Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Around MOND: Lagrangians, Hubble Equations, Perturbations and External
  Field Effect   The MOdified Newtonian Dynamics (MOND) is presented here, as well as a theory
that can be linked to it: the theory of the Aether, a four-vector field
breaking Lorentz invariance. The form of its Lagrangian is studied, then basic
equations of the theory are rederived in a detailed way, and calculated for
different metrics, exploring the impact of non-zero spatial terms of the
Aether. A brief attempt of making the Aether Lagrangian depend on a scalar
field is presented. An analytic solving of a galaxy model with an external
field is described, which highlights the MONDian external field effect that
breaks the strong equivalence principle.

1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con