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location Stony Brook
age 25
visits member for 3 years, 8 months
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Bachelor degree in Physics. Interested in mathematical aspect of quantum field theory(though ironically not mathematically enlightened, but in continuous training). Getting to know some basics of topological insulators. I will start pursuing a Phd in theoretical physics 2015 at Stony Brook University.

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I'm no longer active on physics stackexchange, partly due to the decline of the quality of the site and partly due to the abuse of moderation power. See this meta post.

If you need contact me, please send me an email or find me at www.physicsoverflow.org


Aug
22
awarded  Nice Question
Aug
8
comment Noether charge of local symmetries
Took me 2 years to notice this answer, better than mine, +1.
May
26
awarded  Popular Question
Apr
17
awarded  Nice Question
Mar
22
awarded  Popular Question
Jan
26
comment How much merit is there in the heuristic argument of bulk-edge relation for topological insulators?
@EmilProdan, Hi Prof Prodan, thank you for the reference!(I've just heard of your name from Mihai not too long ago:-))
Jan
5
awarded  Quorum
Dec
30
comment A confusion from Weinberg's QFT text (a vanishing term in Lippmann-Schwinger equation)
@Nogueira, thank you, I'll check it out later,
Dec
25
awarded  Yearling
Nov
28
revised About interchange phase of identical particles in Weinberg's QFT book
deleted 115 characters in body
Nov
27
comment Does the lagrangian contain all the information about the representations of the fields in QFT?
@glance, "why can't I say (or can I?) that Aμ is a spin-1 field for that choice of the Lagrangian?" Yes you definitely can, then the reason to reject (2) becomes the energy bounded below condition, instead of the one Schwartz gave. Qmechanic's comment is right on.
Nov
21
comment Why isn't the path integral defined for non homotopic paths?
+1, informative answer. To nitpick on the terminology, by covering space you actually mean universal covering space.
Nov
17
comment Minimization of a quaradic-like expression when calculating the generating functional for free Dirac field
$\psi,\bar{\psi}$ are treated as independent variables, so the correct analogy here is $y^TSx$, which is still a quadratic form.
Nov
17
comment Minimization of a quaradic-like expression when calculating the generating functional for free Dirac field
1.If minimizing grassman valued function has a meaning at all, then just do partial differentiations and set them to be 0; 2. it certainly is formally a quadratic form, what's your definition of "really a quadratic form"?
Nov
13
comment Are relative phases observable for identical particles but not for non-identical ones?
I suppose it ultimately boils down to superselection?
Nov
13
comment Are terms with spinors analogous to $ ( \partial_\mu \Phi )(\partial^\mu \Phi)$ forbidden in the Lagrangian?
Regarding renormalizability @AndrewMcAddams raised a nontrivial question, but at least let's say such term can't coexist with a conventional Dirac fermion.
Nov
13
comment Are terms with spinors analogous to $ ( \partial_\mu \Phi )(\partial^\mu \Phi)$ forbidden in the Lagrangian?
Sorry I made a mistake, exactly because of the reasoning I mentioned above, it is not about how many spinors you have in the term, it is about how many $\gamma_\mu$ you can sandwich, e.g. $\bar{\psi}\gamma^{\mu}\gamma^{\nu}\psi$ will transform like a rank-2 tensor. I had the instinctual impression that your term isn't invariant because one of your matrix is put in front, not sandwiched. But again it could be my misunderstanding of your notation, in that case I should retreat to my earlier statement about renormalizability.
Nov
12
comment Are terms with spinors analogous to $ ( \partial_\mu \Phi )(\partial^\mu \Phi)$ forbidden in the Lagrangian?
BTW, this is also the reason why people sometimes say "a spinor is half of a vector."
Nov
12
comment Are terms with spinors analogous to $ ( \partial_\mu \Phi )(\partial^\mu \Phi)$ forbidden in the Lagrangian?
vector transformation induced by $\partial_\mu$. As you see, we must be able to sandwich the gamma matrix to induce a vector-like transformation, so for each $\partial_\mu$, we need two spinor fields.
Nov
12
comment Are terms with spinors analogous to $ ( \partial_\mu \Phi )(\partial^\mu \Phi)$ forbidden in the Lagrangian?
@JakobH, I'm not entirely sure about your notations, but if you $\sigma_\mu$ has a similar role as Dirac's $\gamma_\mu$, then you can think about why $\bar{\psi}\gamma^{\mu}\partial_{\mu}\psi$ is invariant. Note $\gamma_\mu$ are just coefficients, they don't really transform upon a spacetime transformation, only $\psi$ transforms. What is going on is each $\psi$ , upon lorentz transformation, contribute a matrix transformation $S$ in spinor rep, and because of the algebraic fact $S^{-1}\gamma^\mu S=(\Lambda^{-1})^{\mu}_{\nu}\gamma^\nu$, it cancels the