Engineering topics
Shan, Gao
Publications and source records attributed to Shan, Gao.
ON THE NEUTRINO NON-DETECTION OF GRB 130427A
The recent gamma-ray burst GRB 130427A has an isotropic electromagnetic energy E{sup iso} {approx} 10{sup 54} erg, suggesting an ample supply of target photons for photo-hadronic interactions, which at its low redshift of z {approx} 0.34 would appear to make it a promising candidate for neutrino detection. However, the IceCube collaboration has reported a null result based on a search during the prompt emission phase. We show that this neutrino non-detection can provide valuable information about this gamma-ray burst's (GRB's) key physical parameters such as the emission radius R{sub d} , the bulk Lorentz factor {Gamma}, and the energy fraction converted into cosmic rays {epsilon}{sub p}. The results are discussed both in a model-independent way and in the specific scenarios of an internal shock (IS) model, a baryonic photospheric (BPH) model, and a magnetic photospheric (MPH) model. We find that the constraints are most stringent for the MPH model considered, but the constraints on the IS and the BPH models are fairly modest.
High energy neutrino emission from the earliest gamma-ray bursts
We discuss the high energy neutrino emission from gamma-ray bursts resulting from the earliest generation (''population III'') stars forming in the Universe, whose core collapses into a black hole. These gamma-ray bursts are expected to produce a highly relativistic, magnetically dominated jet, where protons can be accelerated to ultrahigh energies. These interact with the photons produced by the jet, leading to ultrahigh energy photomeson neutrinos as well as secondary leptons and photons. The photon luminosity and the shock properties, and thus the neutrino spectrum, depend on the mass of the black holes as well as on the density of the surrounding external gas. We calculate the individual source neutrino spectral fluxes and the expected diffuse neutrino flux for various source parameters and evolution scenarios. Both the individual and diffuse signals appear detectable in the 1-300 PeV range with current and planned neutrino detectors such as IceCube and ARIANNA, provided the black hole mass is in excess of 30-100 solar masses. This provides a possible test for the debated mass of the progenitor stellar objects, as well as a probe for the early cosmological environment and the formation rate of the earliest structures.
The Wave Function and Quantum Reality
We investigate the meaning of the wave function by analyzing the mass and charge density distributions of a quantum system. According to protective measurement, a charged quantum system has effective mass and charge density distributing in space, proportional to the square of the absolute value of its wave function. In a realistic interpretation, the wave function of a quantum system can be taken as a description of either a physical field or the ergodic motion of a particle. The essential difference between a field and the ergodic motion of a particle lies in the property of simultaneity; a field exists throughout space simultaneously, whereas the ergodic motion of a particle exists throughout space in a time-divided way. If the wave function is a physical field, then the mass and charge density will be distributed in space simultaneously for a charged quantum system, and thus there will exist gravitational and electrostatic self-interactions of its wave function. This not only violates the superposition principle of quantum mechanics but also contradicts experimental observations. Thus the wave function cannot be a description of a physical field but be a description of the ergodic motion of a particle. For the later there is only a localized particle with mass and charge at every instant, and thus there will not exist any self-interaction for the wave function. It is further argued that the classical ergodic models, which assume continuous motion of particles, cannot be consistent with quantum mechanics. Based on the negative result, we suggest that the wave function is a description of the quantum motion of particles, which is random and discontinuous in nature. On this interpretation, the square of the absolute value of the wave function not only gives the probability of the particle being found in certain locations, but also gives the probability of the particle being there. The suggested new interpretation of the wave function provides a natural realistic alternative to the orthodox interpretation, and it also implies that the de Broglie-Bohm theory and many-worlds interpretation are wrong and the dynamical collapse theories are in the right direction by admitting wavefunction collapse.