Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Implications for the Hubble tension from the ages of the oldest
  astrophysical objects   We use the ages of old astrophysical objects (OAO) in the redshift range $0
\lesssim z \lesssim 8$ as stringent tests of the late-time cosmic expansion
history. Since the age of the Universe at any redshift is inversely
proportional to $H_0$, requiring that the Universe be older than the oldest
objects it contains at any redshift, provides an upper limit on $H_0$. Using a
combination of galaxies imaged from the CANDELS program and various high-$z$
quasars, we construct an age-redshift diagram of $\gtrsim 100$ OAO up to $z
\sim 8$. Assuming the $\Lambda$CDM model at late times, we find the
95\%~confidence level upper limit $H_0<73.2\,{\rm km}/{\rm s}/{\rm Mpc}$, in
slight disagreement with a host of local $H_0$ measurements. Taken at face
value, and assuming that the OAO ages are reliable, this suggests that
ultimately a combination of pre- and post-recombination ($z \lesssim 10$) new
physics might be required to reconcile cosmic ages with early-time and local
$H_0$ measurements. In the context of the Hubble tension, our results motivate
the study of either combined global pre- and post-recombination modifications
to $\Lambda$CDM, or local new physics which only affects the local $H_0$
measurements.

11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin