Unanswered Questions
1,969 questions with no upvoted or accepted answers
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Can the Dirac quantization condition be derived within Lev Vaidman's formalism without gauge fields?
Textbooks often claim that phenomena like the Aharonov-Bohm effect require that any local formulation of quantum gauge theory use gauge potential fields. (It's also sometimes claimed that the A-B ...
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On Ricci flow and 'nonlinear relativistic heat equation
This is somewhat related to a previous question, but is different at the core.
I proposed a Relativistic Ricci flow equation that takes the form
$$\frac{\partial R}{\partial t} = \alpha \Box^2 R = -...
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Resource Recommendation for black hole metrics in General Relativity
In classical textbooks for GR, Schwarzschild and Kerr spacetimes are adequately described. In which books or articles, it is mostly believed that Reissner–Nordstrom, Kerr–Newman, Schwarzschild–de ...
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A Universal Upper Limit on Mass Within a Radius $R$?
Since the universe has a positive cosmological constant, there is an upper limit on the mass of the black holes as evident from the so-called Schwarzschild-de Sitter metric:
$ds^2 = -f(r)dt^2 + \...
CommunityBot
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2
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Auto-parallel Transport or Principle of Extremum Action?
In an affinely connected spacetime with a metric compatible connection, the equation of the curve in which the tangent vector at each point is the result of the parallel transport of every tangent ...
CommunityBot
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Coupling a spinor field to a preexisting scalar field?
So I'm not a physicist, but I'm thinking about a mathematical problem where I think physical insight might be useful.
We're working on a Riemannian manifold $(M,g)$ (positive definite metric) with a ...
CommunityBot
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Is the $\alpha'$ expansion in string theory an asymptotic expansion?
The low-energy bosonic effective actions of string theory lead to Einstein-Hilbert gravity, along with scalars and $p$-form Maxwell fields. For example, the action for type IIA string theory is
$S = \...
CommunityBot
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Is it possible to have fermions in Schwarzschild spacetime?
To my understanding Geroch proved that on 4-dimensional non-compact manifold a necessary and sufficient condition for a manifold to have a notion of spinors is to be parallelizabe .1 (General ...
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BTZ Black Hole Central Charge and Conformal Weight
I have been trying to reproduce a calculation (equation 4.12) in this paper http://arxiv.org/pdf/1107.2678v1.pdf by Carlip reviewing the derivation of the effective central charge of the BTZ Black ...
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The surface area to volume ratio of a sphere and the Bekenstein bound
I am trying to relate the surface-area-to-volume-ratio of a sphere to the Bekenstein bound. Since the surface-area-to-volume-ratio decreases with increasing volume, one would surmise that, per unit of ...
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Do semiclassical GR and charge quantisation imply magnetic monopoles?
Assuming charge quantisation and semiclassical gravity, would the absence of magnetically charged black holes lead to a violation of locality, or some other inconsistency? If so, how?
(I am not ...
CommunityBot
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How come the magnetic field disappears when a neutron star becomes a black hole, while the rotation remains?
The only question I found is this one, but this considers as non-rotating neutron star collapsing:
Our final and most comprehensive test is represented by the collapse to a BH of a magnetized ...
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Thermodynamic inaccessibility and its consequences
Caratheodory's principle, namely, that in any neighborhood of an arbitrary equilibrium state there are states not accessible via adiabatic reversible path, leads to the existence of an integrating ...
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Why are there multiple universes in the Reissner-Nordström solution?
I am trying to make sense of the Penrose diagram of a non extremal Reissner-Nordström spacetime, that is, the solution with two horizons. The coordinates are
$$ v'=\text{exp}\left(\frac{r_+-r_-}{2r_+^...
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Saddle point contributions to the gravitational path integral
In his lectures on black holes and quantum information, Tom Hartman states that the gravitational path integral can be approximated as
$$
Z(\beta) \approx \sum_{g_\text{cl}} e^{-I_E[g_\text{cl}, \phi]}...
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