The CPT-violating effects on neutrons’ gravitational bound state

Abstract

In this paper, the CPT-violating (CPTV) spin interactions on neutron's gravitational bound state are studied. The helicity-dependent phase evolution due to σ • b and σ • ˆ p couplings is transparently demonstrated with analytical solutions. The consequent phenomena include not only spin precession and the azimuthal angle θ− and φ−dependent probability variation, but also transition-frequency shifts between different gravitational bound states. The θ and φ time-dependences due to the Earth motion may lead to sidereal variation of the probability profile, a clear signal of Lorentz violation. We also utilize the gravitational transition frequencies measured precisely in the qBounce experiment [26] to obtain the rough bound | b| < 6.9×10 −21 GeV. Incorporating known systematic errors or using polarized neutron beams may lead to more robust and tighter constraints.

Searches for beyond-Riemann gravity

“…In this section, we consider experiments performed to measure the quantum properties of bouncing neutrons [101,128] and derive some constraints from existing experimental results on nonrelativistic coefficients in the neutron sector. Our analysis complements existing studies of Lorentz violation in this system [129][130][131].…”

Probing of violation of Lorentz invariance by ultracold neutrons in the Standard Model Extension

“…Recently Martín-Ruiz and Escobar [38,39] have used UCNs, quantized in the gravitational field of the Earth, as a tool to probe effects of violation of Lorentz invariance using the experimental data on the energy levels of the ground E 1 and first excited E 2 quantum gravitational states of UCNs [20]. An influence of CPT-violating effects on the quantum gravitational states of UCNs has been also investigated by Zhi Xiao [40]. The analysis, carried out by Martín-Ruiz and Escobar [38,39], has allowed to impose the following upper bounds on the parameters of violation of Lorentz invariance…”

Backgrounds in gravitational effective field theory

“…. , (41) which explicitly reveals the dependence on the gravitational degrees of freedom and illustrates the compactness of the expression kO. This expansion is also appropriate for terms such as L ⊃ (D µ k)O µ , which involve the contraction of a dynamical operator with the derivative of a combination of backgrounds.…”

“…In the pure-gravity sector, phenomenological studies [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and experiments [22][23][24][25][26][27][28][29][30][31][32][33][34] have constrained most minimal terms to impressive sensitivities. The minimal matter-gravity sector has also been widely explored both phenomenologically [35][36][37][38][39][40][41][42] and experimentally [43][44][45][46][47][48][49], with the focus to date being primarily on spin-independent effects. A subset of terms in the pure-gravity sector with operators of larger mass dimensions d ≥ 5 has been constructed and some experimental constraints obtained .…”