97 research outputs found
The kinematical Hilbert space of Loop Quantum Gravity from BF theories
In this work, it is demonstrated how the kinematical Hilbert space of Loop
Quantum Gravity (LQG) can be inferred from the configuration space of BF
theories via the imposition of the Hamiltonian constraints. In particular, it
is outlined how the projection to the representations associated with
Ashtekar-Barbero connections provides the correct procedure to implement
second-class constraints and the corresponding nontrivial induced symplectic
structure. Then, the reduction to SU(2) invariant intertwiners is analyzed and
the properties of LQG states under Lorentz transformations is discussed.Comment: 13 page
Revised Conditions for MRI due to Isorotation Theorem
We re-analyze the physical conditions for Magneto-rotational Instability
(MRI) within a steady axisymmetric stratified disk of plasma, in order to
account for the so-called isorotation theory (the spatial profile of
differential angular velocity depends on the magnetic flux surface). We develop
the study of linear stability around an astrophysical background configuration,
following the original derivation in \cite{Ba:1995}, but implementing the
isorotation condition as the orthogonality between the background magnetic
field and the angular velocity gradient. We demonstrate that a dependence on
the background magnetic field direction is restored in the dispersion relation
and, hence, the emergence of MRI is also influenced by field orientation.Comment: 9 pages, 2 figures, accepted for publication in Physics Letters
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