Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Redshift, Time, Spectrum - the most distant radio quasars with VLBI   The highest-redshift quasars are still rare and valuable objects for
observational astrophysics and cosmology. They provide important constraints on
the growth of the earliest supermassive black holes in the Universe, and
information on the physical conditions in their environment. Among the nearly
60 quasars currently known at redshifts z>5.7, only a handful are "strong"
emitters in radio continuum. These can be targets of sensitive high-resolution
Very Long Baseline Interferometry (VLBI) observations to reveal their innermost
structure, down to ~10 pc linear scales. We review the results of our earlier
European VLBI Network (EVN) experiments on three of the most distant radio
quasars known to date, and give a preliminary report on the EVN detection of a
fourth one. The results obtained so far suggest that we see really young active
galactic nuclei - not just in a cosmological sense but also in terms of their
active life in radio.

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The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
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The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn