We construct ‘‘almost periodic’’ unbounded domains, where a large class of elliptic spectral problems have essential spectra possessing peculiar structure: they consist of monotone, non-negative sequences of isolated points and thus have infinitely many gaps.

中文翻译：

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椭圆形问题的基本频谱的病理学，该问题由周期性辐条变细在无限远处串接的周期珠子

我们构造了``几乎周期的''无界域，其中一大类椭圆光谱问题具有具有特殊结构的基本光谱：它们由孤立点的单调，非负序列组成，因此具有无限多个间隙。