Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · hep-ph/0103025

Pinching phenomenon: Central feature in out of equilibrium thermal field theories

I. Dadic
View original source ↗Read source document ↗Export metadata ↓

Abstract

We continue to study out of equilibrium TFT with switching on the interaction occurring at finite time. We exploit the concept of projected function (PF) and Wigner transform of projected function (WTPF). WTPF's are bare propagators, one-loop self-energies, retarded and advanced components of the resummed propagator. Among WTPF's convolution product is very simple, one does not need gradient expansion. However, WTPF's are completely determined by their infinite time limit and, thus, cannot be the carriers of relaxation phenomena. Furthermore, we observe that the functions capable of carrying relaxation phenomena (non-WTPF) emerge in the mixed ("ill-defined") products of retarded and advanced propagators and self-energies. In particular, only non-WTPF's contribute to time variation of equal-time Green functions (particle number, etc.); contributions from WTPF will be constant in time. As these are generated in mixed products, the pinching phenomenon is being promoted from an obstacle to the central feature of out of equilibrium TFT. We analyze the pinching phenomenon. In the case of naive pinching we reproduce known results. In Schwinger-Dyson equations the Keldysh component of self-energy is well defined even for multiple self-energy insertion contributions. We calaculate explicitly single self-energy contribution to Keldysh component of propagator which generates nontrivial time dependence. For photon production from QCD plasma (finite-lifetime effect) our approximate analytic results agree with the results by S. -Y. Wang and D. Boyanovsky obtained within dynamical renormalisation group approach.

Explore related subjects

hep-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

I. Dadic. 2001-03-02. Pinching phenomenon: Central feature in out of equilibrium thermal field theories. https://arxiv.org/abs/hep-ph/0103025

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Covariant reggeization framework for diffraction. Part I: Hadronic tensors in Minkovsky space-time of any dimension

In this paper we consider the general structure of irreducible tensor representations of the Poincaré group of arbitrary space-time dimension $D$ with multiple sets of Lorentz indices and different ways to construct them from basic elements (Lorentz vectors and the metric tensor). Then we apply the same methods to obtain the expansion of general hadronic tensors in terms of these irreducible tensors. We propose to use an effective approach in hadronic diffraction, which was usually called covariant reggeization, and obtain basic functions and tensors to calculate all the diffractive cross-sections.

hep-ph↗
arXiv2026

Extraction of the pion-nucleon coupling constant using the effective-range expansion with the left-hand cut

We apply the generalized effective-range expansion of Phys. Rev. Lett. 135, 011903(2025), which incorporates the left-hand cut from one-pion exchange, to low-energy neutron-proton scattering in the $^1S_0$ and $^3S_1$ channels. The amplitude zero for the center-of-mass momentum near 0.35 GeV in the $^1S_0$ channel is naturally accommodated within this framework. We extract the pole position, scattering length, effective range, and the pseudoscalar pion-nucleon coupling constant $g_{πN}^2/(4π)$ at different expansion orders. The low-energy parameters are stable and consistent with established values, while $g_{πN}^2/(4π)$ exhibits larger uncertainties. The extraction of $g_{πN}^2/(4π)$ is data-driven, relying on the analytic constraints from the left-hand cut and phase-shift data within the one-pion-exchange approximation. Despite larger uncertainties compared to high-precision extractions, the consistency with established values demonstrates that this framework can probe the left-hand-cut singularity.

hep-ph↗
arXiv2026

Sexaquarks and $H$ dibaryons in the $uuddss$ system: a comparison within a constituent quark model

We study the $uuddss$ multiquark within a constituent quark model framework, solving the corresponding nonrelativistic Schrodinger equation by means of a diffusion Monte Carlo (DMC) method. The total wavefunction is written as the product of a radial component and an exact spin-color-flavor state, restricted to isospin $I$=0. For this isospin, all allowed flavor wave functions are included. We explore two distinct constructions of the six-quark system. In the first one, corresponding to a sexaquark, all six quarks are treated as indistinguishable and the wave function is fully antisymmetric with respect to the exchange of any two quarks. In the second one, corresponding to the $H$ dibaryon, the system is partitioned into two sets of three quarks, effectively mimicking a baryon-baryon-like configuration including hidden color terms in which antisymmetry is imposed only within each three-quark cluster. Only when the system is forced into a baryon-baryon-like configuration, and for certain values of the spin, color and flavor quantum numbers, do we obtain states with masses close to, but above, the two-baryon threshold. Those states are characterized by two loosely bound three-quark clusters separated from one another by a distance of $\sim$ 2.5 fm. The remaining structures are compact objects irrespectively of their internal wavefunction.

hep-ph↗