CHIRALLY EXTENDED QUANTUM CHROMODYNAMICS

1995 ◽  
Vol 06 (05) ◽  
pp. 725-742 ◽  
Author(s):  
RICHARD C. BROWER ◽  
YUE SHEN ◽  
CHUNG-I TAN
Keyword(s):  
Quantum Chromodynamics ◽  
Quark Mass ◽  
Continuum Limit ◽  
Chiral Limit ◽  
Scalar Fields ◽  
Weak Coupling Limit ◽  
Slowing Down ◽  
Large N ◽  
Chiral Invariance ◽  
The Continuum

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.

scholarly journals Effective Action and Measure in Matrix Model of IIB Superstrings

1997 ◽  
Vol 12 (31) ◽  
pp. 2331-2340 ◽  
Author(s):  
L. Chekhov ◽  
K. Zarembo
Keyword(s):  
Matrix Model ◽  
Effective Action ◽  
Continuum Limit ◽  
Auxiliary Field ◽  
Large N ◽  
The Matrix ◽  
Reparametrization Invariance ◽  
The Continuum ◽  
Induced Measure

We calculate an effective action and measure induced by the integration over the auxiliary field in the matrix model recently proposed to describe IIB superstrings. It is shown that the measure of integration over the auxiliary matrix is uniquely determined by locality and reparametrization invariance of the resulting effective action. The large-N limit of the induced measure for string coordinates is discussed in detail. It is found to be ultralocal and, thus, is possibly irrelevant in the continuum limit. The model of the GKM type is considered in relation to the effective action problem.

scholarly journals Topological susceptibility with a single light quark flavour

2018 ◽  
Vol 175 ◽  
pp. 14017 ◽  
Author(s):  
Julien Frison ◽  
Ryuichiro Kitano ◽  
Norikazu Yamada
Keyword(s):  
Quark Mass ◽  
Continuum Limit ◽  
Light Quark ◽  
The Other ◽  
Theoretical Argument ◽  
Up Quark ◽  
Order Of Magnitude ◽  
Quark Flavour ◽  
Definition Of ◽  
The Continuum

One of the historical suggestions to tackle the strong CP problem is to take the up quark mass to zero while keeping md finite. The θ angle is then supposed to become irrelevant, i.e. the topological susceptibility vanishes. However, the definition of the quark mass is scheme-dependent and identifying the mu = 0 point is not trivial, in particular with Wilson-like fermions. More specifically, up to our knowledge there is no theoretical argument guaranteeing that the topological susceptibility exactly vanishes when the PCAC mass does. We will present our recent progresses on the empirical check of this property using Nf = 1 + 2 flavours of clover fermions, where the lightest fermion is tuned very close to [see formula in PDF] and the mass of the other two is kept of the order of magnitude of the physical ms. This choice is indeed expected to amplify any unknown non-perturbative effect caused by mu ≠ md. The simulation is repeated for several βs and those results, although preliminary, give a hint about what happens in the continuum limit.

scholarly journals The continuum limit of the quark mass step scaling function in quenched lattice QCD

2004 ◽  
Vol 2004 (05) ◽  
pp. 001-001 ◽  
Author(s):  
M Guagnelli ◽  
J Heitger ◽  
F Palombi ◽  
C Pena ◽  
A Vladikas
Keyword(s):  
Lattice Qcd ◽  
Quark Mass ◽  
Continuum Limit ◽  
Scaling Function ◽  
The Continuum

scholarly journals Large N scaling and factorization in SU(N) Yang-Mills theory

2018 ◽  
Vol 175 ◽  
pp. 11018 ◽  
Author(s):  
Miguel García Vera ◽  
Rainer Sommer
Keyword(s):  
Lattice Spacing ◽  
Continuum Limit ◽  
Finite Lattice ◽  
Gradient Flow ◽  
Scaling Up ◽  
Wilson Loops ◽  
Yang Mills ◽  
Large N ◽  
The Continuum

We present results for Wilson loops smoothed with the Yang-Mills gradient flow and matched through the scale t0. They provide renormalized and precise operators allowing to test the 1/N2 scaling both at finite lattice spacing and in the continuum limit. Our results show an excellent scaling up to 1/N = 1/3. Additionally, we obtain a very precise non-perturbative confirmation of factorization in the large N limit.

scholarly journals Testing algorithms for critical slowing down

2018 ◽  
Vol 175 ◽  
pp. 02008 ◽  
Author(s):  
Guido Cossu ◽  
Peter Boyle ◽  
Norman Christ ◽  
Chulwoo Jung ◽  
Andreas Jüttner ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Topological Charge ◽  
Continuum Limit ◽  
Critical Slowing Down ◽  
Gauge Fields ◽  
Hybrid Monte Carlo ◽  
Slowing Down ◽  
Testing Algorithms ◽  
New Algorithms ◽  
The Continuum

We present the preliminary tests on two modifications of the Hybrid Monte Carlo (HMC) algorithm. Both algorithms are designed to travel much farther in the Hamiltonian phase space for each trajectory and reduce the autocorrelations among physical observables thus tackling the critical slowing down towards the continuum limit. We present a comparison of costs of the new algorithms with the standard HMC evolution for pure gauge fields, studying the autocorrelation times for various quantities including the topological charge.

Deconfining Phase Transition and the Continuum Limit of Lattice Quantum Chromodynamics

1985 ◽  
Vol 55 (19) ◽  
pp. 1958-1961 ◽  
Author(s):  
S. A. Gottlieb ◽  
J. Kuti ◽  
D. Toussaint ◽  
A. D. Kennedy ◽  
S. Meyer ◽  
...  
Keyword(s):  
Phase Transition ◽  
Quantum Chromodynamics ◽  
Continuum Limit ◽  
Lattice Quantum Chromodynamics ◽  
Lattice Quantum ◽  
The Continuum

scholarly journals Testing a non-perturbative mechanism for elementary fermion mass generation: numerical results

2018 ◽  
Vol 175 ◽  
pp. 08008 ◽  
Author(s):  
Stefano Capitani ◽  
Giulia Maria De Divitiis ◽  
Petros Dimopoulos ◽  
Roberto Frezzotti ◽  
Marco Garofalo ◽  
...  
Keyword(s):  
Elementary Particle ◽  
Continuum Limit ◽  
Scalar Fields ◽  
Higgs Mechanism ◽  
Numerical Results ◽  
Fermion Mass ◽  
Recent Proposal ◽  
Mass Generation ◽  
Complex Scalar ◽  
The Continuum

Based on a recent proposal according to which elementary particle masses could be generated by a non-perturbative dynamical phenomenon, alternative to the Higgs mechanism, we carry out lattice simulations of a model where a non-abelian strongly interacting fermion doublet is also coupled to a doublet of complex scalar fields via a Yukawa and an “irrelevant" Wilson-like term. In this pioneering study we use naive fermions and work in the quenched approximation. We present preliminary numerical results both in the Wigner and in the Nambu-Goldstone phase, focusing on the observables relevant to check the occurrence of the conjectured dynamical fermion mass generation effect in the continuum limit of the critical theory in its spontaneously broken phase.

Instability and Collapse in Discrete Wave Equations

2005 ◽  
Vol 5 (3) ◽  
pp. 223-241
Author(s):  
A. Carpio ◽  
G. Duro
Keyword(s):  
Continuum Limit ◽  
Wave Equations ◽  
Numerical Solutions ◽  
Blow Up ◽  
Theoretical Predictions ◽  
Initial States ◽  
The Impact ◽  
The Continuum

AbstractUnstable growth phenomena in spatially discrete wave equations are studied. We characterize sets of initial states leading to instability and collapse and obtain analytical predictions for the blow-up time. The theoretical predictions are con- trasted with the numerical solutions computed by a variety of schemes. The behavior of the systems in the continuum limit and the impact of discreteness and friction are discussed.

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