Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A uniqueness theorem for 3D semilinear wave equations satisfying the
  null condition   In this paper, we prove a uniqueness theorem for a system of semilinear wave
equations satisfying the null condition in $\mathbb{R}^{1+3}$. Suppose that two
global solutions with $C_c^\infty$ initial data have equal initial data outside
a ball and equal radiation fields outside a light cone. We show that these two
solutions are equal either outside a hyperboloid or everywhere in the
spacetime, depending on the sizes of the ball and the light cone.

7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
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The categories of this paper are: alg-geom
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The categories of this paper are: chao-dyn
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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: econ
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga