Theoretical Aspects of the Equivalence Principle

Abstract

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.

21 pages, no figures; submitted to a "focus issue" of Classical and Quantum Gravity on Tests of the Weak Equivalence Principle, organized by Clive Speake and Clifford Will

References in corpus (9)

• Flux Compactification
• Test of the Equivalence Principle Using a Rotating Torsion Balance
• Equivalence Principle Violations and Couplings of a Light Dilaton
• Phenomenology of the Equivalence Principle with Light Scalars
• Constraints on the variability of quark masses from nuclear binding
• Naturalness of exponential cosmon potentials and the cosmological constant problem
• Likely values of the Higgs vev
• Eotvos bounds on couplings of fundamental parameters to gravity
• The Nuclear Central Force in the Chiral Limit

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