Tuesday Seminar of Analysis

Seminar information archive ~02/06Next seminarFuture seminars 02/07~

Date, time & place Tuesday 16:00 - 17:30 156Room #156 (Graduate School of Math. Sci. Bldg.)
Organizer(s) ISHIGE Kazuhiro, SAKAI Hidetaka, ITO Kenichi

Seminar information archive

2025/01/14

16:00-17:30   Room #128 (Graduate School of Math. Sci. Bldg.)
SUZUKI Kanako (Ibaraki University)
Existence and stability of discontinuous stationary solutions to reaction-diffusion-ODE systems (Japanese)
[ Abstract ]
We consider reaction-diffusion-ODE systems, which consists of a single reaction-diffusion equation coupled with ordinary differential equations. Such systems arise, for example, from modeling of interactions between cellular processes and diffusing growth factors.
Reaction-diffusion-ODE systems in a bounded domain with Neumann boundary condition may have two types of stationary solutions, regular and discontinuous. We can show that all regular stationary solutions are unstable. This implies that reaction-diffusion-ODE systems cannot exhibit spatial patterns, and possible stable stationary solutions must be singular or discontinuous. In this talk, we present sufficient conditions for the existence and stability of discontinuous stationary solutions.
This talk is based on joint works with A. Marciniak-Czochra (Heidelberg University), G. Karch (University of Wroclaw) and S. Cygan (University of Wroclaw).
[ Reference URL ]
https://forms.gle/GtA4bpBuy5cNzsyX8

2024/12/24

16:00-17:30   Room #128 (Graduate School of Math. Sci. Bldg.)
KAKEHI Tomoyuki (University of Tsukuba)
Snapshot problems for the wave equation and for the Euler-Poisson-Darboux equation (Japanese)
[ Abstract ]
In this talk, we deal with snapshot problems for the wave equation and for the Euler-Poisson-Darboux equation. For simplicity, let us consider the wave equation $\partial_t^2 u - \Delta u =0$ on $\mathbb{R}^n$ with the condition $u|_{t=t_1} =f_1, \cdots, u|_{t=t_m} =f_m$. It is natural to ask when the above equation has a unique solution. We call the above problem the snapshot problem for the wave equation, and the set of $m$ functions $\{ f_1, \cdots, f_m \}$ the snapshot data. Roughly speaking, one of our main results is as follows.

Theorem. We assume that $m=3$ and $(t_3-t_1)/(t_2 -t_1)$ is irrational and not a Liouville number. In addition, we assume a certain compatibility condition on the snapshot data $\{ f_1, f_2, f_3 \}$. Then the snapshot problem for the wave equation has a unique solution.

We also consider a similar snapshot problem for the Euler-Poisson-Darboux equation. This is a joint work with Jens Christensen, Fulton Gonzalez, and Jue Wang.
[ Reference URL ]
https://forms.gle/2otzqXYVD6DqM11S8

2024/10/08

16:00-17:30   Room #128 (Graduate School of Math. Sci. Bldg.)
Erik Skibsted (Aarhus University)
Scattering subspace for time-periodic $N$-body Schrödinger operators (English)
[ Abstract ]
We propose a definition of a scattering subspace for many-body Schrödinger operators with time-periodic short-range pair-potentials. This in given in geometric terms. We then show that all channel wave operators exist, and that their ranges span the scattering subspace. This may possibly serve as an intermediate step for proving the longstanding open problem of asymptotic completeness, which may be reformulated as the assertion that the scattering subspace is the orthogonal subspace of the pure point subspace of the monodromy operator.
[ Reference URL ]
https://forms.gle/it1Kc4voAXK5vpcB9

2024/10/01

16:00-17:30   Room #128 (Graduate School of Math. Sci. Bldg.)
Patrícia Gonçalves (Instituto Superior Técnico)
Hydrodynamics, fluctuations, and universality of exclusion processes (English)
[ Abstract ]
In the seventies, Frank Spitzer introduced interacting particle systems to the mathematics community. These systems consist of particles evolving randomly according to Markovian dynamics that conserve certain quantities. Interacting particle systems were already known in the physics and biophysics communities and served as toy models for a variety of interesting phenomena. One of the most classical interacting particle systems is the exclusion process, where particles evolve in a discrete space according to a transition probability, but at each site, only one particle is allowed. One of the goals of studying these models is to derive their hydrodynamic limit, i.e., to deduce the macroscopic equations governing the space-time evolution of the conserved quantities of the system from the underlying random motion of the microscopic particles.
In this talk, I will review the derivation of these limits for the exclusion process. I will also discuss their equilibrium fluctuations, i.e., the fluctuations around the typical profile when the system starts from the invariant measure. Our focus will then shift to the two-species exclusion process, a system with two conservation laws, namely particles of type A and B. We will see that for proper linear combinations of the conserved quantities, their evolution is autonomous. This advances our understanding of the universal behavior of these systems. This presentation is based on joint work with G. Cannizzaro, R. Misturini, and A. Occelli.

2024/07/09

16:00-17:30   Room #128 (Graduate School of Math. Sci. Bldg.)
Serge Richard (Nagoya University)
The topological nature of resonance(s) for 2D Schroedinger operators (English)
[ Abstract ]
In 1986, Gesztesy et al. revealed the surprising behavior of thresholds resonances for two-dimensional scattering systems: their contributions to Levinson's theorem are either 0 or 1, but not 1/2 as previously known for systems in dimension 1 and 3. During this seminar, we shall review this result, and explain how a C*-algebraic framework leads to a better understanding of this surprise. The main algebraic tool consists of a hexagonal algebra of Cordes, replacing a square algebra sufficient for systems in 1D and 3D. No prior C*-knowledge is expected from the audience. This presentation is based on a joint work with A. Alexander, T.D. Nguyen, and A. Rennie.
[ Reference URL ]
https://forms.gle/2fypneTA8CjYrLTX9

2024/06/18

16:00-17:30   Room #128 (Graduate School of Math. Sci. Bldg.)
MORI Ryunosuke (Meiji University)
Blocking and propagation in two-dimensional cylinders with spatially undulating boundary (Japanese)
[ Abstract ]
We consider blocking and propagation phenomena of mean curvature flow with a driving force in two-dimensional cylinders with spatially undulating boundary. In this problem, Matano, Nakamura and Lou in 2006, 2013 characterize the effect of the shape of the boundary to blocking and propagation of the solutions under some slop condition about the boundary that implies time global existence of the classical solutions. In this talk, we consider the effect of the shape of the boundary to blocking and propagation of this problem under more general situation that the solutions may develop singularities near the boundary.
[ Reference URL ]
https://forms.gle/TrFmSZQ1ZeqvSjfP7

2024/05/14

16:00-18:15   Room #128 (Graduate School of Math. Sci. Bldg.)
Heinz Siedentop (LMU University of Munich) 16:00-17:00
The Energy of Heavy Atoms: Density Functionals (English)
[ Abstract ]
Since computing the energy of a system with $N$ particles requires solving a $4^N$ dimensional system of (pseudo-)differential equations in $3N$ independent variables, an analytic solution is practically impossible. Therefore density functionals, i.e., functionals that depend on the particle density (3 variables) only and yield the energy upon minimization, are of great interest.
This concept has been applied successfully in non-relativistic quantum mechanics. However, in relativistic quantum mechanics even the simple analogue of the Thomas-Fermi functional is not bounded from below for Coulomb potential. This problem was addressed eventually by Engel and Dreizler who derived a functional from QED. I will review some known mathematical properties of this functional and show that it yields basic features of physics, such as asymptotic correct energy, stability of matter, and boundedness of the excess charge.
[ Reference URL ]
https://forms.gle/ZEyVso6wa9QpNfxH7
Robert Laister (University of the West of England) 17:15-18:15
Well-posedness for Semilinear Heat Equations in Orlicz Spaces (English)
[ Abstract ]
We consider the local well-posedness of semilinear heat equations in Orlicz spaces, the latter prescribed via a Young function $\Phi$. Many existence-uniqueness results exist in the literature for power-like or exponential-like nonlinearities $f$, where the natural setting is an Orlicz space of corresponding type; i.e. if $f$ is power-like then $\Phi$ is power-like (Lebesgue space), if $f$ is exponential-like then $\Phi$ is exponential-like. However, the general problem of prescribing a suitable $\Phi$ for a given, otherwise arbitrary $f$ is open. Our goal is to provide a suitable framework to resolve this problem and I will present some recent results in this direction. The key is a new (to the best of our knowledge) smoothing estimate for the heat semigroup between two arbitrary Orlicz spaces. Existence then follows familiar lines via monotonicity or contraction mapping arguments. Global solutions are also presented under additional assumptions. This work is part of a collaborative project with Prof Kazuhiro Ishige, Dr Yohei Fujishima and Dr Kotaro Hisa.
[ Reference URL ]
https://forms.gle/ZEyVso6wa9QpNfxH7

2024/03/12

16:00-17:30   Room #123 (Graduate School of Math. Sci. Bldg.)
Kobe Marshall-Stevens (University College London)
On the generic regularity of min-max CMC hypersurfaces (English)
[ Abstract ]
Smooth constant mean curvature (CMC) hypersurfaces serve as effective tools to study the geometry and topology of Riemannian manifolds. In high dimensions however, one in general must account for their singular behaviour. I will discuss how such hypersurfaces are constructed via min-max techniques and some recent progress on their generic regularity, allowing for certain isolated singularities to be perturbed away.
[ Reference URL ]
https://forms.gle/7mqzgLqhtBuAovKB8

2023/11/14

16:15-17:15   Room #126 (Graduate School of Math. Sci. Bldg.)
Arne Jensen (Aalborg University)
Resolvent expansions for magnetic Schrödinger operators (English)
[ Abstract ]
I will present some new results resolvent expansions around threshold zero for magnetic Schrödinger operators in dimension three. The magnetic field and the electric potential are assumed to decay sufficiently fast. Analogous results for Pauli operators will also be presented.
Joint work with H. Kovarik, Brescia, Italy.
[ Reference URL ]
https://forms.gle/qyEUeo4kVuPL1s289

2023/08/22

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
Daniel Parra (Universidad de Santiago de Chile)
Towards a Levinson's Theorem for Discrete Magnetic operators on tubes under finite rank perturbations (English)
[ Abstract ]
In this talk we study a family of magnetic Hamiltonians on discrete tubes under a finite rank perturbation supported on its border. We go into detail for the case of rank $2$ and show how the eigenvalues can be related to the scattering matrix to exhibit an index theorem in the tradition of Levison’s theorem. We then turn to the general case, discuss the different spectral scenarios that can occur and explain the C*-algebraic framework that could allow us to treat this case. This is an ongoing work with S. Richard (Nagoya), V. Austen (Nagoya) and A. Rennie (Wollongong).
[ Reference URL ]
https://forms.gle/VBp4nSnYYKVpXFhB9

2023/07/11

16:00-17:30   Room #123 (Graduate School of Math. Sci. Bldg.)
Julian López-Gómez (Complutense University of Madrid)
Nodal solutions for a class of degenerate BVP’s (English)
[ Abstract ]
In this talk we characterize the existence of nodal solutions for a generalized class of one-dimensional diffusive logistic type equations, including
\[−u''=\lambda u−a(x)u^3,\quad x∈[0,L],\]
under the boundary conditions $u(0)=u(L)=0$, where $\lambda$ is regarded as a bifurcation parameter, and the non-negative weight function $a(x)$ vanishes on some subinterval
\[ [\alpha,\beta]\subset (0,L)\]
with $\alpha<\beta$.

At a later stage, the general case when $a(x)$ vanishes on finitely many subintervals with the same length is analyzed. Finally, we construct some examples with classical non-degenerate weights, with $a(x)>0$ for all $x∈[0,L]$, where the BVP has an arbitrarily large number of solutions with one node in $(0,L)$. These are the first examples of this nature constructed in the literature.

References:

P. Cubillos, J. López-Gómez and A. Tellini, Multiplicity of nodal solutions in classical non-degenerate logistic equations, El. Res. Archive 30 (2022), 898—928.

J. López-Gómez, M. Molina-Meyer and P. H. Rabinowitz, Global bifurcation diagrams of one-node solutions on a class of degenerate boundary value problems, Disc. Cont. Dyn. Syst. B 22 (2017), 923—946.

J. López-Gómez and P. H. Rabinowitz, Nodal solutions for a class of degenerate one dimensional BVP’s, Top. Meth. Nonl. Anal. 49 (2017), 359—376.

J. López-Gómez and P. H. Rabinowitz, The estructure of the set of 1-node solutions for a class of degenerate BVP’s, J. Differential Equations 268 (2020), 4691—4732.

P. H. Rabinowitz, A note on a anonlinear eigenvalue problem for a class of differential equations, J. Differential Equations 9 (1971), 536—548.
[ Reference URL ]
https://forms.gle/S3VgMSWg9wUP69cY6

2023/06/06

17:00-18:30   Room #128 (Graduate School of Math. Sci. Bldg.)
Erik Skibsted (Aarhus University)
Stationary completeness; the many-body short-range case (English)
[ Abstract ]
For a general class of many-body Schr\"odinger operators with short-range pair-potentials the wave and scattering matrices as well as the restricted wave operators are all defined at any non-threshold energy. In fact this holds without imposing any a priori decay condition on channel eigenstates and even for models including long-range potentials of Derezi\'nski-Enss type. For short-range models we improve on the known \emph{weak continuity} statements in that we show that all non-threshold energies are \emph{stationary complete}, resolving in this case a recent conjecture. A consequence is that the above scattering quantities depend \emph{strongly continuously} on the energy parameter at all non-threshold energies (whence not only almost everywhere as previously demonstrated). Another consequence is that the scattering matrix is unitary at any such energy. Our procedure yields (as a side result) a new and purely stationary proof of asymptotic completeness for many-body short-range systems.
[ Reference URL ]
https://forms.gle/kWHDfb6J6kcjfSah8

2023/03/14

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
Piermarco Cannarsa (University of Rome "Tor Vergata")
Parameter reconstruction for degenerate parabolic equations (English)
[ Abstract ]
First, we study degenerate parabolic equations arising in climate dynamics, providing uniqueness and stability estimates for the determination of the insolation function. Then, we address several aspects of the reconstruction of the degenerate diffusion coefficient. Finally, we discuss systems of two equations including a vertical component into the model.
[ Reference URL ]
https://forms.gle/nejpQS824vFKRbMQ6

2022/12/20

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
KATAOKA Kiyoomi (The University of Tokyo)
A commentary on J. Boman's recent two related results about the support of a distribution and its analyticity, and a special relationship between Radon transformations and ellipsoidal regions (Japanese)
[ Abstract ]
Jan Boman's (Stockholm Univ.) recent two papers:
[1], Regularity of a distribution and of the boundary of its support, The Journal of Geometric Analysis vol.32, Article number: 300 (2022).
[2], A hypersurface containing the support of a Radon transform must be an ellipsoid. II: The general case; J. Inverse Ill-Posed Probl. 2021; 29(3): 351–367.
In [1] he proved "Let $f(x_1,…,x_n,y)$ be a non-zero distribution with support in a $C^1$ surface $N=\{y=F(x)\}$. If $f(x,y)$ is depending real analytically on x-variables, then $F(x)$ is analytic". As an application, he reinforced the main result of [2]. These results are obtained essentially by means of matrix algebra and a number theoretic method.
[ Reference URL ]
https://forms.gle/BpciRTzKh9FPUV8D7

2022/12/13

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
TADANO Yukihide (Tokyo University of Science)
Continuum limit problem of discrete Schrödinger operators on square lattices (Japanese)
[ Abstract ]
We consider discrete Schrödinger operators on the square lattice with its mesh size very small. The aim of this talk is to introduce the rigorous setting of continuum limit problems in the view point of operator theory and then to give its proof for the above operators, the one of which is defined on the vertices and the other of which is defined on the edges. This talk is based on joint works with Shu Nakamura (Gakushuin University) and Pavel Exner (Czech Academy of Science, Czech Technical University).
[ Reference URL ]
https://forms.gle/CRha8hydEuXzh71S7

2022/11/29

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
TAKIMOTO Kazuhiro (Hiroshima University)
Bernstein type theorem for the parabolic 2-Hessian equation under weaker assumptions (Japanese)
[ Abstract ]
In the early twentieth century, Bernstein proved that a minimal surface which can be expressed as the graph of a function defined in $\mathbb{R}^2$ must be a plane. For Monge-Ampère equation, it is known that a convex solution to $\det D^2 u=1$ in $\mathbb{R}^n$ must be a quadratic polynomial. Such kind of theorems, which we call Bernstein type theorems in this talk, have been extensively studied for various PDEs. For the parabolic $k$-Hessian equation, Bernstein type theorem has been proved by Nakamori and Takimoto (2015, 2016) under the convexity and some growth assumptions on the solution. In this talk, we shall obtain Bernstein type theorem for the parabolic 2-Hessian equation under weaker assumptions.
[ Reference URL ]
https://forms.gle/93YQ9C6DGYt5Vjuf7

2022/10/04

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
FUKAO Takeshi (Kyoto University of Education)
The Cahn-Hilliard equation with forward-backward dynamic boundary condition via vanishing viscosity (Japanese)
[ Reference URL ]
https://forms.gle/nPfEgKUX2tfUrg5LA

2022/08/23

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
Stefan Neukamm (Dresden University/RIMS)
Quantitative homogenization for monotone, uniformly elliptic systems with random coefficients (English)
[ Abstract ]
Motivated by homogenization of nonlinearly elastic composite materials, we study homogenization rates for elliptic PDEs with monotone nonlinearity in the uniformly elliptic case. Under the assumption of a fast decay of correlations on scales larger than the microscale $\varepsilon$, we establish estimates of optimal order for the approximation of the homogenized operator by the method of representative volumes. Moreover, we discuss applications to nonlinear elasticity random laminates.
[ Reference URL ]
https://forms.gle/V1wxbYhT4mkPF4gY9

2022/07/26

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
KUMAGAI Takashi (Waseda University)
Periodic homogenization of non-symmetric jump-type processes with drifts (Japanese)
[ Abstract ]
Homogenization problem is one of the classical problems in analysis and probability which is very actively studied recently. In this talk, we consider homogenization problem for non-symmetric Lévy-type processes with drifts in periodic media. Under a proper scaling, we show the scaled processes converge weakly to Lévy processes on ${\mathds R}^d$. In particular, we completely characterize the limiting processes when the coefficient function of the drift part is bounded continuous, and the decay rate of the jumping measure is comparable to $r^{-1-\alpha}$ for $r>1$ in the spherical coordinate with $\alpha \in (0,\infty)$. Different scaling limits appear depending on the values of $\alpha$.
This talk is based on joint work with Xin Chen, Zhen-Qing Chen and Jian Wang (Ann. Probab. 2021).
[ Reference URL ]
https://forms.gle/ewZEy1jAXrAhWx1Q8

2022/06/28

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
ISHIDA Atsuhide (Tokyo University of Science)
Mourre inequality for non-local Schödinger operators (Japanese)
[ Abstract ]
We consider the Mourre inequality for the following self-adjoint operator $H=\Psi(-\Delta/2)+V$ acting on $L^2(\mathbb{R}^d)$, where $\Psi: [0,\infty)\rightarrow\mathbb{R}$ is an increasing function, $\Delta$ is Laplacian and $V: \mathbb{R}^d\rightarrow\mathbb{R}$ is an interaction potential. Mourre inequality immediately yields the discreteness and finite multiplicity of the eigenvalues. Moreover, Mourre inequality has the application to the absence of the singular continuous spectrum by combining the limiting absorption principle and, in addition, Mourre inequality is also used for proof of the minimal velocity estimate that plays an important role in the scattering theory. In this talk, we report that Mourre inequality holds under the general $\Psi$ and $V$ by choosing the conjugate operator $A=(p\cdot x+x\cdot p)/2$ with $p=-\sqrt{-1}\nabla$, and that the discreteness and finite multiplicity of the eigenvalues hold. This talk is a joint work with J. Lőrinczi (Hungarian Academy of Sciences) and I. Sasaki (Shinshu University).
[ Reference URL ]
https://forms.gle/sBSeNH9AYFNypNBk9

2022/05/31

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
OKABE Shinya (Tohoku University)
Convergence of Sobolev gradient trajectories to elastica (Japanese)
[ Abstract ]
In this talk we consider a higher order Sobolev gradient flow for the modified elastic energy defined on closed space curves. The $L^2$-gradient flow for the modified elastic energy has been well studied, and standard results are solvability of the flow for smooth initial curve and subconvergence of solutions to elastica. Moreover, stronger convergence results, so called full limit convergence, are generally up to reparametrisation and sometimes translation. In this talk, we consider $H^2$-gradient flow for the modified elastic energy and prove (i) the solvability of the flow for initial curve in the energy class, (ii) full limit convergence to elastica by way of a Lojasiewicz—Simon gradient inequality. This talk is based on a joint work with Philip Schrader (Murdoch University).
[ Reference URL ]
https://forms.gle/wkCbqdmNuz9zr3vA8

2022/05/24

16:00-17:30   Online
Michael Goesswein (The University of Tokyo/University of Regensburg)
Stability analysis for the surface diffusion flow on double bubbles using the Lojasiewicz-Simon (English)
[ Abstract ]
Many strategies for stability analysis use precise knowledge of the set of equilibria. For example, Escher, Mayer, and Simonett used center manifold analysis to study the surface diffusion flow on closed manifolds. Especially in higher dimensional situations with boundaries, this can cause problems as the set of equilibria will have a lot of degrees of freedom. In such situations approaches with a Lojasiewicz-Simon inequality gives an elegant way to avoid this problem. In this talk, we will both explain the general tools and ideas for this strategy and use them to prove the stability of standard double bubbles with respect to the surface diffusion flow. The talk is based on joint work with H. Garcke.
[ Reference URL ]
https://forms.gle/Cam3mpSSEKKVppZr9

2022/04/26

16:00-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
WAKUI Hiroshi (Tokyo University of Science)
Existence of a bounded forward self-similar solution to a minimal Keller-Segel model (Japanese)
[ Abstract ]
In this talk, we consider existence of a bounded forward self-similar solution to the initial value problem of a minimal Keller-Segel model. It is well known that the mass conservation law plays an important role to classify its large time behavior of solutions to Keller-Segel models. On the other hand, we could not expect existence of self-similar solutions to our problem with the mass conservation law except for the two dimensional case due to the scaling invariance of our problem. We will show existence of a forward self-similar solution to our problem. The key idea to guarantee boundedness of its self-similar solution is to choose a concrete upper barrier function using the hypergeometric function.
[ Reference URL ]
https://forms.gle/mrXnjsgctSJJ1WSF6

2022/04/12

16:00-17:30   Online
Amru Hussein (Technische Universität Kaiserslautern)
Maximal $L^p$-regularity and $H^{\infty}$-calculus for block operator matrices and applications (English)
[ Abstract ]
Many coupled evolution equations can be described via $2\times2$-block operator matrices of the form $\mathcal{A}=\begin{bmatrix}A & B \\ C & D \end{bmatrix}$ in a product space $X=X_1\times X_2$ with possibly unbounded entries. Here, the case of diagonally dominant block operator matrices is considered, that is, the case where the full operator $\mathcal{A}$ can be seen as a relatively bounded perturbation of its diagonal part though with possibly large relative bound. For such operators, the properties of sectoriality, $\mathcal{R}$-sectoriality and the boundedness of the $H^\infty$-calculus are studied, and for these properties perturbation results for possibly large but structured perturbations are derived. Thereby, the time-dependent parabolic problem associated with $\mathcal{A}$ can be analyzed in maximal $L^p_t$-regularity spaces, and this is applied to a wide range of problems such as different theories for liquid crystals, an artificial Stokes system, strongly damped wave and plate equations, and a Keller-Segel model.
This talk is based on a joint work with Antonio Agresti, see https://arxiv.org/abs/2108.01962
[ Reference URL ]
https://forms.gle/QbQKex12dbQrt2Lw6

2021/11/16

16:00-17:30   Online
KUBO Hideo (Hokkaido University)
TBA (Japanese)
[ Reference URL ]
https://forms.gle/6ZCp8hQxKA3vq3DB9

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