论文标题
ULAM设置在新设置中
Ulam Sets in New Settings
论文作者
论文摘要
经典的ULAM序列被递归地定义如下:$ a_1 = 1 $,$ a_2 = 2 $和$ a_n $,对于$ n> 2 $,是序列中最小的整数,可以独特地写成两个不同的早期术语的总和。当我们让$ a_2 $变化时,该序列以其神秘的准周期行为和令人惊讶的刚性而闻名。该定义可以推广到具有二进制操作和有效大小的不同设置中的其他一组发电机。由于这些元素并不总是有天然的线性顺序,因此所得的集合称为ULAM集。在本文中,我们研究了新环境中的ULAM集合。首先,我们研究了自由组的规范ULAM集合的结构。这是对非共同组中ULAM集合的首次研究。我们证明了几个对称结果,并证明了最终具有固定前缀的周期性单词的周期性结果。然后,我们在$ \ mathbb {z} \ times(\ mathbb {z}/n \ mathbb {z})$中研究ULAM集合,并证明无限类的初始集合。我们还研究了一种有趣的现象,即后来的元素分解为发电机的总和。最后,我们考虑$ \ MATHCAL {V} $ - SETS,这是一个变体,其中汇总不需要不同;我们专注于$ \ mathcal {v} $ - 在$ \ mathbb {z}^2 $中设置。
The classical Ulam sequence is defined recursively as follows: $a_1=1$, $a_2=2$, and $a_n$, for $n > 2$, is the smallest integer not already in the sequence that can be written uniquely as the sum of two distinct earlier terms. This sequence is known for its mysterious quasi-periodic behavior and its surprising rigidity when we let $a_2$ vary. This definition can be generalized to other sets of generators in different settings with a binary operation and a valid notion of size. Since there is not always a natural linear ordering of the elements, the resulting collections are called Ulam sets. In this paper, we study Ulam sets in new settings. First, we investigate the structure of canonical Ulam sets in free groups; this is the first investigation of Ulam sets in noncommutative groups. We prove several symmetry results and prove a periodicity result for eventually periodic words with fixed prefixes. Then, we study Ulam sets in $\mathbb{Z}\times (\mathbb{Z}/n\mathbb{Z})$ and prove regularity for an infinite class of initial sets. We also examine an intriguing phenomenon about decompositions of later elements into sums of the generators. Finally, we consider $\mathcal{V}$-sets, a variant where the summands are not required to be distinct; we focus on $\mathcal{V}$-sets in $\mathbb{Z}^2$.