Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On weak Fraisse limits   Using the natural action of $S_\infty$ we show that a countable hereditary
class $\mathcal C$ of finitely generated structures has the joint embedding
property (JEP) and the weak amalgamation property (WAP) if and only if there is
a structure $M$ whose isomorphism type is comeager in the space of all
countable, infinitely generated structures with age in $\mathcal C$. In this
case, $M$ is the weak Fra\"iss\'e limit of $\mathcal C$. This applies in
particular to countable structures with generic automorphisms and recovers a
result by Kechris and Rosendal [Proc. Lond. Math. Soc., 2007].

14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
18
The categories of this paper are: econ
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th