Mathematics – Logic
Scientific paper
Apr 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aps..aprw19001t&link_type=abstract
American Physical Society, April Meeting, April 29-May 2, 2000 Long Beach, CA, abstract #W19.001
Mathematics
Logic
Scientific paper
Very high-energy gamma rays and neutrinos could be probes of quantum gravity (QG) nature of vacuum [Amelio-Camella, et al, 1998]. Extreme Energy (EE) photons lose energy by pair production in a vacuum due to the ubiquitous microwave photons. Their path length at EE energies is limited to less than 10 Mpc in ordinary space and they are believed to be unable to reach earth from Gamma Ray BurstUs (GRB) of cosmological distances. However, EE gamma rays in the QG vacuum can pass through a large distance exceeding many Gpc, because electron-pair production with 2.7K (E') microwave background may be kinematically prohibited above 10 TeV under the QG structure of vacuum. The energy-momentum conservation for the pair process does not hold for E >> 10 TeV for E' = 10-3 (Kifune, 1999), because 4 mc^4 = E^2 - (pc)^2 = E^2 (E'/E - k E/E0) < 0, where k = 1. The reported observation of EECRUs above 4 4 10^eV with unaccounted pair or triple coincidence in spatial and temporal ( ~ 2 years) coordinates is also a mystery. They also seem to be correlated with high luminosity GRBUs within 1 year [Milgrom and Usov, 1995; Takahashi, 1998]. If this correlation is true, then the ballpark correlation of one-year is hard to understand with any theory, while a possible explanation is available if Quantum Gravity (QG) is considered with Planck mass (10^28eV/c^2) grain of spacetime (10-33 cm). The QG scheme [Amelio-Camella, et al, 1998] leads to a delay time of gamma rays of the order of 1 year at 5 x 10^19 eV from cosmological distance (L) of GRB's (typically, L ~ 1 Gpc). The reduced speed of EHE gamma rays in QG is v = (1 - k 4 E/E0)c, where E0 is the Planck mass (10^20 eV/c^2) or gravitino mass (E0/k, k as a parameter O(1)). The fundamental question is whether such high energy particle acceleration occurs in GRBUs. Studies of photonic acceleration in extreme photon outburst sites, GRBUs, might lead to an even more profound cosmological test of the vacuum of Universe; in particular, concerning the existence (or non-existence) of quantum gravity. High-intensity, short-pulse lasers (from 10 Terawatt to 1 Petawatt at 0.5 ~ 1 picosec) permit experimental studies of the photonic acceleration processes. Attainable laser power density have risen in the 1990's to the nonlinear optical domain, >1020 W/cm2, e.g., NOVA of the Lawrence Livermore National Laboratory (LLNL). The high-intensity of the photo n beams at laser facilities was achieved by the Chirped-pulse Amplification technology (CPA) since late 1980's, by which the laser power jumped over 108 times that of 1970's. The Petawatt experiments have already demonstrated wakefield (and snowplow) accelerations to about 1 GeV. The electromagnetic fields generated by the ponderomotive potential are EL = 10 GV/cm and ET = 1 TV/cm. Its theory was established in 1980's (which began with the Dawson-Tajima Beat-Wave theory). The monochromatic waves do not make beat waves or wakefields but forward Raman scattering of monochromatic laser injected into plasma or matter makes a variety of incoherent photons with different wavelengths, and form self-modulated beats, and consequently, wakefields. The wakefield acceleration per unit length is proportional to the photon intensity. A straightforward extrapolation of the wakefields to the non-linear QED regime (10^30 W/cm^2) approaches the critical Schwinger field (E = 10^16.5 V/cm). The physics of high fields encounters such a nonlinear QED regime when the irradiance exceeds 10^30 W/cm^2. It is still billion times beyond the capability of current terrestrial laboratories, but observations of GRBUs already imply such a high field in nature. Thus, the highest power laser experiments might shed some light in diagnosing photonic acceleration in GRBUs; and therefore, (via EHE observation), quantum gravity research.
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