Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An Enlargeability Obstruction for Spacetimes with both Big Bang and Big
  Crunch   Given a spacelike hypersurface $M$ of a time-oriented Lorentzian manifold
$(\overline{M}, \overline{g})$, the pair $(g, k)$ consisting of the induced
Riemannian metric $g$ and the second fundamental form $k$ is known as initial
data set. In this article, we study the space of all initial data sets $(g, k)$
on a fixed closed manifold $M$ that are subject to a strict version of the
dominant energy condition. Whereas the pairs of the form $(g, \tau g)$ and $(g,
-\tau g)$, for a sufficiently large $\tau > 0$, belong to the same
path-component of this space when $M$ admits a positive scalar curvature
metric, it was observed in a previous work \cite{arXiv:1906.00099} that this is
not the case when the existence of a positive scalar curvature metric on $M$ is
obstructed by $\alpha(M) \neq 0$. In the present article we extend this
non-connectedness result to Gromov-Lawson's enlargeability obstruction, which
covers many examples, also in dimension $3$. In the context of relativity
theory, this result may be interpreted as excluding the existence of certain
globally hyperbolic spacetimes with both a big bang and a big crunch
singularity

18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
27
The categories of this paper are: comp-gas
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph