Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Is time the real line?   This paper is devoted to discussing the topological structure of the arrow of
time. In the literature, it is often accepted that its algebraic and
topological structures are that of a one-dimensional Euclidean space
$\mathbb{E}^1$, although a critical review on the subject is not easy to be
found. Hence, leveraging on an operational approach, we collect evidences to
identify it structurally as a normed vector space $(\mathbb{Q}, |\cdot|)$, and
take a leap of abstraction to complete it, up to isometries, to the real line.
During the development of the paper, the space-time is recognized as a
fibration, with the fibers being the sets of simultaneous events. The
corresponding topology is also exposed: open sets naturally arise within our
construction, showing that the classical space-time is non-Hausdorff. The
transition from relativistic to classical regimes is explored too.

20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs