2 results
Disjoint hypercyclicity, Sidon sets and weakly mixing operators
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- Journal:
- Ergodic Theory and Dynamical Systems / Volume 44 / Issue 5 / May 2024
- Published online by Cambridge University Press:
- 22 August 2023, pp. 1315-1329
- Print publication:
- May 2024
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We prove that a finite set of natural numbers J satisfies that
$J\cup \{0\}$ is not Sidon if and only if for any operator T, the disjoint hypercyclicity of 
$\{T^j:j\in J\}$ implies that T is weakly mixing. As an application we show the existence of a non-weakly mixing operator T such that 
$T\oplus T^2\oplus\cdots \oplus T^n$ is hypercyclic for every n.
Orbits of homogeneous polynomials on Banach spaces
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- Journal:
- Ergodic Theory and Dynamical Systems / Volume 41 / Issue 6 / June 2021
- Published online by Cambridge University Press:
- 13 April 2020, pp. 1627-1655
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- June 2021
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We study the dynamics induced by homogeneous polynomials on Banach spaces. It is known that no homogeneous polynomial defined on a Banach space can have a dense orbit. We show a simple and natural example of a homogeneous polynomial with an orbit that is at the same time
$\unicode[STIX]{x1D6FF}$-dense (the orbit meets every ball of radius 
$\unicode[STIX]{x1D6FF}$), weakly dense and such that 
$\unicode[STIX]{x1D6E4}\cdot \text{Orb}_{P}(x)$ is dense for every 
$\unicode[STIX]{x1D6E4}\subset \mathbb{C}$ that either is unbounded or has 0 as an accumulation point. Moreover, we generalize the construction to arbitrary infinite-dimensional separable Banach spaces. To prove this, we study Julia sets of homogeneous polynomials on Banach spaces.
