Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Geodesic structure and quasinormal modes of a tidally perturbed
  spacetime   Tidal perturbations play an important role in the study of the dynamics in
the classical two-body system. Understanding tidal effects in strong-field
regions may allow one to use gravitational-wave or electromagnetic observations
to locate or constraint the location of possible companions. Here, we
investigate how timelike and null geodesics of a Schwarzschild black hole are
affected in the presence of a companion. There is a panoply of new effects. In
some limiting cases, we find analytical solutions for closed null or timelike
geodesics. Our results show that light ring period as measured by a far-away
observer can be eiter shorter or longer, depending on the location of the
companion. We also show that there are closed lightlike trajectories which are
elliptic (for equatorial companions), and that timelike particles are affected
in a similar manner. Finally, we attempt at estimating the ringdown from
tidally perturbed geometries. Our results indicate that there are two stages in
the relaxation of such geometries, one associated with a prompt decay of waves
around the deformed photonsphere, and a later relaxation of the global
geometry. These results are consistent with previous, full numerical studies.

23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th