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Journal articles on the topic 'Lattice formulation of QCD'

Author: Grafiati

Published: 4 June 2021

Last updated: 5 February 2022

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1

HATSUDA, TETSUO, SINYA AOKI, NORIYOSHI ISHII, and HIDEKATSU NEMURA. "FROM LATTICE QCD TO NUCLEAR FORCE." Modern Physics Letters A 23, no. 27n30 (2008): 2265–72. http://dx.doi.org/10.1142/s0217732308029174.

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After a brief introduction to the phenomenological nucleon-nucleon (NN) potentials, the basic formulation of deriving the NN potential from lattice QCD simulations on the basis of the equal-time Bethe-Salpeter wave function is presented. The resultant non-local NN potential and its derivative expansion are discussed. Ongoing and planned studies on the lattice with quenched and full QCD simulations are summarized.

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2

NAKAMURA, Atsushi. "Finite Density Simulations: Comparison of Various Approaches." Modern Physics Letters A 22, no. 07n10 (2007): 473–89. http://dx.doi.org/10.1142/s0217732307023067.

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This is a short overview of the lattice QCD simulations of finite density systems. We first describe a brief introduction of the lattice QCD at finite density, including the minimum necessary formulation, where we show why an annoying complex fermion determinant appears, and why in some cases it does not appear. Then we review several approaches of present and past days. We conclude possible directions of lattice QCD simulations at finite density in near future.

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3

Yee, Ken. "Towards an Abelian formulation of lattice QCD confinement." Physical Review D 49, no. 5 (1994): 2574–77. http://dx.doi.org/10.1103/physrevd.49.2574.

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4

Gagliardi, Giuseppe, Jangho Kim, and Wolfgang Unger. "Dual Formulation and Phase Diagram of Lattice QCD in the Strong Coupling Regime." EPJ Web of Conferences 175 (2018): 07047. http://dx.doi.org/10.1051/epjconf/201817507047.

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We present the computation of invariants that arise in the strong coupling expansion of lattice QCD. These invariants are needed for Monte Carlo simulations of Lattice QCD with staggered fermions in a dual, color singlet representation. This formulation is in particular useful to tame the finite density sign problem. The gauge integrals in this limiting case β → 0 are well known, but the gauge integrals needed to study the gauge corrections are more involved. We discuss a method to evaluate such integrals. The phase boundary of lattice QCD for staggered fermions in the μB – T plane has been established in the strong coupling limit. We present numerical simulations away from the strong coupling limit, taking into account the higher order gauge corrections via plaquette occupation numbers. This allows to study the nuclear and chiral transition as a function of β.

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5

Borisenko, Oleg, Volodymyr Chelnokov, and Sergey Voloshyn. "Duals of U(N) LGT with staggered fermions." EPJ Web of Conferences 175 (2018): 11021. http://dx.doi.org/10.1051/epjconf/201817511021.

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Various approaches to construction of dual formulations of non-abelian lattice gauge theories are reviewed. In the case of U(N) LGT we use a theory of the Weingarten functions to construct a dual formulation. In particular, the dual representations are constructed 1) for pure gauge models in all dimensions, 2) in the strong coupling limit for the models with arbitrary number of flavours and 3) for two-dimensional U(N) QCD with staggered fermions. Applications related to the finite temperature/density QCD are discussed.

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6

BROWER, RICHARD C., YUE SHEN, and CHUNG-I. TAN. "CHIRALLY EXTENDED QUANTUM CHROMODYNAMICS." International Journal of Modern Physics C 06, no. 05 (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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7

DI PIERRO, MASSIMO. "AN ALGORITHMIC APPROACH TO QUANTUM FIELD THEORY." International Journal of Modern Physics A 21, no. 03 (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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8

IVANOV, A. N., N. I. TROITSKAYA, M. FABER, M. SCHALER, and M. NAGY. "ON THE BEHAVIOR OF DYNAMICAL QUARK-ANTIQUARK PAIRS IN EXTERNAL CHROMO-ELECTRIC FIELDS." Modern Physics Letters A 08, no. 11 (1993): 1021–27. http://dx.doi.org/10.1142/s0217732393002506.

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The vacuum structure of QCD in an external chromo-electric field is investigated within the continuum space-time formulation of perturbative QCD and the extended NambuJona-Lasinio model, used as a low-energy approximation of QCD. We show that the density of dynamical quark-antiquark pairs decreases with increasing external chromoelectric field strength. These results are compared with recent numerical simulations of lattice QCD which indicate restoration of chiral symmetry in the vicinity of a static color

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9

DINTER, SIMON, VINCENT DRACH, and KARL JANSEN. "DARK MATTER SEARCH AND THE SCALAR QUARK CONTENTS OF THE NUCLEON." International Journal of Modern Physics E 20, supp01 (2011): 110–17. http://dx.doi.org/10.1142/s0218301311040141.

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We present lattice QCD simulation results from the European Twisted Mass Collaboration (ETMC) for the light, strange and charm quark contents of the nucleon. These quantities are important ingredients to estimate the cross-section for the detection of WIMPs as Dark Matter candidates. By employing a particular lattice QCD formulation, i.e. twisted mass fermions, accurate results of the light and strange scalar contents of the nucleon can be obtained. In addition, we provide a bound for the charm quark content of the nucleon.

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10

JANSEN, KARL. "LATTICE FIELD THEORY." International Journal of Modern Physics E 16, no. 09 (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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11

Frezzotti, R. "A local formulation of lattice QCD without unphysical fermion zero modes." Nuclear Physics B - Proceedings Supplements 83-84, no. 1-3 (2000): 941–46. http://dx.doi.org/10.1016/s0920-5632(00)00399-6.

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12

Frezzotti, Roberto, Pietro Antonio Grassi, Stefan Sint, and Peter Weisz. "A local formulation of lattice QCD without unphysical fermion zero modes." Nuclear Physics B - Proceedings Supplements 83-84 (April 2000): 941–46. http://dx.doi.org/10.1016/s0920-5632(00)91852-8.

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13

BOHAČIK, J., O. A. BORISENKO, V. K. PETROV, and G. M. ZINOVJEV. "SUPPLEMENTING ANALYSIS OF DECONFINED PHASE IN LATTICE QCD THERMODYNAMICS." Modern Physics Letters A 06, no. 15 (1991): 1429–35. http://dx.doi.org/10.1142/s0217732391001536.

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Using strong coupling expansion an expectation value of matter field color density is calculated in the Hamiltonian formulation of lattice QCD at finite temperature with the staggered fermions. We found out that this value is related to the imaginary part of fundamental representation character changing the sign under the color charge conjugation. It is also shown that this expectation value could be used as an order parameter of the phase transition associated with the breaking of the color charge conjugation symmetry.

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14

CARMONA, JOSÉ MANUEL, MASSIMO D'ELIA, ADRIANO DI GIACOMO, and BIAGIO LUCINI. "IMPLEMENTATION OF C⋆ BOUNDARY CONDITIONS IN THE HYBRID MONTE CARLO ALGORITHM." International Journal of Modern Physics C 11, no. 04 (2000): 637–53. http://dx.doi.org/10.1142/s0129183100000560.

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In the study of QCD dynamics, C⋆ boundary conditions are physically relevant in certain cases. In this paper, we study the implementation of these boundary conditions in the lattice formulation of full QCD with staggered fermions. In particular, we show that the usual even-odd partition trick to avoid the redoubling of the fermion matrix is still valid in this case. We give an explicit implementation of these boundary conditions for the Hybrid Monte Carlo algorithm.

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15

Hyka (Xhako), Dafina, and Rudina Osmanaj (Zeqirllari). "Fast algorithms for chiral fermions in 2 dimensions." EPJ Web of Conferences 175 (2018): 14005. http://dx.doi.org/10.1051/epjconf/201817514005.

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In lattice QCD simulations the formulation of the theory in lattice should be chiral in order that symmetry breaking happens dynamically from interactions. In order to guarantee this symmetry on the lattice one uses overlap and domain wall fermions. On the other hand high computational cost of lattice QCD simulations with overlap or domain wall fermions remains a major obstacle of research in the field of elementary particles. We have developed the preconditioned GMRESR algorithm as fast inverting algorithm for chiral fermions in U(1) lattice gauge theory. In this algorithm we used the geometric multigrid idea along the extra dimension.The main result of this work is that the preconditioned GMRESR is capable to accelerate the convergence 2 to 12 times faster than the other optimal algorithms (SHUMR) for different coupling constant and lattice 32x32. Also, in this paper we tested it for larger lattice size 64x64. From the results of simulations we can see that our algorithm is faster than SHUMR. This is a very promising result that this algorithm can be adapted also in 4 dimension.

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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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17

HORN, D. "THE t-EXPANSION AND HAMILTONIAN LATTICE QCD." International Journal of Modern Physics A 04, no. 09 (1989): 2147–72. http://dx.doi.org/10.1142/s0217751x89000856.

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The t-expansion is a tool designed to improve on any variational calculation of a quantum theory. It is designed to produce the correct volume behavior of operators appearing in lattice models. We review its formulation and discuss the techniques used for its analysis by testing it on the solvable Heisenberg model in 1+1 dimensions. We discuss its application to the SU(3) lattice gauge theory in 3+1 space-time dimensions. Starting with strong coupling wave functions we investigate the pure glue sector. We review the calculations of the energy-density, the string-tension and several glueball masses. The scalar 0++ glueball follows from the same calculation as the energy-density. The other glueballs which. we study, with the JPC quantum numbers of 1+−, 0−−, 1−− and 2−− are constructed by using wave-functions corresponding to appropriate representations of the cubic symmetry group. Estimates of their physical masses, as obtained from studies of scaling ratios, are presented and discussed. It is quite straightforward to incorporate dynamical quarks in the model. We point out some qualitative features of the structure of the vacuum and the phase transition at high baryon density. Spectra of hadrons including quarks have not yet been calculated with these techniques but the glueball results indicate that this is a viable analytic method for the study of lattice QCD.

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18

UMINO, YASUO. "CRITICAL BEHAVIOR OF STRONGLY COUPLED LATTICE QCD AT FINITE TEMPERATURE." Modern Physics Letters A 21, no. 01 (2006): 55–63. http://dx.doi.org/10.1142/s0217732306018998.

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We study the critical behavior of lattice Quantum Chromodynamics (QCD) in the strong coupling approximation with Kogut–Susskind and Wilson fermions at finite temperature (T) and zero chemical potential. Using the Hamiltonian formulation we construct a mean field solution to the equation of motion at finite T and use it to study the elementary thermal excitations and to extract some critical exponents characterizing the observed second-order phase transition. We find similar critical behaviors for Kogut–Susskind and Wilson fermions at finite T.

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19

Vilela Mendes, R. "A consistent measure for lattice Yang–Mills." International Journal of Modern Physics A 32, no. 02n03 (2017): 1750016. http://dx.doi.org/10.1142/s0217751x17500166.

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The construction of a consistent measure for Yang–Mills is a precondition for an accurate formulation of nonperturbative approaches to QCD, both analytical and numerical. Using projective limits as subsets of Cartesian products of homomorphisms from a lattice to the structure group, a consistent interaction measure and an infinite-dimensional calculus have been constructed for a theory of non-Abelian generalized connections on a hypercubic lattice. Here, after reviewing and clarifying past work, new results are obtained for the mass gap when the structure group is compact.

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20

CRAIGIE, N. S., E. KATZNELSON, and S. MAHMOOD. "A MONTE CARLO STUDY OF SPONTANEOUS CHIRAL SYMMETRY BREAKING IN LATTICE GAUGE THEORIES." International Journal of Modern Physics A 01, no. 04 (1986): 953–69. http://dx.doi.org/10.1142/s0217751x86000356.

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Spontaneous chiral symmetry breaking in lattice QCD is studied by calculating special four fermion correlation functions using the Monte Carlo method. In the continuum theory in the limit of short distance and small mass these functions are related to the order parameter [Formula: see text]. We found a range of quark mass for which the predicted relations approximately hold, using the Susskind formulation of fermions. However, we encountered a theoretical problem in the latter formulation concerning the short distance behavior of the correlation functions of different spin and flavor. This may cast some doubt on the interpretation of spin and flavor in this formulation.

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21

MENDES, TEREZA. "NATURE OF THE PHASE TRANSITION IN QCD AT FINITE TEMPERATURE." International Journal of Modern Physics E 16, no. 09 (2007): 2763–74. http://dx.doi.org/10.1142/s0218301307008392.

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It is clear that the order of the deconfining phase transition in QCD at nonzero temperature and density (with realistic quark masses) is of great experimental interest. The importance of the transition at zero baryon density with only two (degenerate) quark flavors is perhaps less evident. As a matter of fact, the order of the transition in this case is still an open problem and corresponds to the last question mark in the zero-density phase diagram of QCD. We argue that establishing the nature of the transition in this case is also a crucial test for numerical simulations of lattice QCD, allowing precise estimates of the possible systematic errors related to the choice of fermion-simulation algorithm and of discretized formulation for fermions.

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22

Hansen, Martin, Biagio Lucini, Agostino Patella, and Nazario Tantalo. "Simulations of QCD and QED with C* boundary conditions." EPJ Web of Conferences 175 (2018): 09001. http://dx.doi.org/10.1051/epjconf/201817509001.

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We present exploratory results from dynamical simulations of QCD in isolation, as well as QCD coupled to QED, with C* boundary conditions. In finite volume, the use of C* boundary conditions allows for a gauge invariant and local formulation of QED without zero modes. In particular we show that the simulations reproduce known results and that masses of charged mesons can be extracted in a completely gauge invariant way. For the simulations we use a modified version of the HiRep code. The primary features of the simulation code are presented and we discuss some details regarding the implementation of C* boundary conditions and the simulated lattice action. Preprint: CP3-Origins-2017-046 DNRF90, CERN-TH-2017-214

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23

Gattringer, Christof, Michael Mandl, and Pascal Törek. "New Canonical and Grand Canonical Density of States Techniques for Finite Density Lattice QCD." Particles 3, no. 1 (2020): 87–98. http://dx.doi.org/10.3390/particles3010008.

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We discuss two new density of states approaches for finite density lattice QCD (Quantum Chromo Dynamics). The paper extends a recent presentation of the new techniques based on Wilson fermions, while here, we now discuss and test the case of finite density QCD with staggered fermions. The first of our two approaches is based on the canonical formulation where observables at a fixed net quark number N are obtained as Fourier moments of the vacuum expectation values at imaginary chemical potential θ . We treat the latter as densities that can be computed with the recently developed functional fit approach. The second method is based on a direct grand canonical evaluation after rewriting the QCD partition sum in terms of a suitable pseudo-fermion representation. In this form, the imaginary part of the pseudo-fermion action can be identified and the corresponding density may again be computed with the functional fit approach. We develop the details of the two approaches and discuss some exploratory first tests for the case of free fermions where reference results for assessing the new techniques may be obtained from Fourier transformation.

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24

AUBIN, C. "CURRENT PHYSICS RESULTS FROM STAGGERED CHIRAL PERTURBATION THEORY." Modern Physics Letters A 21, no. 39 (2006): 2913–30. http://dx.doi.org/10.1142/s0217732306022468.

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We review several results that have been obtained using lattice QCD with the staggered quark formulation. Our focus is on the quantities that have been calculated numerically with low statistical errors and have been extrapolated to the physical quark mass limit and continuum limit using staggered chiral perturbation theory. We limit our discussion to a brief introduction to staggered quarks, and applications of staggered chiral perturbation theory to the pion mass, decay constant, and heavy–light meson decay constants.

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25

Borisenko, O., M. Faber, and G. Zinovjev. "Deconfinement in QCD with Dynamical Quarks." Modern Physics Letters A 12, no. 13 (1997): 949–61. http://dx.doi.org/10.1142/s0217732397000972.

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We study the phase structure of full QCD within the canonical ensemble (CE) with respect to triality in a lattice formulation. The procedure to calculate the effective potentials (EP) in the CE is given. We calculate the EP for the three-dimensional SU(2) gauge model at finite temperature in the strong coupling region. The potential exhibits a genuine deconfinement phase transition unlike the similar potential obtained in the grand canonical ensemble (GCE). Furthermore, we investigate the EP with the chiral condensate included. Contrary to other recent results we find chiral symmetry restoration in all triality sectors. Dealing with massless staggered fermions we observe chiral symmetry restoration accompanying a deconfinement phase transition of first-order. Above the critical point, besides two Z(2) symmetric "deconfining" vacua there exists a metastable "confining" vacuum in a wide region of the (Nt,γ)-plane. Such a picture could be interpreted as an indication for a mixed state of hadrons and quarks in the vicinity of the critical line.

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26

Giedt, Joel. "A Deconstruction Lattice Description of the D1/D5 Brane World-Volume Gauge Theory." Advances in High Energy Physics 2011 (2011): 1–18. http://dx.doi.org/10.1155/2011/241419.

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I generalize the deconstruction lattice formulation of Endres and Kaplan to two-dimensional super-QCD with eight supercharges, denoted by (4,4), and bifundamental matter. I specialize to a particularly interesting (4,4) gauge theory, with gauge groupU(Nc)×U(Nf), andU(Nf)being weakly gauged. It describes the infrared limit of the D1/D5 brane system, which has been studied extensively as an example of the AdS3/CFT2correspondence. The construction here preserves two supercharges exactly and has a lattice structure quite similar to that which has previously appeared in the deconstruction approach, that is, site, link, and diagonal fields with both the Bose and Fermi statistics. I remark on possible applications of the lattice theory that would test the AdS3/CFT2correspondence, particularly one that would exploit the recent worldsheet instanton analysis of Chen and Tong.

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27

Joseph, Anosh. "N = 2* Yang-Mills on the Lattice." EPJ Web of Conferences 175 (2018): 08019. http://dx.doi.org/10.1051/epjconf/201817508019.

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The N = 2* Yang-Mills theory in four dimensions is a non-conformal theory that appears as a mass deformation of maximally supersymmetric N = 4 Yang-Mills theory. This theory also takes part in the AdS/CFT correspondence and its gravity dual is type IIB supergravity on the Pilch-Warner background. The finite temperature properties of this theory have been studied recently in the literature. It has been argued that at large N and strong coupling this theory exhibits no thermal phase transition at any nonzero temperature. The low temperature N = 2* plasma can be compared to the QCD plasma. We provide a lattice construction of N = 2* Yang-Mills on a hypercubic lattice starting from the N = 4 gauge theory. The lattice construction is local, gauge-invariant, free from fermion doubling problem and preserves a part of the supersymmetry. This nonperturbative formulation of the theory can be used to provide a highly nontrivial check of the AdS/CFT correspondence in a non-conformal theory.

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Francis, Anthony, Renwick J. Hudspith, Randy Lewis, and Kim Maltman. "Lattice Evidence for Bound Heavy Tetraquarks." EPJ Web of Conferences 202 (2019): 06013. http://dx.doi.org/10.1051/epjconf/201920206013.

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We investigate the possibility of qq'$ \bar {Q}\bar {Q}' $ tetraquark bound states using nf = 2 + 1 lattice QCD with pion masses ≃ 164, 299 and 415 MeV. Two types of lattice interpolating operator are chosen, reflecting first diquarkantidiquark and second meson-meson structure. Performing variational analysis using these operators and their mixings, we determine the ground and first excited states from the lattice correlators. Using non-relativistic QCD to simulate the bottom quarks and the Tsukuba formulation of relativistic heavy quarks for charm quarks, we study the ud$ \bar {b}\bar {b} $, ℓs$ \bar {b}\bar {b} $ as well as ud$ \bar {c}\bar {b} $, channels with ℓ= u, d. In the case of the ud$ \bar {b}\bar {b} $ and ℓs$ \bar {b}\bar {b} $ channels unambiguous signals for JP=1+ tetraquarks are found with binding energies 189(10) and 98(7) MeV below the corresponding free two-meson thresholds at the physical point. These tetraquarks are therefore strong-interaction stable, implying they are stable under strong as well as electromagnetic interactions while they can decay weakly. So far these are the first exotic hadrons predicted to have this feature. Further evidence for binding is found in the ud$ \bar {c}\bar {b} $ channel, whereby the binding energy broadly straddles the electromagnetic stability threshold. Studying further the quark mass dependence we vary the heavy quark mass in ud$ \bar {Q}\bar {Q} $, ℓs$ \bar {Q}\bar {Q} $ as well as ud$ \bar {Q}\bar {b} $, ℓs$ \bar {Q}\bar {b} $ between roughly 0.7 and 6.3 times the bottom quark mass. The observed mass dependence of these four flavor channels closely follows a behaviour argued from phenomenological considerations of the heavy baryon spectrum.

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GIEDT, JOEL. "PROGRESS IN FOUR-DIMENSIONAL LATTICE SUPERSYMMETRY." International Journal of Modern Physics A 24, no. 22 (2009): 4045–95. http://dx.doi.org/10.1142/s0217751x09045492.

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We are entering an era where a number of large-scale lattice simulations of four-dimensional supersymmetric theories are under way. Moreover, proposals for how to approach such studies continue to progress. One particular line of research in this direction is described here. General actions for super-QCD, including counterterms required on the lattice, are given. We obtain the number of fine-tunings that is required, once gauge and flavor symmetries are accounted for, provided Ginsparg–Wilson fermions are used for the gauginos. We also review and extend our recent work on lattice formulations of [Formula: see text] super-Yang–Mills and [Formula: see text] super-Yang–Mills that exploit Ginsparg–Wilson fermions.

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Palumbo, Fabrizio. "The chemical potential in the transfer matrix and in the path integral formulation of QCD on a lattice." Nuclear Physics B 645, no. 1-2 (2002): 309–20. http://dx.doi.org/10.1016/s0550-3213(02)00827-1.

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FARIA DA VEIGA, PAULO A., MICHAEL O'CARROLL, ANTÔNIO FRANCISCO NETO, and PETRUS H. R. DOS ANJOS. "ON THE ABSENCE OF PENTAQUARK STATES FROM DYNAMICS IN STRONGLY COUPLED LATTICE QCD." International Journal of Modern Physics A 26, no. 01 (2011): 71–133. http://dx.doi.org/10.1142/s0217751x11051342.

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We consider an imaginary time functional integral formulation of a two-flavor, 3+1 lattice QCD model with Wilson's action and in the strong coupling regime (with a small hopping parameter, κ > 0, and a much smaller plaquette coupling, [Formula: see text], so that the quarks and glueballs are heavy). The model has local SU (3)c gauge and global SU (2)f flavor symmetries, and incorporates the corresponding part of the eightfold way particles: baryons (mesons) of asymptotic mass ≈-3 ln κ(≈-2 ln κ). We search for pentaquark states as meson–baryon bound states in the energy–momentum spectrum of the model, using a lattice Bethe–Salpeter equation. This equation is solved within a ladder approximation, given by the lowest nonvanishing order in κ and β of the Bethe–Salpeter kernel. It includes order κ2 contributions with a [Formula: see text] exchange potential together with a contribution that is a local-in-space, energy-dependent potential. The attractive or repulsive nature of the exchange interaction depends on the spin of the meson–baryon states. The Bethe–Salpeter equation presents integrable singularities, forcing the couplings to be above a threshold value for the meson and the baryon to bind in a pentaquark. We analyzed all the total isospin sectors, I = 1/2, 3/2, 5/2, for the system. For all I, the net attraction resulting from the two sources of interaction is not strong enough for the meson and the baryon to bind. Thus, within our approximation, these pentaquark states are not present up to near the free meson–baryon energy threshold of ≈-5 ln κ. This result is to be contrasted with the spinless case for which our method detects meson–baryon bound states, as well as for Yukawa effective baryon and meson field models. A physical interpretation of our results emerges from an approximate correspondence between meson–baryon bound states and negative energy states of a one-particle lattice Schrödinger Hamiltonian.

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FARIA DA VEIGA, PAULO A., and MICHAEL O'CARROLL. "EXACT DYNAMICAL EIGHTFOLD WAY BARYON SPECTRUM AND CONFINEMENT IN STRONGLY COUPLED LATTICE QCD." International Journal of Modern Physics A 24, no. 16n17 (2009): 3053–72. http://dx.doi.org/10.1142/s0217751x09043183.

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We obtain from the quark–gluon dynamics the eightfold way baryon spectrum exactly in an imaginary time functional integral formulation of 3+1 lattice QCD with Wilson's action in the strong coupling regime (small hopping parameter 0 < κ ≪ 1 and much smaller plaquette coupling [Formula: see text]). The model has SU(3)c local gauge and global SU(3)f flavor symmetries. A decoupling of the hyperplane method naturally unveils the form of the baryon composite fields. In the subspace of the physical Hilbert space of vectors with an odd number of quarks, the baryons are associated with isolated dispersion curves in the energy–momentum spectrum. Spectral representations are derived for the two-baryon correlations, which allow us to detect the energy–momentum spectrum and particles as complex momentum space singularities. The spin 1/2 octet and spin 3/2 decuplet baryons have asymptotic mass -3ln κ and for each baryon there is an antibaryon with identical spectral properties. An auxiliary function method is used to obtain convergent expansions for the masses after subtracting the singular part -3ln κ. The nonsingular part of the mass is analytic in κ and β, i.e. the expansions are controlled to all orders. For β = 0, all the masses have the form M = -3ln κ - 3κ3/4 + κ6r(κ), with r(κ) real analytic. Although we have no Lorentz symmetry in our lattice model, we show that there is a partial restoration of the continuous rotational symmetry at zero spatial momentum, which implies that for all members of the octet (decuplet) r(κ) is the same. So, there is no mass splitting within the octet and within the decuplet. However, there is an octet–decuplet mass difference of [Formula: see text] at β = 0; the splitting persists for β ≠ 0. We also obtain the (anti)baryon dispersion curves which admit the representation [Formula: see text], where [Formula: see text] and [Formula: see text] is of [Formula: see text]. For the octet, [Formula: see text] is jointly analytic in κ and in each pj, for small [Formula: see text]. A new local symmetry, which we call spin flip, is used to establish constraints for the matrix-valued two-baryon correlation and show that all the octet dispersion curves are the same and that the four decuplet dispersion curves are pairwise-identical and depend only on the modulus of the spin z-component. Using a correlation subtraction method we show that the spectrum generated by the baryon and antibaryon fields is the only spectrum, in the odd quark subspace of physical states, up to near the baryon–meson threshold of ≈ -5ln κ. Combining this result with a similar result for the mesons, with mass ≈ -2ln κ, shows that the only spectrum in the entire space of states, up to near the two-meson threshold of ≈ -4ln κ, is generated by the eightfold way hadrons. Hence, for 0 < κ ≪ β ≪ 1, we have shown confinement up to near this threshold.

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33

Hamber, Herbert. "Vacuum Condensate Picture of Quantum Gravity." Symmetry 11, no. 1 (2019): 87. http://dx.doi.org/10.3390/sym11010087.

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In quantum gravity perturbation theory in Newton’s constant G is known to be badly divergent, and as a result not very useful. Nevertheless, some of the most interesting phenomena in physics are often associated with non-analytic behavior in the coupling constant and the existence of nontrivial quantum condensates. It is therefore possible that pathologies encountered in the case of gravity are more likely the result of inadequate analytical treatment, and not necessarily a reflection of some intrinsic insurmountable problem. The nonperturbative treatment of quantum gravity via the Regge–Wheeler lattice path integral formulation reveals the existence of a new phase involving a nontrivial gravitational vacuum condensate, and a new set of scaling exponents characterizing both the running of G and the long-distance behavior of invariant correlation functions. The appearance of such a gravitational condensate is viewed as analogous to the (equally nonperturbative) gluon and chiral condensates known to describe the physical vacuum of QCD. The resulting quantum theory of gravity is highly constrained, and its physical predictions are found to depend only on one adjustable parameter, a genuinely nonperturbative scale ξ in many ways analogous to the scaling violation parameter Λ M ¯ S of QCD. Recent results point to significant deviations from classical gravity on distance scales approaching the effective infrared cutoff set by the observed cosmological constant. Such subtle quantum effects are expected to be initially small on current cosmological scales, but could become detectable in future high precision satellite experiments.

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34

Gattringer, Christof, Daniel Göschl, and Carlotta Marchis. "Worldlines and worldsheets for non-abelian lattice field theories: Abelian color fluxes and Abelian color cycles." EPJ Web of Conferences 175 (2018): 11007. http://dx.doi.org/10.1051/epjconf/201817511007.

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We discuss recent developments for exact reformulations of lattice field theories in terms of worldlines and worldsheets. In particular we focus on a strategy which is applicable also to non-abelian theories: traces and matrix/vector products are written as explicit sums over color indices and a dual variable is introduced for each individual term. These dual variables correspond to fluxes in both, space-time and color for matter fields (Abelian color fluxes), or to fluxes in color space around space-time plaquettes for gauge fields (Abelian color cycles). Subsequently all original degrees of freedom, i.e., matter fields and gauge links, can be integrated out. Integrating over complex phases of matter fields gives rise to constraints that enforce conservation of matter flux on all sites. Integrating out phases of gauge fields enforces vanishing combined flux of matter-and gauge degrees of freedom. The constraints give rise to a system of worldlines and worldsheets. Integrating over the factors that are not phases (e.g., radial degrees of freedom or contributions from the Haar measure) generates additional weight factors that together with the constraints implement the full symmetry of the conventional formulation, now in the language of worldlines and worldsheets. We discuss the Abelian color flux and Abelian color cycle strategies for three examples: the SU(2) principal chiral model with chemical potential coupled to two of the Noether charges, SU(2) lattice gauge theory coupled to staggered fermions, as well as full lattice QCD with staggered fermions. For the principal chiral model we present some simulation results that illustrate properties of the worldline dynamics at finite chemical potentials.

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35

Ouranidis, Andreas, Nikos Gkampelis, Elisavet Vardaka, et al. "Overcoming the Solubility Barrier of Ibuprofen by the Rational Process Design of a Nanocrystal Formulation." Pharmaceutics 12, no. 10 (2020): 969. http://dx.doi.org/10.3390/pharmaceutics12100969.

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Wet media milling, coupled with spay drying, is a commonly proposed formulation strategy for the production and solidification of nanosuspensions in order to overcome the solubility barrier of BCS Class II substances. However, the application of mechanically and thermally intensive processes is not straightforward in the cases of ductile and/or low melting point substances that may additionally be susceptible to eutectic formation. Using ibuprofen (IBU) as a model drug with non-favorable mechanical and melting properties, we attempt to rationalize nanocrystal formulation and manufacturing in an integrated approach by implementing Quality by Design (QbD) methodology, particle informatics techniques and computationally assisted process design. Wet media milling was performed in the presence of different stabilizers and co-milling agents, and the nanosuspensions were solidified by spray-drying. The effects of key process parameters (bead diameter, milling time and rotational speed) and formulation variables (stabilizer type and drug/stabilizer ratio) on the critical quality attributes (CQAs), i.e., Z-average size, polydispersity index (PDI), ζ-potential and redispersibility of spray-dried nanosuspensions were evaluated, while possible correlations between IBU free surface energy and stabilizer effectiveness were studied. The fracture mechanism and surface stabilization of IBU were investigated by computer simulation of the molecular interactions at the crystal lattice level. As a further step, process design accounting for mass-energy balances and predictive thermodynamic models were constructed to scale-up and optimize the design space. Contemplating several limitations, our multilevel approach offers insights on the mechanistic pathway applicable to the substances featuring thermosensitivity and eutectic tendency.

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36

Mackenzie, Paul. "Lattice QCD." Journal of the Physical Society of Japan 76, no. 11 (2007): 111019. http://dx.doi.org/10.1143/jpsj.76.111019.

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37

Aoki, Sinya. "Lattice QCD." Nuclear Physics A 827, no. 1-4 (2009): 145c—152c. http://dx.doi.org/10.1016/j.nuclphysa.2009.05.029.

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38

Bornyakov, V. G. "Lattice QCD." Physics of Atomic Nuclei 68, no. 6 (2005): 1054–63. http://dx.doi.org/10.1134/1.1954834.

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39

AOKI, SINYA. "QCD Phases in Lattice QCD." International Journal of Modern Physics A 21, no. 04 (2006): 682–87. http://dx.doi.org/10.1142/s0217751x06031880.

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40

Loan, Mushtaq, Zhi-Huan Luo, and Yu Yiu Lam. "in lattice QCD." Nuclear Physics B 820, no. 1-2 (2009): 89–98. http://dx.doi.org/10.1016/j.nuclphysb.2009.05.008.

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41

KRONFELD, ANDREAS S., I. F. ALLISON, C. AUBIN, et al. "PREDICTIVE LATTICE QCD." International Journal of Modern Physics A 21, no. 04 (2006): 713–19. http://dx.doi.org/10.1142/s0217751x06031934.

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In the past year, we calculated with lattice QCD three quantities that were unknown or poorly known. They are the q2 dependence of the form factor in semileptonic D → Klν decay, the decay constant of the D meson, and the mass of the Bc meson. In this talk, we summarize these calculations, with emphasis on their (subsequent) confirmation by experiments.

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42

Rossi, Giancarlo. "Improved lattice QCD." Nuclear Physics B - Proceedings Supplements 26 (January 1992): 341–43. http://dx.doi.org/10.1016/0920-5632(92)90270-3.

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43

Büchner, O., M. Ernst, K. Jansen, et al. "Datagrids for lattice QCD." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 559, no. 1 (2006): 57–61. http://dx.doi.org/10.1016/j.nima.2005.11.213.

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44

Frezzotti, R. "Twisted mass Lattice QCD." Nuclear Physics B - Proceedings Supplements 140 (March 2005): 134–40. http://dx.doi.org/10.1016/j.nuclphysbps.2004.11.329.

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45

Petreczky, P. "QCD Thermodynamics on lattice." Nuclear Physics B - Proceedings Supplements 140 (March 2005): 78–91. http://dx.doi.org/10.1016/j.nuclphysbps.2004.11.366.

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46

Shindler, Andrea. "Twisted mass lattice QCD." Physics Reports 461, no. 2-3 (2008): 37–110. http://dx.doi.org/10.1016/j.physrep.2008.03.001.

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47

Christ, N. "Computers for Lattice QCD." Nuclear Physics B - Proceedings Supplements 83-84, no. 1-3 (2000): 111–15. http://dx.doi.org/10.1016/s0920-5632(00)00205-x.

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48

Iwasaki, Y., T. Yoshié, and Y. Tsuboi. "Hdibaryon in lattice QCD." Physical Review Letters 60, no. 14 (1988): 1371–74. http://dx.doi.org/10.1103/physrevlett.60.1371.

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49

Collaborations, Andreas S. Kronfeld for the Fermilab. "Predictions with lattice QCD." Journal of Physics: Conference Series 46 (September 1, 2006): 147–51. http://dx.doi.org/10.1088/1742-6596/46/1/020.

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50

SCHIERHOLZ, G. "PROGRESS IN LATTICE QCD." International Journal of Modern Physics A 22, no. 30 (2007): 5453–63. http://dx.doi.org/10.1142/s0217751x07038712.

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