Questions tagged [quantum-anomalies]
This tag is for anomalies in a symmetry, either in classical or quantum theories. DO NOT USE THIS TAG for anomalies in a measurement.
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How is Berry phase connected with chiral anomaly?
Recently I've read in one article about very strange way to describe chiral anomaly on quasiclassical level (i.e., on the level of Boltzmann equation and distribution function).
Starting from Weyl ...
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Relation among anomaly, unitarity bound and renormalizability
There is something I'm not sure about that has come up in a comment to other question:
Why do we not have spin greater than 2?
It's a good question--- the violation of renormalizability is linked
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QED and anomaly
I've just started to learn anomalies in quantum field theories. I have a question.
How to show that QED is free from vector current anomaly and what would happen if it were not? In other words, how ...
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Why are two Higgs doublets required in SUSY?
I can't really understand why two Higgs doublets are required in SUSY.
From the literature, I have found opaque explanations that say something along the lines of: the superpotential $W$ must be a ...
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Conformal/trace anomaly and index theorem
I am reading the chapters on characteristic classes and the index theorems in Nakahara. It is proven in the text that any chiral or gravitational anomaly $\mathcal{A}$ is given by
$$\mathcal{A}=\int ...
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If gauge symmetries are fake, then why do we care if they are anomalous?
My understanding is that gauge symmetries are fake in that they are only redundancies of our description of the system that we put in (either knowingly or unknowingly) see Gauge symmetry is not a ...
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How are anomalies possible?
From Matthew D. Shwartz Quantum Field Theory textbook, he writes:
"Most of the time, a symmetry of a classical theory is also a symmetry of the quantum theory based on the same Lagrangian. When ...
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Chiral anomaly and decay of the pion
I am told that if all classical symmetries were reflected as quantum symmetries, the decay of the neutral pion $$\pi^0 ~\longrightarrow~ \gamma\gamma$$ would not happen. Why would the conservation of ...
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Chiral anomaly in odd spacetime dimensions
In odd number of space-time dimensions, the Fermions are not reducible (i.e. do not have left-chiral and right-chiral counterparts).
Does this mean that there is no such thing as 'chiral' anomalies ...
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Can anomalies exist without gauge fields?
In Schwartz's QFT book, it is stated that anomalies cannot exist in a theory without gauge fields. This is because anomalies always give equations like
$$\partial_\mu j^\mu \sim F \tilde{F}$$
where ...
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Anomalies for not-on-site discrete gauge symmetries
If a symmetry group $G$ (let's say finite for simplicity) acts on a lattice theory by acting only on the vertex variables, I will call it ultralocal. Any ultralocal symmetry can be gauged. However, in ...
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't Hooft vs ABJ anomalies [closed]
At some point in our physics education, we begin to accumulate a bunch of slogans related to anomalies. At some (later, in my case) point, we learn that actually there were two different kinds of ...
anon
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Is there a 2D manifold on which the Dirac equation has a zero mode?
The two-dimensional (2D) Dirac equation $(\sigma_1iD_1+\sigma_2 iD_2)\psi=E\psi$ admits zero mode ($E=0$) solutions on a non-trivial gauge background, such as the zero mode at the core of a U(1) gauge ...
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On the Axial Anomaly
I know that if we start with a massive theory, the chiral states $L$ and $R$ remain coupled to each other in the massless limit. Because a charged Dirac particle of a given helicity can make a ...
user12732
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Does the Gibbons-Hawking boundary action have an anomaly inflow interpretation?
The Einstein-Hilbert action on a manifold $M$ with boundary is
$$\frac{-1}{16\pi G}\int_M d^n x \sqrt{-g} R +\frac{1}{8\pi G} \int_{\partial M} d^{n-1}x \sqrt{|h|} K$$
where $K$ is the extrinsic ...
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