Lorentz and CPT breaking in gamma-ray burst neutrinos from string theory

Abstract

Previous studies on high-energy gamma-ray burst neutrinos from IceCube suggest a neutrino speed variation at the Lorentz violation (LV) scale of ~6.4 × 1017 GeV, with opposite velocity variances between neutrinos and antineutrinos. Within a spacetime foam model, inspired by string theory, we develop an approach to describe the suggested neutrino/antineutrino propagation properties with both Lorentz invariance and CPT symmetry breaking. A threshold analysis on the bremsstrahlung of electron-positron pair (ν → νee+) for the superluminal (anti)neutrino is performed. We find that, due to the energy violation caused by the quantum foam, such reaction may be restricted to occur at sufficient high energies and could even be kinematically forbidden. Constraints on neutrino LV from vacuum ee+ pair emission are naturally avoided. Future experiments are appealed to test further the CPT violation of cosmic neutrinos and/or neutrino superluminality.

Effects on neutrino propagation in space-time foam of D-branes revisited

“…[21,22], suggesting a neutrino speed variation of v(E) = 1 − E/E LV , where E LV := M P /η ∼ 6 × 10 17 GeV (that is η ≃ 21.7), a scale roughly the same as that determined before by [10][11][12][13][14]. 2 As the analysis [21,22], based on revised data, weakens superluminal signature, i.e., correlations [10][11][12][13][14] of relevant events with GRBs probably are just coincident, it is worth reconsidering whether the finding can still be described in the stringy foam framework championed by our previous works in [16,20], supporting both subluminal and superluminal (i.e., CPT-violating) propagation for IceCube neutrinos. In fact, as has been mentioned as a side remark in ref.…”

“…In fact, as has been mentioned as a side remark in ref. [16] (and will be clear also from the arguments here below), one can envisage space-time foamy situations of brane defects, in which only the deceleration of neutrinos should be expected. We therefore argue that this type of scenaria gain support from the updated result herein [21,22].…”

“…Comparable statistical significance for events delayed and those that advanced by LV is inferred, 1 pointing likely to an opposite effect on the propagation between neutrinos and antineutrinos [12][13][14][15] (a hypothesis that might be relevant because we have no helicity information for IceCube events). It is suggested [16] that the space-time foam model with recoiling (D-brane) cosmic defects [17][18][19] may induce a breakdown of CPT invariance for the neutrino/antineutrino sector and can accommodate [20] then for such an asymmetric impact of LV on the neutrino propagation. A latest reanalysis [21,22] indicates, however, that these previous results might be strongly affected by the significant revision of the directional information for the neutrino events by the collaboration [23] and shows that the prior indication for a QG effect speeding up neutrinos (or antineutrinos) seems not to be favored anymore (given whopping probability of finding accidentally that feature from data), whereas for neutrinos subject to subluminal LV, the result becomes even stronger than those previously reported (using uncorrected neutrino directions) in refs.…”

Consistency of Lorentz-invariance violation neutrino scenarios in time delay analyses

“…In addition, however, the description of time delays is much more involved than in the LIV case and they might even not exist at all [33][34][35][36]. Other scenarios that can also evade the mentioned constraints are some based on string theory, such as the D-brane foam model considered in [37], which leads to a modification of the kinematics of superluminal particle decays.…”

Lorentz Violation in Finsler Geometry

“…However, in quantum gravity (QG) [1], Lorentz violation (LV) may happen at the Planck scale (E Pl 1.22 × 10 19 GeV). There are many kinds of theoretical models including LV effects, including the QG theories such as string theory [2][3][4][5] and loop quantum gravity [6][7][8], spacetime structure theories such as doubly special relativity (DSR) [9][10][11][12] and very special relativity (VSR) [13], and the effective theory with extra terms, such as the standard-model extension (SME) [14][15][16]. For a recent review on Lorentz invariance violation, see [17].…”