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).

I am interested in foundational tests of our best current fundamental theories of physics, the theory of gravity, General Relativity, and the Standard Model of particle physics. So far, I have been studying the theoretical and experimental aspects of testing the Einstein Equivalence Principle, a foundation of General Relativity. In particular I have focused on tests of Lorentz symmetry, the spacetime symmetry of Special Relativity, and also the discrete spacetime symmetry called CPT. The motivation for this work is twofold. First, spacetime symmetries are cornerstone of modern physics. As such, it should be an experimental precedent to test these 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 spacetime symmetry. In the ongoing search for new physics in turns out that high-precision, typically low-energy tests of Lorentz and CPT symmetry offer a promising alternative to conventional high-energy accelerator experiments.

This area of research has grown considerably in the past decades and there is now a dedicated research center at Indiana University called the Indiana University Center for Spacetime Symmetries (IUCSS).

My own work, in the publications below, has been on the electromagnetic, nuclear, and gravitational sectors of a general effective field theory framework for testing Lorentz and CPT 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:

• Search for anisotropic, birefringent spacetime-symmetry breaking in gravitational wave propagation from GWTC-3 , archived pre-print link
• Short-range forces due to Lorentz-symmetry violation , archived pre-print link
• New Signals in Precision Gravity Tests and Beyond, Presented at the Ninth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, May 17-26 link
• Analysis of birefringence and dispersion effects from spacetime-symmetry breaking in gravitational waves, accepted to Universe link
• Construction of higher-order metric fluctuation terms in spacetime symmetry-breaking effective field theory Symmetry 13, 834 (2021), link
• Constraining velocity-dependent Lorentz/CPT-violations using Lunar Laser Ranging Phys. Rev. D 103, 064055 (2021) link
• A 3+1 Formulation of the Standard-Model Extension Gravity Sector Phys. Rev. D 103,044010 (2021) link
• "New Test of Lorentz Invariance Using the MICROSCOPE Space Mission" Phys. Rev. Lett. 123, 231102 (2019) link
• "A 3+1 Decomposition of the minimal Standard-Model Extension Gravitational Sector" presented by Albin Nilsson at the Eighth Meeting on CPT and Lorentz Symmetry, May 2019 link
• "Testing the Gravitational Weak Equivalence Principle in the Standard-Model Extension with Binary Pulsars" Phys. Rev. D 99, 084017 (2019) link
• "Testing velocity-dependent CPT-violating gravitational forces with radio pulsars" Phys. Rev. D 98, 084049 (2018) link
• Relating Noncommutative SO(2,3)* Gravity to the Lorentz-Violating Standard-Model Extension, Symmetry 2018, 10, 480 link
• Velocity-dependent inverse cubic force and solar-system gravity tests, Phys. Rev. D 96, 064035 (2017) link
• Lorentz-symmetry test at Planck-scale suppression with nucleons in a spin-polarized Cesium cold atom clock, (with Helene Pihan-Le Bars et al), Phys. Rev. D 95, 075026 (2017) link
• Tests of Lorentz symmetry in the gravitational sector, with Aurelien Hees et al, review article, Universe 2, 4 (2016) link
• Anisotropic cubic curvature couplings, Phys. Rev. D 94, 065029 (2016) link
• Constraints on SME coefficients from Lunar Laser Ranging, Very Long Baseline Interferometry, and Asteroid Dynamics, (with C. Le Poncin-Lafitte et al) presented at the Seventh Meeting on CPT and Lorentz Symmetry, June 2016, link
• Gravity Sector of the SME, presented at the Seventh Meeting on CPT and Lorentz Symmetry, June 2016, link
• Combined search for Lorentz violation in short-range gravity (with C.G. Shao et al), Phys. Rev. Lett. 117, 071102 (2016) link
• Testing Lorentz symmetry with planetary dynamics (with A. Hees et al.) Phys. Rev. D 92, 064049 (2015) link
• What do we know about Lorentz symmetry? presented at the 50th Rencontres de Moriond, "Gravitation: 100 years after GR" link
• Short-range gravity and Lorentz violation, (with V.A. Kostelecky and Rui Xu), Phys. Rev. D 91 , 022006 (2015) [TOPCITE 100+] link
• Quantum Tests of the Einstein Equivalence Principle with the STE-QUEST Space Mission, Advances in Space Research 55, 501 (2015) link
• Limits on violations of Lorentz Symmetry from Gravity Probe B, Phys. Rev. D 88, 102001 (2013) (with J. Overduin and R. Everett) link
• Local Lorentz-Symmetry Breaking and Gravity, presented at the Sixth Meeting on CPT and Lorentz Symmetry, June 2013, link
• Constraints on violations of Lorentz Symmetry from Gravity Probe B, (with J. Overduin and R. Everett), presented at the Sixth Meeting on CPT and Lorentz Symmetry, June 2013, link
• Light-bending tests of Lorentz invariance, (with undergraduate Rhondale Tso), Phys. Rev. D 84, 085025 (2011) link
• New tests of General Relativity, in Matters of Gravity, The Newsletter of the Topical Group on Gravitation of the American Physical Society, Volume 36, Fall 2010 link
• Gravity Couplings in the Standard-Model Extension, in CPT and Lorentz Symmetry V, World Scientific, 2011. link
• Gravitational Lensing and Light Bending as tests of Lorentz Symmetry,(with Rhondale Tso), in CPT and Lorentz Symmetry V, World Scientific, 2011.
• Lorentz-violating gravitoelectromagnetism, Phys. Rev. D 82, 065012 (2010). [TOPCITE 50+] link
• Lorentz violation with an antisymmetric tensor, (with B. Altschul and V.A. Kostelecky), Phys. Rev. D 81, 065028 (2010). [TOPCITE 100+] link
• Lorentz Violation and Gravity, in Proceedings of the International Astronomical Union (IAU) Symposium 261: Relativity in Fundamental Astronomy, 2009. link
• Catching relativity violations with atoms, Physics 2, 58, 2009. link
• Time-delay and Doppler tests of the Lorentz symmetry of gravity,Phys. Rev. D 80, 044004 (2009). [TOPCITE 50+] link
• Testing Lorentz Symmetry with Gravity, in CPT and Lorentz Symmetry IV, World Scientific, 2008. link
• Lorentz Violation and Gravity, Ph.D. dissertation, Indiana University, 2007.
• Signals for Lorentz Violation in Post-Newtonian Gravity (with V.A. Kostelecky), Phys. Rev. D 74, 045001 (2006). [TOPCITE 300+] link
• Lorentz-Violating Electromagnetostatics, in CPT and Lorentz Symmetry III, World Scientific, 2005. link
• Lorentz-Violating Electrostatics and Magnetostatics (with V.A. Kostelecky), Phys. Rev. D 70, 076006 (2004). [TOPCITE 150+] link

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 (minimal) 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 experiments, solar-system observations, and beyond. 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.

Kostelecky and Tasson have analyzed matter-gravity couplings in the SME framework. Their work reveals new types of unexplored signals for Lorentz violation in gravitational tests:

More recently, Bailey, Kostelecky, Mewes, Tasson and Xu have studied the gravity sector nonminimal SME in a series of publications. This introduces a large number of coefficients classified by the mass dimension of the operators appearing in the lagrangian. These coefficients can be measured in precision short-range gravity tests as well as gravitational wave measurements. The publications on the nonminimal gravitational SME include:

There are nineteen independent coefficients for Lorentz violation in the "minimal" 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.

Gravity sector experimental/observational analyses using the SME framework

• Probing of violation of Lorentz invariance by ultracold neutrons in the Standard Model Extension, A.N. Ivanov et al, accepted in Physics Letters B link
• Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A, B. Abbott et al. (LSC collaboration), Astrophys. J. 848, L2 (2017) link
• Limits on Lorentz violation in gravity form worldwide superconducting gravimeters, accepted in Physical Review D link
• Lorentz symmetry violations from matter-gravity couplings with Lunar Laser Ranging, A. Bourgoin et al., submitted for publication link
• Superconducting Gravimeter Tests of Local Lorentz Invariance, N. Flowers et al., accepted in Phys. Rev. Lett. link
• Testing Lorentz symmetry with Lunar Laser Ranging, A. Bourgoin et al., Phys. Rev. Lett. 117, 241301 (2016) link
• Lorentz symmetry and Very Long Baseline Interferometry, C. Le Poncin-Lafitte, A. Hees, and S. Lambert, Phys. Rev. D 94, 125030 (2016) link
• Tests of gravitation with Gaia observations of Solar System Objects, A. Hees, D. Hestroffer, C. Le Poncin-Lafitte, and P. David link
• Search for Lorentz invariance through tests of the gravitational inverse square law at short-ranges, C.G. Shao et al., Phys. Rev. D 91, 102007 (2015) link
• Search for Lorentz violation in short-range gravity, J.C. Long and V.A. Kostelecky, Phys. Rev. D 91, 092003 (2015) link
• New pulsar limit on local Lorentz invariance violation of gravity in the standard-model extension,Lijing Shao, Phys. Rev. D 90, 122009 (2014) link
• Tests of local Lorentz invariance violation of gravity in the standard model extension with pulsars,Lijing Shao, Phys. Rev. Lett. 112, 111103 (2014) link
• Equivalence Principle and Bound Kinetic Energy, Michael Hohensee, Holger Mueller, and R.B. Wiringa link
• Simulations of Solar System observations in alternative theories of gravity, Aurelien Hees et al., proceedings of the 13th Marcel Grossmann Meeting link
• Orbital effects of Lorentz-violating Standard Model Extension gravitomagnetism around a static body: a sensitivity analysis, Lorenzo Iorio, Class. Quant. Grav. 29, 175007 (2012) link
• Equivalence Principle and Gravitational Redshift, Michael Hohensee, Steven Chu, Achim Peters, Holger Mueller, Phys. Rev. Lett. 106, 151102 (2011). link
• Gravitational Redshift, Equivalence Principle, and Matter Waves, Michael Hohensee et al. link
• Search for Lorentz Violation in a High-Frequency Gravitational Experiment below 50 microns, D. Bennet, V. Skavysh, and J. Long, presented at the Fifth Meeting on CPT and Lorentz Symmetry link
• Atom interferometry tests of local Lorentz invariance in gravity and electrodynamics, Keng-Yeow Chung, Sheng-wey Chiow, Sven Herrmann, Steven Chu, Holger Mueller, Phys. Rev. D 80, 016002 (2009). link
• Atom interferometry tests of the isotropy of post-Newtonian gravity, Holger Mueller, Sheng-wey Chiow, Sven Herrmann, Steven Chu, Keng-Yeow Chung, Phys. Rev. Lett. 100, 031101 (2008). link
• Search for Lorentz Violation in a High-Frequency Gravitational Experiment below 50 microns, Joshua Long, in V.A. Kostelecky (editor), CPT and Lorentz Symmetry IV, World Scientific, 2008.
• Testing for Lorentz Violation: Constraints on Standard-Model Extension Parameters via Lunar Laser Ranging, James B.R. Battat , John F. Chandler, Christopher W. Stubbs, Phys. Rev. Lett. 99, 241103 (2007). link
• From Gravity Probe B to STEP: Testing Einstein in Space, James Overduin, in V.A. Kostelecky (editor), CPT and Lorentz Symmetry IV, World Scientific, 2008.
• Atom Interferometry Experiments in Fundamental Physics, Holger Mueller, in V.A. Kostelecky (editor), CPT and Lorentz Symmetry IV, World Scientific, 2008.

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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