226 research outputs found
Collective fields for QCD
No full textA gauge-symmetric approach to effective Lagrangians is described with special emphasis on derivations of effective low-energy Lagrangians from QCD. The examples we discuss are based on exact rewritings of cut-off QCD in terms of new collective degrees of freedom. These cut-off Lagrangians are thus ``effective'' in the sense that they explicitly contain some of the physical long-distance degrees of freedom from the outset.(Talk presented by P.H. Damgaard at the workshop on ``Quantum Field Theoretical Methods in High Energy Physics'', Kyffhauser, Germany, Sept. 1993. To appear in those proceedings).A gauge-symmetric approach to effective Lagrangians is described with special emphasis on derivations of effective low-energy Lagrangians from QCD. The examples we discuss are based on exact rewritings of cut-off QCD in terms of new collective degrees of freedom. These cut-off Lagrangians are thus ``effective'' in the sense that they explicitly contain some of the physical long-distance degrees of freedom from the outset.(Talk presented by P.H. Damgaard at the workshop on ``Quantum Field Theoretical Methods in High Energy Physics'', Kyffhauser, Germany, Sept. 1993. To appear in those proceedings)
On finite-volume gauge theory partition functions
No full textWe prove a Mahoux–Mehta-type theorem for finite-volume partition functions of SU(Nc≥3) gauge theories coupled to fermions in the fundamental representation. The large-volume limit is taken with the constraint V1/mπ4. The theorem allows one to express any k-point correlation function of the microscopic Dirac operator spectrum entirely in terms of the 2-point function. The sum over topological charges of the gauge fields can be explicitly performed for these k-point correlation functions. A connection to an integrable KP hierarchy, for which the finite-volume partition function is a τ-function, is pointed out. Relations between the effective partition functions for these theories in 3 and 4 dimensions are derived. We also compute analytically, and entirely from finite-volume partition functions, the microscopic spectral density of the Dirac operator in SU(Nc) gauge theories coupled to quenched fermions in the adjoint representation. The result coincides exactly with earlier results based on Random Matrix Theory
The effect of competition between two spatially separated markets - An investigation of two interlinked Bak-Sneppen models
No full textThis paper investigates the effect of competition in a market consisting of interlinked economic agents. In particular, the effect of increased competition from the surrounding markets is demonstrated. The presented work is an extension of the Bak-Sneppen model (Bak and Sneppen 1993). Here are two Bak-Sneppen models interlinked such that if the lowest fitness value of one market exceeds the fitness values of the other market minus transportation cost, all cells lower than this band will receive a new random value. The model shows that interdependency between markets has a strong effect on the competitiveness of the least competitive market. The external competition is able to make the least competitive market perform better as well as worse than on its own.Bak-Sneppen model, interdependency, competition, Marketing,
Quenched Finite Volume Logarithms
No full textQuenched chiral perturbation theory is used to compute the first finite volume correction to the chiral condensate. The correction diverges logarithmically with the four-volume . We point out that with dynamical quarks one can obtain both the chiral condensate and the pion decay constant from the distributions of the lowest Dirac operator eigenvalues.Quenched chiral perturbation theory is used to compute the first finite volume correction to the chiral condensate. The correction diverges logarithmically with the four-volume . We point out that with dynamical quarks one can obtain both the chiral condensate and the pion decay constant from the distributions of the lowest Dirac operator eigenvalues.Quenched chiral perturbation theory is used to compute the first finite volume correction to the chiral condensate. The correction diverges logarithmically with the four-volume V . We point out that with dynamical quarks one can obtain both the chiral condensate and the pion decay constant from the distributions of the lowest Dirac operator eigenvalues
Vector and axial-vector propagators in the epsilon-regime of QCD
No full textDamgaard PH, Hernandez P, Jansen K, Lellouch L, Laine M. Vector and axial-vector propagators in the epsilon-regime of QCD. NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS. 2004;129:754-756.Using quenched and unquenched chiral perturbation theory we compute axial and vector current two-point functions at finite volume and fixed gauge field topology in the c-regime of QCD
Random Surfaces with Ising Spins
No full textBosonic strings can be discretized in terms of dynamically triangulatedrandom surfaces. We investigate the possibility of introducing fermionicdegrees of freedom on the surface in terms of Ising spins, which in twodimensions correspond to Majorana fermions. Critical properties of themodel are estimated using finite-size scaling methods
Low-lying Eigenvalues of the QCD Dirac Operator at Finite Temperature
No full textTheoretical High-Energy Physic
Looking for effects of Topology in the Dirac Spectrum of Staggered Fermions
No full textTheoretical High-Energy Physic
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