Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Topological Censorship   All three-manifolds are known to occur as Cauchy surfaces of asymptotically
flat vacuum spacetimes and of spacetimes with positive-energy sources. We prove
here the conjecture that general relativity does not allow an observer to probe
the topology of spacetime: any topological structure collapses too quickly to
allow light to traverse it. More precisely, in a globally hyperbolic,
asymptotically flat spacetime satisfying the null energy condition, every
causal curve from $\scri^-$ to ${\scri}^+$ is homotopic to a topologically
trivial curve from $\scri^-$ to ${\scri}^+$. (If the Poincar\'e conjecture is
false, the theorem does not prevent one from probing fake 3-spheres).

27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an