Speaker
Description
Many recent experimental works involving quantum tunneling claim their observations are consistent with superluminal or instantaneous barrier traversal times. However, we have recently proved [1] that microcausality prevents superluminal dynamics in the presence of tunneling in a QFT framework in which a potential barrier is represented by a background field. In this talk I will discuss how one can nevertheless define tunneling times that can in certain situations can give rise to superluminal velocities. I will focus on two such situations. First I will look at group velocities defined by connecting the maxima of the density expectation value to the left and to the right of a potential barrier [2]. A second example will involve working with a position operator of the Newton-Wigner type. The density is then propagated by the sole positive energy sector – evading microcausality and leading to densities leaking from the light cone [3]. For each case I will discuss the underlying physics (which turns out to be very different) and draw some lessons. [1] M. Alkhateeb and A. Matzkin, Phys. Rev. D 112, 076005, 2025 [2] D. Sokolovski and A. Matzkin, in preparation (should be posted on arxiv by mid-April) [3] F. Daem and A. Matzkin, Phys. Rev. A 111, L060202, 2025