# Perron-Frobenius operators and the Klein-Gordon equation

Francisco Canto-Martín; Håkan Hedenmalm; Alfonso Montes-Rodríguez

Journal of the European Mathematical Society (2014)

- Volume: 016, Issue: 1, page 31-66
- ISSN: 1435-9855

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topCanto-Martín, Francisco, Hedenmalm, Håkan, and Montes-Rodríguez, Alfonso. "Perron-Frobenius operators and the Klein-Gordon equation." Journal of the European Mathematical Society 016.1 (2014): 31-66. <http://eudml.org/doc/277383>.

@article{Canto2014,

abstract = {For a smooth curve $\Gamma $ and a set $\Lambda $ in the plane $\mathbb \{R\}^2$, let $AC(\Gamma ;\Lambda )$ be the space of finite Borel measures in the plane supported on $\Gamma $, absolutely continuous with respect to the arc length and whose Fourier transform vanishes on $\Lambda $. Following [12], we say that $(\Gamma ,\Lambda )$ is a Heisenberg uniqueness pair if $AC(\Gamma ;\Lambda )=\lbrace 0\rbrace $. In the context of a hyperbola $\Gamma $, the study of Heisenberg uniqueness pairs is the same as looking for uniqueness sets $\Lambda $ of a collection of solutions to the Klein-Gordon equation. In this work, we mainly address the issue of finding the dimension of $AC(\Gamma ;\Lambda )$ when it is nonzero. We will fix the curve $\Gamma $ to be the hyperbola $x_1x_2=1$, and the set $\Lambda = \Lambda _\{\alpha ,\beta \}$ to be the lattice-cross $\Lambda _\{\alpha ,\beta \}=(\alpha \mathbb \{Z\} \times \lbrace 0\rbrace )\cup (\lbrace 0\rbrace \times \beta \mathbb \{Z\})$, where $\alpha , \beta $ are positive reals. We will also consider $\Gamma _+$, the branch of $x_1x_2=1$ where $x_1>0$. In [12], it is shown that $AC(\Gamma ; \Lambda _\{\alpha ,\beta \})=\lbrace 0\rbrace $ if and only if $\alpha \beta \le 1$. Here, we show that for $\alpha \beta > 1$, we get a rather drastic “phase transition”: $AC(\Gamma ; \Lambda _\{\alpha , \beta \})$ is infinite-dimensional whenever $\alpha \beta >1$. It is shown in [13] that $AC(\Gamma _+;\Lambda _\{\alpha ,\beta \})=\lbrace 0\rbrace $ if and only if $\alpha \beta <4$. Moreover, at the edge $\alpha \beta =4$, the behavior is more exotic: the space $AC(\Gamma _+;\Lambda _\{\alpha ,\beta \})$ is one-dimensional. Here, we show that the dimension of $AC(\Gamma _+;\Lambda _\{\alpha ,\beta \})$ is infinite whenever $\alpha \beta >4$. Dynamical systems, and more specifically Perron-Frobenius operators, will play a prominent role in the presentation.},

author = {Canto-Martín, Francisco, Hedenmalm, Håkan, Montes-Rodríguez, Alfonso},

journal = {Journal of the European Mathematical Society},

keywords = {trigonometric system; inversion; Perron-Frobenius operator; Koopman operator; invariant measure; Klein–Gordon equation; ergodic theory; Heisenberg uniqueness; Fourier transform; trigonometric systems; Perron-Frobenius operators; Klein-Gordon equation},

language = {eng},

number = {1},

pages = {31-66},

publisher = {European Mathematical Society Publishing House},

title = {Perron-Frobenius operators and the Klein-Gordon equation},

url = {http://eudml.org/doc/277383},

volume = {016},

year = {2014},

}

TY - JOUR

AU - Canto-Martín, Francisco

AU - Hedenmalm, Håkan

AU - Montes-Rodríguez, Alfonso

TI - Perron-Frobenius operators and the Klein-Gordon equation

JO - Journal of the European Mathematical Society

PY - 2014

PB - European Mathematical Society Publishing House

VL - 016

IS - 1

SP - 31

EP - 66

AB - For a smooth curve $\Gamma $ and a set $\Lambda $ in the plane $\mathbb {R}^2$, let $AC(\Gamma ;\Lambda )$ be the space of finite Borel measures in the plane supported on $\Gamma $, absolutely continuous with respect to the arc length and whose Fourier transform vanishes on $\Lambda $. Following [12], we say that $(\Gamma ,\Lambda )$ is a Heisenberg uniqueness pair if $AC(\Gamma ;\Lambda )=\lbrace 0\rbrace $. In the context of a hyperbola $\Gamma $, the study of Heisenberg uniqueness pairs is the same as looking for uniqueness sets $\Lambda $ of a collection of solutions to the Klein-Gordon equation. In this work, we mainly address the issue of finding the dimension of $AC(\Gamma ;\Lambda )$ when it is nonzero. We will fix the curve $\Gamma $ to be the hyperbola $x_1x_2=1$, and the set $\Lambda = \Lambda _{\alpha ,\beta }$ to be the lattice-cross $\Lambda _{\alpha ,\beta }=(\alpha \mathbb {Z} \times \lbrace 0\rbrace )\cup (\lbrace 0\rbrace \times \beta \mathbb {Z})$, where $\alpha , \beta $ are positive reals. We will also consider $\Gamma _+$, the branch of $x_1x_2=1$ where $x_1>0$. In [12], it is shown that $AC(\Gamma ; \Lambda _{\alpha ,\beta })=\lbrace 0\rbrace $ if and only if $\alpha \beta \le 1$. Here, we show that for $\alpha \beta > 1$, we get a rather drastic “phase transition”: $AC(\Gamma ; \Lambda _{\alpha , \beta })$ is infinite-dimensional whenever $\alpha \beta >1$. It is shown in [13] that $AC(\Gamma _+;\Lambda _{\alpha ,\beta })=\lbrace 0\rbrace $ if and only if $\alpha \beta <4$. Moreover, at the edge $\alpha \beta =4$, the behavior is more exotic: the space $AC(\Gamma _+;\Lambda _{\alpha ,\beta })$ is one-dimensional. Here, we show that the dimension of $AC(\Gamma _+;\Lambda _{\alpha ,\beta })$ is infinite whenever $\alpha \beta >4$. Dynamical systems, and more specifically Perron-Frobenius operators, will play a prominent role in the presentation.

LA - eng

KW - trigonometric system; inversion; Perron-Frobenius operator; Koopman operator; invariant measure; Klein–Gordon equation; ergodic theory; Heisenberg uniqueness; Fourier transform; trigonometric systems; Perron-Frobenius operators; Klein-Gordon equation

UR - http://eudml.org/doc/277383

ER -

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