Browsing by Author "Panagopoulos, Haralambos G."
Now showing items 1-20 of 113
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Article
The 3-loop beta function of QCD
Allés, B.; Christou, Chris; Feo, A.; Panagopoulos, Haralambos G.; Vicari, E. (1997)Using the background field technique, we calculate the 3-loop beta function of lattice SU (N) gauge theories. In the pure gluonic case, we present our results, comparing to those recently obtained by Luescher and Weisz. ...
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Article
The 4D SU(3) gauge theory with an imaginary θ term
Panagopoulos, Haralambos G.; Vicari, E. (2011)We study the scaling behavior of the 4D SU(3) lattice gauge theory in the presence of a θ term, by Monte Carlo simulations computing the topological properties at imaginary θ. The numerical results provide a good evidence ...
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Article
Additive and multiplicative renormalization of topological charge with improved gluon and fermion actions: A test case for 3-loop vacuum calculations, using overlap or clover fermions
Skouroupathis, A.; Panagopoulos, Haralambos G. (2005)We calculate perturbative renormalization properties of the topological charge, using the standard lattice discretization given by a product of twisted plaquettes. We use the overlap and clover action for fermions, and the ...
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Article
Asymptotic scaling corrections in QCD with Wilson fermions from the 3-loop average plaquette
Allés, B.; Feo, A.; Panagopoulos, Haralambos G. (1998)We calculate the 3-loop perturbative expansion of the average plaquette in lattice QCD with Nf massive Wilson fermions and gauge group SU(N). The corrections to asymptotic scaling in the corresponding energy scheme are ...
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Article
Behaviour of the topological susceptibility across the deconfining phase transition
Di Giacomo, A.; Meggiolaro, E.; Panagopoulos, Haralambos G. (1992)We investigate the behaviour of the topological susceptibility of pure SU(2) gauge theory at the deconfining phase transition. The cooling method gives ambiguous results. The susceptibility, determined by the field theoretical ...
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Article
BK-parameter from Nf=2 twisted mass lattice QCD
Constantinou, Martha G.; Dimopoulos, Petros; Frezzotti, R.; Jansen, K.; Gimenez, V.; Lubicz, V.; Mescia, F.; Panagopoulos, Haralambos G.; Papinutto, M.; Rossi, G. C.; Simula, S.; Skouroupathis, A.; Stylianou, Fotos S.; Vladikas, A. (2011)We present an unquenched Nf=2 lattice computation of the B K parameter which controls K0-K̄0 oscillations. A partially quenched setup is employed with two maximally twisted dynamical (sea) light Wilson quarks, and valence ...
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Article
Change of θ dependence in 4D SU(N) gauge theories across the deconfinement transition
Bonati, C.; D'Elia, M.; Panagopoulos, Haralambos G.; Vicari, E. (2013)We study the dependence of 4D SU(N) gauge theories on the topological θ term at finite temperature T. We exploit the lattice formulation of the theory, presenting numerical results for the expansion of the free energy up ...
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Conference Object
The chromomagnetic operator on the lattice
Constantinou, Martha G.; Costa, M. G.; Frezzotti, R.; Lubicz, V.; Martinelli, G.; Meloni, D.; Panagopoulos, Haralambos G.; Simula, S. (Proceedings of Science (PoS), 2013)We study matrix elements of the "chromomagnetic" operator on the lattice. This operator is contained in the strangeness-changing effective Hamiltonian which describes electroweak effects in the Standard Model and beyond. ...
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Article
A complete non-perturbative renormalization prescription for quasi-PDFs
Alexandrou, Constantia; Cichy, K.; Constantinou, Martha; Hadjiyiannakou, Kyriakos; Jansen, K.; Panagopoulos, Haralambos G.; Steffens, F. (2017)In this work we present, for the first time, the non-perturbative renormalization for the unpolarized, helicity and transversity quasi-PDFs, in an RI′ scheme. The proposed prescription addresses simultaneously all aspects ...
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Article
Confining strings in representations with common n-ality
Del Debbio, L.; Vicari, E.; Panagopoulos, Haralambos G. (2003)We study the spectrum of confining strings in SU(3) pure gauge theory, by means of lattice Monte Carlo simulations, using torelon operators in different representations of the gauge group. Our results provide direct evidence ...
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Cooling and the string tension in lattice gauge theories
Campostrini, M.; Di Giacomo, A.; Maggiore, M.; Panagopoulos, Haralambos G.; Vicari, E. (1989)We explore the possibility of improving the determination of the string tension using the cooling method. We present preliminary results for the gauge group SU(2): We find that statistical errors are drastically reduced ...
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Article
Critical hopping parameter in O(a) improved lattice QCD
Panagopoulos, Haralambos G.; Proestos, Y. (2002)We calculate the critical value of the hopping parameter, κ c, in O(a) improved lattice QCD, to two loops in perturbation theory. We employ the Sheikholeslami-Wohlert (clover) improved action for Wilson fermions. The ...
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Article
Critical mass of Wilson fermions: A comparison of perturbative and Monte Carlo results
Follana, E.; Panagopoulos, Haralambos G. (2001)We calculate the critical value of the hopping parameter, κc , in lattice QCD with Wilson fermions, to two loops in perturbation theory. This quantity is an additive renormalization
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Article
Efficiency of the UV-filtered multiboson algorithm
Alexandrou, Constantia; De Forcrand, P.; D'Elia, M.; Panagopoulos, Haralambos G. (2000)We study the efficiency of an improved multiboson algorithm with two flavors of Wilson fermions in a realistic physical situation (β=5.60,κ=0.156 on a 163X24 lattice). The performance of this exact algorithm is compared ...
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Article
Erratum: Asymptotic scaling corrections in QCD with Wilson fermions from the 3-loop average plaquette (Physics Letters, Section B: Nuclear, Elementary Particle (1998) 426 (361))
Allés, B.; Feo, A.; Panagopoulos, Haralambos G. (2003)
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Article
Erratum: Two-loop renormalization of scalar and pseudoscalar fermion bilinears on the lattice (Physical Review D - Particles, Fields, Gravitation and Cosmology (2007) 76 (094514))
Skouroupathis, A.; Panagopoulos, Haralambos G. (2008)
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Article
Fermion-monopole system reexamined. IV
Panagopoulos, Haralambos G.; Yamagishi, H. (1985)The chiral properties of the fermion-monopole system are investigated in detail. For one species of massless Dirac fermions, we show that the chiral symmetry is spontaneously broken, even in the presence of anomalies. The ...
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Article
Field strength correlations in the QCD vacuum
Di Giacomo, A.; Panagopoulos, Haralambos G. (1992)We determine by numerical simulation on a lattice the correlation function of the gauge field strengths in the QCD vacuum. © 1992.
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Article
Field strength correlators in QCD at zero and non-zero temperature
Di Giacomo, A.; Meggiolaro, E.; Panagopoulos, Haralambos G. (1997)We study, by numerical simulations on a lattice, the behaviour of the gauge-invariant field strength correlators in QCD both at zero temperature, down to a distance of 0.1 fm, and at finite temperature, across the deconfinement ...
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Article
Fractal behaviour in the O(3) model
Christou, Chris; Diakonos, Fotis K.; Panagopoulos, Haralambos G. (1995)We study domain formation in the two-dimensional O(3) model near criticality. The fractal dimension of these domains is determined with good statistical accuracy. © 1995.