- #31
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good point!
Criticism of LQG - What do we miss?
- Context: Graduate
- Thread starter tom.stoer
- Start date
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- Lqg
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Discussion Overview
The discussion revolves around criticisms and open issues related to Loop Quantum Gravity (LQG). Participants explore theoretical aspects, potential shortcomings, and comparisons with other approaches like asymptotic safety (AS) and condensed matter physics. The conversation includes speculative reasoning about the implications of LQG's framework and its treatment of spacetime, matter, and fundamental principles.
Discussion Character
- Exploratory
- Debate/contested
- Technical explanation
- Conceptual clarification
Main Points Raised
- Some participants express concerns about LQG's reliance on a specific topology (M3*R) and question whether this background-dependence excludes relevant physical sectors.
- There is skepticism regarding the choice of SU(2) as the gauge group in LQG, with some arguing that this choice may be arbitrary and tied to the assumption of four-dimensional spacetime.
- Participants discuss the implications of having multiple smooth structures in four dimensions and propose that LQG does not adequately address this complexity.
- Some contributors suggest that matter should emerge from spacetime rather than being added to it, criticizing LQG's current approach to integrating matter.
- There are mentions of the asymptotic safety approach indicating that gravity may be non-perturbatively renormalizable, with calls for LQG to incorporate this perspective.
- Concerns are raised about LQG's treatment of the cosmological constant and whether it is an algebraic input or a dynamical output of the theory.
- Some participants highlight the lack of discussion in LQG regarding the holographic principle, which they believe is fundamental to understanding quantum gravity.
- There is a proposal to consider vertices in LQG as scattering events, drawing an analogy to molecular interactions in a gas.
- One participant reflects on the interconnectedness of quantum mechanics, relativity, and renormalization, suggesting that these concepts cannot be fully understood in isolation.
- A non-physicist contributor raises a point about the transformation from the GL(2) group to SU(2) in LQG, questioning its validity in quantum field theory.
- Another participant clarifies that SU(2) is the Euclidean realization for General Relativity, contrasting it with the Lorentzian SL2(C).
Areas of Agreement / Disagreement
Participants express a range of views, with no clear consensus on the criticisms of LQG or the implications of its theoretical framework. Multiple competing perspectives are present regarding the treatment of spacetime, matter, and fundamental principles.
Contextual Notes
Some discussions involve unresolved assumptions about the nature of spacetime and the implications of different gauge groups. The conversation also reflects varying interpretations of the role of renormalization in quantum gravity theories.