Constraints on temporal variation of fundamental constants from GRBs

TL;DR

This paper uses gamma-ray burst observations to set a new, highly stringent limit on the possible temporal variation of Newton's gravitational constant, G_N, over cosmic timescales.

Contribution

It introduces a novel method to constrain the variation of fundamental constants using gamma-ray burst data related to neutron star phase transitions.

Findings

Derived a bound ^{-17} yr^{-1} on G_N/G_N from GRB observations.

Provided constraints that are five orders of magnitude more stringent than previous limits.

Linked neutron star phase transitions to observable gamma-ray burst phenomena.

Abstract

The formation of a strange or hybrid star from a neutron star progenitor is believed to occur when the central stellar density exceeds a critical value. If the transition from hadron to quark matter is of first order, the event has to release a huge amount of energy in a very short time and we would be able to observe the phenomenon even if it is at cosmological distance far from us; most likely, such violent quark deconfinement would be associated with at least a fraction of the observed gamma ray bursts. If we allow for temporal variations of fundamental constants like $\Lambda_{QCD}$ or $G_N$, we can expect that neutron stars with an initial central density just below the critical value can enter into the region where strange or hybrid stars are the true ground state. From the observed rate of long gamma ray bursts, we are able to deduce the constraint $\dot{G}_N/G_N \lesssim 10^{-17} {\rm yr^{-1}}$, which is about 5 orders of magnitude more stringent than the strongest previous bounds on a possible increasing $G_N$.