Phenomenological Estimates Research Articles

Probing 4 × 4 quark mixing matrix

Without adhering to any specific model, we have presented 4 [Formula: see text] 4 quark mixing matrix as an extension of the 3 [Formula: see text] 3 Particle Data Group (PDG) parametrization of the Cabibbo–Kobayashi–Maskawa (CKM) matrix Using unitarity constraints as well as the hierarchy among the elements of the 3 [Formula: see text] 3 CKM matrix, we have found the hierarchy among the fourth row and fourth column elements of the 4 [Formula: see text] 4 quark mixing matrix. Further, for the fourth generation case, we have explicitly found the nine independent rephasing invariant parameters [Formula: see text]. Also, using phenomenological estimates of the fourth row and fourth column elements, we have numerically evaluated these nine parameters.

Quasi particle model vs lattice QCD thermodynamics: extension to Nf=2+1+1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N_f=2+1+1$$\\end{document} flavors and momentum dependent quark masses

In the last decade a quasi-particle model (QPM) has supplied the basis for the study of heavy quark (HQ) production in ultra-relativistic collisions, allowing for a phenomenological estimate of the HQ diffusion coefficient Ds(T)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_s(T)$$\\end{document}. Using the new lattice QCD results for the equation of state (EoS) with 2+1+1 dynamical flavors, we extend the QPM from Nf=2+1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N_f=2+1$$\\end{document} to Nf=2+1+1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N_f=2+1+1$$\\end{document}, where the charm quark is included. Fixing the coupling g(T) by a fit to the lQCD energy density ϵ(T)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\epsilon (T)$$\\end{document}, we evaluate the impact of different temperature parametrizations of charm quark mass on EoS and susceptibilities χq(T)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\chi _q(T)$$\\end{document} of light, χs(T)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\chi _s(T)$$\\end{document} of strange and χc(T)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\chi _c(T)$$\\end{document} of charm quarks, the last favouring a charm quark mass increasing toward Tc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_c$$\\end{document}. We also explore the extension of the QPM to a more realistic approach called QPMp\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_p$$\\end{document}, where quark and gluon masses explicitly depend on their momentum converging to the current quark mass at high momenta, as expected from asymptotic free dynamics. The QPMp\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_p$$\\end{document} allows for a simultaneous quantitative description not only of the EoS but also of the quark susceptibilities (χq(T)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\chi _q(T)$$\\end{document}, χs(T)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\chi _s(T)$$\\end{document}), which instead are underestimated in the simple QPM. Furthermore, evaluating the spatial diffusion coefficient 2πTDs(T)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2\\pi T D_s(T)$$\\end{document} in the QPMp\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_p$$\\end{document}, we find it is also closer than QPM to the recent lQCD data performed including dynamical fermions. Finally, in a 1+1D expanding system, we evaluate the RAA(pT)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$R_{AA}(p_T)$$\\end{document} in the QPM and QPMp\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_p$$\\end{document}, finding a significant reduction at low momenta for QPMp\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_p$$\\end{document} which could lead in a realistic scenario to a better agreement to experimental data.

Analytical design of electrode particle debonding for battery applications

A physics-based analytical methodology is presented to describe the debonding of a statistically representative electrochemically active particle from the surrounding binder-electrolyte matrix in a porous electrode. The proposed framework enables to determine the space of C-Rates and electrode particle radii that suppresses or enhances debonding. Results are graphically summarized into maps where four debonding descriptions are identified: (a) the spontaneous debonding description, which occurs when the electrode particle spontaneously detaches from the matrix; (b) the continuous debonding description, which occurs when the electrode particle gradually loses contact with the surrounding matrix; (c) the electrochemical cycling fatigue description, which causes gradual growth of the flaw due to electrochemical cycling; and (d) the microstructural debonding description, which is a result of the microstructural stochastics of the electrode and is embodied in terms of the debonding probability of particles. The particle-dependent critical C-Rates for debonding power-law relation enables the experimental identification of individual failure mechanisms, thereby providing a context to formulate design strategies to minimize debonding and provide robust, physics-based, phenomenological, and statistics-based estimates for electrochemically driven failure.

Anomalous thresholds in B → (P, V)γ* form factors

We study the effects of anomalous thresholds on the non-local form factors describing the hadronization of the light-quark contribution to B → (P, V)γ* transitions. Starting from a comprehensive discussion of anomalous thresholds in the triangle loop function for different mass configurations, we detail how the dispersion relation for ππ intermediate states is affected by contour deformations mandated by the anomalous branch points. Phenomenological estimates of the size of the anomalous contributions to the form factors are provided with couplings determined from measured branching fractions and Dalitz plot distributions. Our key finding is that anomalous effects are suppressed on the ρ(770) resonance, while off-peak the effects can become as large as O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(10%) of the full (light-quark-loop induced) non-local form factors. We comment on future generalizations towards higher intermediate states and the charm loop, outlining how the dispersive framework established in this work could help improve the non-local form factors needed as input for a robust interpretation of B → (P, V)ℓ+ℓ− decays.

Tunable subdiffusion in the Caputo fractional standard map

The Caputo fractional standard map (C-fSM) is a two-dimensional nonlinear map with memory given in action–angle variables (I,θ). It is parameterized by K and α∈(1,2] which control the strength of nonlinearity and the fractional order of the Caputo derivative, respectively. In this work we perform a scaling study of the average squared action I2 along strongly chaotic orbits, i.e. when K≫1. We numerically prove that I2∝nμ with 0≤μ(α)≤1, for large enough discrete times n. That is, we demonstrate that the C-fSM displays subdiffusion for 1<α<2. Specifically, we show that diffusion is suppressed for α→1 since μ(1)=0, while standard diffusion is recovered for α=2 where μ(2)=1. We describe our numerical results with a phenomenological analytical estimation.

Phenomenological Estimate of Isospin Breaking in Hadronic Vacuum Polarization.

Puzzles in the determination of the hadronic-vacuum-polarization contribution currently impede a conclusive interpretation of the precision measurement of the anomalous magnetic moment of the muon at the Fermilab experiment. One such puzzle concerns tensions between evaluations in lattice QCD and using e^{+}e^{-}→hadrons cross-section data. In lattice QCD, the dominant isospin-symmetric part and isospin-breaking (IB) corrections are calculated separately, with very different systematic effects. Identifying these two pieces in a data-driven approach provides an opportunity to compare them individually and trace back the source of the discrepancy. Here, we estimate the IB component of the lattice-QCD calculations from phenomenology, based on a comprehensive study of exclusive contributions that can be enhanced viainfrared singularities, threshold effects, or hadronic resonances, including, for the first time, in the e^{+}e^{-}→3π channel. We observe sizable cancellations among different channels, with a sum that even suggests a slightly larger result for the QED correction than obtained in lattice QCD. We conclude that the tensions between lattice QCD and e^{+}e^{-} data therefore cannot be explained by the IB contributions in the lattice-QCD calculations.

Heavy Quark Diffusion from 2+1 Flavor Lattice QCD with 320MeV Pion Mass.

We present the first calculations of the heavy flavor diffusion coefficient using lattice QCD with light dynamical quarks corresponding to a pion mass of around 320MeV. For temperatures 195 MeV<T<352 MeV, the heavy quark spatial diffusion coefficient is found to be significantly smaller than previous quenched lattice QCD and recent phenomenological estimates. The result implies very fast hydrodynamization of heavy quarks in the quark-gluon plasma created during ultrarelativistic heavy-ion collision experiments.

Nonlinear Finite Element Calculations of Layered SAW Resonators.

In this work the nonlinear behavior of layered SAW resonators is studied with the help of Finite Element (FE) computations. The full calculations depend strongly on the availability of accurate tensor data. While there are accurate material data for linear computations, the complete sets of higher-order material constants, needed for nonlinear simulations, are still not available for relevant materials. To overcome this problem, scaling factors were used for each available nonlinear tensor. The approach here considers piezoelectricity, dielectricity, eletrostriction and elasticity constants up to fourth order. These factors act as a phenomenological estimate for incomplete tensor data. Since no set of fourth order material constants for LiTaO3 is available, an isotropic approximation for the fourth order elastic constants was applied. As a result, it was found that the fourth order elastic tensor is dominated by one fourth order Lamé constant. With the help of the FE model, derived in two different, but equivalent ways, we investigate the nonlinear behavior of a SAW resonator with a layered material stack. The focus was set to third order nonlinearity. Accordingly, the modeling approach is validated using measurements of third order effects in test resonators. In addition, the acoustic field distribution is analyzed.

Soft pions and transport near the chiral critical point

During the expansion of a heavy ion collision, the system passes close to the $O(4)$ critical point of QCD, and thus the fluctuations of the order parameter $(\sigma, \vec{\pi})$ are expected to be enhanced. Our goal is to compute how these enhanced fluctuations modify the transport coefficients of QCD near the pseudo-critical point. We also make a phenomenological estimate for how chiral fluctuations could effect the momentum spectrum of soft pions. We first formulate the appropriate stochastic hydrodynamic equations close to the $O(4)$ critical point. Then, working in mean field, we determine the correlation functions of the stress tensor and the currents which result from this stochastic real time theory, and use these correlation functions to determine the scaling behavior of the transport coefficients. The hydrodynamic theory also describes the propagation of pion waves, fixing the scaling behavior of the dispersion curve of soft pions. We present scaling functions for the shear viscosity and the charge conductivities near the pseudo-critical point, and estimate the absolute magnitude of the critical fluctuations to these parameters and the bulk viscosity. Using the calculated pion dispersion curve, we estimate the expected critical enhancement of soft pion yields, and this estimate provides a plausible explanation for the excess seen in experiment relative to ordinary hydrodynamic computations. Our results motivate further phenomenological and numerical work on the implications of chiral symmetry on real time properties of thermal QCD near the pseudo-critical point.

Hadronic light-by-light contribution to (g-2)_mu from lattice QCD: a complete calculation

We compute the hadronic light-by-light scattering contribution to the muon g-2 from the up, down, and strange-quark sector directly using lattice QCD. Our calculation features evaluations of all possible Wick-contractions of the relevant hadronic four-point function and incorporates several different pion masses, volumes, and lattice-spacings. We obtain a value of a_mu ^{text {Hlbl}}= 106.8(15.9) times 10^{-11} (adding statistical and systematic errors in quadrature), which is consistent with current phenomenological estimates and a previous lattice determination. It now appears conclusive that the hadronic light-by-light contribution cannot explain the current tension between theory and experiment for the muon g-2.

The anomalous magnetic moment of the muon: status of lattice QCD calculations.

In recent years, the anomalous magnetic moment of the muon has triggered a lot of activity in the lattice QCD community because a persistent tension of about 3.5~sigma is observed between the phenomenological estimate and the Brookhaven measurement. The current best phenomenological estimate has an uncertainty comparable to the experimental one and the error is completely dominated by hadronic effects: the leading order hadronic vacuum polarization (HVP) contribution and the hadronic light-by-light (HLbL) scattering contribution. Both are accessible via lattice simulations and a reduction of the error by a factor 4 is required in view of the forthcoming experiments at Fermilab and J-PARC whose results, expected in the next few years, should reduce the experimental precision down to the level of 0.14 ppm. In this article, I review the status of lattice calculations of those quantities, starting with the HVP. This contribution has now reached sub-percent precision and requires a careful understanding of all sources of systematic errors. The HLbL contribution, that is much smaller, still contributes significantly to the error. This contribution is more challenging to compute, but rapid progress has been made on the lattice in the last few years.

Scattering of Goldstone bosons and resonance production in a composite Higgs model on the lattice

We calculate the coupling between a vector resonance and two Goldstone bosons in SU(2) gauge theory with Nf = 2 Dirac fermions in the fundamental representation. The considered theory can be used to construct a minimal Composite Higgs models. The coupling is related to the width of the vector resonance and we determine it by simulating the scattering of two Goldstone bosons where the resonance is produced. The resulting coupling is gVPP = 7.8 ± 0.6, not far from gρππ ≃ 6 in QCD. This is the first lattice calculation of the resonance properties for a minimal UV completion. This coupling controls the production cross section of the lightest expected resonance at the LHC and enters into other tests of the Standard Model, from Vector Boson Fusion to electroweak precision tests. Our prediction is crucial to constrain the model using lattice input and for understanding the behavior of the vector meson production cross section as a function of the underlying gauge theory. We also extract the coupling {g}_{mathrm{VPP}}^{mathrm{KSRF}} = 9.4 ± 0.6 assuming the vector-dominance and find that this phenomenological estimate slightly overestimates the value of the coupling.

A phenomenological estimate of the true scale of CoViD-19 from primary data.

Estimation of the prevalence of undocumented SARS-CoV-2 infections is critical for understanding the overall impact of CoViD-19, and for implementing effective public policy intervention strategies. We discuss a simple yet effective approach to estimate the true number of people infected by SARS-CoV-2, using raw epidemiological data reported by official health institutions in the largest EU countries and the USA.

Flavor Decomposition for the Proton Helicity Parton Distribution Functions.

We present, for the first time, an abinitio calculation of the individual up, down, and strange quark helicity parton distribution functions for the proton. The calculation is performed within the twisted mass clover-improved fermion formulation of lattice QCD. The analysis is performed using one ensemble of dynamical up, down, strange, and charm quarks with a pion mass of 260MeV. The lattice matrix elements are nonperturbatively renormalized and the final results are presented in the MS[over ¯] scheme at a scale of 2GeV. We give results for Δu^{+}(x), Δd^{+}(x) Δu^{-}(x), Δd^{-}(x), including disconnected quark loop contributions, as well as for Δs^{+}(x) and Δs^{-}(x). For the latter we achieve unprecedented precision compared to the phenomenological estimates.

Propensity of spin fluctuations in disordered NiCoCr alloys: A first principles study

A quantum critical behavior is reported in equi-atomic NiCoCr alloy, where the ferromagnetic transition temperature goes to zero. We perform a systematic study of (NiCo)1−xCrx alloys; 0 ≤ x ≤ 13, by means of density functional theory based Green’s function method, to understand the changes in the electronic structure and magnetic properties of this equi-atomic ternary alloy as a function of Cr at%. Chemical disorder is modeled by means of coherent-potential. approximation. To determine the propensity of spin fluctuations, we adopt to the fixed-spin moment method. A fit to the phenomenological Ginzburg Landau equation and estimation of the second derivative of the total energy with respect to magnetization shows that (NiCo)1−xCrx alloys display an increasing propensity of longitudinal spin fluctuations, proportional to the Cr at% in these alloys.

Axial vector transition form factors in holographic QCD and their contribution to the anomalous magnetic moment of the muon

We evaluate axial vector transition form factors in holographic QCD models that have been shown to reproduce well recent experimental and theoretical results for the pion transition form factor. Comparing with L3 data on $f_1\to\gamma\gamma^*$ we find remarkable agreement regarding the shape of single-virtual form factors. In the double-virtual case, the holographic results differ strongly from a simple dipole form, and this has an important impact on the corresponding estimate of the axial vector contribution to the anomalous magnetic moment of the muon $a_\mu$ through hadronic light-by-light scattering. We demonstrate that hard-wall models satisfy the Melnikov-Vainshtein short-distance constraint for the latter, if and only if the infinite tower of axial vector states is included. The results for $a_\mu$, however, are strongly dominated by the first few resonances. Numerically, these results turn out to be surprisingly large: (2.9 - 4.1)$\times 10^{-10}$ in the hard-wall models, 57-58% of which are due to the longitudinal contribution, which is the one responsible for the Melnikov-Vainshtein short-distance constraint. Rescaling the holographic result to obtain an optimal fit of L3 data, but then matching only 52% of the asymptotic constraint, the result is reduced to $2.2(5)\times 10^{-10}$, which is still significantly larger than most previous phenomenological estimates of the axial vector exchange contribution.

Ab Initio Horizon-scale Simulations of Magnetically Arrested Accretion in Sagittarius A* Fed by Stellar Winds

Abstract We present 3D general relativistic magnetohydrodynamic (GRMHD) simulations of the accretion flow surrounding Sagittarius A* that are initialized using larger-scale MHD simulations of the ∼30 Wolf–Rayet (WR) stellar winds in the Galactic center. The properties of the resulting accretion flow on horizon scales are set not by ad hoc initial conditions but by the observationally constrained properties of the WR winds with limited free parameters. For this initial study we assume a non-spinning black hole. Our simulations naturally produce a ∼10−8 M ⊙ yr−1 accretion rate, consistent with previous phenomenological estimates. We find that a magnetically arrested flow is formed by the continuous accretion of coherent magnetic field being fed from large radii. Near the event horizon, the magnetic field is so strong that it tilts the gas with respect to the initial angular momentum and concentrates the originally quasi-spherical flow to a narrow disk-like structure. We also present 230 GHz images calculated from our simulations where the inclination angle and physical accretion rate are not free parameters but are determined by the properties of the WR stellar winds. The image morphology is highly time variable. Linear polarization on horizon scales is coherent with weak internal Faraday rotation.

Impulse-driven drop

Drop deformation and disintegration regimes have been studied in many contexts ranging from an impact on a solid surface or a liquid layer of varying thickness to a liquid drop suspended in air and hit by a propagating aerodynamic shock wave. As a counterpart, deformation and disintegration of an initially static drop of controlled shape and size sitting on an impulsively driven stiff membrane are explored here experimentally. A significant amount of collected experimental data is used to map the possible drop morphological changes along with the transitions between them. In order to elucidate the effects of impulse intensity, viscosity, surface tension and wetting, we measured the crown height and radius in the drop deformation regimes, as well as the drop detachment and breakup times along with probability density functions of the secondary droplets in the drop disintegration regimes. With the goal to convey the physical mechanisms behind these transient responses, the observations are interpreted with phenomenological models, scalings and estimates highlighting the rich multiscale physics of the impulse-driven drop phenomena.

Viscous Evolution of Magnetized Clumps: A Source for X-Ray Flares in Gamma-Ray Bursts

Abstract X-ray flares may indicate the late-time activity of the central engines of gamma-ray bursts. Such long-term activity has been described through some models, one of which is the viscous evolution of the outer disk’s fragments proposed by Perna et al., and developed quantitatively by Dall’Osso et al. Here, we reconstruct the framework of Dall’Osso et al. by taking both small- and large-scale effects of magnetic field into account. To consider the magnetic barrier as a possible mechanism that might govern the accretion process of each magnetized clump, we construct a simple pattern in boundary conditions through which this mechanism might act. Regarding various model parameters, we probe for their influence and follow some key analogies between our model predictions and previous phenomenological estimates, for two different choices of boundary conditions (with and without a magnetic barrier). Our model is remarkably capable of matching the bolometric and X-ray light curves of flares, as well as reproducing their statistical properties, such as the ratios between rise and decay time, width parameter and peak time, and the power-law correlation between peak luminosity and peak time. Combining our results with the conclusions of previous studies, we are led to interpret a magnetic barrier as a less probable mechanism that might control the evolution of these clumps, especially those created later (or viscously evolved ones).

A1-meson-baryon coupling constants in the framework of soft-wall and hard-wall AdS/QCD models

We calculate the [Formula: see text]-meson-nucleon ([Formula: see text]-baryon) coupling constant in the framework of soft-wall and hard-wall AdS/QCD models. Interaction Lagrangian in the bulk of AdS space was written for a minimal gauge coupling, a magnetic type coupling and a triple coupling of bulk fields. Applying AdS/CFT correspondence from the bulk interaction Lagrangian, we obtain holographic expressions for the [Formula: see text]-axial-vector meson-nucleon ([Formula: see text]-baryon) coupling constant in the boundary QCD theory. Numerical results for the [Formula: see text] coupling constant in the framework of both models are close to the known phenomenological estimates. The [Formula: see text]-axial-vector meson-[Formula: see text]-baryon coupling constant was considered in the framework of hard-wall model.