共查询到20条相似文献,搜索用时 0 毫秒
1.
Michael Creutz 《Annals of Physics》2009,324(7):1573-336
I review some aspects of the interplay between anomalies and chiral symmetry. The quantum anomaly that breaks the U(1) axial symmetry of massless QCD leaves behind a flavor-singlet discrete chiral invariance. When the mass is turned on this residual symmetry has a close connection with the strong CP violating parameter theta. One result is that a first order transition is usually expected when the strong CP violating angle passes through pi. This symmetry can be understood either in terms of effective chiral Lagrangians or in terms of the underlying quark fields. 相似文献
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Yu.P. Goncharov 《Physics letters. [Part B]》1983,133(6):433-435
An originally massless quark flavour multiplet in QCD can be split on masses by a nonsimply connected spacetime topology if the quark flavours are associated with spin structures on the given spacetime. This mechanism is described by the example of spacetime with topology S1 × R3 and flat metric. The possible applications are also discussed. 相似文献
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S.P. De Alwis 《Physics letters. [Part B]》1979,86(1):67-71
The consistency of iso-spin (SU(3)) symmetry of the vacuum with the spontaneous breakdown of chiral symmetry without the appearance of a U(1) Goldstone boson, is investigated. 相似文献
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《Physics letters. [Part B]》1988,212(2):231-237
It is well known that chiral symmetry is spontaneously broken in QCD. To relate this fact to non-perturbative features of the theory, like instantons, we start with a massless lagrangian and perform a non-linear chiral colored singlet transformation on the quark fields which yields (by means of Fujikawa's method) essentially two terms in the lagrangian. First a quark mass term induced by instantons and secondly a coupling between pseudoscalar mesons and the axial anomaly. Ward-Takahashi identities can be derived. To clarify the presence of this induced mass term we calculate its first perturbative part up to the two-loop level. 相似文献
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I. Antoniadis 《Physics letters. [Part B]》1979,84(2):223-224
We calculate the vacuum polarization functions of the vector and axial current for massless quarks in second-order perturbation theory. We find that, contrary to previous speculations, there is no indication, at this level, of spontaneous breaking of chiral symmetry in QCD. 相似文献
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We consider chiral symmetry breaking through nontrivial vacuum structure with an explicit construct for the vacuum with quark antiquark condensates in QCD with Coulomb gauge for different phenomenological potentials. The dimensional parameter for the condensate function gets related to \(\left\langle {\bar \psi \psi } \right\rangle \) of Shifman, Vainshtein and Zakharov. We then relate the condensate function to the wave function of pion as a Goldstone mode. This simultaneously yields the pion also as a quark antiquark bound state as a localised zero mode of vacuum. We then calculate different pionic properties using the wave function as obtained from the vacuum structure. 相似文献
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A recently proposed model for dynamical breaking of chiral symmetry in QCD is extended and developed for the calculation of pion and chiral symmetry breaking parameters. The pion is explicitly realized as a massless Goldstone boson and as a bound state of the constituent quarks. We compute, in the limit of exact chiral symmetry, MQ, the constituent quark mass the pion decay coupling, , the constituent quark loop density, μπ2/mq, the ratio of the Goldstone boson mass squared to the bare quark mass, and 〈r2〉π, the pion electromagnetic charge radius squared. 相似文献
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Rahul Basu R. Parthasarathy 《The European Physical Journal C - Particles and Fields》1998,4(4):679-683
A mechanism for instanton induced chiral symmetry breaking in an extended QCD model (QCD with fundamental scalars) is proposed
to describe quarks and gluons inside a baryon. The model Lagrangian that we use has the same symmetry properties as QCD. The
scalar fields are shown to develop vacuum expectation values in the instanton background and generate masses for the three
generation of quarks. The minimization condition is also used to break the flavour symmetry to make the -quark heavier that the and quarks.
Received: 16 August 1996 / Revised version: 15 October 1997 / Published online: 26 February 1998 相似文献
12.
We present a calculation of the standard model DeltaS=2 matrix element relevant to indirect CP violation in K-->pipi decays which uses Neuberger's chiral formulation of lattice fermions. The computation is performed in the quenched approximation on a 16(3) x 32 lattice that has a lattice spacing a approximately 0.1 fm. The resulting bare matrix element is renormalized nonperturbatively. Our main result is B(RGI)(K)=0.87(8)+2+14-1-14, where the first error is statistical, the second is systematic, and the third is Sharpe's estimate of quenching and flavor-SU(3) breaking uncertainties. 相似文献
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Dyonic classical solutions of Yang-Mills theory are considered and the complete set of fermionic zero modes of these solutions are studied. Representing the QCD vacuum as a gas of dyons, one obtains chiral symmetry breaking due to zero modes similarly to the case of instantonic vacuum. 相似文献
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Yu. A. Simonov 《Physics of Atomic Nuclei》2013,76(4):525-533
The meson spectrum of QCD is studied in the framework of nonperturbative QCD as a function of varying quark masses m q . It is shown that the total spectrum consists of two branches: 1) the standard one, which may be called the flux-tube spectrum, depending approximately linearly on m q , and 2) the chiral symmetry breaking (CSB) spectrum for pseudoscalar (PS) flavor nonsinglet mesons with mass dependence √m q . The formalism for PS mesons is derived from the QCD Lagrangian with m q corrections, and a unified form of the PS propagator was derived. It is shown that the CSB branch of PS mesons joins to the flux-tube branch at around m q = 200 MeV. All these results are in close correspondence with recent numerical data on large lattices. 相似文献
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We study the spectrum of the QCD Dirac operator for two colors with fermions in the fundamental representation and for two or more colors with adjoint fermions. For Nf flavors, the chiral flavor symmetry of these theories is spontaneously broken according to SU (2Nf → Sp (2Nf) and SU (Nf → O (Nf), respectively, rather than the symmetry breaking pattern SU (Nf) × SU (Nf) → SU (Nf) for QCD with three or more colors and fundamental fermions. In this paper we study the Dirac spectrum for the first two symmetry breaking patterns. Following previous work for the third case we find the Dirac spectrum in the domain λ ΛQCD by means of partially quenched chiral perturbation theory. In particular, this result allows us to calculate the slope of the Dirac spectrum at λ = 0. We also show that for λ 1/L2 ΛQCD (wing L the linear size fo the system) the Dirac spectrum is given by a chiral Random Matrix Theory with the symmetries of the Dirac operator. 相似文献
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J. Kapusta 《Physics letters. [Part B]》1984,136(3):201-203
Chiral symmetry in the high-temperature plasma phase of QCD is consistent with at least three qualitatively different quark dispersion relations. The rate for , with zero total momentum of the e+e? pair in the plasma rest frame is direct measure of the quark dispersion relation. For the three plausible dispersion relations the rates differ by orders of magnitude when the e+e? invariant mass M < 2T. 相似文献
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《Nuclear Physics B》1995,437(1):3-24
A matrix model is constructed which describes a chiral version of the large NU (N) gauge theory on a two-dimensional sphere of area A. This theory has three separate phases. The large area phase describes the associated chiral string theory. An exact expression for the free energy in the large area phase is used to derive a remarkably simple formula for the number of topologically inequivalent covering maps of a sphere with fixed branch points and degree n. 相似文献