Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: New Steiner systems from old ones by paramodifications   Techniques of producing new combinatorial structures from old ones are
commonly called trades. The switching principle applies for a broad class of
designs: it is a local transformation that modifies two columns of the
incidence matrix. In this paper, we present a construction, which is a
generalization of the switching transform for the class of Steiner 2-designs.
We call this construction paramodification of Steiner 2-designs, since it
modifies the parallelism of a subsystem. We study in more detail the
paramodifications of affine planes, Steiner triple systems, and abstract
unitals. Computational results show that paramodification can construct many
new unitals.

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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: chao-dyn
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The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an