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Question 1

8votes

1answer

580views

In a stationary, asymptotically flat spacetime, when does a Killing horizon coincide with the event horizon?

In general relativity, the black hole region (B) of an asymptotically flat spacetime $M,g$ is defined globally as$$B := M \setminus J^-(\mathscr I^+),$$and the (future) event horizon is its ...

Heusler

81

askedNov 24 at 1:49

Question 2

2votes

0answers

73views

Most general isotropic spatial metric from Schur's lemma

Consider a generic spatial metric $$\mathrm{d}\ell^2 = \gamma_{ij}(\vec{x}) \, \mathrm{d}x^i \mathrm{d}x^j.$$ Assume isotropy of the universe around the origin. Then the metric can only depend on the ...

MangoIceCream

21

askedNov 22 at 3:17

Question 3

0votes

0answers

41views

On the derivation of the Reissner-Nordstrom (RN) metric [closed]

In the derivation of the Reissner-Nordstrom (RN) metric, the field components only take $(t,r)$ and not mixed components with $\theta$ and $\phi$ but does the assumption of spherical symmetry imply ...

Anusha Mahapatra

1

askedNov 20 at 8:37

Question 4

5votes

2answers

807views

Parity violation clarification: Wu experiment

I recently read about the Wu experiment, but I’m missing something about parity. As I understand it, basic EM would already violate parity. Apparently, it doesn’t, but I’m wondering e.g. what’s ...

Mat

261

askedNov 18 at 14:35

Question 5

3votes

1answer

302views

Time ordering vs symmetry transformation in Euclidean correlation functions

In a QFT with Euclidean signature, the correlation functions can only be well-defined in a time-ordered manner (This is Claim 1 on Page 2 of Simmons-Duffin's lecture note). For example, a scalar 2pt ...

Hezaraki

133

askedNov 15 at 0:52

Question 6

2votes

0answers

88views

Centrifugal term in cylindrical coordinates

When solving an equation of motion with spherical symmetry using the WKB approximation, one usually encounters a centrifugal term that diverges as$$\sim \frac{l(l+1)}{r^2}.$$What is the ...

Alexa Birter

21

askedNov 12 at 20:21

Question 7

5votes

1answer

204views

Do TQFTs have a notion of symmetry?

I've recently started learning about topological quantum field theories (via the Atiyah–Segal axioms), and noticed that I haven't seen any mention of symmetries present. Considering how important ...

Ishan Deo

2,615

askedNov 9 at 2:44

Question 8

2votes

1answer

415views

Does Wigner's theorem only imply left inverse?

From wikipediahttps://en.wikipedia.org/wiki/Wigner%27s_theoremFor unitary case$$\langle U \Psi, U \Phi \rangle = \langle \Psi, \Phi \rangle .\tag{1} $$If I apply the definition of adjointhttps://...

orange

63

askedNov 6 at 0:06

Question 9

0votes

1answer

38views

Dipole moment operator and $C_{1h}$ point group symmetry

Why does the dipole moment have to be perpendicular to the mirror plane in systems with $C_{1h}$ point group symmetry? I am trying to understand the dipole emission of point defects in solid-state ...

foghorn

1

askedNov 5 at 17:43

Question 10

5votes

4answers

883views

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 ...

TinCan

61

askedNov 1 at 21:42

Question 11

1vote

1answer

164views

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 ...

user31415926

363

askedOct 24 at 12:56

Question 12

0votes

0answers

42views

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 ...

Alessio Martinez

77

askedOct 18 at 15:51

Question 13

0votes

0answers

45views

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 ...

Alessio Martinez

77

askedOct 18 at 11:42

Question 14

1vote

0answers

28views

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 ...

Dev

327

askedOct 17 at 13:44

Question 15

1vote

1answer

131views

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 ...

Josh Newey

1,015

askedOct 10 at 8:16

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Stack Exchange Network

Questions tagged [symmetry]

In a stationary, asymptotically flat spacetime, when does a Killing horizon coincide with the event horizon?

Most general isotropic spatial metric from Schur's lemma

On the derivation of the Reissner-Nordstrom (RN) metric [closed]

Parity violation clarification: Wu experiment

Time ordering vs symmetry transformation in Euclidean correlation functions

Centrifugal term in cylindrical coordinates

Do TQFTs have a notion of symmetry?

Does Wigner's theorem only imply left inverse?

Dipole moment operator and $C_{1h}$ point group symmetry

Why is the Stress Tensor a Diagonal Matrix for Static Fluids?

Spontaneous symmetry breaking in quantum mechanics

Particle-Hole Symmetry in Bloch Hamiltonians and Fock Space

Particle-Hole symmetry in the CAR Algebra

What symmetries constrain the magnetic dipole moment to be proportional to angular momentum?

Do topological operators for higher form Symmetries have to be embeddable in a single time slice?

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