Can neutrino-cooled accretion disks be an origin of gamma-ray bursts?

It is often proposed that a massive torus with approximately solar mass surrounding a stellar-mass black hole could be a central engine of gamma-ray bursts. We study the properties of such massive accretion tori (or disks) based on the alpha viscosity model. For surface density exceeding about 10(20) g cm(-2), which is realized when similar to1 M. of material is contained within a disk of size similar to5 x 10(6) cm, we nd that (1) the luminosity of photons is practically zero because of significant photon trapping, (2) neutrino cooling dominates over advective cooling, (3) the pressure of degenerate electrons dominates over the pressure of gas and photons, and (4) the magnetic field strength exceeds the critical value of about 4 x 10(13) G, even if we take 0.1% of the equipartition value. The possible observable quantum electrodynamical (QED) effects arising from supercritical fields are discussed. Most interestingly, photon splitting may occur, producing a significant number of photons of energies below similar to511 keV, thereby possibly suppressing e(+/-) pair creation.