Showing papers on "Chiral anomaly published in 1993"
TL;DR: In this article, the authors construct a model in which four-dimensional chiral fermions arise on the boundaries of a five-dimensional lattice with free boundary conditions in the fifth direction.
568 citations
TL;DR: In this paper, a complete geometric description of conformal anomalies in arbitrary, (necessarily even) dimenison is given, which fall into two distinct classes: the first, based on Weyl invariants that vanish at integer dimensions, arises from finite contributions to the effective gravitational action through a mechanism analogous to that of the (gauge field) chiral anomaly.
561 citations
TL;DR: In this article, a chiral perturbation theory in heavy-fermion formalism is developed for meson exchange currents in nuclei and applied to nuclear axial-charge transitions.
104 citations
TL;DR: The connection between calculations based on dispersion relations and on chiral perturbation theory is established by matching the low-energy chiral amplitude with that given by a full dispersive treatment.
Abstract: Recent attempts to detect the pion polarizability via analysis of $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}$ measurements are examined The connection between calculations based on dispersion relations and on chiral perturbation theory is established by matching the low-energy chiral amplitude with that given by a full dispersive treatment Using the values for the polarizability required by chiral symmetry, predicted and experimental cross sections are shown to be in agreement
100 citations
TL;DR: The application of chiral perturbation theory to low energy processes of abnormal intrinsic parity (anomalous) is discussed in this article, where estimates of the finite part of the effective Lagrangian from vector meson dominance and the chiral constituent quark model are obtained.
Abstract: The application of chiral perturbation theory to low energy processes of abnormal intrinsic parity (anomalous) is discussed. The full infinite part at next-to-leading order is calculated. Estimates of the finite part of the effective Lagrangian from vector meson dominance and the chiral constituent quark model are obtained. This is then applied to decays of pseudoscalars to photon–photon and photon–three-pseudoscalar couplings.
87 citations
TL;DR: In this article, the authors studied the scaling relations for chiral symmetry restoration and deconfinement at finite temperature and/or density, based on assuming universal scaling relations of some hadron masses.
69 citations
01 Mar 1993
TL;DR: In this article, a lattice theory of massive interacting fermions in 2n + 1 dimensions coupled to a domain wall was used to simulate the behaviour of massless chiral Fermions.
Abstract: I show that a lattice theory of massive interacting fermions in 2n + 1 dimensions coupled to a domain wall may be used to simulate the behaviour of massless chiral fermions in 2n dimensions. The massless states arise as zeromodes bound to the mass defect, and all doublers can be given large gauge invariant masses. The manner in which the anomalies are realized is transparent: chiral anomalies in the 2n dimensional subspace correspond to charge flow into the extra dimension. I also suggest a method for incorporating dynamical gauge fields.
62 citations
TL;DR: In this paper, the hadron spectrum has been calculated in a large scale simulation of QCD with dynamical staggered fermions on a 16(3) x 24 lattice at m = 0.01 and beta = 5.15.
51 citations
TL;DR: The model proposed by Eichten and Preskill for obtaining theories with chiral fermions from the lattice is shown to undergo spontaneous symmetry breaking as mentioned in this paper, and the Fermions appear to be to Dirac-like everywhere in the phase diagram with no room for undoubled Weyl ferns.
47 citations
TL;DR: In this article, the authors studied the utility of working directly with the velocity-dependent "super" fields which appear in the chiral lagrangian and whose interactions manifestly preserve heavy quark spin symmetry rather than their individual spin components.
45 citations
TL;DR: In this paper, the relevance of chiral symmetry to nuclear physics is summarized, and possible consequences of this tendency are discussed, such as changes of hadron properties in dense matter.
TL;DR: In this article, a non-linear chiral perturbation theory of linear SU(2) L + R × nonlinear SU( 2) L − R gives us control of both the tree and quantum loop levels of the theory, where an isosinglet combination of even numbers of pions carries the primary long range attractive force.
TL;DR: In this article, an effective meson-nucleon lagrangian obeying the QCD requirements of chiral symmetry, scale invariance and trace anomaly is constructed, which takes the form of the scaled sigma model supplemented by the gauged vector field and dilation (glueball) field.
TL;DR: In this article, the authors give a complete geometric description of conformal anomalies in arbitrary, (necessarily even) dimension, which fall into two distinct classes: the first, based on Weyl invariants that vanish at integer dimensions, arises from finite -- and hence scale-free -- contributions to the effective gravitational action through a mechanism analogous to that of the (gauge field) chiral anomaly.
Abstract: We give a complete geometric description of conformal anomalies in arbitrary, (necessarily even) dimension. They fall into two distinct classes: the first, based on Weyl invariants that vanish at integer dimensions, arises from finite -- and hence scale-free -- contributions to the effective gravitational action through a mechanism analogous to that of the (gauge field) chiral anomaly. Like the latter, it is unique and proportional to a topological term, the Euler density of the dimension, thereby preserving scale invariance. The contributions of the second class, requiring introduction of a scale through regularization, are correlated to all local conformal scalar polynomials involving powers of the Weyl tensor and its derivatives; their number increases rapidly with dimension. Explicit illustrations in dimensions 2, 4 and 6 are provided.
TL;DR: A scaling theory for the ratio Rπ of the pion to sigma masses is presented in this paper, which can be used to locate critical points and measure critical indices such as δ.
TL;DR: In this article, a light scalar meson serves as both the chiral partner of the pion and mediator of the intermediate-range nucleon-nucleon attraction, and an alternative scenario, which features a heavy chiral scalar and dynamical generation of the [ital NN] attraction is discussed.
Abstract: Relativistic chiral models with a light scalar meson appear to provide an economical marriage of successful relativistic mean-field theories and chiral symmetry. The scalar meson serves as both the chiral partner of the pion and the mediator of the intermediate-range nucleon-nucleon ([ital NN]) attraction. However, while some of these models can reproduce the empirical nuclear matter saturation point, they fail to reproduce observed properties of finite nuclei, such as spin-orbit splittings, shell structure, charge densities, and surface energetics. These deficiencies imply that this realization of chiral symmetry is incorrect. An alternative scenario, which features a heavy chiral scalar and dynamical generation of the [ital NN] attraction, is discussed.
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TL;DR: In this paper, the current status of chiral symmetry restoration is reviewed, and the open question of whether at the restoration point $T=T_c$ the $U(1)_A$ chirality is or is not (approximately) restored is discussed.
Abstract: We review the current status of the problem of chiral symmetry restoration, discussing an open question of whether at the $SU(N_f)_A$ restoration point $T=T_c$ the $U(1)_A$ chiral symmetry is or is not (approximately) restored. New lattice and instanton-based studies are considered, and some new calculations are suggested to clarify the issue. We also speculate on possible experimental manifestations of two possible scenarios.
TL;DR: In this paper, the O(p6) corrections to the anomalous form factors appearing in π+, K+ → e+νγ, μ+nγ and K14 decays in chiral perturbation theory were calculated.
TL;DR: In this paper, the authors use chiral perturbation theory to compute the leading corrections to these predictions which are generated at low momentum, below the chiral symmetry breaking scale.
TL;DR: In this article, the authors analyzed chiral defect fermions on the lattice in 4 + 1 dimensions using mean field theory, where the fermion propagator has a localized chiral model in weak coupling but loses it when the coupling in the unphysical fifth direction becomes too large.
CERN1
TL;DR: In this paper, the first moment of the polarized photon structure function is determined by the anomalous three-current axial vector vector (AVV) correlation function and its dependence on the off-shell momentum κ2 of the target photon is a direct probe of how chiral symmetry is realized in the AVV function.
Abstract: The first moment of the polarized photon structure function is determined by the anomalous three-current axial-vector-vector (AVV) correlation function. Its dependence on the off-shell momentum κ2 of the target photon is a direct probe of the way chiral symmetry is realized in the AVV function. A careful account is given of the effect of different realizations of chiral symmetry on the AVV correlation function with special emphasis on the delicate chiral limit, where the occurrence of singularities in the invariant amplitudes makes the relation with the first moment of more subtle. The behavior of as κ2 is increased through the thresholds associated with the different quarks and leptons is described.
TL;DR: In this paper, the evolution of the density of the quark condensate in an extended nuclear medium was studied, and it was shown that the distortion acts as a reaction against the restauration of chiral symmetry.
TL;DR: In this article, the authors analyzed the Gribov problem for U(n) and SU(n ) gauge theories on a cylinder (1+1) dimensional spacetime with compact space S 1, and showed that the space of gauge orbits is an orbifold.
01 Jan 1993
TL;DR: In this article, the chiral Lagrangian approach involving pions and nucleons is applied to a few problems in nuclear physics, and a nucleon-nucleon potential is derived up to a certain order in chiral perturbation theory; a reasonable fit to phase shifts is obtained up to laboratory energies of about 100 MeV.
Abstract: The chiral Lagrangian approach involving pions and nucleons is applied to a few problems in nuclear physics. A nucleon-nucleon potential is derived up to a certain order in chiral perturbation theory; a reasonable fit to phase shifts is obtained up to laboratory energies of about 100 MeV, and deuteron properties fall within 20% of observed values. Few-body forces are also considered to the same order, and some empirical features are recovered. Isospin violation from both the down-up quark mass difference and electromagnetism is shown to be generically small in low-energy hadronic phenomena as a consequence of the structure of the chiral lagrangian. Finally, an attempt is made at estimating two parameters that appear in such a lagrangian, the axial vector coupling and the anomalous magnetic moment of nucleons; this is done using sum rules and a chirallagrangian involving pions and constituent quarks, in the limit of a large number of colors.
TL;DR: In this paper, the axial anomaly in a vector-like, gauge invariant model for arbitrary $n, and the consistent anomaly in an infinite lattice chiral model with a chiral spectrum were investigated.
Abstract: Chiral defect fermions in the background of an external, $2n$ dimensional gauge field are considered. Assuming first a finite extra dimension, we calculate the axial anomaly in a vector-like, gauge invariant model for arbitrary $n$, and the consistent anomaly in a gauge {\it variant} model with a chiral spectrum. For technical reasons, the latter calculation is limited to the $2+1$ dimensional case. We also show that the infinite lattice chiral model, when properly defined, is in fact a limiting case of the above gauge-variant model. The behaviour of this model with a dynamical gauge field is discussed.
TL;DR: In this article, the authors calculate the corrections to the anomalous form factors appearing in Chiral Perturbation Theory in terms of the O(p^6) dimension of the lagrangian.
Abstract: We calculate the $O(p^6)$ corrections to the anomalous form factors appearing in $\pi^+$, $K^+ \to e^+
u \gamma,\ \mu^+
u\gamma$ and $K_{l4}$ decays in Chiral Perturbation Theory. The relevant dimension $6$ terms of the lagrangian are evaluated assuming their saturation by the vector meson contribution.
01 Mar 1993
TL;DR: The status of several proposals for defining a theory of chiral fermions on the lattice is reviewed and some new estimates for the upper bound on the Higgs mass are presented in this article.
Abstract: The status of several proposals for defining a theory of chiral fermions on the lattice is reviewed and some new estimates for the upper bound on the Higgs mass are presented.
TL;DR: In this article, the Nambu-Jona-Lasinio model was used to study the manifestation of chiral symmetry and q- q pair creation in the presence of the external color-electromagnetic field.
Abstract: We study the manifestation of chiral symmetry and q- q pair creation in the presence of the external color-electromagnetic field, using the Nambu-Jona-Lasinio model. We derive the compact formulae of the effective potential, the Dyson equation for the dynamical quark mass and the q- q pair creation rate in the covariantly constant color-electromagnetic field. Our results are compared with those in other approaches. The chiral-symmetry restoration takes place by a strong color-electric field, and the rapid reduction of the dynamical quark mass is found around the critical field strength, e cr""4 GeV Ifm. Natural extension to the three-flavor case including s-quarks is also done. Around quarks or anti quarks, chiral symmetry would be restored by the sufficiently strong color-electric field, which may lead to the chiral bag picture of hadrons. For the early stage for ultrarelativistic heavy-ion collisions, the possibility of the chiral-symmetry restoration is indicated in the central region just after the collisions.
TL;DR: In this article, the generalized Hartree-Fock method was used to break the chiral symmetry in massless QCD by the use of low energy quark mass in the zero momentum limit.
Abstract: We study dynamical chiral symmetry breaking in massless QCD by the use of the generalized Hartree-Fock method. As the order parameter of chiral symmetry we choose the dynamical quark mass in the zero momentum limit which we call low energy quark mass. We calculate the low energy mass to the second order of diagrammatic expansion around shifted perturbative vacuum. We then show that the mass is finite and renormalization group invariant. After the improvement of the result by the method of effective charges we estimate the mass in the true vacuum under the gap and stationarity conditions and demonstrate that both of them produce non-zero mass proportional to a conventional scale, which breaks down the chiral symmetry.
TL;DR: In this paper, it was shown that for some processes and in a preasymptotic region which may roughly include charmonium and bottomonium, the use of the spin-symmetry may be useful in conjunction with chiral symmetry for light hadrons (soft exchange approximation regime, SEA).