Discussion Overview
The discussion revolves around the possibility of expressing gravitational energy as a product of the gravitational field and a moment, similar to how magnetic and electric energy are expressed. Participants explore whether this formulation necessitates the existence of negative mass and its relation to gravitational waves.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- Some participants propose that gravitational energy could be expressed as a product of the gravitational field and a moment, questioning if this requires negative mass.
- One participant notes that the source term for gravitational radiation is a time-varying quadrupole moment, emphasizing that a dipole term is not possible due to the positivity of mass.
- Another participant mentions that the energy of the gravitational field is well-defined only in stationary cases, which contradicts the application to a changing quadrupole moment.
- There is a suggestion that while one could rearrange the gravitational potential energy formula (U = mgh) to U = g(mh), the rationale behind this is questioned.
- One participant highlights that there are multiple definitions of energy in General Relativity (GR) derived from the metric, specifically mentioning Bondi, ADM, and Komar definitions, which do not align with the proposed formulation.
- Concerns are raised regarding the applicability of these energy definitions in the context of an infinite expanding universe.
Areas of Agreement / Disagreement
Participants express differing views on the feasibility of expressing gravitational energy in the proposed manner, with no consensus reached on the necessity of negative mass or the applicability of existing energy definitions in GR.
Contextual Notes
Participants note limitations regarding the definitions of energy in GR, particularly their dependence on asymptotic flatness and the implications for an infinite expanding universe.