Quentin's Research Interests

Attention Space Physics students with an interest in theory! I have several research projects related to my research area which I have designed with the Space Physics curriculum in mind. Anyone interested is encouraged to come and talk to me (email:baileyq@erau.edu).

My research is currently focused on the theoretical and experimental aspects of testing Lorentz symmetry, the spacetime symmetry of Special Relativity. The motivation for this work is twofold. First, Lorentz symmetry is a cornerstone of modern physics. As such, it should be an experimental precedent to test this principle in as many ways as possible. Second, recent work on fundamental theories of physics, that attempt to unify the Standard Model of particle physics and General Relativity, has pointed to the possibility of deviations from perfect Lorentz symmetry. In the ongoing search for new physics, high-precision, typically low-energy tests of Lorentz symmetry offer a promising alternative to conventional high-energy accelerator experiments.


My own work, in the publications below, has been focused on the electromagnetic and gravitational sectors of a general theoretical framework for testing Lorentz symmetry called the Standard-Model Extension (SME). Information about the SME theoretical and experimental program, including links to refereed journal articles, books, and popular magazine articles, can be found at this link: Information about CPT and Lorentz Violation.

Publications:

In the SME formalism, Lorentz violation for a given particle type (species) is described by its coefficients for Lorentz violation. In certain special cases, we can visualize these coefficients as a background field of arrows, pointing in some direction, that affects our measuring apparatus (rods and clocks) as they move or rotate through the background. This is illustrated in the animation above for blue and green rods and clocks. As the two sets of rods and clocks rotate their relative lengths and ticking rates will change if Lorentz symmetry is violated.

If deviations from perfect Lorentz symmetry occur in nature, they must be miniscule. This implies that the best method for finding Lorentz violation is to use the most sensitive "rods" and "clocks" available with today's technology.

In practice, a variety of real physical systems can be used as effective rods and clocks. For example, some of the systems that have been used to test Lorentz symmetry include hydrogen atoms, cesium atoms, torsion pendula, superconducting gravimeters, electromagnetic resonant cavities, the Earth-Moon system, and even distant light propagating from the early universe.

For weak gravitational fields, there are nine independent coefficients for Lorentz violation in the pure-gravity sector of the SME. These coefficients would vanish in the limit that (local) Lorentz symmetry holds for gravity. Searches for nonzero gravity coefficients include a variety of laboratory and solar system experiments. For example, analysis of lunar laser ranging data can place stringent constraints on these coefficients. In the figure below, Lorentz violation (arrows) could cause the Moon to deviate from its usual elliptical path.

In contrast to gravity, there are nineteen independent coefficients for Lorentz violation in the simplest version of the photon sector of the SME. Astrophysical observations and laboratory resonant-cavity tests have probed for these photon coefficients. Lorentz violation could also affect other known particles, such as neutrinos, and many experiments have already been performed.

So far, no statistically convincing evidence exists that any coefficients for Lorentz violation are nonzero. However, future experiments may dramatically improve existing sensitivities, and may yet discover miniscule Lorentz violation.

Pure-gravity sector SME experimental analysis:

Other SME experiments

A summary of the current experimental constraints on the many coefficients for Lorentz violation in the SME can be found here.

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