Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Faint galaxies around quasars at z=1 and gravitational lensing of
  distant objects   Very deep imaging data of three optically luminous radio-loud quasars with
redshifts between z=0.9 and z=1.36 are presented. The data are complete for
galaxies down to R=26. There is no evidence for excess numbers of galaxies
around the quasars; foreground galaxy clusters are excluded by the data as well
as clusters with richness classes greater than 1 associated with the quasars.
We find clear evidence for gravitational lensing for two quasars. It is further
shown that due to the high surface density of galaxies all distant (z>1)
objects are moderately affected by gravitational lensing; the amplification
factors are estimated to be in the range 1.1-1.5.

16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin