Recently a series of analyses on the flight time of cosmic photons and neutrinos suggests that the speed of light \emph{ in vacuo} takes the energy-dependent form $v(E)\simeq 1-E/E_{ \text{ LIV}}^{ \gamma }$ with $E_{ \text{ LIV}}^{ \gamma }\approx 3.6\times 10^{ 17}~\text{ GeV}$, and meanwhile the speed of neutrinos is proposed to be $v(E)\simeq 1\pm E/E_{ \text{ LIV}}^{ \nu }$ with $E_{ \text{ LIV}}^{ \nu }\approx 6.5\times 10^{ 17}~\text{ GeV}$ and $\pm { }$ representing the helicity dependence. This novel picture immediately urges us to provide a satisfactory theoretical explanation. Among all the attempts to predict the speed variations from quantum gravity, we find that loop quantum gravity can serve as a good candidate for explaining the aforementioned picture consistently.
Categories: hep-ph astro-ph.HE gr-qc