相关论文: Infrared Divergence and Low Energy Theorem in Non-…
In this paper we revisit the classical fluctuation-dissipation theorem with derivations and interpretations based on quantum electrodynamics (QED). As a starting point we take the widely cited semiclassical expression of the theorem…
After presenting a brief summary of functional approaches to QCD at vanishing temperatures and densities the application of QCD Green's functions at non-vanishing temperature and vanishing density is discussed. It is pointed out in which…
The high-energy scattering amplitude of two colour-singlet quark-antiquark pairs is governed by the correlation function of two Wilson loops, which follow the classical straight lines for quark (antiquark) trajectories. This quantity is…
We derive the Ward-Takahashi identity and establish the gauge-invariant response theory for open quantum systems described by Lindbladians to show that particle-number conservation is not necessary to satisfy gauge invariance. We construct…
We present a new perspective on the study of the behavior of the strong coupling $\alpha_s(Q^2)$ -- the fundamental coupling underlying the interactions between quarks and gluons as described by the Quantum Chromodynamics (QCD) -- in the…
We study the infrared (IR) structure of $SU(N) \times U(1)$ (QCD $\times$ QED) gauge theory with $n_f$ quarks and $n_l$ leptons within the framework of perturbation theory. In particular, we unravel the IR structure of the form factors and…
A detailed investigation of the low-energy chiral expansion is presented within a model truncation of QCD. The truncation allows for a phenomenological description of the quark-quark interaction in a framework which maintains the global…
We derive the low-energy limit of quantum chromodynamics (QCD) and provide evidence that in the 't Hooft limit, i.e. for a very large number of colors and increasing 't Hooft coupling, quark confinement is recovered. The low energy limit of…
We describe the implementation of infrared subtractions for two-loop QCD corrections to quark-antiquark annihilation to electroweak final states. The subtractions are given as form-factor integrands whose integrals are known. The resulting…
We show that QCD undergoes dimensional reduction at high temperatures also in the quark sector. In the kinematic region relevant to screening physics, where the lowest Matsubara modes are close to their ``mass-shells'', all static Green's…
We discuss the infrared structure of processes with massive quarks in the initial state. It is well known that, starting from next-to-next-to-leading order in perturbative QCD, such processes exhibit a violation of the Bloch-Nordsieck…
Functional equations like exact renormalisation group and Dyson-Schwinger equations have contributed to a better understanding of non-perturbative phenomena in quantum field theories in terms of the underlying Green functions. In Yang-Mills…
We investigate the renormalization group flow and beta functions of Yang-Mills theory and adjoint QCD in a strong, stable, self-dual background field $F$. In deep UV, theory runs according to the standard beta function, $\beta_0$. Treating…
A nonperturbative approach to two-dimensional covariant gauge QCD is presented in the context of the Schwinger-Dyson equations and the corresponding Slavnov-Taylor identities. The distribution theory, complemented by the dimensional…
Due to asymptotic freedom, QCD is guaranteed to be accessible to perturbative methods at asymptotically high temperatures. However, in 1979 Linde has pointed out the existence of an "infrared wall", beyond which an infinite number of…
We revisit the non-Abelian dipole problem in the context of a simple semiclassical approach that incorporates some essential features of the infrared sector of Yang-Mills theories in the Landau gauge, in particular, the fact that both the…
We show that the gauge-fermion interaction in multiflavour $(2+1)$-dimensional quantum electrodynamics with a finite infrared cut-off is responsible for non-fermi liquid behaviour in the infrared, in the sense of leading to the existence of…
A detailed investigation of the low-energy chiral expansion is presented within a model truncation of QCD. The model dependence of the chiral coefficients is tested for several forms of the quark-quark interaction by varying the form of the…
Hadronic annihilation rate of $1^{+-}$ heavy quarkonium is given to next-to-leading order in $\alpha_s$ and leading order in $v^2$ using a recently developed factorization formalism which is based on NRQCD. The result includes both the…
Using gluon and ghost propagators obtained from Schwinger-Dyson equations (SDEs), we construct the non-perturbative effective charge of QCD. We employ two different definitions, which, despite their distinct field-theoretic origin, give…