Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Isomorphic limit ultrapowers for infinitary logic   The logic L^1_\theta introduced in [Sh:797]; it is the maximal logic below
L_theta theta in which a well ordering is not definable. We investigate it for
theta a compact cardinal. We prove it satisfies several parallel of classical
theorems on first order logic, strengthening the thesis that it is a natural
logic. In particular, two models are L^1_theta-equivalent iff for some
omega-sequence of theta-complete ultrafilters, the iterated ultra-powers by it
of those two models are isomorphic.

18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
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The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
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The categories of this paper are: hep-ex
28
The categories of this paper are: alg-geom