17
votes
Accepted
How does physics research work?
Is there a group of (paid) researchers that work on M-Theory 24/7,
hoping that someday they'll finally unify physics? Or is it more like
a thing that passionate people do in their spare time?
...
- 3,967
13
votes
Accepted
Is the recent Nature paper by Minev et al. evidence of new physics?
The trick here in "observing a quantum jump" is that this is not equivalent to doing a strong measurement that "collapses" the wavefunction.
The archetypal quantum jump is a two ...
- 129k
11
votes
Accepted
On a rigorous definition of Feynman's functional integral$.$
The definition you are using in your question is the one that everybody who does rigorous perturbative renormalization uses. The particular choice of method BPHZ vs. Epstein-Glaser, etc. doesn't ...
- 6,262
8
votes
Lindblad and Input-Output Formalism in Quantum Optics
There is already a nice answer but I feel that some important aspects deserve additional attention. My answer is simply a list of observations:
Master equations involve approximations: It is ...
- 11.7k
7
votes
Accepted
SLE applied to theoretical physics (eg. CFT), too untractable? not informative enough?
My name is Raoul Santachiara and I am a CNRS researcher at the Paris-Saclay university. My core expertise are the CFTs and their applications to 2D critical statistical model. I have worked (and I am ...
7
votes
Accepted
Definition for long range entanglement (LRE) by generalized local unitary (gLU) and generalized stochastic local (gSL) transformations
I think it is a typo.
It is helpful to sketch a short history:
In 2010, Chen, Gu and Wen wrote a paper (arXiv:1004.3835) where they introduced the notion of local unitary evolution and used it to ...
- 9,311
6
votes
Accepted
Perturbative Results Kitaev Model with Magnetic Field
Yes, the precise result can be found in Eq. (30) of our paper arXiv:1109.4155:
$$\kappa = \frac{h_xh_yh_z}{8 u_0^2 J^2},$$
where $u_0$ is a numerical factor obtained by solving the mean field ...
- 12k
6
votes
Accepted
Ground state degeneracy: Spin vs Fermionic language
Your claim is not correct: After a Jordan-Wigner transformation, the Ising model is mapped to a free fermion chain which has either periodic or anti-periodic boundary conditions, depending whether the ...
- 21.4k
6
votes
Relationship between different $Z_{16}$ classifications
Besides the obvious relationship that the representation theory of Majorana zero modes is the leverage point for each, the two are related in an intricate network of bosonization and dimensional ...
- 8,134
6
votes
Accepted
Specific experiments that affirm particle-in-a-box QM theory
Search for papers/ videos on GaAs/AlGaAs heterostructures. It is possible to construct quantum wells by combining certain types of semiconductors with different band gaps. For example, you can build a ...
- 98
5
votes
Essentials to learn before reading condensed matter papers?
If you have graduate level understanding of quantum physics, make sure you have an advanced understanding of statistical mechanics as well. Pathria is a classic, as is Huang, although the latter can ...
5
votes
Apparent failure of SUSY nonrenormalization theorem
There actually can be a violation of no-renormalization theorem in case where massless fields are involved in the the computation as in the first and second graphs. These inconsistencies appear as ...
- 797
5
votes
Existence of the Unruh effect
I find that the "derivation" by using a Bogoliubov transformation and then tracing out part of the field is sufficiently dubious that one could not confidently expect the effect based on that ...
- 61.8k
5
votes
Accepted
Wightman's theorem, in terms of time-ordered functions$.$
You can't get the $G_n$ from the $W_n$ as easily as you say because this involves multiplying distributions by non-smooth Heaviside functions of time differences. That's mathematically illegal. The ...
- 6,262
5
votes
Accepted
Relation between cobordism and unitary fusion category classification of TQFT/ SPT phase
The Turaev-Viro state sums are for constructing non-invertible 3d TQFTs, since there are no nontrivial invertible ones without adding extra symmetry. You can do that, and it leads to a G-equivariant ...
- 8,134
5
votes
Accepted
What does 3D buckling reconstruction mean?
In the "structural reconstruction" context it means that the crystal structure has changed -- often at a surface. In particular a "buckling reconstrction" means that the ...
- 56.5k
5
votes
What does 3D buckling reconstruction mean?
Surfaces of materials don't look like the inside of the bulk, otherwise you'd have dangling bonds and a ton of energy. So the dangling bonds combine in a certain way to minimize that energy. This is ...
- 1,951
5
votes
Negative energy particle effect on observable object
That is one of the issues I personally see with that paper. Logan J. Fisher already mentioned the issue with taking particles too literally, but also there is the matter that since they use path ...
- 23k
5
votes
Accepted
Negative energy particle effect on observable object
The paper is just plain wrong and not in a few subtleties but in its basic assumption of relevance of obtained local effective action for black hole radiance.
Since the paper puts a lot of emphasis on ...
- 16.6k
5
votes
Specific experiments that affirm particle-in-a-box QM theory
A very common example used in introductory physical chemistry is modeling the $\pi$ electrons in a conjugated polyene like $\beta$ carotene. When you model the electrons this way, you get a ...
- 3,422
4
votes
Strong interacting v.s. Strong Coupling v.s. Strong Correlated
From the point of view of the condensed matter physics, the distinction between strong coupling and strongly correlated seems rather evident, and largely agrees with the point of view expressed in the ...
- 65k
4
votes
Hamiltonian for the Periodic Kitaev Model
This is due to the diagonalization with Nambu state. If you need $(c_k,c^\dagger_{-k})$, you also need to handle $c_{-k} c^\dagger_{-k}$ term in the Hamiltonian.
$c^\dagger_{j}c^\dagger_{j+1}$ and its ...
- 41
4
votes
Explicit construction for unitary extensions of completely positive and trace preserving (CPTP) maps?
This is just to complement the other answer by providing a more explicit derivation.
We have a map $\Phi(\rho)=\sum_k A_k \rho A_k^\dagger$ and we want to find a unitary $\mathcal U$, acting on a ...
- 15.2k
4
votes
Discovery of anti-deuteron and the implication of CPT violation
From your link:
Dirac came out of his depression when he received a phone call from his friend Abdus Salam, saying: "Relax Paul, my friend Nino Zichichi has discovered the antideuteron".
This is ...
rob♦
- 94.2k
4
votes
Accepted
Quark condensate alignment with Yukawa Higgs couplings
The Yukawa couplings start life as an awful off-diagonal mess, and, upon diagonalization of the induced mass matrix they define flavor, as the resulting eigenstates. From this point on, we may ignore ...
- 66.3k
4
votes
Accepted
In 3D ${\cal N}=2$ SUSY, the linear multiplet contains a global current. How is this related to the gauge field?
A linear multiplet is defined as $\Sigma=\epsilon^{\dot{\alpha}\beta}\bar{D}_{\dot{\alpha}}D_{\beta}V$ where $V$ is the vector multiplet corresponding to a U(1) gauge symmetry.
You have no "dotted ...
- 148
4
votes
Accepted
"Weak" and "Strong" topological insulators
When we compute the reduced KO theory of $\bar S^d$, a sphere, by the Atiyah-Hirzebruch spectral sequence it's
$$\tilde H^d(\bar S^d, KO_{-q-d}(pt)) = KO_{-q-d}(pt).$$
Note that $\tilde H^0(\bar S^d, ...
- 8,134
Only top scored, non community-wiki answers of a minimum length are eligible