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Journal articles on the topic 'Effective field theory; QCD; lattice QCD'

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Published: 10 December 2022

Last updated: 28 January 2023

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1

Prelovsek, Sasa. "QCD confronts heavy-flavor and exotic hadrons." EPJ Web of Conferences 274 (2022): 01014. http://dx.doi.org/10.1051/epjconf/202227401014.

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A review of QCD-based theory approaches to study the heavy-flavor and exotic hadrons is given. The focus is on the results from lattice QCD and from lattice QCD complemented by effective field theories. Both approaches are first briefly introduced and applied in few examples. Then the status of various hadrons sectors is presented.

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2

SHNIR, YASHA. "THE COLOR–FLAVOR TRANSFORMATION OF INDUCED QCD." International Journal of Modern Physics A 20, no. 20n21 (August 20, 2005): 4965–93. http://dx.doi.org/10.1142/s0217751x05025401.

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The color–flavor transformation is applied to the U (Nc) lattice gauge model, in which the gauge theory is induced by a heavy chiral scalar field sitting on lattice sites. The flavor degrees of freedom can encompass several "generations" of the auxiliary field, and for each generation, remaining indices are associated with the elementary plaquettes touching the lattice site. The effective, color–flavor transformed theory is expressed in terms of gauge singlet matrix fields carried by lattice links. The effective action is analyzed for a hypercubic lattice in arbitrary dimension. The saddle points equations of the model in the large-Nc limit are discussed.

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THOMAS, ANTHONY W., DEREK B. LEINWEBER, ROSS D. YOUNG, and STEWART V. WRIGHT. "QCD AND HADRON STRUCTURE." Modern Physics Letters A 18, no. 02n06 (February 28, 2003): 347–55. http://dx.doi.org/10.1142/s0217732303010478.

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There is considerable interest in the possibility of extracting model independent information on the masses and other properties of hadrons from lattice QCD, even though the state of the art involves light quark masses considerably higher than those found in nature. We review the applicability of effective field theory to this problem. Taking the rho meson as an example, we show that conventional, dimensionally regularized field theory is not sufficiently convergent to provide a reliable method of extrapolation. The reason for the poor convergence is discussed, along with the solution which this suggests. Finally we outline a very interesting suggestion of a connection between hadron masses in full and quenched QCD, using the nucleon and delta as examples.

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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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Chu, M. C., Marcello Lissia, and J. W. Negele. "Test of the Skyrme effective field theory using quenched lattice QCD." Nuclear Physics A 570, no. 3-4 (April 1994): 521–42. http://dx.doi.org/10.1016/0375-9474(94)90072-8.

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6

Renzo, Francesco Di. "Simulating lattice field theories on multiple thimbles." EPJ Web of Conferences 175 (2018): 07015. http://dx.doi.org/10.1051/epjconf/201817507015.

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Simulating thimble regularization of lattice field theory can be tricky when more than one thimble is to be taken into account. A couple of years ago we proposed a solution for this problem. More recently this solution proved to be effective in the case of 0+1 dimensional QCD. A few lessons we can learnt, including the role of symmetries and general hints on algorithmic solutions.

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7

Meißner, Ulf-G. "Towards a theory of baryon resonances." EPJ Web of Conferences 241 (2020): 02003. http://dx.doi.org/10.1051/epjconf/202024102003.

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In this talk, I discuss methods that allow for a systematic and model-independent calculation of the hadron spectrum. These are lattice QCD and/or its corresponding Effective Field Theories. Assorted results are shown and I take the opportunity to discuss some misconceptions often found in the literature.

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Kim, Seyong, Peter Petreczky, and Alexander Rothkopf. "In-medium quarkonium properties from a lattice QCD based effective field theory." Nuclear Physics A 956 (December 2016): 713–16. http://dx.doi.org/10.1016/j.nuclphysa.2015.12.011.

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9

Steinhauser, Marc, André Sternbeck, Björn Wellegehausen, and Andreas Wipf. "Spectroscopy of four-dimensional N = 1 supersymmetric SU(3) Yang-Mills theory." EPJ Web of Conferences 175 (2018): 08022. http://dx.doi.org/10.1051/epjconf/201817508022.

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Supersymmetric gauge theories are an important building block for extensions of the standard model. As a first step towards Super-QCD we investigate the pure gauge sector with gluons and gluinos on the lattice, in particular the low energy mass spectrum: meson-like gluinoballs, gluino-glueballs and pure glueballs. We report on some first calculations performed with clover improved Wilson fermions on rather small lattices. The supersymmetric continuum limit and particle masses are discussed and compared to predictions from effective field theory.

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10

Gupta, Sourendu, and Rishi Sharma. "Real-time warm pions from the lattice using an effective theory." International Journal of Modern Physics A 35, no. 33 (November 30, 2020): 2030021. http://dx.doi.org/10.1142/s0217751x20300215.

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Lattice measurements provide adequate information to fix the parameters of long-distance effective field theories in Euclidean time. Using such a theory, we examine the analytic continuation of long-distance correlation functions of composite operators at finite temperature from Euclidean to Minkowski space–time. We show through an explicit computation that the analytic continuation of the pion correlation function is possible and gives rise to nontrivial effects. Among them is the possibility, supported by lattice computations of Euclidean correlators, that long distance excitations can be understood in terms of (very massive) pions even at temperatures higher than the QCD crossover temperature.

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11

Verbaarschot, J. J. M., and T. Wettig. "Random Matrix Theory and Chiral Symmetry in QCD." Annual Review of Nuclear and Particle Science 50, no. 1 (December 2000): 343–410. http://dx.doi.org/10.1146/annurev.nucl.50.1.343.

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▪ Abstract Random matrix theory is a powerful way to describe universal correlations of eigenvalues of complex systems. It also may serve as a schematic model for disorder in quantum systems. In this review, we discuss both types of applications of chiral random matrix theory to the QCD partition function. We show that constraints imposed by chiral symmetry and its spontaneous breaking determine the structure of low-energy effective partition functions for the Dirac spectrum. We thus derive exact results for the low-lying eigenvalues of the QCD Dirac operator. We argue that the statistical properties of these eigenvalues are universal and can be described by a random matrix theory with the global symmetries of the QCD partition function. The total number of such eigenvalues increases with the square root of the Euclidean four-volume. The spectral density for larger eigenvalues (but still well below a typical hadronic mass scale) also follows from the same low-energy effective partition function. The validity of the random matrix approach has been confirmed by many lattice QCD simulations in a wide parameter range. Stimulated by the success of the chiral random matrix theory in the description of universal properties of the Dirac eigenvalues, the random matrix model is extended to nonzero temperature and chemical potential. In this way we obtain qualitative results for the QCD phase diagram and the spectrum of the QCD Dirac operator. We discuss the nature of the quenched approximation and analyze quenched Dirac spectra at nonzero baryon density in terms of an effective partition function. Relations with other fields are also discussed.

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12

BROWER, RICHARD C., YUE SHEN, and CHUNG-I. TAN. "CHIRALLY EXTENDED QUANTUM CHROMODYNAMICS." International Journal of Modern Physics C 06, no. 05 (October 1995): 725–42. http://dx.doi.org/10.1142/s0129183195000599.

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We propose an extended Quantum Chromodynamics (XQCD) Lagrangian in which the fermions are coupled to elementary scalar fields through a Yukawa coupling which preserves chiral invariance. Our principle motivation is to find a new lattice formulation for QCD which avoids the source of critical slowing down usually encountered as the bare quark mass is tuned to the chiral limit. The phase diagram and the weak coupling limit for XQCD are studied. They suggest a conjecture that the continuum limit of XQCD is the same as the continuum limit of conventional lattice formulation of QCD. As examples of such universality, we present the large N solutions of two prototype models for XQCD, in which the mass of the spurious pion and sigma resonance go to infinity with the cut-off. Even if the universality conjecture turns out to be false, we believe that XQCD will still be useful as a low energy effective action for QCD phenomenology on the lattice. Numerical simulations are recommended to further investigate the possible benefits of XQCD in extracting QCD predictions.

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13

UMINO, YASUO. "EQUATION OF STATE OF STRONGLY COUPLED HAMILTONIAN LATTICE QCD AT FINITE DENSITY." Modern Physics Letters A 17, no. 38 (December 14, 2002): 2513–21. http://dx.doi.org/10.1142/s0217732302009234.

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We calculate the equation of state of strongly coupled Hamiltonian lattice QCD at finite density by constructing a solution to the equation of motion corresponding to an effective Hamiltonian describing the ground state of the theory with Wilson fermions. To lowest order in N c we find that the pressure of the quark Fermi sea can be negative indicating its mechanical instability. This new mean field result is in qualitative agreement with continuum models and should be verifiable by future numerical simulations.

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Höllwieser, Roman, and Jeff Greensite. "Preliminary QCD phase transition line for 695 MeV dynamical staggered fermions from effective Polyakov line actions." EPJ Web of Conferences 175 (2018): 07022. http://dx.doi.org/10.1051/epjconf/201817507022.

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We present a phase diagram for SU(3) lattice gauge theory with 695 MeV dynamical staggered fermions, in the plane of temperature and chemical potential, obtained from effective Polyakov line actions. The derivation is via the method of relative weights, and the effective theories are solved at finite chemical potential by mean field theory.

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15

Tarrús Castellà, Jaume. "Doubly heavy baryons in Born-Oppenheimer EFT." EPJ Web of Conferences 258 (2022): 04003. http://dx.doi.org/10.1051/epjconf/202225804003.

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We report on the recent progress on the computation of the doubly heavy baryon spectrum in effective field theory. The effective field theory is built upon the heavy-quark mass and adiabatic expansions. The potentials can be expressed as NRQCD Wilson loops with operator insertions. These are nonperturbative objects and so far only the one corresponding to the static potential has been computed with lattice QCD. We review the proposal for a parametrization of the potentials based in an interpolation between the shortand long-distance regimes. The long-distance description is obtained with a newly proposed Effective String Theory which coincides with the previous ones for pure gluodynamics but it is extended to contain a fermion field. We show the doubly heavy baryon spectrum with hyperfine contributions obtained using these parametrizations for the hyperfine potentials.

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Pang, Jin-Yi. "Three-particle system in a finite volume: formalism, quantization condition, spectrum and energy shift." EPJ Web of Conferences 241 (2020): 02005. http://dx.doi.org/10.1051/epjconf/202024102005.

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Lattice QCD calculations provide an ab initio access to hadronic process. These calculations are usu ally performed in a small cubic volume with periodic boundary conditions. The infinite volume extrapolations for three-body systems are indispensable to understand many systems of high current interest. We derive the three-body quantization condition in a finite volume using an effective field theory in the particle-dimer picture. Our work shows a powerful and transparent method to read off three-body physical observables from lattice simulations. In this paper, we review the formalism, quantization condition, spectrum analysis and energy shifts calculation both for 3-body bound states and scattering states.

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17

Capitani, S., M. Della Morte, D. Djukanovic, G. M. von Hippel, J. Hua, B. Jäger, P. M. Junnarkar, H. B. Meyer, T. D. Rae, and H. Wittig. "Isovector axial form factors of the nucleon in two-flavor lattice QCD." International Journal of Modern Physics A 34, no. 02 (January 20, 2019): 1950009. http://dx.doi.org/10.1142/s0217751x1950009x.

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We present a lattice calculation of the nucleon isovector axial and induced pseudoscalar form factors on the CLS ensembles using [Formula: see text] dynamical flavors of nonperturbatively [Formula: see text]-improved Wilson fermions and an [Formula: see text]-improved axial current together with the pseudoscalar density. Excited-state effects in the extraction of the form factors are treated using a variety of methods, with a detailed discussion of their respective merits. The chiral and continuum extrapolation of the results is performed both using formulae inspired by Heavy Baryon Chiral Perturbation Theory (HBChPT) and a global approach to the form factors based on a chiral effective field theory (EFT) including axial vector mesons. Our results indicate that careful treatment of excited-state effects is important in order to obtain reliable results for the axial form factors of the nucleon, and that the main remaining error stems from the systematic uncertainties of the chiral extrapolation. As final results, we quote [Formula: see text], [Formula: see text], and [Formula: see text] for the axial charge, axial charge radius and induced pseudoscalar charge, respectively, where the first error is statistical and the second is systematic.

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18

ANTONOV, D. V. "NONPERTURBATIVE FIELD CORRELATOR AND STRING REPRESENTATION FOR THE 't HOOFT LOOP AVERAGE IN THE ABELIAN HIGGS MODEL." Modern Physics Letters A 13, no. 09 (March 21, 1998): 659–71. http://dx.doi.org/10.1142/s0217732398000711.

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Making use of the duality transformation, we derive in the Londons' limit of the Abelian Higgs model string representation for the 't Hooft loop average defined on the string worldsheet, which yields the values of two coefficient functions parametrizing the bilocal correlator of the dual field strength tensors. The asymptotic behaviors of these functions agree with the ones obtained within the method of vacuum correlators in QCD in the lowest order of perturbation theory. We demonstrate that the bilocal approximation to the method of vacuum correlators is an exact result in the Londons' limit, i.e. all the higher cumulants in this limit vanish. We also show that at large distances, apart from the integration over metrics, the obtained string effective theory (which in this case reduces to the nonlinear massive axionic sigma model) coincides with the low energy limit of the dual version of 4D compact QED, the so-called universal confining string theory. We derive string tension of the Nambu–Goto term and the coupling constant of the rigidity term for the obtained string effective theory and demonstrate that the latter is always negative, which means the stability of strings, while the positiveness of the former is confirmed by the present lattice data. These data enable us to find the Higgs boson charge and the vacuum expectation value of the Higgs field, which well-described QCD. We also study dynamics of the weight factor of the obtained string representation for the 't Hooft average in the loop space. In conclusion, we obtain string representation for the partition function of the correlators of an arbitrary number of Higgs currents, by virtue of which we rederive the structure of the bilocal correlator of the dual field strength tensors, which yields the surface term in the string effective action.

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19

Chorozidou, Arsenia, and Theodoros Gaitanos. "Momentum dependent mean-fields of hyperons & antihyperons." EPJ Web of Conferences 252 (2021): 05006. http://dx.doi.org/10.1051/epjconf/202125205006.

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The in-medium properties of hyperons and antihyperons are studied with the Non-Linear Derivative (NLD) model and focus is made on the momentum dependence of strangeness optical potentials. The NLD model is based on the Relativistic Mean Field (RMF) approximation to Relativistic Hadrodynamics (RHD) approach of nuclear systems, but it incorporates an explicit momentum dependence of mean-fields. The extension of the NLD model to the baryon and antibaryon octet is based on SU(6) and G-parity arguments. It is demonstrated that with a proper choice of momentum cut-offs, the Λ and Σ optical potentials are consistent with recent studies of the chiral effective field theory(χ -EFT) and optical potentials are consistent with Lattice-QCD calculations, over a wide momentum region. We also present NLD predictions for the in-medium momentum dependence of ∧¯, ∑¯ and Ξ¯ hyperons. This work is important for future experimental studies, like CBM, PANDA at FAIR and is relevant to nuclear astrophysics as well.

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Chorozidou, Arsenia, and Theodoros Gaitanos. "The Non-Linear Derivative (NLD) model for the in-medium hyperons & antihyperons dynamics." HNPS Advances in Nuclear Physics 28 (October 17, 2022): 54–59. http://dx.doi.org/10.12681/hnps.3574.

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The in-medium properties of hyperons and antihyperons are studied with the Non-Linear Derivative (NLD) model and focus is made on the momentum dependence of strangeness optical potentials[1]. The NLD model is based on the Relativistic Mean Field (RMF) approximation to Relativistic Hadrodynamics (RHD) approach of nuclear systems, but it incorporates an explicit momentum dependence of mean-fields. The extension of the NLD model to the baryon and antibaryon octet is based on SU(6) and G-parity arguments. It is demonstrated that with a proper choice of momentum cut-offs, the Λ and Σ optical potentials are consistent with recent studies of the chiral effective field theory and Ξ optical potentials are consistent with Lattice-QCD calculations, over a wide momentum region. We also present NLD predictions for the in-medium momentum dependence of antiΛ, antiΣ and antiΞ hyperons. This work is important for future experimental studies, like CBM, PANDA at FAIR and is relevant to nuclear astrophysics as well.

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21

Gasbarro, Andrew. "Can a Linear Sigma Model Describe Walking Gauge Theories at Low Energies?" EPJ Web of Conferences 175 (2018): 08024. http://dx.doi.org/10.1051/epjconf/201817508024.

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In recent years, many investigations of confining Yang Mills gauge theories near the edge of the conformal window have been carried out using lattice techniques. These studies have revealed that the spectrum of hadrons in nearly conformal ("walking") gauge theories differs significantly from the QCD spectrum. In particular, a light singlet scalar appears in the spectrum which is nearly degenerate with the PNGBs at the lightest currently accessible quark masses. This state is a viable candidate for a composite Higgs boson. Presently, an acceptable effective field theory (EFT) description of the light states in walking theories has not been established. Such an EFT would be useful for performing chiral extrapolations of lattice data and for serving as a bridge between lattice calculations and phenomenology. It has been shown that the chiral Lagrangian fails to describe the IR dynamics of a theory near the edge of the conformal window. Here we assess a linear sigma model as an alternate EFT description by performing explicit chiral fits to lattice data. In a combined fit to the Goldstone (pion) mass and decay constant, a tree level linear sigma model has a Χ2/d.o.f. = 0.5 compared to Χ2/d.o.f. = 29.6 from fitting nextto-leading order chiral perturbation theory. When the 0++ (σ) mass is included in the fit, Χ2/d.o.f. = 4.9. We remark on future directions for providing better fits to the σ mass.

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22

WANG, W. Y., and Y. L. WU. "A CONSISTENT CALCULATION OF HEAVY MESON DECAY CONSTANTS AND TRANSITION WAVE FUNCTIONS IN THE COMPLETE HQEFT." International Journal of Modern Physics A 16, no. 03 (January 30, 2001): 377–408. http://dx.doi.org/10.1142/s0217751x01002385.

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Within the complete heavy quark effective field theory (HQEFT), the QCD sum rule approach is used to evaluate the decay constants including 1/mQcorrections and the Isgur–Wise function and other additional important wave functions concerned at 1/mQfor the heavy–light mesons. The number of unknown wave functions or form factors in HQEFT is shown to be much less than the one in the usual heavy quark effective theory (HQET). The values of wave functions at zero recoil are found to be consistent with the ones extracted from the interesting relations (which are resulted from the HQEFT) between the hadron masses and wave functions at zero recoil. The results for the decay constants are consistent with the ones from full QCD sum rule and Lattice calculations. The 1/mQcorrections to the scaling law [Formula: see text] are found to be small in HQEFT, which demonstrates again the validity of 1/mQexpansion in HQEFT. It is also shown that the residual momentum v·k of heavy quark within heavy–light hadrons is indeed around the binding energy [Formula: see text] of the heavy hadrons, which turns out to be in agreement with the expected one in the HQEFT. Therefore such a calculation provides a consistent check on the HQEFT and shows that the HQEFT is more reliable than the usual HQET for describing a slightly off-mass shell heavy quark within hadron as the usual HQET seems to lead to large 1/mQcorrections in evaluating the meson decay constants. It is emphasized that the introduction of the "dressed heavy quark" mass is useful for the heavy–light mesons (Qq) with [Formula: see text], while for heavy–heavy bound states (ψ1ψ2) with masses m1, [Formula: see text], like bottom-charm hadrons or similarly for muonium in QED, one needs to treat both particles as heavy effective particles via 1/m1and 1/m2expansions and redefine the effective bound states and modified "dressed heavy quark" masses within the HQEFT.

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23

Kamleh, Waseem, Derek Leinweber, Zhan-wei Liu, Finn Stokes, Anthony Thomas, Samuel Thomas, and Jia-jun Wu. "Structure of the Nucleon and its Excitations." EPJ Web of Conferences 175 (2018): 06019. http://dx.doi.org/10.1051/epjconf/201817506019.

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The structure of the ground state nucleon and its finite-volume excitations are examined from three different perspectives. Using new techniques to extract the relativistic components of the nucleon wave function, the node structure of both the upper and lower components of the nucleon wave function are illustrated. A non-trivial role for gluonic components is manifest. In the second approach, the parity-expanded variational analysis (PEVA) technique is utilised to isolate states at finite momenta, enabling a novel examination of the electric and magnetic form factors of nucleon excitations. Here the magnetic form factors of low-lying odd-parity nucleons are particularly interesting. Finally, the structure of the nucleon spectrum is examined in a Hamiltonian effective field theory analysis incorporating recent lattice-QCD determinations of low-lying two-particle scattering-state energies in the finite volume. The Roper resonance of Nature is observed to originate from multi-particle coupled-channel interactions while the first radial excitation of the nucleon sits much higher at approximately 1.9 GeV.

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24

Bietenholz, Wolfgang. "Hadron physics from lattice QCD." International Journal of Modern Physics E 25, no. 07 (July 2016): 1642008. http://dx.doi.org/10.1142/s0218301316420088.

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We sketch the basic ideas of the lattice regularization in Quantum Field Theory, the corresponding Monte Carlo simulations, and applications to Quantum Chromodynamics (QCD). This approach enables the numerical measurement of observables at the non-perturbative level. We comment on selected results, with a focus on hadron masses and the link to Chiral Perturbation Theory. At last, we address two outstanding issues: topological freezing and the sign problem.

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DI PIERRO, MASSIMO. "AN ALGORITHMIC APPROACH TO QUANTUM FIELD THEORY." International Journal of Modern Physics A 21, no. 03 (January 30, 2006): 405–47. http://dx.doi.org/10.1142/s0217751x06028965.

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The lattice formulation provides a way to regularize, define and compute the Path Integral in a Quantum Field Theory. In this paper, we review the theoretical foundations and the most basic algorithms required to implement a typical lattice computation, including the Metropolis, the Gibbs sampling, the Minimal Residual, and the Stabilized Biconjugate inverters. The main emphasis is on gauge theories with fermions such as QCD. We also provide examples of typical results from lattice QCD computations for quantities of phenomenological interest.

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26

Giusti, L., P. Hernández, S. Necco, C. Pena, J. Wennekers, and H. Wittig. "Testing chiral effective theory with quenched lattice QCD." Journal of High Energy Physics 2008, no. 05 (May 8, 2008): 024. http://dx.doi.org/10.1088/1126-6708/2008/05/024.

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27

JANSEN, KARL. "LATTICE FIELD THEORY." International Journal of Modern Physics E 16, no. 09 (October 2007): 2638–79. http://dx.doi.org/10.1142/s0218301307008355.

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Starting with the example of the quantum mechanical harmonic oscillator, we develop the concept of euclidean lattice field theory. After describing Wilson's formulation of quantum chromodynamics on the lattice, we will introduce modern lattice QCD actions which greatly reduce lattice artefacts or are even chiral invariant. The substantial algorithmic improvements of the last couple of years will be shown which led to a real breakthrough for dynamical Wilson fermion simulations. Finally, we will present some results of present simulations with dynamical quarks and demonstrate that nowadays even at small values of the quark mass high precision simulation results for physical quantities can be obtained.

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28

Gupta, Sourendu, and Rishi Sharma. "Effective Field Theory Models for Thermal QCD." Nuclear Physics A 967 (November 2017): 716–19. http://dx.doi.org/10.1016/j.nuclphysa.2017.04.036.

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29

Alexandrou, C., G. Koutsou, H. Neff, J. W. Negele, W. Schroers, and A. Tsapalis. "Nucleon Electromagnetic Structure from Lattice QCD." HNPS Proceedings 15 (January 1, 2020): 31. http://dx.doi.org/10.12681/hnps.2617.

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We present an evaluation of nucleon to Δ electromagnetic form factors within Lattice QCD. The EMR and CMR ratios are calculated both in the quenched theory and using two degenerate flavors of dynamical Wilson fermions. We obtain values in qualitative agreement to experiment. In addition, we evaluate the isovector Sachs electromagnetic form factors of the nucleon both in the quenched and unquenched theory for momentum transfer squared in the range between 0.1 and 2 GeV2. The nucleon magnetic moment and r.m.s. radii are obtained using chiral effective theory to extrapolate to the physical pion mass.

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KHOKHLACHEV, S., and YU MAKEENKO. "ADJOINT FERMIONS INDUCE QCD." Modern Physics Letters A 07, no. 39 (December 21, 1992): 3653–67. http://dx.doi.org/10.1142/s0217732392003086.

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We propose to induce QCD by fermions in the adjoint representation of the gauge group SU (Nc) on the lattice. We consider various types of lattice fermions: chiral, Kogut-Susskind and Wilson ones. Using the mean field method we show that a first order large-N phase transition occurs with decreasing fermion mass. We conclude, therefore, that adjoint fermions induce QCD. We draw the same conclusion for the adjoint scalar or fermion models at large number of flavors Nf when they induce a single-plaquette lattice gauge theory. We find an exact strong coupling solution for the adjoint fermion model and show that it is quite similar to that for the Kazakov-Migdal model with the quadratic potential. We discuss the possibility for the adjoint fermion model to be solvable as Nc→∞ in the weak coupling region where the Wilson loops obey normal area law.

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Münster, Gernot, and Raimar Wulkenhaar. "The Leutwyler–Smilga relation on the lattice." Modern Physics Letters A 35, no. 01 (September 23, 2019): 1950346. http://dx.doi.org/10.1142/s0217732319503462.

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According to the Leutwyler–Smilga relation, in Quantum Chromodynamics (QCD), the topological susceptibility vanishes linearly with the quark masses. Calculations of the topological susceptibility in the context of lattice QCD, extrapolated to zero quark masses, show a remnant nonzero value as a lattice artefact. Employing the Atiyah–Singer theorem in the framework of Symanzik’s effective action and chiral perturbation theory, we show the validity of the Leutwyler–Smilga relation in lattice QCD with lattice artefacts of order a2 in the lattice spacing a.

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32

Campbell, Bruce A., John Ellis, and Keith A. Olive. "QCD phase transitions in an effective field theory." Nuclear Physics B 345, no. 1 (November 1990): 57–78. http://dx.doi.org/10.1016/0550-3213(90)90608-g.

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33

Lin, Huey-Wen. "Parton Distribution Functions and Lattice QCD." EPJ Web of Conferences 206 (2019): 01003. http://dx.doi.org/10.1051/epjconf/201920601003.

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Recently, there have been rapid developments in lattice-QCD calculations of proton structure, especially in the parton distribution functions (PDFs). We overcame a longstanding obstacle and for the first time in lattice-QCD are able to directly calculate the Bjorken-x dependence of the quark, helicity and transversity distributions. The PDFs are obtained using the large-momentum eﬀective field theory (LaMET) framework where the full Bjorken-x dependence of finite-momentum PDFs, called “quasi-PDFs”, can be calculated on the lattice. The quasi-PDF nucleon matrix elements are renormalized non-perturbatively in RI/MOM-scheme. Following a nonperturbative renormalization of the parton quasi-distribution in a regularization-independent momentum-subtraction scheme, we establish its matching to the $ \overline {{\rm{MS}}} $ PDF and calculate the non-singlet matching coeﬃcient at next-to-leading order in perturbation theory. In this proceeding, I will show the progress that has been made in recent years, highlighting the latest state-of-the art PDF calculations at the physical pion mass. Future impacts on the large-x global PDF fits are also discussed.

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Suganuma, Hideo, and Hiroki Ohata. "Local Correlation among the Chiral Condensate, Monopoles, and Color Magnetic Fields in Abelian Projected QCD." Universe 7, no. 9 (August 28, 2021): 318. http://dx.doi.org/10.3390/universe7090318.

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Using the lattice gauge field theory, we study the relation among the local chiral condensate, monopoles, and color magnetic fields in quantum chromodynamics (QCD). First, we investigate idealized Abelian gauge systems of (1) a static monopole–antimonopole pair and (2) a magnetic flux without monopoles, on a four-dimensional Euclidean lattice. In these systems, we calculate the local chiral condensate on quasi-massless fermions coupled to the Abelian gauge field, and find that the chiral condensate is localized in the vicinity of the magnetic field. Second, using SU(3) lattice QCD Monte Carlo calculations, we investigate Abelian projected QCD in the maximally Abelian gauge, and find clear correlation of distribution similarity among the local chiral condensate, monopoles, and color magnetic fields in the Abelianized gauge configuration. As a statistical indicator, we measure the correlation coefficient r, and find a strong positive correlation of r≃0.8 between the local chiral condensate and an Euclidean color-magnetic quantity F in Abelian projected QCD. The correlation is also investigated for the deconfined phase in thermal QCD. As an interesting conjecture, like magnetic catalysis, the chiral condensate is locally enhanced by the strong color-magnetic field around the monopoles in QCD.

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35

Soto, J., P. Talavera, and J. Tarrús. "Chiral effective theory with a light scalar and lattice QCD." Nuclear Physics B 866, no. 3 (January 2013): 270–92. http://dx.doi.org/10.1016/j.nuclphysb.2012.09.005.

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36

Bilić, Neven, H. Gausterer, and S. Sanielevici. "Complex Langevin solution to an effective theory of lattice QCD." Physical Review D 37, no. 12 (June 15, 1988): 3684–90. http://dx.doi.org/10.1103/physrevd.37.3684.

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37

Nieto, Agustin. "Perturbative QCD at High Temperature." International Journal of Modern Physics A 12, no. 08 (March 30, 1997): 1431–64. http://dx.doi.org/10.1142/s0217751x97001043.

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Recent developments of perturbation theory at finite temperature based on effective field theory methods are reviewed. These methods allow the contributions from the different scales to be separated and the perturbative series to be reorganized. The construction of the effective field theory is shown in detail for ϕ4 theory and QCD. It is applied to the evaluation of the free energy of QCD at order g5 and the calculation of the g6 term is outlined. Implications for the application of perturbative QCD to the quark–gluon plasma are also discussed.

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38

Zhao, Yong. "Unraveling high-energy hadron structures with lattice QCD." International Journal of Modern Physics A 33, no. 36 (December 30, 2018): 1830033. http://dx.doi.org/10.1142/s0217751x18300338.

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Parton distribution functions are key quantities for us to understand the hadronic structures in high-energy scattering, but they are difficult to calculate from lattice QCD. Recent years have seen fast development of the large-momentum effective theory which allows extraction of the x-dependence of parton distribution functions from a quasi-parton distribution function that can be directly calculated on lattice. The extraction is based on a factorization formula for the quasi-parton distribution function that has been derived rigorously in perturbation theory. A systematic procedure that includes renormalization, perturbative matching, and power corrections has been established to calculate parton distribution functions. Latest progress from lattice QCD has shown promising signs that it will become an effective tool for calculating parton physics.

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39

Suganuma, H., S. Umisedo, S. Sasaki, H. Toki, and O. Miyamura. "Monopole Dominance for Nonperturbative QCD." Australian Journal of Physics 50, no. 1 (1997): 233. http://dx.doi.org/10.1071/p96045.

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Monopole dominance for the nonperturbative features in QCD is studied both in the continuum and the lattice gauge theories. First, we study the dynamical chiral-symmetry breaking (DχSB) in the dual Higgs theory using the effective potential formalism. We find that the main driving force for DχSB is brought from the confinement part in the nonperturbative gluon propagator rather than the short-range part, which means monopole dominance for DχSB. Second, the correlation between instantons and QCD–monopoles is studied. In the Polyakov-like gauge, where A4(x) is diagonalized, the QCD–monopole trajectory penetrates the centre of each instanton, and becomes complicated in the multi-instanton system. Finally, using the SU(2) lattice gauge theory with 164 and 163 × 4, the instanton number is measured in the singular (monopole-dominating) and regular (photon-dominating) sectors, respectively. Instantons and anti-instantons only exist in the monopole sector both in the maximally abelian gauge and in the Polyakov gauge, which means monopole dominance for the topological charge.

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40

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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41

NE’EMAN, YUVAL, and DJORDJE ŠIJAČKI. "CHROMOGRAVITY: QCD-INDUCED DIFFEOMORPHISMS." International Journal of Modern Physics A 10, no. 30 (December 10, 1995): 4399–412. http://dx.doi.org/10.1142/s0217751x95002047.

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We expand the QCD gluon field [Formula: see text] around a constant “pure gauge” solution [Formula: see text] in the IR sector, i.e. [Formula: see text] and provide a mathematical definition for an “IR limit” in which the frequencies of the fluctuating field [Formula: see text] vanish. We prove that in this limit, SU (3) color gauge transformations become equivalent to space-time diffeomorphisms. A gravity-like contribution is then shown to emerge from the overall “n-gluon exchange” component in the expansion of the generating functional of QCD Green functions, with the two-gluon term acting like the metric field in gravity. This QCD-induced “chromogravity” provides an effective long range action, i.e. longer-ranged than the contribution of quark-antiquark (meson) exchanges. We conjecture chromogravity to be responsible for many of the features of the hadron spectrum and of color confinement, issues for which there is as yet no proof in QCD (including lattice calculations), beyond general qualitative arguments. The method exhibits a smooth transition to the perturbative and semiperturbative treatment of high energy hadron scattering, including the emergence of the Pomeranchuk trajectory.

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42

Hong, Deog Ki. "An effective field theory of QCD at high density." Physics Letters B 473, no. 1-2 (January 2000): 118–25. http://dx.doi.org/10.1016/s0370-2693(99)01472-0.

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43

SIEGEL, W. "ACTIONS FOR QCD-LIKE STRINGS." International Journal of Modern Physics A 13, no. 03 (January 30, 1998): 381–92. http://dx.doi.org/10.1142/s0217751x98000160.

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We introduce a random lattice corresponding to ordinary Feynman diagrams, with 1/p2 propagators instead of the Gaussians used in the usual strings. The continuum limit defines a new type of string action with two world sheet metrics, one Minkowskian and one Euclidean. The propagators correspond to curved lightlike paths with respect to the Minkowskian world sheet metric. Space–time dimensionality of four is implied not only as the usual critical dimension of renormalizable quantum field theory, but also from T-duality.

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44

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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45

LUO, XIANG-QIAN, and QI-ZHOU CHEN. "ESTIMATE FOR THE 0++ GLUEBALL MASS IN QCD." Modern Physics Letters A 11, no. 30 (September 28, 1996): 2435–41. http://dx.doi.org/10.1142/s0217732396002423.

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We obtain accurate result for the lightest glueball mass of QCD in three dimensions from lattice Hamiltonian field theory. Using the dimensional reduction argument, we suggest that a good approximation for confining theories in the 0++ glueball mass in (3+1)-dimensional QCD is about 1.71 GeV.

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46

Gómez Nicola, Angel. "Aspects on Effective Theories and the QCD Transition." Symmetry 12, no. 6 (June 3, 2020): 945. http://dx.doi.org/10.3390/sym12060945.

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We review recent advances in the understanding of the Quantum Chromodynamics (QCD) transition and its nature, paying special attention to the analysis of chiral symmetry restoration within different approaches based on effective theories. After presenting some of the main aspects of the current knowledge of the phase diagram from the theoretical, experimental and lattice sides, we discuss some recent problems where approaches relying on effective theories have been particularly useful. In particular, the combination of ideas such as Chiral Perturbation Theory, unitarity and Ward Identities allows us to describe successfully several observables of interest. This is particularly relevant for quantities expected to be dominated by the light meson components of the hadron gas such as the scalar and topological susceptibilities. In addition, ward identities and effective Lagrangians provide systematic results regarding chiral and U ( 1 ) A partner degeneration properties which are of great importance for the interplay between those two transitions and the nature of chiral symmetry restoration. Special attention is paid to the connection of this theoretical framework with lattice simulations.

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47

Matsui, Tetsuo. "U(1) Gauge Theory as a Collective Field Theory for Hubbard Model." International Journal of Modern Physics B 02, no. 05 (October 1988): 613–23. http://dx.doi.org/10.1142/s0217979288000433.

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I construct a collective field theory for Hubbard model of high Tc superconductivity, using a path-integral method in the third quantized (slave boson) form. It is a U(1) gauge invariant theory consisting of a U(1) gauge field and a Higgs scalar. The gauge field stands for resonating valence bonds and describes a (short range) antiferro-paramagnet phase transition by a condensation machanism. The Higgs scalar represents spinless holes carrying electric charges. Through the confining gauge force, there formed bounded hole pairs on each link, which correspond to the vector mesons in lattice QCD. A superconducting phase is to be described by a condensation of a gauge invariant order parameter for these hole pairs, and to be compared with the color confining chirally broken phase in QCD. A Ginzburg-Landau theory for the vector hole-pair field is proposed.

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48

SCHÜTTE, D., A. WICHMANN, and V. WETHKAMP. "QCD GLUEBALLS WITHIN A COUPLED CLUSTER APPROACH." International Journal of Modern Physics B 15, no. 10n11 (May 10, 2001): 1732–35. http://dx.doi.org/10.1142/s0217979201006252.

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The validity of the coupled cluster method is studied within the lattice gauge field theory given by a SU(2) pure glue theory in 2+1 dimensions. Satisfactory convergence is observed for the ground state, but the method is less successful for the prediction of glueballs. We propose to improve the coupled cluster method for excited state by combining it with standard Monte-Carlo techniques which potentially cure the non-hermiticity problems caused by the truncation.

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49

Schäfer, Thomas. "Non-Fermi Liquid Effective Field Theory of Dense QCD Matter." Nuclear Physics A 785, no. 1-2 (March 2007): 110–13. http://dx.doi.org/10.1016/j.nuclphysa.2006.11.054.

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50

Jaffe, R. L. "Limitations on the validity of effective field theory in QCD." Nuclear Physics A 522, no. 1-2 (January 1991): 365–76. http://dx.doi.org/10.1016/0375-9474(91)90068-h.

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