7
votes
Can someone explain this Feynman Diagram in the picture?
The short line in the middle is a gluon.
I don't know from where you got the diagram.
But it contains some mistakes.
The antiquarks ($\bar{u}$ and $\bar{s}$) need to be drawn
with their arrows ...
- 31.6k
3
votes
Accepted
Integrating high momentum modes using Wilson's approach to renormalization
Assuming that you are comfortable with eq. (12.5) of Peskin-Schroeder,
$$\begin{align}Z &= \ldots \\ &= \int \! \mathcal{D} \phi \, e^{-\int \mathcal{L}(\phi)} \! \! \int \! \mathcal{D}\hat{\...
- 2,683
3
votes
Accepted
Peskin and Schroeder, Linear sigma model, renormalized perturbation theory
That's a good question.
The linear sigma model (11.14) has 3 terms, and hence 3 counterterms, and hence needs 3 renormalization conditions (11.17a+b+c).
Yes, since the $N$th component
$$\phi^N(x)~=~ ...
- 184k
2
votes
Integrating high momentum modes using Wilson's approach to renormalization
Eq. (12.7) is the kinetic term for the high/heavy modes $\hat{\phi}$. Since the mass term is treated as a perturbation term, eq. (12.7) is the free part of the perturbative action for the path ...
- 184k
2
votes
Accepted
Can we eliminate gauge degrees of freedom in QFT by quantizing the field strength directly?
Schwartz has likely manifestly gauge-invariant formulations of QED in mind, such as e.g. Ref. 1. Its eq. (5) displays a non-local Lagrangian.
References:
I. Goldberg, Gauge-Invariant Quantum ...
- 184k
1
vote
Does an excitation of any quantum field extend forever through space?
It depends.
For your example of the metal sheet, the wave is vibration of the metal sheet itself, so it doesn't make sense for that to extend beyond the sheet. However the sheet will also cause ...
- 1,503
1
vote
Is crossing symmetry violated in the difference between positron emission and electron capture?
If you are interested in spectator electrons, it's helpful to include them in your decay relations:
\begin{align}
\left[
Z e^- + {^A_Z X}
\right]_\text{bound}
&\to
\left[(Z-1)e^- + {^A_{Z-1}Y}
\...
rob♦
- 80.2k
1
vote
Which configurations are important in lattice QCD?
In zero-temperature QCD it is generally BPST instantons. These are
known to explain spontanteous breaking of $SU(N_f)_A$ chiral
symmetry, which provides quarks with constituent mass. These
gauge-...
- 5,064
1
vote
What is a CP number? In terms of CP-Symmetry and CP-Violation?
Background. P is an operation that mirror-reflects a state in space, and C an operation that converts particles into antiparticles, reversing their charge, flavor, baryon #, lepton #, fermion #, and ...
- 54k
1
vote
Which configurations are important in lattice QCD?
The issue with perturbation theory in QCD is that it only works when the interaction strength is small compared to the energy scale you're considering. In terms of field configurations in a monte ...
- 3,574
1
vote
How to derive gravitational path integral from the Hamiltonian operator formalism?
At the classical level, the equivalence goes as follows:
The Lagrangian Einstein-Hilbert (EH) action with variables $g_{\mu\nu}$
is replaced with the first-order Palatini action with variables $(g_{...
- 184k
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