Lorentz-Violating Matter-Gravity Couplings in Small-Eccentricity Binary Pulsars

Abstract

Lorentz symmetry is an important concept in modern physics. Precision pulsar timing was used to put tight constraints on the coefficients for Lorentz violation in the pure-gravity sector of the Standard-Model Extension (SME). We extend the analysis to Lorentz-violating matter-gravity couplings, utilizing three small-eccentricity relativistic neutron star (NS) -white dwarf (WD) binaries. We obtain compelling limits on various SME coefficients related to the neutron, the proton, and the electron. These results are complementary to limits obtained from lunar laser ranging and clock experiments.

Nonminimal Lorentz Violation

“…Improvements on these rough constraints are expected in detailed studies of planetary ephemerides [92,93] and through lunar laser ranging [94][95][96]. Binary pulsars offer another promising area of study that is particularly sensitive to Lorentz violations in neutrons [12,40,[97][98][99][100][101]. Section 3.3 gives the Lorentz-violating Lagrange density for continuous media (51).…”

“…Since the velocity v is periodic with period 2π/ω, the C ab components in (40) drive changes in the motion at harmonics of ω. We characterize this driving force using the form…”

“…Binary pulsars provide another test of Lorentz invariance in orbital dynamics [12,97]. These systems have been used to test Lorentz invariance to parts in 10 11 in gravity [98,99] and matter-gravity couplings [40]. They've also been used to search for velocity-dependent effects from dimension d = 5 terms [100] and from d = 8 cubic terms in the gravity sector of the SME [101].…”

“…The α and η angles for the eight planets are given in Table 2. To solve (40), we first seek force-free homogeneous solutions. Several homogeneous solutions exist that can be connected to conventional perturbations to circular orbits.…”

“…To date, constraints on minimal c w (4) eff coefficients have been placed in studies involving astrophysics [15,[34][35][36][37][38][39][40][41], tests of the equivalence principle [34,42,43], gravimeters [44], accelerators [45][46][47], electromagnetic cavities [48][49][50], atomic systems [51][52][53][54][55][56][57][58][59][60][61][62], and acoustic resonators [63]. The sensitivities in electrons have reached levels of parts in 10 20 in experiments involving atomic clocks [58] and trapped ions [59,60].…”