All Questions
7
questions
2
votes
0
answers
45
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Equivalent definitions of (dis)continuous phase transitions at criticality
Consider a classical lattice model on $\mathbb{Z}^d$ and suppose that the system undergoes a phase transition as you lower the temperature, i.e., increase $\beta$. The most general definition of a ...
- 2,123
6
votes
2
answers
1k
views
At the critical point, is Kramers-Wannier duality a unitary symmetry of the model?
I have in mind the transverse ising model and its (self-dual) generalizations, such as
$$H_{TI} = \sum_i \sigma^z_{i}\sigma^z_{i+1} + h \sigma^x_{i}$$
and
$$H_{SDANNI} = \sum_i (\sigma^z_{i}\sigma^z_{...
- 2,292
2
votes
1
answer
729
views
Proof of Mermin-Wagner Theorem
There are many presentations of the proof of the Mermin-Wagner theorem in many different contexts (which talk about quantum vs. classical, existence of unique Gibbs measure or non-zero mean ...
- 2,024
2
votes
0
answers
95
views
What is the critical temperature for a BKT transition in the 2D quantum XY model with $S=1$ (not $S=1/2$)?
What is the critical temperature for a BKT transition in the 2D quantum XY model with $S=1$ (not $S=1/2$)? For instance, the classical XY model has KTc/J = 0.898 and the quantum XY model with S=1/2 ...
- 21
9
votes
2
answers
522
views
Integrability of a non-integrable quantum spin model at critical point
Is it right, that non-integrable quantum spin models in one dimension become integrable at their critical points? Or do they stay nonintegrable at the critical point also? Are there any examples known?...
- 5,697
1
vote
0
answers
499
views
Why the correlation function of 2D classical XY model is written so?
2D classical XY model $$H = -J\cos(\theta_{i}-\theta_{j})%$$ is famous for Berezinskii-Kosterlitz-Thouless phase transition. This is because of the difference of correlation function between hot and ...
- 61
1
vote
1
answer
1k
views
Why is the critical exponent $\alpha$ negative at the Ising spin-glass transition?
The specific heat usually diverges at a phase transition - typically as a power-law, giving a critical exponent $\alpha > 0$. (Although in 2D, sometimes the divergence is only logarithmic, as with ...
- 48.4k