Questions tagged [symmetry]
Symmetries play a big role in modern physics and have been a source of powerful tools and techniques for understanding theories and their dynamics. We say that something is symmetric if there is some transformation we can perform on that object that leaves some property unchanged. The set of symmetry transformations of an object forms a group, and the name of this group is used as the name of the symmetry of the object.
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Why is the Stress Tensor a Diagonal Matrix for Static Fluids?
I am studying fluid dynamics and there is a section in our textbook that handles fluids at rest. It starts by mentioning that for fluids at rest ($\vec{v}=0$) the sheer stresses have to vanish and ...
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Spontaneous symmetry breaking in quantum mechanics
I am learning QM and trying to understand the (absence of) SSB in QM. I have read statements from several posts in the forum about the absence of SSB in few-body QM (and I'm not sure if they are ...
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General Dimensional Crystallographic Symmetries
I'm working on a project that requires me to derive the form of the symmetry operations of my model in a general dimension $d$. I have the general dimensional form of the primitive lattice vectors $\...
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Particle-Hole Symmetry in Bloch Hamiltonians and Fock Space
I am having trouble understanding how Charge Conjugation is defined in Fock Space and in particular when applied to Bloch Hamiltonians.
In particular I would start by defining the PH operator ($P$)in ...
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Particle-Hole symmetry in the CAR Algebra
I'm trying to define a Particle-Hole symmetry operator in the CAR Algebra in a general way.
I am finding very confusing to understand weather it should be treated as a linear or antilinear operator ...
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What symmetries constrain the magnetic dipole moment to be proportional to angular momentum?
While working on calculations regarding dipole moments in quantum dots, I noticed an interesting difference between the form of magnetic and electric dipole moment operators in quantum mechanics (bold ...
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Do topological operators for higher form Symmetries have to be embeddable in a single time slice?
I have a question about higher form symmetries. I can't find anything about this in the literature. The story you usually hear is: higher form symmetries are always abelian because the topological ...
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Active and passive transformations act on different things
In a classical (say, relativistic) theory, one interprets continuous coordinate transformations (pushbacks and pullbacks) as either active or passive. From my understanding, active transformations act ...
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Are these two notions of "conserved angular momentum" in axially symmetric spacetimes the same?
In Schwarzschild and Kerr spacetimes, when one studies the problem of a test particle undergoing geodesic motion, the use of symmetries is crucial in showing integrability and in solving the dynamical ...
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Is relative velocity necessarily symmetric? [duplicate]
In his 1905 paper, when Einstein posits a relative velocity v between two frames, he assumes that each frame will get the same number. Is this necessarily true, tautologically? That is, if they ...
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On OPE of primary fields in RCFTs with generalized symmetries
Firstly recall the following fact: let $\phi_a,\,a=1,\dots,n$ be the chiral primary fields of a RCFT with respect to the Virasoro symmetry, then we have the following OPE:
$$\phi_{a}(z)\phi_{b}(w)=\...
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Problem with finding heat field on surface of infinite cylinder (with complex Green's function) [closed]
I am trying to determine field produced by heat source on the intrinsic surface of infinitely high cylinder. Because we are only looking at the surface, I can "unroll" it into complex plane. ...
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How can the magnetometers in migratory birds' eyes sense the *direction* of the Earth's magnetic field?
Scientists believe that migratory birds probably navigate by sensing the Earth's magnetic field via cryptochrome proteins in their retinas (technical article and popular article).
As I understand the ...
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Do Killing fields give conservation laws for momentum of photons?
Any Killing field gives a conserved quantity
$$ K_\mu u^\mu $$
And in the case of massive particles one can multiply by the rest mass and obtain that
$$ K_\mu p^\mu $$
is a conserved quantity.
However ...
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The boundary condition of symTFT construction for 1+1D $\mathbb{Z}_2\times\mathbb{Z}_2$ SPT with two copies of toric code
I am reading a lecture note on topological holography: https://xiechen.caltech.edu/documents/28637/UQM2024_XC.pdf
In section 2 of the note, a transverse Ising model is obtained by sandwiching a toric ...
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