8 papers
Comment on "Uncertainty in measurements of distance"
Y. Jack Ng, H. van Dam
We have argued that quantum mechanics and general relativity give a lower bound on the measurement uncertainty of any distance much greater than…
Anomalous particle-production thresholds through systematic and non-systematic quantum-gravity effects
Giovanni Amelino-Camelia, Y. Jack NG, Hendrik Van Dam
A growing number of studies is being devoted to the identification of plausible quantum properties of spacetime which might give rise to observably large effects. The literature on…
Why 3 + 1 metric rather than 4 + 0 or 2 + 2?
H. van Dam, Y. Jack Ng
Why does the physical 4-dimensional space have a 3 + 1 signature rather than a 4 + 0 or a 2 + 2 for its metric? We give a simple explanation based largely on a group-theoretic argu…
Energy-momentum uncertainties as possible origin of threshold anomalies in UHECR and TeV-gamma ray events
Y. Jack Ng, D. -S. Lee, M. C. Oh +1
A threshold anomaly refers to a theoretically expected energy threshold that is not observed experimentally. Here we offer an explanation of the threshold anomalies encountered in…
A small but nonzero cosmological constant
Y. Jack Ng, H. van Dam
Recent astrophysical observations seem to indicate that the cosmological constant is small but nonzero and positive. The old cosmological constant problem asks why it is so small;…
On Wigner's clock and the detectability of spacetime foam with gravitational-wave interferometers
Y. J. Ng, H. van Dam
A recent paper (gr-qc/9909017) criticizes our work on the structure of spacetime foam. Its authors argue that the quantum uncertainty limit for the position of the quantum clock in…