Learn More
We study the issue of duality violations in the V V −AA vacuum polarization function in the chiral limit. This is done with the help of a model with an expansion in inverse powers of the number of colors, Nc, allowing us to consider resonances with a finite width. Due to these duality violations, the Operator Product Expansion (OPE) and the moments of the(More)
We construct the most general chirally invariant Lagrangian for mesons in the presence of external sources coupled to the tensor current ψ̄ σμνψ. In order to have only even terms in the chiral expansion, we consider the new source of O(p). With this choice, we build the even-parity effective Lagrangian up to the p-order (NLO). While there are only 4 new(More)
We consider the Standard Model, including a light scalar boson h, as an effective theory at the weak scale v = 246 GeV of some unknown dynamics of electroweak symmetry breaking. This dynamics may be strong, with h emerging as a pseudo-Goldstone boson. The symmetry breaking scale Λ is taken to be at 4πv or above. We review the leading-order Lagrangian within(More)
We consider the electroweak chiral Lagrangian, including a light scalar boson, in the limit of small ξ = v2/f 2. Here v is the electroweak scale and f is the corresponding scale of the new strong dynamics. We show how the conventional SILH Lagrangian, defined as the effective theory of a strongly-interacting light Higgs (SILH) to first order in ξ , can be(More)
We argue that the large-Nc expansion of QCD can be used to treat a Lagrangian of resonances in a perturbative way. As an illustration of this we compute the L10 coupling of the Chiral Lagrangian by integrating out resonance fields at one loop. This is how one can answer in a concrete and unambiguous manner questions such as at what scale resonance(More)
Besides their appearance at short distances >∼ 1/MW , local dimension-eight operators also contribute to kaon matrix elements at long distances of order ∼ 1/μope, where μope is the scale controlling the Operator Product Expansion in pure QCD, without weak interactions. This comes about in the matching condition between the effective quark Lagrangian and the(More)
We study contributions to the ∆S = 2 weak Chiral Lagrangian producing K0 −K mixing which are not enhanced by the charm mass. For the real part, these contributions turn out to be related to the box diagram with up quarks but, unlike in perturbation theory, they do not vanish in the limit mu → 0. They increase the leading contribution to the KL−KS mass(More)
We examine whether the fact that QCD is chirally invariant at short distances necessarily leads to the prediction that hadrons form approximate parity doublets, as has been recently put forward by Glozman and collaborators. We show that this is not the case, and we exhibit some of the pitfalls of trying to link the operator product expansion to the hadron(More)
We reassess a work done by Migdal on the spectrum of low-energy vector mesons in QCD in the light of the AdS-QCD correspondence. Recently, a tantalizing parallelism was suggested between Migdal’s work and a family of holographic duals of QCD. Despite the intriguing similarities, both approaches face a major drawback: the spectrum is in conflict with(More)