Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theoretical Aspects of the Equivalence Principle   We review several theoretical aspects of the Equivalence Principle (EP). We
emphasize the unsatisfactory fact that the EP maintains the absolute character
of the coupling constants of physics while General Relativity, and its
generalizations (Kaluza-Klein,..., String Theory), suggest that all absolute
structures should be replaced by dynamical entities. We discuss the
EP-violation phenomenology of dilaton-like models, which is likely to be
dominated by the linear superposition of two effects: a signal proportional to
the nuclear Coulomb energy, related to the variation of the fine-structure
constant, and a signal proportional to the surface nuclear binding energy,
related to the variation of the light quark masses. We recall the various
theoretical arguments (including a recently proposed anthropic argument)
suggesting that the EP be violated at a small, but not unmeasurably small
level. This motivates the need for improved tests of the EP. These tests are
probing new territories in physics that are related to deep, and mysterious,
issues in fundamental physics.

23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat