Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Simple Quantum-Mechanical Model of Spacetime I: Microscopic Properties
  of Spacetime   This is the first part in a series of two papers, where we consider a
specific microscopic model of spacetime. In our model Planck size quantum black
holes are taken to be the fundamental building blocks of space and time.
Spacetime is assumed to be a graph, where black holes lie on the vertices. In
this first paper we construct our model in details, and show how classical
spacetime emerges at the long distance limit from our model. We also consider
the statistics of spacetime.

4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph