Chebyshev Laboratory, St. Petersburg State University St. Petersburg Department of Steklov Mathematical Institute International conference COMPLEX ANALYSIS AND RELATED TOPICS ABSTRACTS St. Petersburg, April 14–18, 2014 Organizing Committee: Alexander Aptekarev, Co-chair Keldysh Institute of Applied Mathematics Stanislav Smirnov, Co-chair University of Geneva and St. Petersburg State University Anton Baranov St. Petersburg State University Evgenii Chirka Steklov Mathematical Institute Sergey Kislyakov St. Petersburg Department of Steklov Mathematical Institute Konstantin Fedorovskiy Bauman Moscow State Technical University Local Organizing Committee: Anton Baranov St. Petersburg State University Yurii Belov St. Petersburg State University Svetlana Likhova Chebyshev Laboratory Nikolai Osipov St. Petersburg Department of Steklov Mathematical Institute Sponsors: Chebyshev Laboratory under RF Government grant 11.G34.31.0026 JSC «Gazprom Neft» INVITED PLENARY LECTURES Kari ASTALA (University of Helsinki) Multifractal spectra for bi-Lipschitz and quasiconformal mappings I will describe a recent joint work with T. Iwaniec, I. Prause and E. Saksman on the theme: ’Given an L-bi-Lipschitz mapping of the plane, how large can be the set E where the map rotates or spirals with a given rate γ?’ We describe the optimal bounds for the size of such sets in terms of the dimension; it turns out that always the Hausdorff dimension dim(E) ≤ 2 − |γ|2L/(L2 − 1), where for some sets E and maps f the equality holds. The key points of the proof are holomorphic deformations of bi-Lipschitz mappings and a new kind of interpolation on Lp -spaces, where we can interpolate with complex exponents p. ∗ ∗ ∗ Farit AVKHADIEV (Kazan Federal University) Hardy type inequalities We will present our main results about Hardy inequalities in plane and space domains including inequalities a) plane domains with uniformly perfect boundary, b) for convex domains and c) for arbitrary domains. In particular we will present some new results on a geometrical description of non-convex domains for which Hardy’s constants are best possible. ∗ ∗ ∗ Bo BERNDTSSON (Chalmers University of Technology) Convexity of some functionals in K¨ ahler geometry In the study of extremal metrics on a K¨ahler manifold, certain functionals defined on the space of all K¨ahler metrics in a fixed cohomology class play an important role. The most important of these are the Mabuchi K-energy and the Ding functional whose critical points are metrics of constant scalar curvature and K¨ahler–Einstein metrics respectively. We will discuss convexity properties of these functionals and relations to questions of existence and uniqueness of extremal metrics. This is partly joint work with Robert Berman. ∗ ∗ ∗ Vladimir DUBININ (Far Eastern Federal University, Vladivostok ) Some resent applications of the capacitary approach symmetrization to the geometric function theory and We discuss the basic properties of the generalized condensers on the open subsets of the Riemann sphere [1]. As simple applications of the monotonicity of 3 the capacity, some theorems for the univalent holomorphic functions are proved. We obtain distortion theorems, inequalities for the Schwarzian derivative and propositions describing the boundary behavior of such functions. We also give new applications of the Steiner symmetrization. A lower bound for the half-plane capacity of the compact sets and the inequality for the initial coefficient of some class of univalent functions are established [1] - [3]. Thereafter a new version of circular symmetrization for condensers on the Riemann surface is considered [4]. As application of such symmetrization, a two-point distortion theorem for complex polynomials is proved [5]. The corollaries of this theorem are an exact lower bound for maximal moduli of critical values of polynomials and a new version of Markovtype inequality for an arbitrary compact sets. [1] V.N. Dubinin, Condenser capacity and symmetrization in the geometric function theory of a complex variable, Dalnauka, Vladivostok, 2009, 401 p. [2] V.N. Dubinin, Lower bounds for the half-plane capacity of compact sets and symmetrization, Sbornik: Mathematics, 201:11 (2010), 1–12. [3] V.N. Dubinin, Steiner symmetrization and the initial coefficients of univalent functions, Izvestiya: Mathematics, 74:4 (2010), 735–742. [4] V.N. Dubinin, A new version of circular symmetrization with applications to p-valent functions, Sbornik: Mathematics, 203:7 (2012), 996–1011. [5] V.N. Dubinin, On one extremal problem for complex polynomials with constrains on critical values, Siberian Mathematical Journal, 55:1 (2014), 63–71. ∗ ∗ ∗ Stephen GARDINER (University College Dublin) Universal Taylor series and potential theory In various mathematical contexts it is possible to find a single object which, when subjected to a countable process, yields approximations to the whole universe under study. Such an object is termed "universal"and, contrary to expectations, such objects often turn out to be generic rather than exceptional. This talk will focus on this phenomenon in respect of the Taylor series of a holomorphic function, and how the partial sums behave outside the domain of the function. It will discuss how potential theory reveals much about the boundary behaviour of such functions, and their relationship with conformal mappings. ∗ ∗ ∗ Dmitry KHAVINSON (University of South Florida) The fundamental theorem of algebra, complex analysis and astrophysics The Fundamental Theorem of Algebra first rigorously proved by Gauss states that each complex polynomial of degree n has precisely n complex roots. In recent years various extensions of this celebrated result have been considered. We shall discuss the extension of the FTA to harmonic polynomials of degree n. 4 In particular, the theorem of D. Khavinson and G. Swiatek that shows that the harmonic polynomial z¯ − p(z), deg p = n > 1 has at most 3n − 2 zeros as was conjectured in the early 90´s by T. Sheil-Small and A. Wilmshurst. L. Geyer was able to show that the result is sharp for all n. G. Neumann and D. Khavinson proved that the maximal number of zeros of rational harmonic functions z¯ − r(z), deg r = n > 1 is 5n − 5. It turned out that this result confirmed several consecutive conjectures made by astrophysicists S. Mao, A. Petters, H. Witt and, in its final form, the conjecture of S. H. Rhie that were dealing with the estimate of the maximal number of images of a star if the light from it is deflected by n co-planar masses. The first non-trivial case of one mass was already investigated by A. Einstein around 1912. We shall also discuss the problem of gravitational lensing of a point source of light, e.g., a star, by an elliptic galaxy, more precisely the problem of the maximal number of images that one can observe. Under some more or less “natural” assumptions on the mass distribution within the galaxy one can prove (A. Eremenko and W. Bergweiler – 2010, also, DK - E. Lundberg – 2010) that the number of visible images can never be more than four in some cases and six in the other. Interestingly, the former situation can actually occur and has been observed by astronomers. Still there are much more open questions than there are answers. ∗ ∗ ∗ Ari LAPTEV (Imperial College London & Institute Mittag-Leffler ) Spectral inequalities for Partial Differential Equations and their applications We shall discuss properties of the discrete and continuous spectrum of different classes of self-adjoint differential operators including Schr¨odinger operators. ∗ ∗ ∗ Yurii LYUBARSKII (Norwegian University of Science and Technology, Trondheim) Composition operators in model spaces We consider the composition operator acting from a model space KΘ into the Hardy space. We study when such operators are compact or belong to Schatten classes. In the case of one component Θ one can obtain complete answer to these questions. We also give necessary and (separately) sufficient conditions for the general case. ∗ ∗ ∗ 5 Stefan NEMIROVSKI (Steklov Mathematical Institute, Moscow ) Rational approximations and symplectic topology The talk will survey recent advances in the understanding of the topology and geometry of rationally convex sets and domains achieved using ideas and methods from symplectic geometry. ∗ ∗ ∗ Eero SAKSMAN (University of Helsinki) On the multiplicative chaos We consider some basic properties of multiplicative chaos, especially at criticality. Also we try to explain connections to complex analysis and related topics. The talk is based on joint work with J. Barral, A. Kupiainen, M. Nikula and C. Webb. ∗ ∗ ∗ Kristian SEIP (Norwegian University of Science and Technology, Trondheim) Poisson integrals on polydiscs We consider the problem of estimating the Poisson integral of the square of the modulus of a holomorphic polynomial at a point in the infinite dimensional polydisc. The problem can be seen to originate in metric number theory and is related to Granville and Soundararajan’s resonance method. We obtain optimal or nearly optimal results in the particular case when the point in the polydisc is the sequence of a fixed negative power of the primes, thus solving a problem studied by Dyer and Harman in 1986. The talk is based on joint work with Christoph Aistleitner and Istvan Berkes and joint work with Andriy Bondarenko. ∗ ∗ ∗ Armen SERGEEV (Steklov Mathematical Institute, Moscow ) Universal Teichm¨ uller space and its quantization Universal Teichm¨ uller space T is the quotient of the group QS(S 1 ) of quasisymmetric homeomorphisms of S 1 modulo M¨obius transformations. In particular, this space contains the quotient S of the group Diff+ (S 1 ) of diffeomorphisms of S 1 modulo M¨obius transformations. Both groups act naturally 1/2 on Sobolev space H := H0 (S 1 , R). Quantization problem for T and S arises in string theory where these spaces are considered as phase manifolds. To solve the problem for a given phase manifold means to fix a Lie algebra of functions (observables) on it and construct its irreducible representation in a Hilbert (quantization) space. For S the algebra of observables is given by the Lie algebra Vect(S 1 ) of Diff+ (S 1 ). For quantization space we take the Fock space 1/2 F (H), associated with Sobolev space H = H0 (S 1 , R). Infinitesimal version of Diff+ (S 1 )-action on H generates an irreducible representation of Vect(S 1 ) in 6 F (H), yielding quantization of S. For T the situation is more subtle since QS(S 1 )action on T is not smooth. So there is no classical Lie algebra, associated to QS(S 1 ). However, we can define a quantum Lie algebra of observables Derq (QS), generated by quantum differentials, acting on F (H). These differentials are given by integral operators dq h on H with kernels, given essentially by finite-difference derivatives of h ∈ QS(S 1 ). ∗ ∗ ∗ Yum-Tong SIU (Harvard University) Application of d-bar estimates to effective very ampleness and abundance We will discuss some analytic methods of construction of sections of vector bundles motivated by algebraic and complex geometric problems. We will especially focus on the very ampleness part of the Fujita conjecture and the abundance conjecture. ∗ ∗ ∗ Xavier TOLSA (ICREA & Universitat Autonoma de Barcelona) Square functions, Riesz transforms, and rectifiability In this talk I will survey recent results about the characterization of uniform rectifiability in terms of square functions involving densities and in terms of L2 boundedness of Riesz transforms. ∗ ∗ ∗ Avgust TSIKH (Siberian Federal University, Krasnoyarsk ) Singular strata of cuspidal type for the classical discriminant We consider an algebraic equation with variable complex coefficients. For the reduced discriminant set of this equation we get a parametrization of singular strata accountable for existence of roots with prescribed multiplicity. This parametrization is the restriction to a flag of linear subspaces of the Horn– Kapranov uniformization for the whole reduced discriminant set. We prove that the mentioned strata are birationally isomorphic to some A-discriminant sets, and therefore they are of maximum likelihood degree one. This is a joint submitted paper with E. N. Mikhalkin. ∗ ∗ ∗ 7 TALKS AND POSTERS Irina ANTIPOVA (Siberian Federal University, Krasnoyarsk ) On the structure of the residue current of the Bochner–Martinelli type Let X be a complex analytic n-dimensional manifold. Consider a holomorphic mapping f = (f1 , . . . , fp ) on X (p is less or equal n). We consider the residue integral I() over the tube defined by the mapping f with vector radius for the compactly supported test form of the bidegree (n, n − p). For the case p = 1 the limit of the residue integral as tends to zero defines the Herrera–Lieberman current. The local structure of this current was studied by P. Dolbeault. If p > 1 then the limit of the function I() does not exist in general. So it is reasonable to consider some kinds of mean values of the residue integral. The mean value on the base of Bochner-Martinelli kernel was realized by M. Passare, A. Tsikh and A. Yger. We present the description of the local structure for the currents of the Bochner–Martinelli type in the case of monomial mapping f . We prove the following assertion. Theorem. The residue current of the Bochner–Martinelli type is the finite sum, where every summand is a product of q Herrera–Lieberman residue currents and (n − q)-fold principal value, multiplied by certain hypergeometric function. ∗ ∗ ∗ Laurent BARATCHART (INRIA) Pseudo-holomorphic functions with L2 coefficients and conjugate Beltrami equation with tanh-W 1,2 coefficients For D the unit disk and α ∈ L2 (D), we consider the equation ¯ = αw. ∂w ¯ (1) This equation defines pseudo-holomorphic functions w and it has been extensively studied by I. N. Vekua, L. Bers and many others, when α lies in Lr (D) for some r > 2, see e.g. [1–5]. The main novelty here is that we consider r = 2, a case where solutions need no longer be continuous nor even locally bounded. Below we put T to mean the unit circle and, for any function f defined on D, we let fρ (z) := f (ρz), z ∈ D. We prove a M. Riesz-type theorem as follows: Theorem 1. For 1 < p < ∞, λ a real number, and ψ ∈ Lp (T), there uniquely exists w meeting (1) such that sup rkwr kLp (T) < c(kψkLp (T) + λ), 0<r<1 Z p lim <(wr ) = ψ in L (T), r→1− 8 =(wr ) = λ. lim r→1− T (2) In (2), the constant c depends only on p and α. Theorem 1 has the following consequences. If we let σ be a nonnegative function on D such that log σ ∈ W 1,2 (D) with W 1,2 (D) the familiar Sobolev space on D, then the Dirichlet problem for the conductivity equation div(σ∇u) = 0 is well posed in D with boundary value φ in the weighted space Lp (T, σ 1/2 dm) where m is Lebesgue measure on T. Note that this conductivity equation may not be strictly elliptic for σ could vanish on a set of 2-Riesz capacity zero, and that coefficients may not even be bounded for σ could be +∞ on another set of 2-Riesz capacity zero. In fact, u solving the above Dirichlet problem is the real part of a function f = u + iv, unique up to addition of a pure imaginary constant, satisfying the conjugate Beltrami equation ¯ = ν ∂¯f¯, ∂f ν = (1 − σ)/(1 + σ), tanh−1 ν ∈ W 1,2 (D), f being moreover such that sup rkσ 1/2 ur + iσ −1/2 vr kLp (T) < +∞. 0<r<1 The results extend to Dini-smooth domains. We shall discuss extensions to complex valued dilation coefficient ν. This is joint work with A. Borichev and S. Chaabi. [1] L. Baratchart, Y. Fischer, J. Leblond, Dirichlet/Neumann problems and Hardy classes for the planar conductivity equation, to appear in Complex variables and elliptic equations. [2] L. Baratchart, J. Leblond, S. Rigat, E. Russ, Hardy spaces for the conjugate Beltrami equation in smooth domains of the complex plane, J. Funct. Anal. 259 (2010), 384–427. [3] L. Bers, Theory of pseudo-analytic functions, New York University, 1953. [4] I. N. Vekua, Generalized Analytic Functions, Addison–Wesley, 1962. [5] S. B. Klimentov, Hardy classes of generalized analytic functions, Izvestia Vuzov Sev.-Kav. Reg., Natural Science 3 (2003) 6–10 (in Russian). ∗ ∗ ∗ Aleksandr BEKNAZARYAN (Kazan State Power Engineering University) Bohr–Riemann surfaces The talk is about the Bohr–Riemann surfaces over the generalized plane ∆. The group structures of the covering spaces will be presented which allow to show that each n-fold covering of the punctured generalized plane ∆0 is an algebraic Galois covering. Also, the notion of equivalent points on the Bohr–Riemann 9 surfaces will be given and it will be shown that the points of a Bohr–Riemann surface locally have the same number of equivalent points. ∗ ∗ ∗ Yurii BELOV (St. Petersburg State University) Mixed completeness problems in the spaces of entire functions Let {kλ }λ∈Λ be a system of reproducing kernels in some space of entire functions and {gλ }λ∈Λ be a biorthogonal system. We consider the completeness problem for the system {kλ }λ∈Λ1 ∪ {gλ }λ∈Λ2 , Λ = Λ1 ∪ Λ2 . This property corresponds to the spectral synthesis property for some linear operator. We give a survey of results of this type in various situations. For example using this technique we answer a question posed by A. Aleman and B. Korenblum about differentiation invariant subspaces of C ∞ (a, b). The talk is based on joint works with Anton Baranov, Alexander Borichev and Alexandru Aleman. ∗ ∗ ∗ Sergey BEZRODNYKH, Vladimir VLASOV (Dorodnicyn Computing Centre of RAS, Moscow ) Riemann–Hilbert problem in a singularly deforming domain The Riemann–Hilbert problem with piecewise constant coefficients and a growth condition of its solution is considered in a domain G, which represents a decagon being an exterior of system of cuts. The considered problem gives the Somov model of magnetic reconnection emerging in Solar flares. In the work an analytic solution of the considered Riemann–Hilbert problem has been obtained. With the help of the conformal mapping theory of singularly deforming domains, the asymptotics of the obtained solution has been derived corresponding to special cases of singular deformation of the domain G. These asymptotics show that magnetic fields of Syrovatskii’s and Petscheck’s models follow from Somov’s model as special limit cases. ∗ ∗ ∗ Markus BORN (University of Trier ) A note on lacunary approximation of Mergelyan type Let K ⊂ C \ (−∞, 0) be compact and star-like with respect to the origin. For a given subset Λ of the natural numbers we consider the set P PΛ of polynomials with exponents in Λ. We show that if 0 ∈ Λ, the condition n∈Λc n−1 < ∞ is sufficient for PΛ to be dense in A(K), the space of all functions continous on K and holomorphic in the interior, endowed with it’s usual norm. This is related to a result of Anderson which states that for a given α ∈ [0, π), a M¨ untz-type condition is necessary and sufficient for PΛ to be dense in every A(K), where K is contained in the sector Kα = {z ∈ C : arg z < α}. ∗ ∗ ∗ 10 Petr BORODIN (M. V. Lomonosov Moscow State University) Approximation by simplest partial fractions The talk contains results on the density of the set of simplest partial fractions (logarithmic derivatives of polynomials) and their generalizations in different spaces of functions defined on subsets of the complex plane. ∗ ∗ ∗ Victor BUSLAEV (Steklov Mathematical Institute, Moscow ) Convergence of two-point Pade approximants Assume that algebraic functions f0 and f∞ are holomorphic at the points z = 0 and z = ∞ respectively and have nonempty finite sets of branch points. Let πn be a two-point Pade approximant of f0 and f∞ , i.e. πn is a rational function Pn /Qn such that deg Pn ≤ n, deg Qn ≤ n, Qn 6≡ 0 and (Qn f0 − Pn )(z) = O(z n ), z → 0, (Qn f∞ − Pn )(z) = O 1/z , z → ∞. Using potential theory methods we will show that the sequence of Pade approximants {πn }∞ n=1 converges in capacity to the function f0 in some domain D0 3 0 and to the function f∞ in some domain D∞ 3 ∞. The geometrical properties of the complement C \ (D0 ∪ D∞ ) will be described. ∗ ∗ ∗ Andrey DNESTRYAN (Moscow Institute of Physics and Technology) On the lower bound of the output entropy of the tensor product of two Markov maps A lower bound of von Neumann entropy of an operator is obtained, which is the modus operandi of the tensor product of two Markov maps on the algebra of bounded operators on a Hilbert space. ∗ ∗ ∗ Evgueni DOUBTSOV (St. Petersburg Department of Steklov Mathematical Institute) Reverse estimates in spaces of holomorphic functions Given a radial weight w on the unit disk D, the growth space Aw consists of those f ∈ Hol(D) for which |f (z)| ≤ Cw(z), z ∈ D. A natural problem motivated by applications is to find test functions f1 , . . . , fk ∈ Aw such that the following reverse estimate holds: |f1 | + · · · + |fk | ≥ Cw(z), z ∈ D. First, we characterize, up to equivalence, those w for which the reverse estimate problem is solvable. Second, we consider the weighted Bloch space B w defined by the estimate 11 |f 0 (z)|(1 − |z|) ≤ Cw(z), z ∈ D. We show that the sharp reverse estimates in B w depend on the quadratic integral Z 1 2 w (t) dt. t x Similar results hold for the complex unit ball and for circular strictly convex domains. Also, we discuss applications related to Carleson measures and composition operators; in particular, we give a solution of the Bloch-to-BMOA problem in several variables. ∗ ∗ ∗ Konstantin DYAKONOV (ICREA & Universitat de Barcelona) Gauss–Lucas type theorems on the disk The classical Gauss–Lucas theorem describes the location of the critical points of a polynomial. There is also a hyperbolic version, due to Walsh, in which the role of polynomials is played by finite Blaschke products on the unit disk. We study similar phenomena for generic inner functions, as well as for certain "locally inner" self-maps of the disk. ∗ ∗ ∗ Yurii DYMCHENKO (Far Eastern Federal University, Vladivostok ) The condition of small girth on Carnot groups We show that if a compact set is removable for capacity on the Carnot group, then it satisfies the condition for small girth in terms of horizontal curves, that is, for any positive Borel function and almost all curves of a certain family of horizontal curves with a finite module the following condition holds: this curve can be deformed to a finite number of sections so that the resulting curve does not pass through a removable set and the integral of this function on the modified sections of the curve is less than any given positive number. ∗ ∗ ∗ Anastasia FROLOVA (University of Bergen) Cowen–Pommerenke type inequalities for univalent functions We present a new estimate for angular derivatives of univalent maps at the fixed points. The method we use is based on the properties of the reduced modulus of a digon and the problem of extremal partition of a Riemann surface. Joint work with M. Levenshtein, D. Shoikhet and A. Vasil’ev. ∗ ∗ ∗ 12 Anna GLADKAYA, Oleg VINOGRADOV (St. Petersburg State University) Entire functions of exponential type deviating least from zero with a weight Classical results of P.L. Chebyshev and S.N. Bernstein on polynomials of least deviation from zero with a weight are extended to entire functions of exponential type. Let ρm be a function from the Carthwright class C of type m which is positive on the real axis and let σ > m. Put fσ (z) = 1 ∗ (G (z) + G(z)) , 2 Fσ (z) = 1 (G∗ (z) − G(z)) , 2iz 2 (z), ρm (x) = |gm (x)|2 , G∗ (z) = G(z). For the functions fσ where G(z) = e−iσz gm and Fσ the following theorems are proved. Theorem 1. For any nonzero entire function q from the class C of type less than σ we have the inequality fσ − q > sup fσ . sup ρm ρm R R Theorem 2. For any nonzero entire function Q of type less than σ summable on the real axis with the weight | · |/ρm we have the inequality Z∞ −∞ |Fσ (x) − Q(x)| − |Fσ (x)| |x| dx > 0. ρm (x) Thus, the functions fσ and Fσ are strictly deviating least from the zero in the uniform and integral metrics with the weights 1/ρm and | · |/ρm , respectively. Analogous statements hold true for fσ in the integral metric with the weight 1/ρm and for Fσ in the uniform metric with the weight | · |/ρm . Functions fσ and Fσ generalize Chebyshev polynomials of first and second kind. We note that they are not summable with respect to the above-mentioned weights. ∗ ∗ ∗ Victor GORYAINOV (Moscow Institute of Physics and Technology) Loewner–Kufarev equation for conformal mappings of strips The infinitesimal description of semigroups of conformal mappings of strips is obtained. Some approximative property of the semigroup is given. ∗ ∗ ∗ 13 Antti HAIMI (Norwegian University of Science and Technology, Trondheim) Polyanalytic Bergman kernels We discuss Hilbert spaces of polyanalytic functions on the complex plane. The norm on these spaces is given by integration against a weight e−mQ(z) where Q is a strictly subharmonic function and m a large positive scaling parameter. We obtain a near-diagonal asymptotic expansion for the reproducing kernels as m tends to infinity. In the setting of one complex variable, this generalizes the work of Tian–Yau–Catlin–Zelditch from analytic functions to polyanalytic functions. We also study reproducing kernels of corresponding polynomials spaces. These are spanned by functions z¯r z j where 0 ≤ r ≤ q − 1 and 0 ≤ j ≤ n − 1. The inner product is induced by the same weight as before. Keeping q fixed and letting n and m go to infinity, we obtain scaling limits for the kernels in so called bulk regime. In the model case Q(z) = |z|2 , this investigation has applications in statistical quantum mechanics. Some of the results are joint work with Haakan Hedenmalm. ∗ ∗ ∗ Olena HLADKA (National University of Water Management and Nature Resources, Rivne) The complex analysis method of numerical identification of parameters of nonlinear quasiideal processes The method for solving nonlinear model problems of complex potential theory in doubly-layered curvilinear domain with identification of parameters (conductivity coefficient, characteristic values of the potential on the equipotential lines of section layers, and the flows across the border parts bounded by the flow lines that separate layers) was developed on the basis of numerical methods of quasiconformal mappings and summary representations in conjunction with domain decomposition method by Schwartz. ∗ ∗ ∗ Andreas JUNG (University of Trier ) Universality of composition operators for Fatou components of an entire function Let f be an entire function and let U be an invariant component of the Fatou set of f . For a domain Ω ⊃ U in the complex plane, we investigate which level of ‘universality’ a sequence of composition operators Tf n : H(Ω) → H(U ), g 7→ g ◦ f n can have (here f n denotes the n-th iterate of f ). In this situation, we are looking for g ∈ H(Ω) having the property, that the set {Tf n (g) : n ∈ N} is dense in H(U ). Such functions are called universal for (Tf n ). Starting with local universality results in open neighborhoods W of (super-)attracting or neutral fixed points of f , for which the restriction f W is injective, we try to expand those local results via conjugation to finite Blaschke products into more global results, which 14 are valid in an entire invariant Fatou component U of f where in general f U is not injective. ∗ ∗ ∗ Georgy IVANOV (University of Bergen) Slit holomorphic stochastic flows We consider the general case of holomorphic stochastic flows that have slit geometry, as well as their deterministic counterparts. We compare the random families of curves generated by these flows with those generated by SchrammLoewner evolution, which is a particular example of a slit holomorphic stochastic flow. This is joint work with Alexey Tochin and Alexander Vasil’ev. ∗ ∗ ∗ Valery KALYAGIN (Higher School of Economics, Nizhny Novgorod ) Asymptotics of sharp constants in Markov–Bernstein inequalities We apply a new methods of matching asymptotics of solutions of difference equations with boundary value problems in the complex plane to the investigation of sharp constants in Markov–Bernstein inequality in a weighted functional spaces. As a result we obtain asymptotics in terms of the smallest zero of appropriate Bessel functions. ∗ ∗ ∗ Ilgiz KAYUMOV (Kazan Federal University) An efficient algorithm for computation the integral means spectrum for conformal mappings generated by lacunary power series with Hadamard gaps A computation of the integral means spectrum for certain domains with fractal type boundaries is a very nontrivial problem. Such problems were investigated by J. Littlewood, Ch. Pommerenke, N. G. Makarov, L. Carleson, P. W. Jones, S. K. Smirnov, D. Beliaev and by many other mathematicians. Lacunary series with Hadamard gaps was firstly used by Makarov to disprove one famous conjecture about the behavior of the integral means spectrum near the point t=1/3. In the report we (jointly with D. V. Maklakov) present an efficient algorithm that allows us to compute such the spectrum with a very high precision for conformal mappings generated by lacunary power series with Hadamard gaps of the type 2n . In particular, we will show that the integral means spectrum is less than t2 /4 for t < 1 in this case. ∗ ∗ ∗ 15 Vladimir KESELMAN (Moscow State Industrial University) Conformal capacity and conformal classification of non-compact Riemannian manifolds Non-compact connected Riemannian manifolds can be divided into two conformally invariant classes (types): manifolds of conformally parabolic type (as Euclidean space) and manifolds of conformally hyperbolic type (as Lobachevski space) according to the conformal capacity of the manifold at infinity which is equal to zero or is positive, respectively. We give some geometric conditions and prove criteria for conformal type of a Riemannian manifold. In particular, we prove that the isoperimetric inequality (or isoperimetric function) of the manifold can be reduced, by the conformal change of the initial Riemannian metric of the manifold, to the normal form of a manifold of Euclidian or Lobachevski type, depending of the conformal type of the manifold under consideration. ∗ ∗ ∗ Vitaly KIM (Institute of Mathematics, Ufa) Hypercyclic operators on spaces of holomorphic functions An operator (linear and continuous) on a topological vector space is hypercyclic if there exists a vector whose orbit under the operator is dense. In this talk I will discuss various aspects of hypercyclic operators on spaces of holomorphic functions and their connection with complete systems of analytic functions. ∗ ∗ ∗ Bulat KHABIBULLIN (Bashkir State University, Ufa) Zero subsequences of entire functions of exponential type with restrictions on their growth along the real line Denote by R and C the sets of real and complex numbers. Let M : C → R be a continuous function such that M is harmonic on C \ R, M (z) ≤ O |z| , R (x)| z → ∞, sup M (w) ≤ M (z) + const, z ∈ C, R |M 1+x2 dx < +∞, and |z−w|≤1 1 M (x) ≤ 2 π t + r 1 dt, M (x + t) log t t − r R Z 0 < r < r(x), x ∈ R. Let Λ = {λk }∞ k=1 ⊂ C be a point sequence without limit points in C. We give a complete description of Λ for which there is an entire function f 6= 0 vanishing on Λ and such that f (z) ≤ M (z) for all z ∈ C. This description differs from the description given in our paper [1] for special weight function M (z) = σ|Im z|, z ∈ C, 0 < σ ∈ R. [1] B.N. Khabibullin, G.R. Talipova, F.B. Khabibullin, Zero subsequences for 16 Bernstein’s spaces and the completeness of exponential systems in spaces of functions on an interval, Algebra i Analiz (St. Petersburg Math. Journal), 26:2 (2014), 193–223. ∗ ∗ ∗ Alexander KOMLOV (Steklov Mathematical Institute, Moscow ) Second order differential equation and strong asymptotics for a twopoint analogue of Jacobi polynomials First of all we consider two-point Pade approximants for function from some class of multivalued analytic functions with p > 1 branch points. We obtain a differential equation of the second order with accessory parameters satisfied by numerators of two-point Pade approximants of this function and the corresponding remainder functions. After that we consider the case p = 2, then the numerators of two-point Pade approximants are two-point analogue of Jacobi polynomials. Applying the classical Liouville–Steklov method to obtained differential equation we get strong asymptotic formula for this analogue. ∗ ∗ ∗ Evgeny KOROTYAEV (St. Petersburg State University) Global properties of resonances for Dirac and Stark operators We consider the Dirac and Stark operators perturbed by a compactly supported potential (of a certain class) on the real line. We determine upper and lower bounds of the number of resonances in complex discs at large radius and express the trace formula in terms of resonances only. Moreover, we estimate the sum of the negative power of all resonances and eigenvalues in terms of the norm of the potential and the diameter of its support. The proof is based on harmonic analysis and Carleson measures arguments. ∗ ∗ ∗ Olesya KRIVOSHEYEVA (Bashkir State University, Ufa) A basis in an invariant subspace of entire function The existence problem for a basis in a differentiation-invariant subspace of entire function is investigated. It is proved that in any such subspace a basis composed of linear combinations of eigenfunctions and associated functions exists. The linear combinations is generated in exponents clusters of an arbitrarily small relative diameter. ∗ ∗ ∗ 17 Nikolay KRUZHILIN (Steklov Mathematical Institute, Moscow ) Isolated singularities, finite maps, and function algebras Relations of isolated singularities of complex hypersurfaces to relevant functiona algebras are discussed. The problem of the reconsruction of a homogeneous singularity from its Milnor algebra is solved. ∗ ∗ ∗ Galina KUZ’MINA (St. Petersburg Department of Steklov Mathematical Institute) The extremal metric method in the geometric function theory The method of extremal metric is a general method of the function theory. The determining role in the development of this method is due to J. A. Jenkins. One form of this method in the geometric function theory is the method of modules of curve families. This method obtained the development in the recent works of the Leningrad mathematical school and found many applications. The characteristic feature of the modules method is the immediately use of the properties of quadratic differentials. ∗ ∗ ∗ Andrei LISHANSKII (St. Petersburg State University) A class of Toeplitz operators with hypercyclic subspaces We use a theorem by Gonzalez, Leon-Saavedra and Montes-Rodriguez to construct a class of coanalytic Toeplitz operators which have an infinitedimensional closed subspace, where any non-zero vector is hypercyclic. ∗ ∗ ∗ Alexander LOBODA (Voronezh State Academy of Building and Architecture) Homogeneous real hypersurfaces of three-dimensional complex spaces The classification problems for the affine homogeneous and holomorphically homogeneous real hypersurfaces will be discussed. The scheme will be presented of complete description of strictly pseudo convex homogeneous surfaces in affine case and full solution of the question under consideration in some subcases. Some necessary conditions for the Taylor coefficients will be obtained for the holomorphic homogeneous hypersurfaces with 5-dimensional transitive group actions. ∗ ∗ ∗ Lev MAERGOIZ (Siberian Federal University, Krasnoyarsk ) Extensions of a class of entire functions of many variables The object of investigation is the class H(Tn ) of holomorphic functions in the multidimensional torus space Tn . We study the subclass of functions equivalent 18 to a class of entire functions in the following sense: a function g ∈ H(Tn ) belongs to the mentioned subclass if there exists a monomial map F such that f = g ◦ F is an entire function. Description of functions in these subclasses in terms of geometrical properties of supports of their Laurent series is obtained. A multidimensional analog of holomorphic function expansion in Laurent series and structure of functions in H(Tn ) are presented. Characteristics of growth of these functions are studied. New results and problems are discussed. [1] L.S. Maergoiz, Multidimensional analogue of the Laurent series expansion of a holomorphic function and related issues, Doklady Mathematics, 88:2 (2013), 569–572. ∗ ∗ ∗ Eugenia MALINNIKOVA (Norwegian University of Science and Technology, Trondheim) Coefficients of harmonic functions in growth spaces and multipliers Let h∞ g be the space of harmonic functions in the unit ball that are bounded by some increasing radial function g(r) with limr→1 g(r) = +∞; these spaces are called growth spaces. We describe functions in growth spaces by the Ces`aro means of their expansions in harmonic polynomials and apply this characterization to study coefficient multipliers between growth spaces. A series of examples of multipliers will be given and the law of the iterated logarithm for the radial oscillation will be explained. The talk is based on joint works with Yu. Lyubarskii, K. S. Eikrem, and P. Mozolyako. ∗ ∗ ∗ Alexey MARKOVSKIY (Kuban State University) Equilibrium constant of compact plane set We consider the variational problem of finding the function which is least deviating from zero on a given compact set. This function is from the class of complex products with a given number of zeros concentrated on this compact set and having non-algebraic singularities with sum of multiplicities equal to one. Properties of solutions of this problem are investigated. For plane compact set the equilibrium constant is determined as the limit values of extreme products; it is proved that this constant is equal to the capacity of the compact set. ∗ ∗ ∗ Maxim MAZALOV (Moscow Power Engineering Institute, Smolensk Branch) Conditions of C m approximability by harmonic and bianalytic functions Some recent results of C m approximability of functions on compact subsets of Rd by harmonic and bianalytic functions will be discussed. ∗ ∗ ∗ 19 Mark MELNIKOV (Universitat Aut´onoma de Barcelona) On one conjecture of the ‘domain expansion principle’ type Let G be a domain in the complex plane, a ∈ G, and γ(G, a) = max |f 0 (a)|, where the maximum is taken over all holomorphic in G functions f such that |f | ≤ 1 in G. One conjecture concerning the behavior of the quantity γ(G, a) when the domain G expands is discussed. We consider variation of the quantity γ(G, a) under special variations of the boundary of G. ∗ ∗ ∗ Pavel MOZOLYAKO (Norwegian University of Science and Technology, Trondheim) On the minimum of harmonic functions in the n-dimensional ball A well-known theorem by M. Cartwright states that if a harmonic in the unit disk function u satisfies the one-sided growth condition u(z) ≤ w(|z|), where w(r) = 1 (1−r)p z∈D for some p > 1, then the reverse inequality holds u(z) ≥ −Cw(|z|), z ∈ D, where C depends only on p. This result was extended in many ways to different types of weights, the works by N. Nikolskii and A. Borichev should be mentioned in particular. Some of the techniques they used however were limited to the complex plane, so it was not obvious how one should obtain these kinds of results in higher dimensions. We are planning to prove the extension of Cartwright’s theorem for the unit ball in Rn for sufficiently regular weights w. ∗ ∗ ∗ ¨ J¨ urgen MULLER (University of Trier ) Limit functions on small parts of the Julia set In the theory of dynamical systems the notion of ω-limit sets of points is classical. In this talk, the existence of limit functions on subsets of the underlying space is treated. It is shown that in the case of topologically (weak-)mixing systems, plenty of limits functions on small subsets of X exist. On the other hand, such sets necessarily have to be small in various respects. The results for general discrete systems are applied in the case of Julia sets of rational and entire functions. Further results are formulated in the case of the existence of Siegel disks. ∗ ∗ ∗ 20 Ildar MUSIN (Institute of Mathematics, Ufa) Weighted spaces of entire functions New results on relationship between a global growth of entire functions of several complex variables of certain classes and behavior of these functions on sets of multidimensional real space will be reported. For the considered spaces theorems of Paley-Wiener type (or Paley–Wiener–Schwartz type) will be established. ∗ ∗ ∗ Valentin NAPALKOV (Institute of Mathematics, Ufa) Generalized Bargmann-Fock spaces and spectral synthesis Applying the solution of the problem about the description of the operator adjoint to the operator of multiplication in the Bargmann–Fock spaces we solve the problems of spectral synthesis. ∗ ∗ ∗ Valerii NAPALKOV (Institute of Mathematics, Ufa) Ortosimilar expansion systems in Hilbert spaces of analytic function We consider ortosimilar expansion systems (expansion systems similar to orthogonal ones) in Hilbert spaces of analytic function. We study the problem of describing the adjoint operator to the operator of multiplication by the independent variable in the Bargmann–Fock space. Newman–Shapiro’s problem is considered. In this talk we will show how to apply the theory of orthosimilar expansion systems to solve this problem. Also we will discuss one problem associated with Ahlfors’ quasiconformal reflection in the complex plane. ∗ ∗ ∗ Petr PARAMONOV (M. V. Lomonosov Moscow State University) Smooth subharmonic extensions of Runge and Walsh types on open Riemann surfaces Several settings of the C m -subharmonic extension problem on open Riemann surfaces is planned to discuss. The problem was completely solved (for all m ∈ [0, +∞)) for the so-called Runge-type extensions. Several (in some sense sharp) sufficient conditions and counterexamples were found also for the Walshtype extensions. As applications, these results allow to prove the existence of C m -subharmonic extensions, automorphic with respect to some special groups of conformal mappings. The results of joint work of the author with A. Boivin and P. M. Gauthier (Canada). ∗ ∗ ∗ 21 Sergey POPENOV (Institute of Mathematics, Ufa) Interpolation with real nodes by series of exponentials in the spaces of analytic functions We obtain the necessary and sufficient conditions for interpolation with real nodes by series of exponentials in the spaces of analytic functions in unbounded convex domains. Furthermore necessary conditions are found for interpolation by elements from invariant subspaces. ∗ ∗ ∗ Aleksandr ROTKEVICH (St. Petersburg State University) A constructive characterization of Besov spaces on convex domains In 1981 E. M. Dyn’kin gave the characterization of holomorphic Besov spaces on domains on complex plane by means of polynomial approximations. He suggested the method of ‘pseudoanalytical continuation’ as a tool to study spaces of holomorphic functions. This talk concerns the generalization of this method to the case of convex domains in the space of several complex variables. ∗ ∗ ∗ Timur SADYKOV (Plekhanov Russian State University of Economics, Moscow ) Maximally reducible monodromy of bivariate hypergeometric systems I will present a joint work with S. Tanabe. We investigate branching of solutions to holonomic bivariate hypergeometric systems of Horn type. Special attention is paid to the invariant subspace of Puiseux polynomial solutions. We mainly study (1) Horn systems defined by simplicial configurations, (2) Horn systems whose Ore–Sato polygon is either a zonotope or a Minkowski sum of a triangle and segments. We prove a necessary and sufficient condition for the monodromy representation to be maximally reducible, that is, for the space of holomorphic solutions to split into the direct sum of one-dimensional invariant subspaces. ∗ ∗ ∗ Anton SAVIN, Boris STERNIN (Peoples Friendship University, Moscow ) Differential equations on complex manifolds In this talk we deal with the theory of differential equations on complex manifolds. Namely, we study linear differential equations in CN and, more generally, on complex manifolds. This theory is remarkable and interesting. It turns out that to study equations on complex manifolds, one has to use essentially new methods, than in the classical (real) theory. These methods will be described in the talk, in particular, we shall describe Sternin–Shatalov transform, which enables one to solve equations with constant coefficients. 22 Complex theory has important applications in mathematics and physics. In particular, we shall show how the methods described in the talk enable one to solve balayage inwards problem (Poincare). ∗ ∗ ∗ Nikolay SHCHERBINA (University of Wuppertal ) On Liouville type properties of the core of a domain For a domain G in a complex manifold M we introduce the notion of the core c(G) of G as the set of all points where every smooth and bounded from above plurisubharmonic function on G fails to be strictly plurisubharmonic. We study then the following questions related to the structure of the core: 1) Let L be a connected component of c(G). Does it follow that every bounded from above plurisubharmonic function on G is constant on L? 2) In which cases one can ensure the existence of analytic structure on c(G)? ∗ ∗ ∗ Vladimir SHLYK (Far Eastern Federal University & Vladivostok Branch of Russian Customs Academy) On the problem of decomposition and composition of normal rectangle open sets There is an extensive literature devoted to investigations of the properties of normal domains (normal domains in the Gr¨otzsch sense or minimal domains in the Koebe sense). Here, using the method of extremal metric in Fuglede’s sense we give a solution of the problem of decomposition and composition of p-normal rectangle open sets, 1 < p < ∞, in the n-dimensional Euclidean space Rn , n ≥ 2. ∗ ∗ ∗ Mikhail SKOPENKOV (Institute for Information Transmission Problems, Moscow ) Discrete complex analysis: convergence results Various discretizations of complex analysis have been actively studied since 1920s because of applications to numerical analysis, statistical physics, and inegrable systems. This talk concerns complex analysis on quadrilateral lattices tracing back to the works of J. Ferrand. We solve a problem of S. K. Smirnov on convergence of discrete harmonic functions on planar nonrhombic lattices to their continuous counterparts under lattice refinement. This generalizes the results of R. Courant–K. Friedrichs–H. Lewy, L. Lusternik, D. S. Chelkak–S. K. Smirnov, P. G. Ciarlet–P.-A. Raviart. We also prove convergence of discrete period matrices and discrete Abelian integrals to their continuous counterparts (this is a joint 23 work with A. I. Bobenko). The proofs are based on energy estimates inspired by electrical network theory. ∗ ∗ ∗ Dmitriy TULYAKOV (Keldysh Institute of Applied Mathematics, Moscow ) Abelian integral of Nuttall on the Riemann surface of the cubic root of the third degree polynomial We consider the geometry of Hermite–Pade approximants for two functions with three common branch points. This problem has an interest with the connection to the Nuttall’s conjecture, which states that an algebraic function of the third order appears as the Cauchy transform of limiting measures of poles of the approximants. We discuss the case of the algebraic function of the genus one. This is a joint work with A. I. Aptekarev. ∗ ∗ ∗ Askhab YAKUBOV (Chechen State University) On one classical Chebyshev’s problem on inequalities To be announced ∗ ∗ ∗ Rinad YULMUKHAMETOV (Institute of Mathematics, Ufa) Entire functions and unconditional bases in weighted spaces The talk is devoted to a problem of construction of unconditional basis of exponentials in weighted Hilbert spaces on segment of real axis. We assume that a weight function has a slow growth. ∗ ∗ ∗ 24 LIST OF PARTICIPANTS Evgeny Abakumov University Paris-Est Marne-la-Vallee, [email protected] Alexei Aleksandrov St. Petersburg Department of Steklov Mathematical Institute, [email protected] Irina Antipova Siberian Federal University, Krasnoyarsk, [email protected] Alexander Aptekarev Keldysh Institute of Applied Mathematics, Moscow, [email protected] Kari Astala University of Helsinki, [email protected] Farit Avkhadiev Kazan Federal University, [email protected] Anton Baranov St. Petersburg State University, [email protected] Laurent Baratchart INRIA, [email protected] Mikhail Basok St. Petersburg State University, [email protected] Aleksandr Beknazaryan Kazan State Power Engineering University, [email protected] Yurii Belov St. Petersburg State University, [email protected] Bo Berndtsson Chalmers University of Technology, [email protected] Sergey Bezrodnykh Dorodnicyn Computing Centre of RAS, [email protected] Markus Born University of Trier, [email protected] Petr Borodin M.V. Lomonosov Moscow State University, [email protected] Ekaterina Borovik Bauman Moscow State Technical University, [email protected] Victor Buslaev Steklov Mathematical Institute, Moscow, [email protected] 25 Evgenii Chirka Steklov Mathematical Institute, Moscow, [email protected] Andrey Dnestryan Moscow Institute of Physics and Technology, [email protected] Evgueni Doubtsov St. Petersburg Department of Steklov Mathematical Institute, [email protected] Mikhail Dubashinskiy St. Petersburg State University, [email protected] Vladimir Dubinin Far Eastern Federal University, Vladivostok, [email protected] Yuri Dymchenko Far Eastern Federal University, Vladivostok, [email protected] Konstantin Dyakonov ICREA & Universitat de Barcelona, [email protected] Konstantin Fedorovskiy Bauman Moscow State Technical University, [email protected] Anastasia Frolova University of Bergen, [email protected] Stephen Gardiner University College Dublin, [email protected] Anna Gladkaya St. Petersburg State University, [email protected] Victor Goryainov Moscow Institute of Physics and Technology, [email protected] Antti Haimi Norwegian University of Science and Technology, Trondheim, [email protected] Olena Hladka National University of Water Management and Nature Resources, Rivne, [email protected] Georgy Ivanov University of Bergen, [email protected] Alexei Ilyin Keldysh Institute of Applied Mathematics, Moscow, [email protected] Andreas Jung University of Trier, [email protected] Valery Kalyagin Higher School of Economics, Nizhny Novgorod, [email protected] 26 Vladimir Kapustin St. Petersburg Department of Steklov Mathematical Institute, [email protected] Ilgiz Kayumov Kazan Federal University, [email protected] Vladimir Keselman Moscow State Industrial University, [email protected] Bulat Khabibullin Bashkir State University, Ufa, [email protected] Dmitry Khavinson University of South Florida, [email protected] Vitaly Kim Institute of Mathematics, Ufa, [email protected] Sergey Kislyakov St. Petersburg Department of Steklov Mathematical Institute, [email protected] Alexander Komlov Steklov Mathematical Institute, Moscow, [email protected] Anna Kononova St. Petersburg State University, [email protected] Evgeny Korotyaev St. Petersburg State University, [email protected] Aleksandr Kotochigov St. Petersburg Elektrotechnical University, [email protected] Olesya Krivosheeva Bashkir State University, Ufa, [email protected] Nikolai Kruzhilin Steklov Mathematical Institute, Moscow, [email protected] Galina Kuz’mina St. Petersburg Department of Steklov Mathematical Institute, [email protected] Maria Lapik Keldysh Institute of Applied Mathematics, Moscow, [email protected] Ari Laptev Imperial College London, [email protected] Elena Lebedeva St. Petersburg State University, [email protected] Andrei Lishanskii St. Petersburg State University, [email protected] 27 Alexander Loboda Voronezh State Academy of Building and Architecture, [email protected] Alexander Logunov St. Petersburg State University, [email protected] Vladimir Lysov Keldysh Institute of Applied Mathematics, Moscow, [email protected] Yurii Lyubarskii Norwegian University of Science and Technology, Trondheim, [email protected] Lev Maergoiz Siberian Federal University, Krasnoyarsk, [email protected] Eugenia Malinnikova Norwegian University of Science and Technology, Trondheim, [email protected] Vesna Manojlovic Mathematical Institute of the Serbian Academy of Sciences, [email protected] Alexey Markovskiy Kuban State University, [email protected] Maxim Mazalov Moscow Power Engineering Institute (Smolensk Branch), [email protected] Mark Melnikov Universitat Aut´onoma de Barcelona, [email protected] Pavel Mozolyako Norwegian University of Science and Technology, Trondheim, [email protected] Juergen Mueller University of Trier, [email protected] Ildar Musin Institute of Mathematics, Ufa, [email protected] Valentin Napalkov Institute of Mathematics, Ufa, [email protected] Valerii Napalkov Institute of Mathematics, Ufa, [email protected] Stefan Nemirovski Steklov Mathematical Institute, Moscow, [email protected] Nikolai Osipov St. Petersburg Department of Steklov Mathematical Institute, [email protected] 28 Petr Paramonov M.V. Lomonosov Moscow State University, [email protected] Sergey Popenov Institute of Mathematics, Ufa, [email protected] Aleksandr Rotkevich Higher School of Economics, St. Petersburg, [email protected] Marianna Russkikh St. Petersburg State University, [email protected] Timur Sadykov Plekhanov Russian State University of Economics, Moscow, [email protected] Eero Saksman University of Helsinki, [email protected] Anton Savin Peoples Friendship University, Moscow, [email protected] Walter Sch¨ afer Technische Universit¨at Darmstadt, [email protected] Kristian Seip Norwegian University of Science and Technology, Trondheim, [email protected] Armen Sergeev Steklov Mathematical Institute, Moscow, [email protected] Nikolay Shcherbina University of Wuppertal, [email protected] Nikolai Shirokov St. Petersburg State University, [email protected] Vladimir Shlyk Far Eastern Federal University, Vladivostok, [email protected] Yum-Tong Siu Harvard University, [email protected] Mikhail Skopenkov Institute for Information Transmission Problems, Moscow, [email protected] Boris Sternin Peoples Friendship University, Moscow, [email protected] Dmitriy Stolyarov St. Petersburg Department of Steklov Mathematical Institute, [email protected] Alexandre Sukhov University Lille-1, [email protected] 29 Xavier Tolsa ICREA & Universitat Aut´onoma de Barcelona, [email protected] Avgust Tsikh Siberian Federal University, Krasnoyarsk, [email protected] Dmitriy Tulyakov Keldysh Institute of Applied Mathematics, Moscow, [email protected] Vasily Vasyunin St. Petersburg Department [email protected] of Steklov Mathematical Institute, Ilya Videnskii St. Petersburg State University, [email protected] Oleg Vinogradov St. Petersburg State University, [email protected] Vladimir Vlasov Dorodnicyn Computing Centre of RAS, Moscow, [email protected] Rinad Yulmukhametov Institute of Mathematics, Ufa, [email protected] Askhab Yakubov Chechen State University, [email protected] Pavel Zatitsky St. Petersburg Department of Steklov Mathematical Institute, [email protected] 30
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