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Feb2313 08:38 AM
ZapperZ

1 
30,476 
I have a question in Srednicki's book regarding path integrals, but first I'll set it up so that no familiarity of the...

Aug1909 01:49 AM
RedX

2 
828 
In eqn. (82.37) Srednicki derives for the string tension between two quarks as \tau=\frac{c(g)}{a^2} where...

Aug2309 11:05 PM
Avodyne

7 
1,266 
For the free photonfield:
Z=exp(\frac{i}{2} \int d^4x \int d^4y J^\mu(x)\Delta_{\mu \nu}} (xy) J^\nu(y))
...

Aug2809 01:29 AM
Ben Niehoff

3 
698 
The Lagrangian \mathcal L =\psi^{\dagger}\gamma^0 \gamma^\mu (1\gamma^5)\partial_\mu \psi should violate parity, but...

Sep509 12:51 AM
RedX

6 
2,328 
If the Hamiltonian is given by H(x,p)=p^2+p then is it Hermitian?
I'm guessing it's not, because...

Sep709 09:04 AM
Fredrik

1 
822 
What's the difference between SU(N)xU(1) and U(N)? They seem to have the same # of generators: indeed, their...

Sep1609 08:47 AM
Hurkyl

11 
2,342 
If you model the quarks as massless, there should be no flavor mixing, because flavor mixing is achieved through the...

Sep2209 04:01 PM
Avodyne

9 
1,559 
Is it really necessary to learn how to calculate loop diagrams in QFT?
In the Wilsonian approach, you only need to...

Oct1509 04:30 AM
Demystifier

3 
1,005 
A Dirac field can be written as two Weyl fields stacked on top of each other: \Psi= \left( \begin{array}{cc} \psi \\...

Oct2209 11:04 PM
RedX

0 
742 
Both (i d/dx) and (i d/dx ) are Hermitian. For some reason (i d/dx ) is chosen to be the momentum operator, and the...

Oct2409 12:08 AM
Ben Niehoff

1 
634 
In the expression ln(s^2i\epsilon) , s^2 and \epsilon are positive (this expression can result from for example a...

Nov1009 10:35 AM
RedX

2 
614 
How does one begin to prove the renormalizability of a theory? Powercounting can give you a big clue about...

Nov1009 10:28 AM
RedX

0 
575 
In classical mechanics, scattering depends on initial momentum and position.
In quantum mechanics, the initial...

Dec409 03:04 AM
RedX

7 
771 
If you make the length of a finite well shorter, then the energy levels should increase, because for example the...

Dec909 02:16 AM
kof9595995

7 
1,219 
I read somewhere that the irreducible representations of Lie groups were countable. But what about translations? Isn't...

Dec1209 09:28 PM
RedX

11 
1,318 
When solving Schrodinger's eqn. one comes across the expression:
\frac{d^2 \psi}{dx^2}=(VE)\psi
where the mass...

Dec1709 04:18 PM
RedX

0 
816 
What are the dimensions of a scalar field \phi ? The Lagrangian density is:
\mathcal L= \partial_\mu \phi...

Dec2809 01:39 PM
RedX

11 
1,383 
In electrodynamics, the Coulomb gauge is specified by \nabla \cdot A=0 , i.e., the 3divergence of the 3vector...

Jun610 06:53 PM
RedX

3 
1,682 
I heard that in classical field theory, terms in the Lagrangian cannot have more than two derivatives acting on them....

Jun810 05:46 PM
genneth

3 
1,813 
Is there a way to measure how large a numerical value a loop integral will give?
For example, take this integral...

Jun2210 01:55 PM
RedX

0 
648 
In Kaku's book, the selfenergy in a \phi^4 scalar theory is expanded in a Taylor series as:
\Sigma(p^2)=\Sigma...

Jul1110 03:50 AM
RedX

1 
748 
I was looking at a paper that used dimensional regularization and the following expression was derived:
\int dx...

Jul2110 08:45 PM
RedX

2 
1,137 
Say you want to evaluate this integral:
\int^{\infty}_{\infty} \frac{dx}{x^2A}
Since the bottom factors into...

Aug510 10:42 PM
RedX

5 
1,484 
I got a quick question about the transformation matrix from the spinz basis to the spinx basis for spin1/2...

Oct1610 05:09 PM
RedX

2 
1,128 
In thermodynamics, two variables A and B are uncorrelated when:
<AB>=<A><B>
where <> are the expectation values...

Jan2511 02:00 AM
A. Neumaier

5 
1,139 
The integral:
\int \Pi_k d\phi_k e^{\phi_i A_{ij} \phi_j}
is a Gaussian and is equal to:
...

Jan1511 10:12 AM
kof9595995

4 
1,139 
On page 68, equation (8.13) of Srednicki's QFT book is the equation for the scalar propagator:
...

Jan2011 11:28 AM
A. Neumaier

12 
1,696 
If you have a Grassman number \eta that anticommutes with the creation and annihilation operators, then is the...

Jan2111 02:56 AM
A. Neumaier

1 
825 
In field theory, the commutator of two fields vanishes at spacelike separations. The explanation given is...

Jan2311 02:05 PM
A. Neumaier

3 
988 
According to Wikipedia ( http://en.wikipedia.org/wiki/Propagator_%28Quantum_Theory%29#Feynman_propagator ) the...

Jan2911 07:39 PM
RedX

0 
520 
For some reason I can't derive the Hamiltonian from the Lagrangian for the E&M field. Here's what I have (using +...

Feb711 03:31 AM
bigubau

2 
788 
I don't understand how to find the irreducible representations of a group.
Under transformation U:...

Feb1911 12:23 AM
RedX

1 
1,867 
Not every state can be represented by a direct product. Do states that can be written as a direct product have...

Mar1111 05:13 PM
RedX

1 
1,377 
I'm a little confused about what constitutes a distinct particle.
For example, a muon is not an electron as they've...

Mar1411 10:39 AM
A. Neumaier

5 
1,171 
Should one view correlation functions as:
(1) \; \langle T{\phi(x)\phi(y)}\rangle
or
(2) \; \langle...

Mar1611 05:46 AM
A. Neumaier

1 
1,096 
Can renormalization of QED really be interpreted as a dielectric shielding of the vacuum by electron/positron pairs...

Apr1211 06:30 PM
Bill_K

1 
506 
I was posting on another thread and it got me wondering: how come a photon is absorbed in the photoelectric effect but...

Aug1409 02:02 AM
vin300

6 
1,293 
I've never really understood how electron taking the form of a standing wave in the orbit of a nucleus can have...

Aug1909 01:50 PM
Naty1

27 
2,375 
I'm really confused on this concept. Why is gravity considered a fictitious force and is it true that this concept is...

Jul2310 06:11 PM
Glen Bartusch

3 
1,308 
After finding and reading Geroch's notes on Quantum Mechanics formulated within Differential Geometry, I was wondering...

Feb1510 08:24 PM
humanino

3 
924 