Nuclear Theory·nucl-th

Thursday·March 4, 2021

14 papers—4 primary·10 cross-listed

01
[Submitted on 2 Mar 2021]
Photon polarization tensor in a magnetized plasma: Absorptive part
Xinyang Wang🇨🇳 · Igor Shovkovy🇺🇸
We calculate the absorptive part of the photon polarization tensor in a hot magnetized relativistic plasma. In the derivation, we utilize a Landau-level representation for the fermion Green's function in a mixed coordinate-momentum space and obtain a closed-form expression for the one-loop polarization tensor. At the leading order in the coupling, its absorptive part is determined by particle and antiparticle splitting processes ( $e^{-} \leftrightarrow e^{-} + γ$ and $e^{+} \leftrightarrow e^{+} + γ$ , respectively), as well as by particle-antiparticle annihilation processes ( $e^{-} + e^{+} \leftrightarrow γ$ ). The interpretation in terms of quantum transitions between Landau levels is also given. By making use of the photon polarization tensor, we study the differential photon emission rate in the quantum limit of magnetized relativistic plasma. At low energies, the photon emission has a prolate profile with the symmetry axis along the line of the magnetic field. At high energies, on the other hand, the photon emission has an oblate profile. The underlying reasons for such emission profiles are given in both regimes. The general result for the photon polarization tensor is also used to calculate the longitudinal and transverse components of magneto-optical conductivity.
Comments:
31 pages, 15 multipanel figures; published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
2103.01967 [pdf]
PRD(2021)·40 citations
02
[Submitted on 2 Mar 2021]
Non-perturbative methods for NN singular interactions
D.R. Entem🇪🇸 · J.A. Oller🇪🇸
Chiral Effective Field Theory ( $χ$ EFT) has been extensively used to study the $N N$ interaction during the last three decades. In Effective Field Theories (EFTs) the renormalization is performed order by order including the necessary counter terms. Due to the strong character of the $N N$ interaction a non-perturbative resummation is needed. In this work we will review some of the methods proposed to completely remove cutoff dependencies. The methods covered are renormalization with boundary conditions, renormalization with one counter term in momentum space (or equivalently substractive renormalization) and the exact $N / D$ method. The equivalence between the methods up to one renormalization condition will be checked showing results in the $N N$ system. The exact $N / D$ method allows to go beyond the others, and using a toy model it is shown how it can renormalize singular repulsive interactions.
Comments:
Contribution to EPJ ST "Topics in Light-Quark Physics"
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2103.02069 [pdf]
Eur.Phys.J.ST(2021)·8 citations
03
[Submitted on 2 Mar 2021]
Building a testable shear viscosity across the QCD phase diagram
Emma McLaughlin🇺🇸 · Jacob Rose🇩🇪 · Travis Dore🇺🇸 · Paolo Parotto🇩🇪 · Claudia Ratti🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸
Current experiments at the Relativistic Heavy Ion Collider (RHIC) are probing finite baryon densities where the shear viscosity to enthalpy ratio $η T / w$ of the Quark Gluon Plasma remains unknown. We use the Hadron Resonance Gas (HRG) model with the most up-to-date hadron list to calculate $η T / w$ at low temperatures and at finite baryon densities $ρ_{B}$ . We then match $η T / w$ to a QCD-based shear viscosity calculation within the deconfined phase to create a table across ${T, μ_{B}}$ for different cross-over and critical point scenarios at a specified location. We find that these new $η T / w (T, μ_{B})$ values would require initial conditions at significantly larger $ρ_{B}$ , compared to ideal hydrodynamic trajectories, in order to reach the same freeze-out point.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2103.02090 [pdf]
PRC(2022)·39 citations
04
[Submitted on 3 Mar 2021]
Microscopic theory of pygmy- and giant resonances:Accounting for complex 1p1h\otimes phonon and two-phonon configurations
Sergei Kamerdzhiev (1) · Michael Shitov (1) · Dimitri Voitenkov (2) ((1) National Research Center Kurchatov Institute, Moscow, Russia. (2) Science and Innovation Joint-Stock Company, Moscow, Russia.)
The self-consistent Theory of Finite Fermi Systems (TFFS) is consistently generalized for the case of accounting for phonon coupling (PC) effects in the energy region of pygmy- and giant multipole resonances (PDR and GMR) in magic nuclei with the aim to consider particle-hole (ph) and both complex 1p1h\otimes phonon and two-phonon configurations. The article is the direct continuation and generalization of the previous article [S.Kamerdzhiev, M.Shitov, Eur.Phys.J.A. 56, 265 (2020)],referred to as [I], where 1p1h- and only complex 1p1h\otimes phonon configurations were considered. The newest equation for the TFFS main quantity, the effective field (vertex), which describes the nuclear polarizability, has been obtained. It has considerably generalized the results of the previous article and accounts for two-phonon configurations. Two variants of the newest vertex equation have been derived: (1)the first variant contains complex 1p1h\otimes phonon configurations and the full 1p1h-interaction amplitude \Gamma instead of the known effective interaction F in [I], (2) the second one contains both 1p1h\otimes phonon and two-phonon configurations. Both variants contain new, as compared to usual approaches, PC contributions, which are of interest in the energy region under consideration and, at least, should result in a redistribution of the PDR and GMR strength, which is important for the explanation of the PDR and GMR fine structure. The qualitative analysis and discussion of the new terms and the comparison to the known time-blocking approximation are performed.
Comments:
11pages, 9 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2103.02596 [pdf]
0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Photon polarization tensor in a magnetized plasma: Absorptive part

Non-perturbative methods for NN singular interactions

Building a testable shear viscosity across the QCD phase diagram

Microscopic theory of pygmy- and giant resonances:Accounting for complex 1p1h\otimes phonon and two-phonon configurations

Affiliations