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Fuglede's conjecture fails in 4 dimensions over odd prime fields. (arXiv:1901.08734v2 [math.NT] UPDATED)
来源于:arXiv
Fuglede's conjecture in $\mathbb{Z}_{p}^{d}$, $p$ a prime, says that a subset
$E$ tiles $\mathbb{Z}_{p}^{d}$ by translation if and only if $E$ is spectral,
meaning any complex-valued function $f$ on $E$ can be written as a linear
combination of characters orthogonal with respect to $E$. We disprove Fuglede's
conjecture in $\mathbb{Z}_p^4$ for all odd primes $p$, by using log-Hadamard
matrices to exhibit spectral sets of size $2p$ which do not tile, extending the
result of Aten et al. that the conjecture fails in $\mathbb{Z}_p^4$ for primes
$p \equiv 3 \pmod 4$ and in $\mathbb{Z}_p^5$ for all odd primes $p$. We also
prove the conjecture in $\mathbb{Z}_2^4$, resolving all cases of
four-dimensional vector spaces over prime fields. We give an example showing
that our simple proof method does not extend to higher dimensions. However, we
include a link to a computer program which the authors have used to verify
that, nevertheless, the conjecture holds in $\mathbb{Z}_2^5$ and
$\mathbb{Z}_2^6$ 查看全文>>