Lorentz Invariance Violation in High-Energy Astrophysics

Lorentz invariance underpins modern physics by asserting that the laws of nature remain the same for all observers regardless of their constant velocity. However, several quantum gravity frameworks predict minute departures from exact Lorentz symmetry at energy scales approaching the Planck energy. In high-energy astrophysics, these departures may manifest as energy-dependent variations in particle velocities, altered threshold conditions for particle interactions and novel dispersion effects over cosmological distances. Gamma-ray bursts, active galactic nuclei flares and high-energy neutrino events provide natural laboratories in which accumulated tiny signals of Lorentz invariance violation (LIV) can be sought. By comparing arrival times of photons or neutrinos across a broad energy span and examining unexpected transparency of the universe to very high-energy particles, researchers look to constrain or detect LIV-induced modifications. These investigations not only probe fundamental spacetime structure but also offer insights into the viability of candidate theories of quantum gravity, with implications for cosmology, particle physics and our understanding of causality at the highest energies.

Research from Nature Portfolio

Recent studies have exploited observations of high-energy neutrinos detected by large-volume Cherenkov telescopes to place unprecedented limits on energy-dependent speed variations. By analysing millisecond timing precision across different neutrino energies, researchers have constrained any deviation from the universal speed of light to parts in 10¹⁸, reinforcing Lorentz invariance up to extreme regimes.

Advances in gamma-ray astronomy have enabled the detailed examination of TeV-scale photons from distant blazars. New results indicate no statistically significant delay between low- and high-energy photon arrivals, tightening bounds on linear and quadratic LIV terms. Complementary observations of very high-energy transients have further refined constraints on threshold anomalies, effectively ruling out large regions of parameter space in several effective-field-theory models.

Lorentz Invariance Violation in High-Energy Astrophysics publication trend

The graph below shows the total number of articles in lorentz invariance violation in high-energy astrophysics across all publications each year (not limited to Nature Index journals).

Technical terms

Lorentz invariance: The principle that physical laws are unchanged under transformations between inertial frames.

Dispersion relation: An equation relating particle energy to momentum, whose deformation indicates LIV.

Threshold anomaly: A shift in the energy required for particle interactions, such as photon pair production.

Spacetime foam: A hypothesised quantum-gravity structure causing fluctuating geometry at the Planck scale.

Effective field theory: A low-energy approximation that includes additional terms modelling potential LIV effects.

References

1. Lorentz and CPT breaking in gamma-ray burst neutrinos from string theory. Journal of High Energy Physics (2023).
2. Searching Lorentz invariance violation from cosmic photon attenuation. European Physical Journal C (2023).
3. Speed variations of cosmic photons and neutrinos from loop quantum gravity. Physics Letters B (2023).