User xiaohuamao

50 votes

0 answers

2k views

Can Lee-Yang zeros theorem account for triple point phase transition?

asked Nov 8, 2013 at 1:41

18 votes

1 answer

2k views

Does magnetic monopole violate $U(1)$ gauge symmetry?

quantum-mechanics electromagnetism quantum-field-theory differential-geometry magnetic-monopoles

asked Feb 25, 2015 at 9:24

14 votes

2 answers

2k views

Why do spin-$\frac{1}{2}$ nuclei have zero electric quadrupole moment?

quantum-mechanics electromagnetism nuclear-physics quantum-spin

asked Dec 14, 2014 at 9:15

13 votes

1 answer

927 views

Is Elitzur's theorem valid only in lattice field theory?

quantum-field-theory gauge-theory symmetry-breaking lattice-model

asked Apr 22, 2015 at 6:25

10 votes

2 answers

5k views

Why does adjoint representation matter in some field theories?

quantum-field-theory group-theory group-representations magnetic-monopoles higgs

asked Nov 19, 2013 at 10:21

10 votes

5 answers

2k views

Why does group representation theory look linear?

quantum-mechanics symmetry group-theory representation-theory non-linear-systems

asked Jun 2 at 8:51

8 votes

1 answer

3k views

Numerical analytic continuation for Green's function

condensed-matter solid-state-physics greens-functions computational-physics

asked Jun 3, 2014 at 7:47

7 votes

2 answers

552 views

First-principles calculation of the critical temperature of a superconductor

quantum-mechanics condensed-matter solid-state-physics superconductivity computational-physics

asked Nov 19, 2016 at 12:08

7 votes

1 answer

3k views

How to calculate Zak phase from numerical wavefunctions with arbitray phase?

condensed-matter solid-state-physics computational-physics topological-field-theory topological-insulators

asked Apr 15, 2018 at 14:29

7 votes

1 answer

222 views

How to dress free Green functions with constant broadening?

quantum-field-theory condensed-matter solid-state-physics greens-functions non-equilibrium

asked Dec 26, 2020 at 12:09

6 votes

1 answer

317 views

Is topological surface state always tangential to bulk bands?

condensed-matter solid-state-physics electronic-band-theory topological-insulators topological-phase

asked Jul 3, 2018 at 11:37

6 votes

2 answers

249 views

"Bosons are either gapped or condensated, except physical principle protected cases (Goldstone boson, photon)."?

quantum-mechanics quantum-field-theory condensed-matter solid-state-physics bosons

asked Jul 31, 2014 at 7:07

6 votes

1 answer

1k views

Are they the same thing: Wigner distribution in quantum Boltzmann equation and Wigner function in quantum optics?

quantum-mechanics solid-state-physics quantum-information greens-functions wigner-transform

asked Mar 14, 2014 at 2:13

6 votes

2 answers

2k views

When is quasiparticle same as elementary excitation, and when is not?

quantum-field-theory condensed-matter solid-state-physics quasiparticles

asked Dec 17, 2013 at 6:31

5 votes

2 answers

662 views

Do we have a quantum field theory of monopoles?

quantum-field-theory magnetic-monopoles

asked Nov 16, 2013 at 9:01

5 votes

1 answer

270 views

Meaning of approximation $\cos(\phi)=\frac{\phi^2}{2}\mathrm{e}^{-\frac{1}{2}\langle{\phi^2}\rangle}$ in a field theory?

quantum-field-theory condensed-matter solid-state-physics renormalization wick-theorem

asked Aug 15, 2016 at 3:53

5 votes

2 answers

165 views

Does free phonon propagator always vanish at zero momentum?

quantum-field-theory condensed-matter solid-state-physics feynman-diagrams phonons

asked Dec 16, 2021 at 14:07

4 votes

1 answer

92 views

Is self-energy $\mathrm{Im}\Sigma^r<0$ always true?

quantum-field-theory condensed-matter solid-state-physics greens-functions self-energy

asked Jan 14 at 7:33

4 votes

0 answers

469 views

Matsubara frequency summation when residue theorem is suspicious?

quantum-field-theory condensed-matter solid-state-physics many-body greens-functions

asked Sep 19, 2016 at 7:35

4 votes

0 answers

369 views

Fields with SO(3) diagonal subgroup symmetry

quantum-field-theory group-theory group-representations magnetic-monopoles higgs

asked Nov 4, 2013 at 15:22

3 votes

2 answers

754 views

Infinitely many degeneracy of Landau level: Countable or Uncountable?

quantum-mechanics magnetic-fields wavefunction schroedinger-equation hilbert-space

asked Sep 20, 2014 at 6:26

3 votes

1 answer

707 views

Why does total spin conservation law forbid the spin wave gap in Heisenberg magnets?

condensed-matter solid-state-physics symmetry quantum-spin symmetry-breaking

asked Dec 17, 2013 at 6:39

3 votes

3 answers

271 views

Why can we quantize macro(meso)scopic harmonic oscillator?

quantum-mechanics condensed-matter solid-state-physics nanoscience

asked Jan 25, 2014 at 13:38

3 votes

1 answer

313 views

Group analysis forbids band-crossing in 1D?

quantum-mechanics condensed-matter solid-state-physics spacetime-dimensions group-theory

asked Jan 28, 2014 at 14:59

3 votes

0 answers

200 views

Can the occupation of Floquet bands be calculated from the Keldysh Green's function?

quantum-mechanics condensed-matter solid-state-physics greens-functions non-equilibrium

asked Jan 8, 2016 at 13:10

3 votes

1 answer

217 views

In what circumstances, can exchange interaction acquire temperature dependence?

quantum-mechanics electromagnetism condensed-matter solid-state-physics quantum-spin

asked Feb 8, 2016 at 8:54

3 votes

0 answers

232 views

Does nonlocal theory violate causality?

quantum-mechanics quantum-field-theory quantum-information causality locality

asked Mar 25, 2014 at 6:24

3 votes

1 answer

196 views

Bosonization for unequal left/right Fermi velocities

quantum-mechanics condensed-matter solid-state-physics quantum-spin bosonization

asked Jun 21, 2016 at 5:24

3 votes

1 answer

241 views

Time reversal of Hall conductivity

condensed-matter solid-state-physics time-reversal-symmetry quantum-hall-effect

asked Feb 7, 2020 at 9:04

3 votes

1 answer

83 views

How to realize Heaviside $\theta(t-t')$ and Dirac $\delta(t-t')$ as matrices in numerics?

quantum-field-theory condensed-matter computational-physics greens-functions dirac-delta-distributions

asked Feb 13, 2021 at 12:40

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62 Questions

Can Lee-Yang zeros theorem account for triple point phase transition?

Does magnetic monopole violate $U(1)$ gauge symmetry?

Why do spin-$\frac{1}{2}$ nuclei have zero electric quadrupole moment?

Is Elitzur's theorem valid only in lattice field theory?

Why does adjoint representation matter in some field theories?

Why does group representation theory look linear?

Numerical analytic continuation for Green's function

First-principles calculation of the critical temperature of a superconductor

How to calculate Zak phase from numerical wavefunctions with arbitray phase?

How to dress free Green functions with constant broadening?

Is topological surface state always tangential to bulk bands?

"Bosons are either gapped or condensated, except physical principle protected cases (Goldstone boson, photon)."?

Are they the same thing: Wigner distribution in quantum Boltzmann equation and Wigner function in quantum optics?

When is quasiparticle same as elementary excitation, and when is not?

Do we have a quantum field theory of monopoles?

Meaning of approximation $\cos(\phi)=\frac{\phi^2}{2}\mathrm{e}^{-\frac{1}{2}\langle{\phi^2}\rangle}$ in a field theory?

Does free phonon propagator always vanish at zero momentum?

Is self-energy $\mathrm{Im}\Sigma^r<0$ always true?

Matsubara frequency summation when residue theorem is suspicious?

Fields with SO(3) diagonal subgroup symmetry

Infinitely many degeneracy of Landau level: Countable or Uncountable?

Why does total spin conservation law forbid the spin wave gap in Heisenberg magnets?

Why can we quantize macro(meso)scopic harmonic oscillator?

Group analysis forbids band-crossing in 1D?

Can the occupation of Floquet bands be calculated from the Keldysh Green's function?

In what circumstances, can exchange interaction acquire temperature dependence?

Does nonlocal theory violate causality?

Bosonization for unequal left/right Fermi velocities

Time reversal of Hall conductivity

How to realize Heaviside $\theta(t-t')$ and Dirac $\delta(t-t')$ as matrices in numerics?