Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the global existence of time   The existence of a global time is often taken for granted but should instead
be considered as a matter of investigation. By using the tools of global
Lorentzian geometry I show that, under physically reasonable conditions, the
impossibility of finding a global time implies the singularity of spacetime.

26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys