Author: Bing Zhang
Abstract: Recent broad-band observations of Gamma-Ray Burst (GRB) prompt emission sharpened the debates regarding several open questions in GRB physics, including jet composition, energy dissipation mechanism, particle acceleration mechanism, and radiation mechanism. Here I review these open questions, the arguments in support of the opponents on both sides of the debates, as well as observational clues and tests that can be used to settle down these debates in the future. In particular, I will show that even though the quasi-thermal photosphere component is observed in some GRBs, the dominant emission component in most GRBs is likely synchrotron emission from an optically thin region. Different GRBs may have different values of magnetization parameter at the central engine, which may result in the diverse spectral behaviors as observed in different GRBs.