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Zero modes ~ zero eigenvalue modes ~ zero energy modes?

What is the significance of the QCD scale parameter $\Lambda$?

What are zero modes?

How do instantons cause vacuum decay?

How to Perform Wick Rotation in the Lagrangian of a Gauge Theory (like QCD)?

What's the real resolution of the $U(1)_A$ problem?

The Spin Connection

What is the difference between Chiral anomaly, ABJ anomaly, and Axial anomaly?

Counting the number of propagating degrees of freedom in Lorenz Gauge Electrodynamics

Interacting Fields in QFT

Variation of the metric with respect to the metric

Can massive fermions have zero modes?

Understanding multiple instanton contributions to vacuum tunneling in a double potential well

Question about physical degree of freedom in Maxwell Theory: Why Coulomb gauge can fix all redundant degree of freedom

How do Faddeev-Popov (FP) ghosts help path integrals?

Dirac Equation in General Relativity

The relationship between spin and spinor curvature

Scalar field lagrangian in curved spacetime

$U(1)$ abelian/axial/chiral anomaly in 4D

Field action of linearized gravity associated with spin-2 particle in Thorne book

How can we have a quark condensate without a quark potential?

Proof of Goldstone's theorem

Why does the classical path give the dominant contribution in the path integral?

Power counting and (superficial) non-renormalizability

Possible divergence structures of a renormalizable and non-renormalizable theory

Obtaining the effective Lagrangian for axions from the spontaneous breakdown of Peccei-Quinn symmetry

Why doesn't a renormalizable $\phi^4$ theory have odd diagrams?

The use of $a^\dagger(\mathbf{k}) = -i \int d^3x e^{ikx}\stackrel{\leftrightarrow}{\partial}_0 \phi(x)$ in the derivation of the LSZ-formula

R-matrix and S-matrix in QFT

Convert propagators from Euclidean to Minkowski spacetime