Extended partially conserved axial-vector current hypothesis and chiral-symmetry breaking

1977 ◽  
Vol 15 (5) ◽  
pp. 1350-1360 ◽  
Author(s):  
C. A. Dominguez
Keyword(s):  
Symmetry Breaking ◽  
Chiral Symmetry ◽  
Chiral Symmetry Breaking ◽  
Axial Vector ◽  
Vector Current ◽  
Axial Vector Current

scholarly journals Nuclear currents in chiral effective field theory

2020 ◽  
Vol 56 (9) ◽  
Author(s):  
Hermann Krebs
Keyword(s):  
Field Theory ◽  
Chiral Symmetry ◽  
Effective Field Theory ◽  
Unitary Transformation ◽  
Axial Vector ◽  
Vector Current ◽  
Effective Field ◽  
Axial Vector Current ◽  
Leading Order ◽  
Chiral Effective Field Theory

Abstract In this article, we review the status of the calculation of nuclear currents within chiral effective field theory. After formal discussion of the unitary transformation technique and its application to nuclear currents we give all available expressions for vector, axial-vector currents. Vector and axial-vector currents are discussed up to order Q with leading-order contribution starting at order $$Q^{-3}$$ Q - 3 . Pseudoscalar and scalar currents will be discussed up to order $$Q^0$$ Q 0 with leading-order contribution starting at order $$Q^{-4}$$ Q - 4 . This is a complete set of expressions in next-to-next-to-next-to-leading-order (N$$^3$$ 3 LO) analysis for nuclear scalar, pseudoscalar, vector and axial-vector current operators. Differences between vector and axial-vector currents calculated via transfer-matrix inversion and unitary transformation techniques are discussed. The importance of a consistent regularization is an additional point which is emphasized: lack of a consistent regularization of axial-vector current operators is shown to lead to a violation of the chiral symmetry in the chiral limit at order Q. For this reason a hybrid approach at order Q, discussed in various publications, is non-applicable. To respect the chiral symmetry the same regularization procedure needs to be used in the construction of nuclear forces and current operators. Although full expressions of consistently regularized current operators are not yet available, the isoscalar part of the electromagnetic charge operator up to order Q has a very simple form and can be easily regularized in a consistent way. As an application, we review our recent high accuracy calculation of the deuteron charge form factor with a quantified error estimate.

scholarly journals BARYONS AS THREE-FLAVOR SOLITONS

1996 ◽  
Vol 11 (14) ◽  
pp. 2419-2544 ◽  
Author(s):  
HERBERT WEIGEL
Keyword(s):  
Symmetry Breaking ◽  
Vector Meson ◽  
Degrees Of Freedom ◽  
Magnetic Moments ◽  
Axial Vector ◽  
Vector Current ◽  
Bound State ◽  
Axial Vector Current ◽  
Flavor Symmetry ◽  
Matrix Elements

The description of baryons as soliton solutions of effective meson theories for three-flavor (up, down and strange) degrees of freedom is reviewed and the phenomenological implications are illuminated. In the collective approach the soliton configuration is equipped with baryon quantum numbers by canonical quantization of the coordinates describing the flavor orientation. The baryon spectrum resulting from exact diagonalization of the collective Hamiltonian is discussed. The prediction of static properties, such as the baryon magnetic moments and the Cabibbo matrix elements for semileptonic hyperon decays, are explored with regard to the influence of flavor symmetry breaking. In particular, the role of strange degrees of freedom in the nucleon is investigated for both the vector and axial vector current matrix elements. The latter are discussed extensively within the context of the proton spin puzzle. The influence of flavor symmetry breaking on the shape of the soliton is examined, and observed to cause significant deviations from flavor-covariant predictions on the baryon magnetic moments. Short range effects are incorporated by a chirally invariant inclusion of vector meson fields. These extensions are necessary for properly describing the singlet axial vector current and the neutron–proton mass difference. The effects of the vector meson excitations on baryon properties are also considered. The bound state description of hyperons and its generalization to baryons containing a heavy quark are illustrated. In the case of the Skyrme model a comparison is made between the collective quantization scheme and the bound state approach. Finally, the Nambu–Jona-Lasinio model is employed to demonstrate that hyperons can be described as solitons in a microscopic theory of the quark flavor dynamics. This is explained for both the collective and the bound state approaches to strangeness.

scholarly journals CHIRAL PARTNERS IN A CHIRALLY BROKEN WORLD

2009 ◽  
Vol 24 (02n03) ◽  
pp. 229-236 ◽  
Author(s):  
STEFAN LEUPOLD ◽  
MARKUS WAGNER
Keyword(s):  
Chiral Symmetry ◽  
Chiral Symmetry Breaking ◽  
Axial Vector ◽  
Vector Current ◽  
The Other ◽  
Other Hand ◽  
Chiral Transformation ◽  
Pion Interaction ◽  
Hadronic Level ◽  
Prominent Peak

The isovector–vector and the isovector–axial-vector current are related by a chiral transformation. These currents can be called chiral partners at the fundamental level. In a world where chiral symmetry was not broken, the corresponding current-current correlators would show the same spectral information. In the real world chiral symmetry is spontaneously broken. A prominent peak — the ρ-meson — shows up in the vector spectrum (measured in e+e--collisions and τ-decays). On the other hand, in the axial-vector spectrum a broad bump appears — the a1-meson (also accessible in τ-decays). It is tempting to call ρ and a1 chiral partners at the hadronic level. Strong indications are brought forward that these "chiral partners" do not only differ in mass but even in their nature: The ρ-meson appears dominantly as a quark-antiquark state with small modifications from an attractive pion-pion interaction. The a1-meson, on the other hand, can be understood as a meson-molecule state mainly formed by the attractive interaction between pion and ρ-meson. A key issue here is that the meson-meson interactions are fixed by chiral symmetry breaking. It is demonstrated that one can understand the vector and the axial-vector spectrum very well within this interpretation. It is also shown that the opposite cases, namely ρ as a pion-pion molecule or a1 as a quark-antiquark state lead to less satisfying results. Finally speculations on possible in-medium changes of hadron properties are presented.

scholarly journals Axial vector current of exact chiral symmetry on the lattice

1999 ◽  
Vol 547 (1-2) ◽  
pp. 413-423 ◽  
Author(s):  
Yoshio Kikukawa ◽  
Atsushi Yamada
Keyword(s):  
Chiral Symmetry ◽  
Axial Vector ◽  
Vector Current ◽  
Axial Vector Current

scholarly journals CHIRAL SYMMETRY BREAKING IN A SOFT-WALL MODEL OF AdS/QCD

2010 ◽  
Vol 25 (02n03) ◽  
pp. 453-463 ◽  
Author(s):  
JOSEPH I. KAPUSTA ◽  
THOMAS M. KELLEY ◽  
TONY GHERGHETTA
Keyword(s):  
Symmetry Breaking ◽  
Chiral Symmetry ◽  
Mass Spectra ◽  
Chiral Symmetry Breaking ◽  
Scalar Potential ◽  
Axial Vector ◽  
Wall Model ◽  
Quartic Term ◽  
Soft Wall Model ◽  
Soft Wall

We incorporate chiral symmetry breaking in a soft-wall version of the AdS/QCD model by using a modified dilaton profile and a quartic term in the bulk scalar potential. This allows one to separate the dependence on spontaneous and explicit chiral symmetry breaking. The resulting mass spectra in the scalar, vector and axial-vector sectors compares favorably with the respective QCD resonances.

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