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I'm a physics grad student just trying to figure out all this stuff like everyone else.


Oct
2
comment Field theory:functional derivative involving Fourier Transform
Are you using the same convention for the sign of the exponent in the Fourier transform?
Oct
1
revised How is $ g^2 N$ held fixed in the large N limit?
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Oct
1
asked How is $ g^2 N$ held fixed in the large N limit?
Sep
27
comment Is $w=mg$ the right way to calculate mass?
Your numbers and method look reasonable to me. Are you sure you aren't getting things mixed up? A mass of .58kg and weight of 5.8N would be consistent with a gravitational acceleration of 9.8 $\frac{m}{s^2} \approx 10 \frac{m}{s^2}$ of earth.
Sep
21
awarded  Custodian
Sep
21
comment Gauss law in classical U(1) gauge theory
Thank you very much!
Sep
20
comment Finding $\psi(x,t)$ for a free particle starting from a Gaussian wave profile $\psi(x)$
I am a bit confused, why are you trying to find $\psi (k)$ ? Or as you write it, $\theta (k)$ ?
Sep
19
comment Gauss law in classical U(1) gauge theory
just curious, what textbook is this from?
Sep
13
answered Introduction to AdS/CFT
Sep
13
comment About calculation of anomalous dimension in Peskin and Schroeder's book.
@user6818 - To my knowledge, the safest way to get $\gamma$ is to calculate the bare couplings and extremize them with respect to the RG scale $\mu$. Then you will get a set of coupled first order equations $\gamma$, $\beta$ and $\gamma_m$( the anomalous dimension for the mass term) which you can solve. Ramond goes through this in his text - ' Field Theory: A moden Primer.' Peskin has a few tricks to get just $\beta$ or $\gamma$ for some particular cases in particular limits, but I don't think that they work in general.
Sep
12
revised About calculation of anomalous dimension in Peskin and Schroeder's book.
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Sep
12
answered About calculation of anomalous dimension in Peskin and Schroeder's book.
Sep
6
comment Why is the $\langle v_{x}^{2} \rangle=\frac{1}{3} \langle v^2 \rangle$?
I don't believe that this is the case, I can certainly set up states whose expectation value of velocity in a certain direction is zero: $e^{i p x}$ has $\langle v_y \rangle \sim \langle \partial_y \rangle = 0$.
Sep
5
comment Improved energy-momentum tensor
There are a set of lectures by Jaume Gomis on conformal field theory where he talks about the improved energy-momentum tensor which might be of interest to you. I'm sorry but I forget which lecture he talks about this particular issue though (there are ~14 lectures). pirsa.org/index.php?p=speaker&name=Jaume_Gomis
Aug
31
comment Deriving Lagrangian density for electromagnetic field
You do however get terms of the form $ \log tr (k^2+{F^{\mu \nu}}^2)$ when calculating the effective action in the presence of a background field gauge field. See Chap 16 of Peskin.
Aug
31
comment Deriving Lagrangian density for electromagnetic field
@MistakeInk - $\epsilon_{\mu \nu \rho \sigma } F^{\mu \nu }F^{\rho \sigma } $is a fine candidate term for the Lagragian, its just that its a total derivative so it doesn't affect the classical EOM and vanishes in perturbation theory. It still does have some consequences though - see en.wikipedia.org/wiki/CP_violation#Strong_CP_problem. As for $Det(F)$ I don't think this term is renormalizable since its equal to $e^{tr \log F}$ which you could expand about some background field value and get arbitrarily high powers of the field strength.
Aug
31
comment Is the braket notation of the Dirac delta function symmetric?
@MistakeInk - thanks. I updated to reflect this.
Aug
31
revised Is the braket notation of the Dirac delta function symmetric?
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Aug
31
answered Is the braket notation of the Dirac delta function symmetric?
Aug
24
asked What exactly is the weak portion of the SM gauge group?