Journal articles: 'Quarks, gluons and lattices'

1

Stoddart, J. C. "Quarks, Gluons and Lattices: Cambridge Monographs on Mathematical Physics." Physics Bulletin 37, no. 5 (May 1986): 225. http://dx.doi.org/10.1088/0031-9112/37/5/031.

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IIDA, HIDEAKI, TORU T. TAKAHASHI, and HIDEO SUGANUMA. "PROPERTIES OF SCALAR-QUARK SYSTEMS IN SU(3)c LATTICE QCD." Modern Physics Letters A 23, no. 27n30 (September 30, 2008): 2344–47. http://dx.doi.org/10.1142/s0217732308029344.

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We perform the first study for the bound states of colored scalar particles ϕ (“scalar quarks”) in terms of mass generation with quenched SU (3)c lattice QCD. We investigate the bound states of ϕ, ϕ†ϕ and ϕϕϕ (“scalar-quark hadrons”), as well as the bound states of ϕ and quarks ψ, i.e., ϕ†ψ, ψψϕ and ϕϕψ (“chimera hadrons”). All these new-type hadrons including ϕ have a large mass of several GeV due to large quantum corrections by gluons, even for zero bare scalar-quark mass mϕ = 0 at a−1 ~ 1 GeV . We find a similar mψ-dependence between ϕ†ψ and ϕϕψ, which indicates their similar structure due to the large mass of ϕ. From this study, we conjecture that all colored particles generally acquire a large effective mass due to dressed gluons.

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Musakhanov, Mirzayusuf. "Gluons, Heavy and Light Quarks in the QCD Vacuum." EPJ Web of Conferences 182 (2018): 02092. http://dx.doi.org/10.1051/epjconf/201818202092.

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We are discussing the properties of the QCD vacuum which might be important especially for the understanding of hadrons with small quark core size ~ 0:3 fm: We assume that at these distances the QCD vacuum can be described by the Instanton Liquid Model (ILM). At larger distances, where confinement is important, ILM should be extended to Dyons Liquid Model (DLM). The ILM has only two free parameters, average instanton size ρ ≈ 0:3 fm and average inter-instanton distance R ≈ 1 fm, and can successfully describe the key features of light hadron physics. One of the important conceptual results was prediction of the momentum dependent dynamical quark mass M ~ (packing f raction)1/2 ρ-1 ≈ 360 MeV, later confirmed numerically by evaluations in the lattice. The estimates show that gluon-instanton interaction strength is also big and is controlled by the value of dynamical gluon mass Mg ≈ M. Heavy quarks interact with instantons much weaker. The heavy quark-instanton interaction strength is given by ΔmQ ~ packing fraction ρ-1 ≈ 70 MeV: Nevertheless, the direct instanton contribution to the colorless heavy-heavy quarks potential is sizable and must be taken into account. At small distances, where one-gluon exchange contribution to this potential is dominated, we have to take into account dynamical gluon mass Mg. Also, instantons are generating light-heavy quarks interactions and allow to describe the nonperturbative effects in heavy-light quarks systems.

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Fan, Zhouyou, Rui Zhang, and Huey-Wen Lin. "Nucleon gluon distribution function from 2 + 1 + 1-flavor lattice QCD." International Journal of Modern Physics A 36, no. 13 (April 28, 2021): 2150080. http://dx.doi.org/10.1142/s0217751x21500809.

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The parton distribution functions (PDFs) provide process-independent information about the quarks and gluons inside hadrons. Although the gluon PDF can be obtained from a global fit to experimental data, it is not constrained well in the large-[Formula: see text] region. Theoretical gluon-PDF studies are much fewer than those of the quark PDFs. In this work, we present the first lattice-QCD results that access the [Formula: see text]-dependence of the gluon unpolarized PDF of the nucleon. The lattice calculation is carried out with nucleon momenta up to 2.16 GeV, lattice spacing [Formula: see text] fm, and with valence pion masses of 310 and 690 MeV. We use reduced Ioffe-time distributions to cancel the renormalization and implement a one-loop perturbative pseudo-PDF gluon matching. We neglect mixing of the gluon operator with the quark singlet sector. Our matrix-element results in coordinate space are consistent with those obtained from the global PDF fits of CT18 NNLO and NNPDF3.1 NNLO. Our fitted gluon PDFs at both pion masses are consistent with global fits in the [Formula: see text] region.

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JI, XIANGDONG, and YONG ZHAO. "PHYSICS OF GLUON HELICITY." International Journal of Modern Physics: Conference Series 25 (January 2014): 1460028. http://dx.doi.org/10.1142/s2010194514600283.

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The total gluon helicity in a polarized proton is shown to be a matrix element of a gauge-invariant but nonlocal, frame-dependent gluon spin operator [Formula: see text] in the large momentum limit. The operator [Formula: see text] is fit for the calculation of the total gluon helicity in lattice QCD. This calculation also implies that parton physics can be studied through the large momentum limit of frame-dependent, equal-time correlation functions of quarks and gluons.

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Machahari, Luxmi, and D. K. Choudhury. "Q2 dependence of the fractional momenta carried by small x quarks and gluons in models of proton structure function." Modern Physics Letters A 34, no. 33 (October 28, 2019): 1950273. http://dx.doi.org/10.1142/s0217732319502730.

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Recently, we suggested two alternative analytical models of proton structure function [Formula: see text] and gluon distribution [Formula: see text] at small [Formula: see text] [L. Machahari and D. K. Choudhury, Eur. Phys. J. A 54, 69 (2018); Commun. Theor. Phys. 71, 56 (2019)] derived from the coupled DGLAP equations for quarks and gluons approximated by Taylor expansion. In this work, we compute the partial momentum fractions carried by quarks and gluons in limited small [Formula: see text] range: [Formula: see text] and compare them with few other models available in the current literature. The analysis leads to understand qualitatively the effects of notions like Froissart saturation and self-similarity in the proton at small [Formula: see text]. We also study if our results conform to the total momentum fractions as predicted in perturbative and lattice QCD.

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Dey, Jayanta, Sarthak Satapathy, Ankita Mishra, Souvik Paul, and Sabyasachi Ghosh. "From noninteracting to interacting picture of quark–gluon plasma in the presence of a magnetic field and its fluid property." International Journal of Modern Physics E 30, no. 06 (June 2021): 2150044. http://dx.doi.org/10.1142/s0218301321500440.

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We have attempted to build a parametric-based simplified and analytical model to map the interaction of quarks and gluons in the presence of magnetic field, which has been constrained by quark condensate and thermodynamical quantities like pressure, energy density, etc., obtained from the calculation of lattice quantum chromodynamics (QCDs). To fulfill that mapping, we have assumed a parametric temperature and magnetic field-dependent degeneracy factor, average energy, momentum and velocity of quarks and gluons. Implementing this QCD interaction in calculation of transport coefficient at finite magnetic field, we have noticed that magnetic field and interaction both are two dominating sources, for which the values of transport coefficients can be reduced. Though the methodology is not so robust, but with the help of its simple parametric expressions, one can get a quick rough estimation of any phenomenological quantity, influenced by temperature and magnetic field-dependent QCD interaction.

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Morningstar, Colin. "PWA AND THE LATTICE." International Journal of Modern Physics A 18, no. 03 (January 30, 2003): 377–86. http://dx.doi.org/10.1142/s0217751x03014290.

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Bietenholz, W., and U. J. Wiese. "Perfect lattice actions for quarks and gluons." Nuclear Physics B 464, no. 1-2 (April 1996): 319–50. http://dx.doi.org/10.1016/0550-3213(95)00678-8.

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Ishikawa, K. I., Y. Iwasaki, Yu Nakayama, and T. Yoshie. "Nontrivial center dominance in high temperature QCD." Modern Physics Letters A 31, no. 25 (August 9, 2016): 1650150. http://dx.doi.org/10.1142/s0217732316501509.

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We investigate the properties of quarks and gluons above the chiral phase transition temperature [Formula: see text], using the renormalization group (RG) improved gauge action and the Wilson quark action with two degenerate quarks mainly on a [Formula: see text] lattice. In the one-loop perturbation theory, the thermal ensemble is dominated by the gauge configurations with effectively [Formula: see text] center twisted boundary conditions, making the thermal expectation value of the spatial Polyakov loop take a nontrivial [Formula: see text] center. This is in agreement with our lattice simulation of high temperature quantum chromodynamics (QCD). We further observe that the temporal propagator of massless quarks at extremely high temperature [Formula: see text] remarkably agrees with the temporal propagator of free quarks with the [Formula: see text] twisted boundary condition for [Formula: see text], but differs from that with the [Formula: see text] trivial boundary condition. As we increase the mass of quarks [Formula: see text], we find that the thermal ensemble continues to be dominated by the [Formula: see text] twisted gauge field configurations as long as [Formula: see text] and above that the [Formula: see text] trivial configurations come in. The transition is similar to what we found in the departure from the conformal region in the zero-temperature many-flavor conformal QCD on a finite lattice by increasing the mass of quarks.

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Kenway, Richard. "Lattice QCD Results and Prospects." International Journal of Modern Physics A 18, supp01 (February 2003): 1–26. http://dx.doi.org/10.1142/s0217751x03016549.

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In the Standard Model, quarks and gluons are permanently confined by the strong interaction into hadronic bound states. The values of the quark masses and the strengths of the decays of one quark flavour into another cannot be measured directly, but must be deduced from experiments on hadrons. This requires calculations of the strong-interaction effects within the bound states, which are only possible using numerical simulations of lattice QCD. These are computationally intensive and, for the past twenty years, have exploited leading-edge computing technology. In conjunction with experimental data from B Factories, over the next few years, lattice QCD may provide clues to physics beyond the Standard Model. These lectures provide a non-technical introduction to lattice QCD, some of the recent results, QCD computers, and the future prospects.

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Nilima, Indrani, and Vineet Kumar Agotiya. "Equation of States and Charmonium Suppression in Heavy-Ion Collisions." Advances in High Energy Physics 2019 (August 6, 2019): 1–13. http://dx.doi.org/10.1155/2019/9574136.

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The present article is the follow-up of our work Bottomonium suppression in quasi-particle model, where we have extended the study for charmonium states using quasi-particle model in terms of quasi-gluons and quasi quarks/antiquarks as an equation of state. By employing medium modification to a heavy quark potential thermodynamic observables, viz., pressure, energy density, speed of sound, etc. have been calculated which nicely fit with the lattice equation of state for gluon, massless, and as well massive flavored plasma. For obtaining the thermodynamic observables we employed the debye mass in the quasi particle picture. We extended the quasi-particle model to calculate charmonium suppression in an expanding, dissipative strongly interacting QGP medium (SIQGP). We obtained the suppression pattern for charmonium states with respect to the number of participants at mid-rapidity and compared it with the experimental data (CMS JHEP) and (CMS PAS) at LHC energy (Pb+Pb collisions, sNN = 2.76 TeV).

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Teryaev, O. V. "Some QCD/gravity intersections." International Journal of Modern Physics A 31, no. 28n29 (October 19, 2016): 1645032. http://dx.doi.org/10.1142/s0217751x16450329.

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Gravitational form factors are the matrix elements of the Belinfante energy momentum tensor (EMT) which naturally incorporate the hadron structure and the equivalence principle. The relocalization property allowing to transform EMT to the Belinfante form provides the “kinematical” counterpart of the famous [Formula: see text] problem. The equivalence principle may be approximately valid for quarks and gluons separately in non-perturbative (NP)QCD, and this conjecture is supported by the experimental and lattice data. The extra-dimensional gravity leading to holographic AdS/QCD is supporting the relation of quark transverse momentum to the Regge slope, discovered by V.N. Gribov.

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MEI, ZHONG-HAO, and XIANG-QIAN LUO. "EXOTIC MESONS FROM QUANTUM CHROMODYNAMICS WITH IMPROVED GLUON AND QUARK ACTIONS ON THE ANISOTROPIC LATTICE." International Journal of Modern Physics A 18, no. 31 (December 20, 2003): 5713–24. http://dx.doi.org/10.1142/s0217751x03017038.

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Hybrid (exotic) mesons, which are important predictions of quantum chromodynamics (QCD), are states of quarks and antiquarks bound by excited gluons. First principle lattice study of such states would help us understand the role of "dynamical" color in low energy QCD and provide valuable information for experimental search for these new particles. In this paper, we apply both improved gluon and quark actions to the hybrid mesons, which might be much more efficient than the previous works in reducing lattice spacing error and finite volume effect. Quenched simulations were done at β=2.6 and on a ξ=3 anisotropic 123×36 lattice using our PC cluster. We obtain 2013±26±71 MeV for the mass of the 1-+ hybrid meson [Formula: see text] in the light quark sector, and 4369±37±99 MeV in the charm quark sector; the mass splitting between the 1-+ hybrid meson [Formula: see text] in the charm quark sector and the spin averaged S-wave charmonium mass is estimated to be 1302±37±99 MeV. As a byproduct, we obtain 1438±32±57 MeV for the mass of a P-wave 1++[Formula: see text] or [Formula: see text] meson and 1499±28±65 MeV for the mass of a P-wave 1++[Formula: see text] meson, which are comparable to their experimental value 1426 MeV for the f1(1420) meson. The first error is statistical, and the second one is systematical. The mixing of the hybrid meson with a four quark state is also discussed.

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Reinhardt, H., G. Burgio, D. Campagnari, E. Ebadati, J. Heffner, M. Quandt, P. Vastag, and H. Vogt. "Hamiltonian Approach to QCD in Coulomb Gauge: A Survey of Recent Results." Advances in High Energy Physics 2018 (2018): 1–21. http://dx.doi.org/10.1155/2018/2312498.

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We report on recent results obtained within the Hamiltonian approach to QCD in Coulomb gauge. Furthermore this approach is compared to recent lattice data, which were obtained by an alternative gauge-fixing method and which show an improved agreement with the continuum results. By relating the Gribov confinement scenario to the center vortex picture of confinement, it is shown that the Coulomb string tension is tied to the spatial string tension. For the quark sector, a vacuum wave functional is used which explicitly contains the coupling of the quarks to the transverse gluons and which results in variational equations which are free of ultraviolet divergences. The variational approach is extended to finite temperatures by compactifying a spatial dimension. The effective potential of the Polyakov loop is evaluated from the zero-temperature variational solution. For pure Yang–Mills theory, the deconfinement phase transition is found to be second order for SU(2) and first order for SU(3), in agreement with the lattice results. The corresponding critical temperatures are found to be 275 MeV and 280 MeV, respectively. When quarks are included, the deconfinement transition turns into a crossover. From the dual and chiral quark condensate, one finds pseudocritical temperatures of 198 MeV and 170 MeV, respectively, for the deconfinement and chiral transition.

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THOMAS, ANTHONY W. "SPIN AND ORBITAL ANGULAR MOMENTUM IN THE PROTON." International Journal of Modern Physics E 18, no. 05n06 (June 2009): 1116–34. http://dx.doi.org/10.1142/s0218301309013403.

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Since the announcement of the proton spin crisis by the European Muon Collaboration there has been considerable progress in unravelling the distribution of spin and orbital angular momentum within the proton. We review the current status of the problem, showing that not only have strong upper limits have been placed on the amount of polarized glue in the proton but that the experimental determination of the spin content has become much more precise. It is now clear that the origin of the discrepancy between experiment and the naive expectation of the fraction of spin carried by the quarks and anti-quarks in the proton lies in the non-perturbative structure of the proton. We explain how the features expected in a modern, relativistic and chirally symmetric description of nucleon structure naturally explain the current data. The consequences of this explanation for the presence of orbital angular momentum on quarks and gluons is reviewed and comparison made with recent results from lattice QCD and experimental data.

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DeTar, Carleton, James E. King, Sai Ping Li, and Larry McLerran. "Axial gauge propagators for quarks and gluons on the Polyakov-Wilson lattice." Nuclear Physics B 249, no. 4 (February 1985): 621–43. http://dx.doi.org/10.1016/0550-3213(85)90025-2.

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Boyle, P. A., R. D. Kenway, and C. M. Maynard. "UKQCD software for lattice quantum chromodynamics." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, no. 1897 (June 28, 2009): 2585–94. http://dx.doi.org/10.1098/rsta.2009.0057.

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Quantum chromodynamics (QCD) is the quantum field theory of the strong nuclear interaction and it explains how quarks and gluons are bound together to make more familiar objects such as the proton and neutron, which form the nuclei of atoms. UKQCD is a collaboration of eight UK universities that have come together to obtain and pool sufficient resources, both computational and manpower, to perform lattice QCD calculations. This paper explains how UKQCD uses and develops this software, how performance critical kernels for diverse architectures such as quantum chromodynamics-on-a-chip, BlueGene and XT4 are developed and employed and how UKQCD collaborates both internally and externally, with, for instance, the US SciDAC lattice QCD community.

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Dzierba, Alex R. "THE SCIENCE OF CONFINEMENT AND THE GLUEX/HALL D PROJECT AT JEFFERSON LAB." International Journal of Modern Physics A 18, no. 03 (January 30, 2003): 397–404. http://dx.doi.org/10.1142/s0217751x03014319.

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One of the outstanding and fundamental questions in physics is the quantitative understanding of the confinement of quarks and gluons in quantum chromodynamics (QCD). Confinement is a unique feature of QCD. Exotic hybrid mesons manifest gluonic degrees of freedom and their spectroscopy will provide the crucial data needed to test assumptions in lattice QCD and phenomenology leading to confinement. Photo-production is expected to be particularly effective in producing exotic hybrids but data using photon probes are sparse. At Jefferson Lab, plans are underway to use the coherent bremsstrahlung technique to produce a linearly polarized photon beam. A solenoid-based hermetic detector will be used to collected data on meson production and decays with statistics that will exceed the current photoproduction data in hand by several orders of magnitude after the first year of running. In order to reach the ideal photon energy of 9 GeV/c for this mapping of the exotic spectra, the energy of the Jefferson Lab electron accelerator, CEBAF, will be doubled from its current maximum of 6 GeV to 12 GeV. The physics and project are described.

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Choudhury, D. K., Baishali Saikia, and K. Kalita. "Momentum fractions carried by quarks and gluons in models of proton structure functions at small x." International Journal of Modern Physics A 32, no. 18 (June 27, 2017): 1750107. http://dx.doi.org/10.1142/s0217751x1750107x.

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In this paper, we report an analysis of partial momentum fractions carried by quarks and gluons in six alternative phenomenological models of proton structure function valid in limited small [Formula: see text] regions: [Formula: see text], [Formula: see text] to 6; the limits being determined by phenomenological range of validity in each model. Since the physics of small [Formula: see text] is not completely understood at this point, we have considered both self-similarity-based as well as QCD-based models. The procedure by which one can determine the applicability ranges in [Formula: see text] and [Formula: see text] of the models is presented. We find that while the self-similarity-based models with linear rise in [Formula: see text] has limited phenomenological ranges of validity, an improved version with linear rise in [Formula: see text] has a wider phenomenological range. We then compare the partial momentum fractions in all the small [Formula: see text] models. Our analysis implies that the role of small [Formula: see text] sea quarks in calculating the second moments of parton distribution is minor one. We have also made a comprehensive comparison of all the phenomenological models considered to the available perturbative QCD, lattice QCD as well as Ads/QCD results.

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Lévai, Péter, and Ulrich Heinz. "Massive gluons and quarks and the equation of state obtained from SU(3) lattice QCD." Physical Review C 57, no. 4 (April 1, 1998): 1879–90. http://dx.doi.org/10.1103/physrevc.57.1879.

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Farchioni, F., K. Jansen, I. Montvay, E. Scholz, L. Scorzato, A. Shindler, N. Ukita, C. Urbach, and I. Wetzorke. "The phase structure of lattice QCD with two flavors of Wilson quarks and renormalization group improved gluons." European Physical Journal C 42, no. 1 (July 2005): 73–87. http://dx.doi.org/10.1140/epjc/s2005-02262-5.

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Costa, Marios, and Haralambos Panagopoulos. "Renormalization of Supersymmetric QCD on the Lattice." EPJ Web of Conferences 175 (2018): 14001. http://dx.doi.org/10.1051/epjconf/201817514001.

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We perform a pilot study of the perturbative renormalization of a Supersymmetric gauge theory with matter fields on the lattice. As a specific example, we consider Supersymmetric N=1 QCD (SQCD). We study the self-energies of all particles which appear in this theory, as well as the renormalization of the coupling constant. To this end we compute, perturbatively to one-loop, the relevant two-point and three-point Green’s functions using both dimensional and lattice regularizations. Our lattice formulation involves theWilson discretization for the gluino and quark fields; for gluons we employ the Wilson gauge action; for scalar fields (squarks) we use naive discretization. The gauge group that we consider is SU(Nc), while the number of colors, Nc, the number of flavors, Nf, and the gauge parameter, α, are left unspecified. We obtain analytic expressions for the renormalization factors of the coupling constant (Zg) and of the quark (ZΨ), gluon (Zu), gluino (Zλ), squark (ZA±), and ghost (Zc) fields on the lattice. We also compute the critical values of the gluino, quark and squark masses. Finally, we address the mixing which occurs among squark degrees of freedom beyond tree level: we calculate the corresponding mixing matrix which is necessary in order to disentangle the components of the squark field via an additional finite renormalization.

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Kirscher, J. "Matching effective few-nucleon theories to QCD." International Journal of Modern Physics E 25, no. 05 (May 2016): 1641001. http://dx.doi.org/10.1142/s0218301316410019.

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The emergence of complex macroscopic phenomena from a small set of parameters and microscopic concepts demonstrates the power and beauty of physical theories. A theory which relates the wealth of data and peculiarities found in nuclei to the small number of parameters and symmetries of quantum chromodynamics is by that standard of exceptional beauty. Decade-long research on computational physics and on effective field theories facilitate the assessment of the presumption that quark masses and strong and electromagnetic coupling constants suffice to parametrize the nuclear chart. By presenting the current status of that enterprise, this article touches the methodology of predicting nuclei by simulating the constituting quarks and gluons and the development of effective field theories as appropriate representations of the fundamental theory. While the nuclear spectra and electromagnetic responses analyzed computationally so far with lattice QCD are in close resemblance to those which intrigued experimentalists a century ago, they also test the theoretical understanding which was unavailable to guide the nuclear pioneers but developed since then. This understanding is shown to be deficient in terms of correlations amongst nuclear observables and their sensitivity to fundamental parameters. By reviewing the transition from one effective field theory to another, from QCD to pionful chiral theories to pionless and eventually to cluster theories, we identify some of those deficiencies and conceptual problems awaiting a solution before QCD can be identified as the high-energy theory from which the nuclear landscape emerges.

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Buras, Andrzej J. "The Dual QCD @ Work: 2018." EPJ Web of Conferences 192 (2018): 00048. http://dx.doi.org/10.1051/epjconf/201819200048.

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The Dual QCD (DQCD) framework, based on the ideas of ’t Hooft and Witten, and developed by Bill Bardeen, Jean-Marc Gérard and myself in the 1980s is not QCD, a theory of quarks and gluons, but a successful low energy approximation of it when applied to K → ππ decays and K¯0 - K0 mixing. After years of silence, starting with 2014, this framework has been further developed in order to improve the SM prediction for the ratio ε'/ε, the ΔI = 1/2 rule and B^K. Most importantly, this year it has been used for the calculation of all K → ππ hadronic matrix elements of BSM operators which opened the road for the general study of ε'/ε in the context of the SM effective theory (SMEFT). This talk summarizes briefly the past successes of this framework and discusses recent developments which lead to a master formula for ε'/ε valid in any extension of the SM. This formula should facilitate the search for new physics responsible for the ε'/ε anomaly hinted by 2015 results from lattice QCD and DQCD.

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Müller-Preussker, M. "Creutz, M., Quarks, Gluons and Lattices. Cambridge etc. Cambridge University Press 1983. VI, 169 S., £ 7.95, $ 12.95. ISBN 0-521-31535-2. (Cambridge Monogr. on Mathematical Physics)." ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik 67, no. 1 (1987): 16. http://dx.doi.org/10.1002/zamm.19870670104.

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Pan, Ying-Hua, and Wei-Ning Zhang. "Chemical Evolution of Strongly Interacting Quark-Gluon Plasma." Advances in High Energy Physics 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/952607.

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At very initial stage of relativistic heavy ion collisions a wave of quark-gluon matter is produced from the break-up of the strong color electric field and then thermalizes at a short time scale (~1 fm/c). However, the quark-gluon plasma (QGP) system is far out of chemical equilibrium, especially for the heavy quarks which are supposed to reach chemical equilibrium much late. In this paper a continuing quark production picture for strongly interacting QGP system is derived, using the quark number susceptibilities and the equation of state; both of them are from the results calculated by the Wuppertal-Budapest lattice QCD collaboration. We find that the densities of light quarks increase by 75% from the temperatureT=400 MeV toT=150 MeV, while the density of strange quark annihilates by 18% in the temperature region. We also offer a discussion on how this late production of quarks affects the final charge-charge correlations.

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ALKOFER, R., C. S. FISCHER, F. J. LLANES-ESTRADA, and K. SCHWENZER. "WHAT THE INFRARED BEHAVIOR OF QCD VERTEX FUNCTIONS IN LANDAU GAUGE CAN TELL US ABOUT CONFINEMENT." International Journal of Modern Physics E 16, no. 09 (October 2007): 2720–32. http://dx.doi.org/10.1142/s0218301307008367.

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The infrared behavior of Landau gauge QCD vertex functions is investigated employing a skeleton expansion of the Dyson–Schwinger and Renormalization Group equations. Results for the ghost-gluon, three-gluon, four-gluon and quark-gluon vertex functions are presented. Positivity violation of the gluon propagator, and thus gluon confinement, is demonstrated. Results of the Dyson–Schwinger equations for a finite volume are compared to corresponding lattice data. It is analytically demonstrated that a linear rising potential between heavy quarks can be generated by infrared singularities in the dressed quark-gluon vertex. The selfconsistent mechanism that generates these singularities necessarily entails the scalar Dirac amplitudes of the full vertex and the quark propagator. These can only be present when chiral symmetry is broken, either explicitly or dynamically.

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Andreev, Oleg. "Drag force on heavy quarks and spatial string tension." Modern Physics Letters A 33, no. 06 (February 28, 2018): 1850041. http://dx.doi.org/10.1142/s0217732318500414.

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Heavy quark transport coefficients in a strongly coupled Quark–Gluon Plasma can be evaluated using a gauge/string duality and lattice QCD. Via this duality, one can argue that for low momenta the drag coefficient for heavy quarks is proportional to the spatial string tension. Such a tension is well-studied on the lattice that allows one to straightforwardly make non-perturbative estimates of the heavy quark diffusion coefficients near the critical point. The obtained results are consistent with those in the literature.

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SUGANUMA, HIDEO, ARATA YAMAMOTO, NAOYUKI SAKUMICHI, TORU T. TAKAHASHI, HIDEAKI IIDA, and FUMIKO OKIHARU. "INTER-QUARK POTENTIALS IN BARYONS AND MULTI-QUARK SYSTEMS IN QCD." Modern Physics Letters A 23, no. 27n30 (September 30, 2008): 2331–39. http://dx.doi.org/10.1142/s0217732308029320.

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We perform the first studies of various inter-quark potentials in SU(3)c lattice QCD. From the accurate lattice calculation for more than 300 different patterns of three-quark (3Q) systems, we find that the static 3Q potential V3Q is well described by Y-Ansatz, i.e., the Coulomb plus Y-type linear potential. Quark confinement mechanism in baryons is also investigated in maximally-Abelian projected QCD. We next study the multi-quark potentials VnQ (n = 4,5) in SU(3)c lattice QCD, and find that they are well described by the one-gluon-exchange Coulomb plus multi-Y type linear potential, which supports the flux-tube picture even for the multi-quarks. Finally, we study the heavy-heavy-light quark (QQq) potential both in lattice QCD and in a lattice-QCD-based quark model.

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GORENSTEIN, M. I., H. G. MILLER, R. A. RITCHIE, and SHIN NAN YANG. "THERMODYNAMICAL FUNCTIONS AND THE HEAVY-QUARK POTENTIAL IN AN SU(2) GLUON PLASMA." Modern Physics Letters A 10, no. 39 (December 21, 1995): 3001–7. http://dx.doi.org/10.1142/s0217732395003136.

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Monte-Carlo lattice data for thermodynamical functions and the heavy-quark potential for an SU(2) gluon plasma are considered in the “cutoff” model with a temperature dependent cutoff parameter. Good agreement with the data in both cases was found. We compare these results with a model of gluons with a thermal mass and find little difference between the two models. The results obtained for the heavy-quark potential are significantly better in both cases than those obtained from pure perturbative calculations.

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32

Vollmer, G., K. Hepp, F. Haake, R. Sexl, P. Warneck, H. A. Kastrup, and K. Suchy. "Zeh: Die Physik der Zeitrichtung/Pauli: Physik und Erkenntnistheorie/Kümmel: Introduction to Quantum Mechanics/Kanitscheider, Törnebohm, Drieschner: Moderne Naturphilosophie/Fabian: Atmosphäre und Umwelt/Creutz: Quarks, gluons and lattices/Ebeling, Kraeft." Physik Journal 41, no. 2 (February 1985): 53–55. http://dx.doi.org/10.1002/phbl.19850410213.

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33

Villegas, Kristian Hauser, and Jose Perico Esguerra. "Lattice gauge theory and gluon color-confinement in curved spacetime." Modern Physics Letters A 30, no. 05 (February 3, 2015): 1550020. http://dx.doi.org/10.1142/s0217732315500200.

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The lattice gauge theory (LGT) for curved spacetime is formulated. A discretized action is derived for both gluon and quark fields which reduces to the generally covariant form in the continuum limit. Using the Wilson action, it is shown analytically that for a general curved spacetime background, two propagating gluons are always color-confined. The fermion-doubling problem is discussed in the specific case of Friedman–Robertson–Walker (FRW) metric. Last, we discussed possible future numerical implementation of lattice QCD in curved spacetime.

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BEGUN, V. V., M. I. GORENSTEIN, and O. A. MOGILEVSKY. "MODIFIED BAG MODELS FOR THE QUARK–GLUON PLASMA EQUATION OF STATE." International Journal of Modern Physics E 20, no. 08 (August 2011): 1805–15. http://dx.doi.org/10.1142/s0218301311019623.

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The modified versions of the bag model equation of state (EoS) are considered. They are constructed to satisfy the main qualitative features observed for the quark–gluon plasma EoS in the lattice QCD calculations. A quantitative comparison with the lattice results at high temperatures T are done in the SU(3) gluodynamics and in the full QCD with dynamical quarks. Our analysis advocates a negative value of the bag constant B.

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35

Shanahan, Phiala. "The gluon structure of hadrons and nuclei from lattice QCD." EPJ Web of Conferences 175 (2018): 01015. http://dx.doi.org/10.1051/epjconf/201817501015.

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I discuss recent lattice QCD studies of the gluon structure of hadrons and light nuclei. After very briefly highlighting new determinations of the gluon contributions to the nucleon’s momentum and spin, presented by several collaborations over the last year, I describe first calculations of gluon generalised form factors. The generalised transversity gluon distributions are of particular interest since they are purely gluonic; they do not mix with quark distributions at leading twist. In light nuclei they moreover provide a clean signature of non-nucleonic gluon degrees of freedom, and I present the first evidence for such effects, based on lattice QCD calculations. The planned Electron-Ion Collider, designed to access gluon structure quantities, will have the capability to test this prediction, and measure a range of gluon observables including generalised gluon distributions and transverse momentum dependent gluon distributions, within the next decade.

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Hajizadeh, Ouraman, Tamer Boz, Axel Maas, and Jon-Ivar Skullerud. "Gluon and ghost correlation functions of 2-color QCD at finite density." EPJ Web of Conferences 175 (2018): 07012. http://dx.doi.org/10.1051/epjconf/201817507012.

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2-color QCD, i. e. QCD with the gauge group SU(2), is the simplest non-Abelian gauge theory without sign problem at finite quark density. Therefore its study on the lattice is a benchmark for other non-perturbative approaches at finite density. To provide such benchmarks we determine the minimal-Landau-gauge 2-point and 3-gluon correlation functions of the gauge sector and the running gauge coupling at finite density. We observe no significant effects, except for some low-momentum screening of the gluons at and above the supposed high-density phase transition.

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Potvin, Jean. "La physique de la matière hadronique à haute température telle que décrite par la chromodynamique quantique sur réseau espace–temps." Canadian Journal of Physics 67, no. 12 (December 1, 1989): 1228–49. http://dx.doi.org/10.1139/p89-206.

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The numerical simulation of quantum chromodynamics on a space–time lattice allows for the calculation of many properties of hadronic matter at high temperature in a direct and in a nonperturbative fashion. This paper will be a review of the calculation techniques and results published in the past 5 years. Among other things, I will discuss the order of the phase transition, the critical temperature, the force between heavy quarks, as well as the thermodynamics and the spectroscopy of the quark–gluon plasma.

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Aarts, Gert, Chris Allton, Davide de Boni, Simon Hands, Benjamin Jäger, Chrisanthi Praki, and Jon-Ivar Skullerud. "Baryons in the plasma: In-medium effects and parity doubling." EPJ Web of Conferences 171 (2018): 14005. http://dx.doi.org/10.1051/epjconf/201817114005.

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We investigate the fate of baryons made out of u, d and s quarks in the hadronic gas and the quark-gluon plasma, using nonperturbative lattice simulations, employing the FASTSUManisotropic Nf = 2+1 ensembles. In the confined phase a strong temperature dependence is seen in the masses of the negative-parity groundstates, while the positiveparity groundstate masses are approximately temperature independent, within the error. At high temperature parity doubling emerges. A noticeable effect of the heavier s quark is seen. We give a simple description of the medium-dependent masses for the negativeparity states and speculate on the relevance for heavy-ion phenomenology via the hadron resonance gas.

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Fan, Zhou-You, Wen-Kai Fan, Qing-Wu Wang, and Hong-Shi Zong. "NJL model with the modified quark-dependent coupling strength G." Modern Physics Letters A 32, no. 20 (June 9, 2017): 1750107. http://dx.doi.org/10.1142/s0217732317501073.

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In this paper, the coupling strength G of the Nambu–Jona-Lasinio (NJL) model is modified by incorporating quark’s feedback into the gluon propagator. The modified two-flavor NJL model with the quark-dependent coupling strength is explored. The quark condensate in this framework has a conspicuous agreement with the lattice quantum chromodynamics (QCD) results at finite temperature. Then, it is compared with the original NJL model in both zero (chiral limit) and nonzero current quark mass. The QCD phase diagram and susceptibilities are investigated in the temperature–chemical potential [Formula: see text] plane. Therefore, the pseudo-critical temperature [Formula: see text] and the critical end point (CEP) are worked out and compared with original NJL model or lattice QCD results. In addition, the pion mass and decay constant are studied at finite temperature.

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László Jenkovszky. "Quarks, Gluons and Glueballs." Physics of Particles and Nuclei 51, no. 4 (July 2020): 686–89. http://dx.doi.org/10.1134/s106377962004036x.

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41

Wilczek, Frank. "Liberating quarks and gluons." Nature 391, no. 6665 (January 1998): 330–31. http://dx.doi.org/10.1038/34778.

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42

Liang, Bin. "On Quarks and Gluons." Journal of Modern Physics 06, no. 07 (2015): 982–89. http://dx.doi.org/10.4236/jmp.2015.67102.

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MATHIEU, VINCENT, NIKOLAI KOCHELEV, and VICENTE VENTO. "THE PHYSICS OF GLUEBALLS." International Journal of Modern Physics E 18, no. 01 (January 2009): 1–49. http://dx.doi.org/10.1142/s0218301309012124.

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Glueballs are particles whose valence degrees of freedom are gluons and therefore in their description the gauge field plays a dominant role. We review recent results in the physics of glueballs with the aim set on phenomenology and discuss the possibility of finding them in conventional hadronic experiments and in the Quark Gluon Plasma. In order to describe their properties we resort to a variety of theoretical treatments which include, lattice QCD, constituent models, AdS/QCD methods, and QCD sum rules. The review is supposed to be an informed guide to the literature. Therefore, we do not discuss in detail technical developments but refer the reader to the appropriate references.

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NISHIJIMA, KAZUHIKO. "CONFINEMENT OF QUARKS AND GLUONS." International Journal of Modern Physics A 09, no. 21 (August 20, 1994): 3799–819. http://dx.doi.org/10.1142/s0217751x94001539.

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It is proved without recourse to any approximation that quarks and gluons are confined simultaneously when the anomalous dimension of the gluon field is negative in the weak coupling limit. The proof is based on the BRS invariance of quantum chromodynamics and the Oehme–Zimmermann superconvergence relation for the spectral function of the gluon field.

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45

Gottlieb, Steve. "Quarks and gluons get real." Physics World 18, no. 7 (July 2005): 22–23. http://dx.doi.org/10.1088/2058-7058/18/7/32.

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46

SIMJI, P., and VISHNU M. BANNUR. "PHENOMENOLOGICAL MODELS OF GLUON PLASMA IN THE LARGE TEMPERATURE RANGE." International Journal of Modern Physics A 28, no. 25 (October 8, 2013): 1350121. http://dx.doi.org/10.1142/s0217751x13501212.

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Quasiparticle quark–gluon plasma (qQGP) model and strongly coupled quark–gluon plasma (SCQGP) are two different phenomenological models of quark–gluon plasma (QGP) that try to explain the nonideal behavior seen in lattice simulation of QCD and in relativistic heavy ion collisions. These models almost successfully explain the existing lattice data up to 5Tc. Here, we investigate how better these models fit the recent lattice data results of precision SU(3) thermodynamics for a large temperature range (up to 1000Tc) by studying the statistical mechanics and thermodynamics of gluon plasma and hence we have a complete phenomenological description of the equation of state of QGP from the phase transition through the perturbative region up to Stefan–Boltzmann limit. We also study the effect of orders of running coupling constants on the models and used the equation of state obtained using these models in predicting behavior of quantity like velocity of sound in high temperature, which has no lattice QCD results for such high temperatures.

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HARRIS, JOHN W. "EVIDENCE FOR A QUARK-GLUON PLASMA AT RHIC." International Journal of Modern Physics E 16, no. 03 (April 2007): 643–59. http://dx.doi.org/10.1142/s0218301307006186.

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This presentation is given in honor of Walter Greiner's 70th birthday, in recognition of the pioneering work of his "Frankfurt School" and their contributions to the field of heavy ion physics. Ultra-relativistic collisions of heavy nuclei at the Relativistic Heavy Ion Collider (RHIC) form an extremely hot system at energy densities greater than 5 GeV/fm3, where normal hadrons cannot exist. Upon rapid cooling of the system to a temperature T ~ 175 MeV and vanishingly small baryo-chemical potential, hadrons coalesce from quarks at the quark-hadron phase boundary predicted by lattice QCD. A large amount of collective (elliptic) flow at the quark level provides evidence for strong pressure gradients in the initial partonic stage of the collision when the system is dense and highly interacting prior to coalescence into hadrons. The suppression of both light (u,d,s) and heavy (c,b) hadrons at large transverse momenta, that form from fragmentation of hard-scattered partons, and the quenching of di-jets provide evidence for extremely large energy loss of partons as they attempt to propagate through the dense, strongly-coupled, colored medium created at RHIC.

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LIU, WEI, CHE MING KO, and BEN-WEI ZHANG. "JET CONVERSIONS IN QGP AND SUPPRESSION OF IDENTIFIED HADRONS." International Journal of Modern Physics E 16, no. 07n08 (August 2007): 1930–36. http://dx.doi.org/10.1142/s021830130700726x.

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A gluon or quark jet traversing through a quark-gluon plasma can be converted into a quark or gluon jet through scatterings with thermal partons. Their conversion rates due to two-body elastic and inelastic scattering as well as scatterings involving gluon radiation are evaluated in the lowest order in Quantum Chromodynamics (QCD). Including both energy loss and conversions of quark and gluon jets in the expanding quark-gluon plasma produced in relativistic heavy ion collisions, we find a net conversion of quark jets to gluon jets. This reduces the difference between the nuclear modification factors for quark and gluon jets in central heavy ion collisions and thus enhances the p/π+ and [Formula: see text] ratios at high transverse momentum. Using the larger QCD coupling constant from lattice QCD calculations than that given by the perturbative QCD further enhances the net quark to gluon jet conversion rate, leading to a closer similarity between these ratios at high transverse momentum in central Au + Au collisions at [Formula: see text] and in p + p collisions at same energy as observed in experiments.

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Blaschke, David, Kirill A. Devyatyarov, and Olaf Kaczmarek. "Quark Cluster Expansion Model for Interpreting Finite-T Lattice QCD Thermodynamics." Symmetry 13, no. 3 (March 21, 2021): 514. http://dx.doi.org/10.3390/sym13030514.

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In this work, we present a unified approach to the thermodynamics of hadron–quark–gluon matter at finite temperatures on the basis of a quark cluster expansion in the form of a generalized Beth–Uhlenbeck approach with a generic ansatz for the hadronic phase shifts that fulfills the Levinson theorem. The change in the composition of the system from a hadron resonance gas to a quark–gluon plasma takes place in the narrow temperature interval of 150–190 MeV, where the Mott dissociation of hadrons is triggered by the dropping quark mass as a result of the restoration of chiral symmetry. The deconfinement of quark and gluon degrees of freedom is regulated by the Polyakov loop variable that signals the breaking of the Z(3) center symmetry of the color SU(3) group of QCD. We suggest a Polyakov-loop quark–gluon plasma model with O(αs) virial correction and solve the stationarity condition of the thermodynamic potential (gap equation) for the Polyakov loop. The resulting pressure is in excellent agreement with lattice QCD simulations up to high temperatures.

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Hansson, J. "A simple explanation of the nonappearance of physical gluons and quarks." Canadian Journal of Physics 80, no. 9 (September 1, 2002): 1093–97. http://dx.doi.org/10.1139/p02-034.

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We show that the nonappearance of gluons and quarks as physical particles is a rigorous and automatic result of the full, i.e., nonperturbative, nonabelian nature of the color interaction in quantum chromodynamics (QCD). This makes it, in general, impossible to describe the color field as a collection of elementary quanta (gluons). Neither can a quark be an elementary quantum of the quark field, as the color field of which it is the source is itself a source, making isolated noninteracting quarks, crucial for a physical particle interpretation, impossible. In geometrical language, the impossibility of quarks and gluons as physical elementary particles arises due to the fact that the color YangMills space does not have a constant trivial curvature. In QCD, the particles "gluons" and "quarks" are merely artifacts of an approximation method (the perturbative expansion) and are simply absent in the exact theory. This also coincides with the empirical, experimental evidence. PACS Nos.: 12.38Aw, 03.70+k, 11.15-q

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Journal articles on the topic 'Quarks, gluons and lattices'

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