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    The theoretical status of the discreteness result in loop... — Carmelics
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    The theoretical status of the discreteness result in loop quantum gravity is questionable as a genuine physical prediction

    SkepticismTruth & Knowledge
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    2 reasons for
    1 reason against

    Reasons For

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    Reason for 1 of 2
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    • 1.Physical predictions require invariance under the full symmetry group of the theory, a criterion emphasized by Dirac's constrained Hamiltonian formalism.
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    • 2.The area and volume operators in LQG are constructed prior to solving the diffeomorphism and Hamiltonian constraints, making them kinematical artifacts.
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    • 3.A quantity that changes under gauge transformation cannot represent a measurable physical magnitude, regardless of its mathematical elegance or heuristic appeal.
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    Reason for 2 of 2
    ?
    • 1.The underdetermination problem identified by Belot and Earman shows that quantization ambiguities in background-independent theories systematically infect putative physical results.
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    • 2.LQG's discrete spectra depend on the choice of the Ashtekar-Barbero connection, which is not a spacetime covariant object but a gauge-dependent internal variable.
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    Reasons Against

    1 perspective
    Reason against
    ?
    • 1.The discreteness result has been shown to hold only for operators on the kinematical Hilbert space
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    • 2.Operators on the kinematical Hilbert space are gauge-variant quantities
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    • 3.Genuine observables must be gauge-invariant (defined on the physical Hilbert space, satisfying all constraints)
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    Related

    A quantity that changes under gauge transformation cannot represent a measurable...Genuine observables must be gauge-invariant (defined on the physical Hilbert spa...It is an open question whether the discreteness result transfers to gauge-invari...LQG's discrete spectra depend on the choice of the Ashtekar-Barbero connection, ...
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    Operators on the kinematical Hilbert space are gauge-variant quantitiesPhysical predictions require invariance under the full symmetry group of the the...The area and volume operators in LQG are constructed prior to solving the diffeo...The discreteness result has been shown to hold only for operators on the kinemat...The underdetermination problem identified by Belot and Earman shows that quantiz...

    Similar

    Observing evidence of discreteness of space would not suffice to selec...87%The discreteness of area and volume operators are concrete predictions...87%Many approaches to quantum gravity involve discreteness of space80%Quantum probabilities and quantum computing do not vindicate a discret...78%

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    SEP: quantum-gravity
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    Loop quantum gravity is seemingly less plagued by a lack of predictions, and indeed it is often claimed that the discreteness of area and volume operators are concrete predictions of the theory, with potentially testable consequences. Proponents of this approach argue that this makes the theory more susceptible to falsification, and thus more scientific (in the sense of Popper; see the entry on Karl Popper) than string theory (see Smolin 2006 for this line of argument). However, it is still qu
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    Details

    Type
    claim
    Perspectives
    3 (2 for, 1 against)
    Edits
    1 edit