189 research outputs found
Chiral Perturbation Theory with tensor sources
We construct the most general chirally-invariant Lagrangian for mesons in the
presence of external sources coupled to the tensor current
\bar{\psi}\sigma_{\mu\nu}\psi. In order to have only even terms in the chiral
expansion, we consider the new source of O(p^2). With this choice, we build the
even-parity effective Lagrangian up to the p^6-order (NLO). While there are
only 4 new terms at the p^4-order, at p^6-order we find 78 terms for n_f=2 and
113 terms for n_f=3. We provide a detailed discussion on the different
mechanisms that ensure that our final set of operators is complete and
non-redundant. We also examine the odd-parity sector, to conclude that the
first operators appear at the p^8-order (NNLO).Comment: 23 pages, one figure; typos corrected, one paragraph added, new
section added, references added, published versio
Large-Nc QCD, Harmonic Sums and the Riemann Zeros
It is shown that in Large-Nc QCD, two--point functions of local operators
become Harmonic Sums. We comment on the properties which follow from this fact.
This has led us to an aside observation concerning the zeros of the Riemann
zeta--function seen from the point of view of Dispersion Relations in Quantum
Theory.Comment: Invited talk at the Montpellier QCD 2010 Conferenc
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