52 research outputs found
The finite tiling problem is undecidable in the hyperbolic plane
In this paper, we consider the finite tiling problem which was proved
undecidable in the Euclidean plane by Jarkko Kari in 1994. Here, we prove that
the same problem for the hyperbolic plane is also undecidable
Tiling Problems on Baumslag-Solitar groups
We exhibit a weakly aperiodic tile set for Baumslag-Solitar groups, and prove
that the domino problem is undecidable on these groups. A consequence of our
construction is the existence of an arecursive tile set on Baumslag-Solitar
groups.Comment: In Proceedings MCU 2013, arXiv:1309.104
About the domino problem in the hyperbolic plane from an algorithmic point of view
In this paper, we prove that the general problem of tiling the hyperbolic
plane with \`a la Wang tiles is undecidable.Comment: 11 pages, 6 figure
The large scale geometry of strongly aperiodic subshifts of finite type
A subshift on a group G is a closed, G-invariant subset of A^G, for some
finite set A. It is said to be a subshift of finite type (SFT) if it is defined
by a finite collection of 'forbidden patterns', to be strongly aperiodic if all
point stabilizers are trivial, and weakly aperiodic if all point stabilizers
are infinite index in G. We show that groups with at least 2 ends have a
strongly aperiodic SFT, and that having such an SFT is a QI invariant for
finitely presented torsion free groups. We show that a finitely presented
torsion free group with no weakly aperiodic SFT must be QI-rigid. The domino
problem on G asks whether the SFT specified by a given set of forbidden
patterns is empty. We show that decidability of the domino problem is a QI
invariant.Comment: 23 pages, 6 figures. The proof of the main theorem has been
simplified and some new corollaries deduce
Around the Domino Problem – Combinatorial Structures and Algebraic Tools
Given a finite set of square tiles, the domino problem is the question of whether is it possible to tile the plane using these tiles. This problem is known to be undecidable in the planar case, and is strongly linked to the question of the periodicity of the tiling. In this thesis we look at this problem in two different ways: first, we look at the particular case of low complexity tilings and second we generalize it to more general structures than the plane, groups.
A tiling of the plane is said of low complexity if there are at most mn rectangles of size m × n appearing in it. Nivat conjectured in 1997 that any such tiling must be periodic, with the consequence that the domino problem would be decidable for low complexity tilings. Using algebraic tools introduced by Kari and Szabados, we prove a generalized version of Nivat’s conjecture for a particular class of tilings (a subclass of what is called of algebraic subshifts). We also manage to prove that Nivat’s conjecture holds for uniformly recurrent tilings, with the consequence that the domino problem is indeed decidable for low-complexity tilings.
The domino problem can be formulated in the more general context of Cayley graphs of groups. In this thesis, we develop new techniques allowing to relate the Cayley graph of some groups with graphs of substitutions on words. A first technique allows us to show that there exists both strongly periodic and weakly-but-not-strongly aperiodic tilings of the Baumslag-Solitar groups BS(1, n). A second technique is used to show that the domino problem is undecidable for surface groups. Which provides yet another class of groups verifying the conjecture saying that the domino problem of a group is decidable if and only if the group is virtually free
On the injectivity of the global function of a cellular automaton in the hyperbolic plane (extended abstract)
In this paper, we look at the following question. We consider cellular
automata in the hyperbolic plane, (see Margenstern, 2000, 2007 and Margenstern,
Morita, 2001) and we consider the global function defined on all possible
configurations. Is the injectivity of this function undecidable? The problem
was answered positively in the case of the Euclidean plane by Jarkko Kari, in
1994. In the present paper, we show that the answer is also positive for the
hyperbolic plane: the problem is undecidable
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