The discussion centers around Katherine Freese's recent address on dark matter, exploring various theories and candidates for dark matter, including MACHOs, WIMPs, and the role of the quantum vacuum. Participants examine the implications of these theories and the evidence supporting them, as well as the limitations of current models.
Participants express differing views on the adequacy of current dark matter models and the significance of the quantum vacuum, indicating that multiple competing perspectives remain without consensus.
Some claims rely on assumptions about the nature of dark matter and the quantum vacuum, and there are unresolved questions regarding the distribution of dark matter and the implications of recent detection claims.
I will refrain from making comments on my own opinions on the Dark Matter problem so your thread will not be locked. A little epistemology is in order here, and I do not see it happening.The quantum vacuum is the ground state of energy for the Universe, the lowest possible level. Attempts to perceive the vacuum directly only lead to a confrontation with a void, a background that appears to be empty. But, in fact, the quantum vacuum is the source of all potentiality. For example, quantum entities have both wave and particle characteristics. It is the quantum vacuum that such characteristics emerge from, particles `stand-out' from the vacuum, waves `undulate' on the underlying vacuum, and leave their signature on objects in the real Universe.
In this sense, the Universe is not filled by the quantum vacuum, rather it is `written on' it, the substratum of all existence.
With respect to the origin of the Universe, the quantum vacuum must have been the source of the laws of Nature and the properties that we observe today. How those laws and properties emerge is unknown at this time.
I will begin by reviewing the evidence for Dark Matter in the Universe, as well as the candidates for dark matter. At most 20% of the dark matter in galaxies can be in the form of MACHOs (Massive Compact Halo Objects); the remainder appears to be some unknown exotic component. The most sensible candidates from the point of view of particle physics are axions and WIMPs (Weakly Interacting Massive Particles), where WIMPs may be supersymmetric particles. Three recent claims of possible detection of WIMP dark matter are tantalizing and will be discussed: the DAMA annual modulation, the HEAT positron excess, and gamma-rays from the Galactic Center. In addition, I will discuss the dependence of signals in detectors on the mass distribution in the Galactic Halo. In particular, the Sagittarius stream can be a smoking gun for WIMP detection.
That dog won't hunt.ohwilleke said:The abstract:Bottom line, in this mainstream restatement of the state of the field (yes, state of the union is a good analogy). You need axions or WIMPS which have not been discovered yet, to make it fly. This is also weak on addressing issues with how dark matter gets distributed in the manner that it does.