

We give a short proof of a theorem of Guth relating volume of balls and Uryson width. The same approach applies to Hausdorff content implying a recent result of Liokumovich–Lishak–Nabutovsky–Rotman. We show also that for any \(C>0\) there is a Riemannian metric g on a 3-sphere such that \({\hbox {vol}}(S^3,g)=1\) and for any map \(f:S^3\rightarrow {\mathbb {R}}^2\) there is some \(x\in {\mathbb {R}}^2\)

I show that quasidiagonality and AF embeddability are equivalent properties for traceless \(\mathrm C^*\)-algebras and are characterised in terms of the primitive ideal space. For nuclear \(\mathrm C^*\)-algebras the same characterisation determines when Connes and Higson’s E-theory can be unsuspended.

We prove two results on arithmetic quantum chaos for dihedral Maaß forms, both of which are manifestations of Berry’s random wave conjecture: Planck scale mass equidistribution and an asymptotic formula for the fourth moment. For level 1 forms, these results were previously known for Eisenstein series and conditionally on the generalised Lindelöf hypothesis for Hecke–Maaß eigenforms. A key aspect of

We prove that all flexible Weinstein fillings of a given contact manifold with vanishing first Chern class have isomorphic integral cohomology. As an application, we show that in dimension at least 5 any almost contact class that has an almost Weinstein filling has infinitely many different contact structures. We also construct the first known infinite family of almost symplectomorphic Weinstein domains

The Loewner energy of a Jordan curve is the Dirichlet energy of its Loewner driving term. It is finite if and only if the curve is a Weil–Petersson quasicircle. In this paper, we describe cutting and welding operations on finite Dirichlet energy functions defined in the plane, allowing expression of the Loewner energy in terms of Dirichlet energy dissipation. We show that the Loewner energy of a unit

Let \((M^n,g)\) be simply connected, complete, with non-positive sectional curvatures, and \(\Sigma \) a 2-dimensional closed integral current (or flat chain mod 2) with compact support in M. Let S be an area minimising integral 3-current (resp. flat chain mod 2) such that \(\partial S = \Sigma \). We use a weak mean curvature flow, obtained via elliptic regularisation, starting from \(\Sigma \), to

We study a class of discrete-time random dynamical systems with compact phase space. Assuming that the deterministic counterpart of the system in question possesses a dissipation property, its linearisation is approximately controllable, and the driving noise is bounded and has a decomposable structure, we prove that the corresponding family of Markov processes has a unique stationary measure, which

In this article we show that in any dimension there exist infinitely many pairs of formally contact isotopic isocontact embeddings into the standard contact sphere which are not contact isotopic. This is the first example of rigidity for contact submanifolds in higher dimensions. The contact embeddings are constructed via contact push-offs of higher-dimensional Legendrian submanifolds, a construction

In this paper we propose a class of local definitions of weak lower scalar curvature bounds that is well defined for \(C^0\) metrics. We show the following: that our definitions are stable under greater-than-second-order perturbation of the metric, that there exists a reasonable notion of a Ricci flow starting from \(C^0\) initial data which is smooth for positive times, and that the weak lower scalar

This paper accomplishes two things. First, we construct a geometric analog of the rational Tits building for general noncompact, complete, finite volume n-manifolds M of bounded nonpositive curvature. Second, we prove that this analog has dimension less than \(\lfloor n/2\rfloor \).

All \(\mathrm {GL}(2, \mathbb {R})\) orbits in hyperelliptic components of strata of abelian differentials in genus greater than two are closed, dense, or contained in a locus of branched covers.

We describe a method to construct smooth and compactly supported solutions of 3D incompressible Euler equations and related models. The method is based on localizable Grad–Shafranov equations and is inspired by the recent result (Gavrilov in A steady Euler flow with compact support. Geom Funct Anal 29(1):90–197, [Gav19]).

We prove analogues of the Szemerédi–Trotter theorem and other incidence theorems using \(\delta \)-tubes in place of straight lines, assuming that the \(\delta \)-tubes are well spaced in a strong sense.

We prove that on a closed, orientable surface of genus g, the maximum cardinality of a set of simple loops with the property that no two are homotopic or intersect in more than k points grows as a function of g like \(g^{k+1}\), up to a factor of \(\log g\). The proof of the upper bound uses arguments from probabilistic combinatorics and a theorem of Scott related to the fact that surface groups are

In a seminal paper published in 1980, P. C. Yang and S.-T. Yau proved an inequality bounding the first eigenvalue of the Laplacian on an orientable Riemannian surface in terms of its genus \(\gamma \) and the area. The equality in Yang–Yau’s estimate is attained for \(\gamma =0\) by an old result of J. Hersch and it was recently shown by S. Nayatani and T. Shoda that it is also attained for \(\gamma

In this article, we study the smallest gaps between eigenvalues of the Gaussian orthogonal ensemble (GOE). The main result is that the smallest gaps, after being normalized by n, will converge to a Poisson distribution, and the limiting density of the kth normalized smallest gap is \(2{}x^{2k-1}e^{-x^{2}}/(k-1)!\). The proof is based on the method developed in Feng and Wei (Small gaps of circular \(\beta

In this paper we consider the large genus asymptotics for two classes of Siegel–Veech constants associated with an arbitrary connected stratum \(\mathcal {H} (\alpha )\) of Abelian differentials. The first is the saddle connection Siegel–Veech constant \(c_{\mathrm{sc}}^{m_i, m_j} \big ( \mathcal {H} (\alpha ) \big )\) counting saddle connections between two distinct, fixed zeros of prescribed orders

Given a non-conformal repeller \(\Lambda \) of a \(C^{1+\gamma }\) map, we study the Hausdorff dimension of the repeller and continuity of the sub-additive topological pressure for the sub-additive singular valued potentials. Such a potential always possesses an equilibrium state. We then use a substantially modified version of Katok’s approximating argument, to construct a compact invariant set on

Properly discontinuous actions of a surface group by affine automorphisms of \({\mathbb {R}}^d\) were shown to exist by Danciger–Gueritaud–Kassel. We show, however, that if the linear part of an affine surface group action is in the Hitchin component, then the action fails to be properly discontinuous. The key case is that of linear part in \({{\mathsf {S}}}{{\mathsf {O}}}(n,n-1)\), so that the affine

The hypergraph regularity lemma—the extension of Szemerédi’s graph regularity lemma to the setting of k-uniform hypergraphs—is one of the most celebrated combinatorial results obtained in the past decade. By now there are several (very different) proofs of this lemma, obtained by Gowers, by Nagle–Rödl–Schacht–Skokan and by Tao. Unfortunately, what all these proofs have in common is that they yield

Let f be a transcendental entire function, and let \({U,V \subset \mathbb{C}}\) be disjoint simply-connected domains. Must one of \({f^{-1}(U)}\) and \({f^{-1}(V)}\) be disconnected? In 1970, Baker implicitly gave a positive answer to this question, in order to prove that a transcendental entire function cannot have two disjoint completely invariant domains. (A domain \({U\subset \mathbb{C}}\) is completely

We use the gluing method to give a refined description of the collapsing Calabi–Yau metrics on Calabi–Yau 3-folds admitting a Lefschetz K3 fibration.

In this article we address a number of features of the moduli space of spherical metrics on connected, compact, orientable surfaces with conical singularities of assigned angles, such as its non-emptiness and connectedness. We also consider some features of the forgetful map from the above moduli space of spherical surfaces with conical points to the associated moduli space of pointed Riemann surfaces

We prove new bounds on the dimensions of distance sets and pinned distance sets of planar sets. Among other results, we show that if \(A\subset {\mathbb {R}}^2\) is a Borel set of Hausdorff dimension \(s>1\), then its distance set has Hausdorff dimension at least \(37/54\approx 0.685\). Moreover, if \(s\in (1,3/2]\), then outside of a set of exceptional y of Hausdorff dimension at most 1, the pinned

This note is dedicated to the study of the asymptotic behaviour of sets of finite perimeter over \({{\,\mathrm{RCD}\,}}(K,N)\) metric measure spaces. Our main result asserts existence of a Euclidean tangent half-space almost everywhere with respect to the perimeter measure and it can be improved to an existence and uniqueness statement when the ambient is non collapsed. As an intermediate tool, we

In this paper, we study the weighted n-dimensional badly approximable points on manifolds. Given a \(C^n\) differentiable non-degenerate submanifold \({\mathcal {U}} \subset {\mathbb {R}}^n\), we will show that any countable intersection of the sets of the weighted badly approximable points on \({\mathcal {U}}\) has full Hausdorff dimension. This strengthens a result of Beresnevich (Invent Math 202(3):1199–1240

Let \(G_1, \ldots , G_k\) be vector spaces over a finite field \({\mathbb {F}} = {\mathbb {F}}_q\) with a non-trivial additive character \(\chi \). The analytic rank of a multilinear form \(\alpha :G_1 \times \cdots \times G_k \rightarrow {\mathbb {F}}\) is defined as \({\text {arank}}(\alpha ) = -\log _q \mathop {\mathbb {E}} _{x_1 \in G_1, \ldots , x_k\in G_k} \chi (\alpha (x_1,\ldots , x_k))\).

Extending the notion of bounded variation, a function \(u \in L_c^1(\mathbb {R}^n)\) is of bounded fractional variation with respect to some exponent \(\alpha \) if there is a finite constant \(C \ge 0\) such that the estimate$$\begin{aligned} \biggl |\int u(x) \det D(f,g_1,\ldots ,g_{n-1})_x \, dx\biggr | \le C\text{ Lip }^\alpha (f) \text{ Lip }(g_1) \cdots \text{ Lip }(g_{n-1}) \end{aligned}$$holds

We study the dynamics of \({{\rm SL_3}(\mathbb{R})}\) and its subgroups on the homogeneous space X consisting of homothety classes of rank-2 discrete subgroups of \({\mathbb{R}^3}\). We focus on the case where the acting group is Zariski dense in either \({{\rm SL_3}(\mathbb{R})}\) or \({{\rm SO(2,1)}(\mathbb{R})}\). Using techniques of Benoist and Quint we prove that for a compactly supported probability

For every positive, continuous and homogeneous function f on the space of currents on a compact surface \({{{\overline{\Sigma }}}}\), and for every compactly supported filling current \(\alpha \), we compute as \(L \rightarrow \infty \), the number of mapping classes \(\phi \) so that \(f(\phi (\alpha ))\le L\). As an application, when the surface in question is closed, we prove a lattice counting

We study the problem of embedding arbitrary \({\mathbb {Z}}^k\)-actions into the shift action on the infinite dimensional cube \(\left( [0,1]^D\right) ^{{\mathbb {Z}}^k}\). We prove that if a \({\mathbb {Z}}^k\)-action X satisfies the marker property (in particular if X is a minimal system without periodic points) and if its mean dimension is smaller than D / 2 then we can embed it in the shift on

We develop a variational principle between mean dimension theory and rate distortion theory. We consider a minimax problem about the rate distortion dimension with respect to two variables (metrics and measures). We prove that the minimax value is equal to the mean dimension for a dynamical system with the marker property. The proof exhibits a new combination of ergodic theory, rate distortion theory

In this paper, we prove that in any projective manifold, the complements of general hypersurfaces of sufficiently large degree are Kobayashi hyperbolic. We also provide an effective lower bound on the degree. This confirms a conjecture by S. Kobayashi in 1970. Our proof, based on the theory of jet differentials, is obtained by reducing the problem to the construction of a particular example with strong

We prove that Bernoulli bond percolation on any nonamenable, Gromov hyperbolic, quasi-transitive graph has a phase in which there are infinitely many infinite clusters, verifying a well-known conjecture of Benjamini and Schramm (1996) under the additional assumption of hyperbolicity. In other words, we show that \(p_c