The theory of the strong interaction, quantum chromodynamics (QCD), describes the generation of hadronic masses and the state of hadronic matter during the early stages of the evolution of the universe. As a complement, experiments with ultracold fermionic atoms provide a clean environment to benchmark our understanding of dynamical formation of condensates and the generation of bound states in strongly interacting many-body systems. Renormalization Group (RG) techniques offer great potential for theoretical advances in both hot and dense QCD and many-body physics, but their connections have not yet been investigated in great detail. We aim to take a further step to bridge this gap. A cross-fertilization is indeed promising since it may eventually provide us with an ab initio description of hadronization, condensation and bound-state formation in strongly interacting theories. After giving a thorough introduction to the derivation and analysis of fermionic RG flows, we giv...

A setup of two coupled and damped pendula is used to demonstrate the main features of transitions between the neutral mesons K ⁰, D ⁰, B ⁰ and their antiparticles, including CP violation in the K ⁰ system. The transitions are described by two-state Schrödinger equations. Since the real parts of their solutions obey the same differential equations as the pendula coordinates, the pendulum motions can be used to represent the meson transitions. Movie clips of the motions are available as supplementary material.

In addition to well-motivated scenarios like supersymmetric particles, the so-called exotic matter (quirky matter, hidden valley models, etc) can show up at the LHC and ILC, by exploring the spectroscopy of high mass levels and decay rates. In this paper, we use QCD-inspired potential models, though without resorting to any particular one, to calculate level spacings of bound states and decay rates of the aforementioned exotic matter in order to design discovery strategies. We mainly focus on quirky matter, but our conclusions can be extended to other similar scenarios.

We consider an effective model formed by usual QED (minimal coupling) with the addition of a nonminimal Lorentz-violating interaction (proportional to a fixed 4-vector b _μ) which may radiatively generate both CPT even and odd terms in the pure gauge sector. We show that gauge invariance from usual QED, considered as a limit of the model for b _μ → 0, plays an important role in the discussion of the radiatively induced Lorentz-violating terms at one-loop order. Moreover, despite the nonrenormalizability of the (effective) model preventing us from readily extending our discussion to higher orders, it is still possible to display the general form of the breaking terms of the photon sector in the on-shell limit organized in powers of b _μ which in turn can be considered as a small expansion parameter.

Recent lattice studies exhibit infrared finite effective QCD charges. The corresponding gluon propagator in the Landau gauge is finite and nonzero, suggesting that the mechanism of dynamical gluon mass generation is in the operation. In this paper, the analytical continuation of the Euclidean (spacelike) pinch technique–background field method solution of the Schwinger–Dyson equation for the gluon propagator to the timelike region of q ² is found. We found the continuation numerically showing good agreement with a generalized Lehman representation for small Schwinger coupling. The associated non-positive spectral function has an unexpected behavior. Albeit the infrared Euclidean space solution naively suggests a like single-scale ‘massive’ propagator, the obtained spectrum of the gluon propagator does not correspond to the delta function at single scale q = m; instead more possible singularities are generated. The pattern depends on the details of t...

The equation of state and the phase diagram in two-flavor quantum chromodynamics (QCD) are investigated by the Polyakov-loop extended Nambu–Jona-Lasinio (PNJL) model with an entanglement vertex between the chiral condensate and the Polyakov loop. The entanglement-PNJL (EPNJL) model reproduces lattice QCD (LQCD) data at μ ⩾ 0 better than the PNJL model. Hadronic degrees of freedom are taken into account by the free-hadron-gas approximation with the volume-exclusion effect due to the hadron generation. The hadron degrees of freedom improve agreement of the EPNJL model with LQCD data particularly at low temperature. The quarkyonic phase survives, even if the correlation between the chiral condensate and the Polyakov loop is strong and hadron degrees of freedom are taken into account. However, the location of the quarkyonic phase is sensitive to the strength of the volume exclusion.

We perform a phenomenological analysis on the use of π NΔ(1232) alternative couplings in π N scattering, within a single and well-controlled dynamical model. We compare numerical results for the elastic cross section obtained using the conventional couplings, already adopted in several reaction calculations, with those obtained with the so-called ‘spin-3/2 gauge-invariant’ vertexes suggested recently. Confronting with experimental cross-sectional data in the region around the resonance, we see that these results are by no means equivalent and the differences between them cannot be eliminated by a readjustment of free parameters of the meson-exchange contributions. We find that the use of the conventional couplings leads to better fits.

Multiplicity scaling of target protons emitted from nucleus–nucleus ( ¹⁶O–AgBr interactions at 2.1 AGeV and ³²S–AgBr interactions at 200 AGeV), pion–nucleus (π ⁻–AgBr interactions at 350 GeV/ c) and proton–nucleus interactions (p–AgBr interactions at 200 GeV/ c) has been investigated. The experimental points are found to lie approximately on the curve described by ψ( z) = Azexp ( − Bz) with A = 3.36 ± 0.19 and B = 1.74 ± 0.06 for all the four interactions. A comparison of the fit with the function ψ( z) = ( Az + Bz ³ + Cz ⁵ + Dz ⁷)exp ( − Ez) has also been performed.

The equivalent two-body method has been applied to investigate a three-body system with attractive r ⁻² two-body interactions, which are the division between short- and long-range potentials. An effective potential of the R ⁻² form is derived. Infinitely many bound states are obtained in the system with two heavy particles and one light particle even if all the two-body subsystems have no bound states. This is possible evidence of the Efimov effect.

The Breit equation with two electromagnetic form factors is studied to obtain a potential with finite-size corrections. This potential with proton structure effects includes, apart from the standard Coulomb term, the Darwin term, retarded potentials, spin–spin and spin–orbit interactions corresponding to the fine and hyperfine structures in the hydrogen atom. Analytical expressions for the hyperfine potential with form factors and the subsequent energy levels including the proton structure corrections are given using the dipole form of the form factors. Numerical results are presented for the finite-size corrections in the 1S and 2S hyperfine splittings in the hydrogen atom, the Sternheim observable D ₂₁ and the 2S and 2P hyperfine splittings in muonic hydrogen. Finally, a comparison with some other existing methods in the literature is presented.