FEMTOLENSING OF GAMMA-RAY BURSTERS

If gamma-ray bursters are at cosmological distances, they can be used to probe for "femtolenses," extremely small (approximately 10(-13)-10(-16) M.) dark-matter objects. The time delay induced by such a lens would be approximately 10(-17)-10(-20) s, approximately equal to the period of a gamma ray. Interference between the two images would induce a characteristic interference pattern as a function of detected frequency. The pattern would be stable on time scales of 1 s, but might slowly drift on time scales of 10 s in response to the relative motion of the lens and source. The signal from a femtolens would be quite distinct and would be well within the sensitivity of present detectors.