Equivalence principles, spacetime structure and the cosmic connection

Abstract

After reviewing the meaning of various equivalence principles and the structure of electrodynamics, we give a fairly detailed account of the construction of the light cone and a core metric from the equivalence principle for the photon (no birefringence, no polarization rotation and no amplification/attenuation in propagation) in the framework of linear electrodynamics using cosmic connections/observations as empirical support. The cosmic nonbirefringent propagation of photons independent of energy and polarization verifies the Galileo Equivalence Principle [Universality of Propagation] for photons/electromagnetic wave packets in spacetime. This nonbirefringence constrains the spacetime constitutive tensor to high precision to a core metric form with an axion degree and a dilaton degree of freedom. Thus comes the metric with axion and dilation. Constraints on axion and dilaton from astrophysical/cosmic propagation are reviewed. Eötvös-type experiments, Hughes-Drever-type experiments, redshift experiments then constrain and tie this core metric to agree with the matter metric, and hence a unique physical metric and universality of metrology. We summarize these experiments and review how the Galileo equivalence principle constrains the Einstein Equivalence Principle (EEP) theoretically. In local physics this physcical metric gives the Lorentz/Poincaré covariance. Understanding that the metric and EEP come from the vacuum as a medium of electrodynamics in the linear regime, efforts to actively look for potential effects beyond this linear scheme are warranted. We emphasize the importance of doing Eötvös-type experiments or other type experiments using polarized bodies/polarized particles. We review the theoretical progress on the issue of gyrogravitational ratio for fundamental particles and update the experimental progress on the measurements of possible long range/intermediate range spin-spin, spin-monopole and spincosmos interactions.

Lorentz-violating scalar Hamiltonian and the equivalence principle in a static metric

“…We divide the right hand side of ( 16) into two parts. In fact, comparing with the NR Hamiltonian ( 26) obtained by a quite different method, we find that except for the ∇χ • ˆ p term (belonging to the latter brace), the part enclosed by the former brace is consistent with (26) up to the desired orders, while those in the latter brace may be classified as divergent higher order terms. Indeed we can even verify this coincidence (of the NR results obtained with different methods) by choosing another metric, for example, the uniform accelerating metric.…”

“…Compared with (26), we see that except for the LV term proportional to ˆ p 2 4m 3 , the NR Hamiltonian obtained by direct FWT is completely the same as that obtained with CVZ method, though to the next lowest order, the latter can be obtained without substantially calculating any commutators. At first glance, this is a little surprising, because the results are expected to differ by a pseudounitary transformation, however, inspecting the CVZ method, we see that it is exactly the pseudounitary transformation which ensures the NR Hamiltonian is the same as that obtained with direct FWT [38].…”

“…In this subsection, we show that direct FWT on (19) can also lead to the same result in (26). For calculational convenience, we can separate both E and O into LI and LV parts, i.e., E = E LI + E LV and O = O LI + O LV .…”

“…Many generalized theories of gravity [11] [15] [25] [26] fit into this category, but in our viewpoint, the gravity sector of SME [8] is more suitable for such a task. In SME, WEP violation is associated with Lorentz and CPT violation since various LV coefficients can also be speciesdependent, which enables more exotic violation effects [27] and makes this framework as broad as it can be.…”

Premetric approach in gravity and electrodynamics

“…• Natural extensions with axion, skewon, and dilaton fields 9 • Natural extension to parity odd contributions 5,10 • Convenient framework to discuss Lorentz violating models 11 • Nonlinear gravity models, f (R) and f (T ), in particular 12,13 • Nonlocal constitutive laws 14,15…”