On the SaleckerWigner limit and the use of interferometers in spacetimefoam studies
Abstract
The recent paper grqc/9909017 criticizes the limit on the measurability of distances that was derived by Salecker and Wigner in the 1950s. If justified, this criticism would have important implications for all the recent studies that have used in various ways the celebrated SaleckerWigner result, but I show here that the analysis reported in grqc/9909017 is incorrect. Whereas Salecker and Wigner sought an operative definition of distances suitable for the Planck regime, the analysis in grqc/9909017 relies on several assumptions that appear to be natural in the context of most presentday experiments but are not even meaningful in the Planck regime. Moreover, contrary to the claim made in grqc/9909017, a relevant quantum uncertainty which is used in the SaleckerWigner derivation cannot be truly eliminated; unsurprisingly, it can only be traded for another comparable contribution to the total uncertainty in the measurement. I also comment on the role played by the SaleckerWigner limit in my recent proposal of interferometrybased tests of quantum properties of spacetime, which was incorrectly described in grqc/9909017. In particular, I emphasize that, as discussed in detail in grqc/9903080, only some of the quantumgravity ideas that can be probed with modern interferometers are motivated by the SaleckerWigner limit. The bulk of the insight we can expect from such interferometric studies concerns the properties of ``foamy'' models of spacetime, which are intrinsically interesting independently of the SaleckerWigner limit.
 Publication:

Physics Letters B
 Pub Date:
 March 2000
 DOI:
 10.1016/S03702693(00)002318
 arXiv:
 arXiv:grqc/9910023
 Bibcode:
 2000PhLB..477..436A
 Keywords:

 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology
 EPrint:
 LaTex, 18 pages