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82 votes
1 answer
6k views

Why exactly do sometimes universal covers, and sometimes central extensions feature in the application of a symmetry group to quantum physics?

  • 107k
45 votes
5 answers
9k views

Have we figured out how to analyze turbulent fluids?

32 votes
6 answers
2k views

Is the density operator a mathematical convenience or a 'fundamental' aspect of quantum mechanics?

24 votes
1 answer
664 views

Anyons as particles?

  • 9,815
16 votes
2 answers
1k views

Braiding statistics of anyons from a Non-Abelian Chern-Simon theory

  • 7,340
16 votes
2 answers
948 views

In a universe with four spatial dimensions would there be elementary particles with intrinsic isoclinic spin?

15 votes
1 answer
433 views

Gauge invariant but not gauge covariant regularization

  • 203
14 votes
2 answers
1k views

Calculating $\mathrm{Tr}[\log \Delta_F]$

  • 2,638
14 votes
0 answers
844 views

Where does a fermionic coherent state live (which Hilbert space)?

  • 730
12 votes
1 answer
468 views

Group theory and quantum optics

11 votes
0 answers
498 views

Capturing (perturbatively) non-equilibrium field theory effects using "elementary" methods

11 votes
5 answers
3k views

Fermion boundary conditions at finite temperature

  • 291
10 votes
1 answer
431 views

Two interacting electrons in infinite square potential - is there a solution?

10 votes
1 answer
539 views

Matsubara frequencies and analytic continuation - Domain and uniqueness

  • 2,680
9 votes
1 answer
602 views

Significance of Dirac cones in condensed matter physics

  • 3,676
9 votes
2 answers
933 views

Experimental evidence for non-abelian anyons?

  • 1,253
9 votes
2 answers
318 views

Is there no mode expansion for $:e^{i k_\mu X^\mu(z, \bar z)}:$ in the free boson CFT?

  • 10.9k
7 votes
1 answer
1k views

Symmetry Breaking and Vacuum Expectation Values

7 votes
1 answer
501 views

Is there a rigorous proof that photons do not acquire mass through renormalization?

  • 11.9k
6 votes
1 answer
372 views

Exact solution of SU($N$) model in large $N$ limit

6 votes
0 answers
155 views

SUSY sigma model in QM, bosonic sector?

  • 7,628
6 votes
0 answers
200 views

Can a quantum state with infinite variance of photon number be found in nature or artificially created?

  • 251
5 votes
1 answer
878 views

Ambiguity in Beta Functions (2-loop)

  • 2,517
5 votes
0 answers
183 views

Why is a particles magnetic moment proportional to its spin?

  • 329
4 votes
1 answer
192 views

Diffeomorphism invariance for QFT in curved space

  • 193
4 votes
0 answers
74 views

Temperature of spin-glass transition

4 votes
2 answers
126 views

Mathematical understanding of band energy

  • 1,648
3 votes
0 answers
170 views

Entanglement entropy for finite interval using heat kernel method

  • 151
3 votes
0 answers
111 views

Stratonovich integral in quantum field theory

3 votes
1 answer
535 views

Gauge invariance of non-Abelian theories under Pauli-Villars-Regularisation

  • 1,179