Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The dimensionless age of the Universe: a riddle for our time   We present the interesting coincidence of cosmology and astrophysics that
points toward a dimensionless age of the universe H_0*t_0 that is close to one.
Despite cosmic deceleration for 9 Gyr and acceleration since then, we find
H_0t*_0 = 0.96 +/- 0.01 for the LCDM model that fits SN Ia data from
Pan-STARRS, CMB power spectra, and baryon acoustic oscillations. Similarly,
astrophysical measures of stellar ages and the Hubble constant derived from
redshifts and distances point to H_0*t ~ 1.0 +/- 0.1$. The wide range of
possible values for H_0*t_0 realized during comic evolution means that we live
at what appears to be a special time. This "synchronicity problem" is not
precisely the same as the usual Coincidence problem because there are
combinations of Omega_Matter and Omega_Lambda for which the usual coincidence
problem holds but for which H_0*t_0 is not close to 1.

28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
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The categories of this paper are: eess
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat