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de Azcarraga, J. A., Izquierdo, J. M., & Picon, M. (2011). Contractions of Filippov algebras. J. Math. Phys., 52(1), 013516–24pp.
Abstract: We introduce in this paper the contractions B-c of n-Lie (or Filippov) algebras B and show that they have a semidirect structure as their n = 2 Lie algebra counterparts. As an example, we compute the nontrivial contractions of the simple A(n+1) Filippov algebras. By using the. Inonu-Wigner and the generalized Weimar-Woods contractions of ordinary Lie algebras, we compare (in the B = A(n+1) simple case) the Lie algebras Lie B-c (the Lie algebra of inner endomorphisms of B-c) with certain contractions (Lie B)(IW) and (Lie B)(W-W) of the Lie algebra Lie B associated with B.
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Yamagata-Sekihara, J., Nieves, J., & Oset, E. (2011). Couplings in coupled channels versus wave functions in the case of resonances: Application to the two A(1405) states. Phys. Rev. D, 83(1), 014003–15pp.
Abstract: In this paper we develop a formalism to evaluate wave functions in momentum and coordinate space for the resonant states dynamically generated in a unitary coupled channel approach. The on-shell approach for the scattering matrix, commonly used, is also obtained in quantum mechanics with a separable potential, which allows one to write wave functions in a trivial way. We develop useful relationships among the couplings of the dynamically generated resonances to the different channels and the wave functions at the origin. The formalism provides an intuitive picture of the resonances in the coupled channel approach, as bound states of one bound channel, which decays into open ones. It also provides an insight and practical rules for evaluating couplings of the resonances to external sources and how to deal with final state interaction in production processes. As an application of the formalism we evaluate the wave functions of the two A(1405) states in the pi Sigma, (K) over barN, and other coupled channels. It also offers a practical way to study three-body systems when two of them cluster into a resonance.
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Aguilar, A. C., & Papavassiliou, J. (2011). Chiral symmetry breaking with lattice propagators. Phys. Rev. D, 83(1), 014013–17pp.
Abstract: We study chiral symmetry breaking using the standard gap equation, supplemented with the infrared-finite gluon propagator and ghost dressing function obtained from large-volume lattice simulations. One of the most important ingredients of this analysis is the non-Abelian quark-gluon vertex, which controls the way the ghost sector enters into the gap equation. Specifically, this vertex introduces a numerically crucial dependence on the ghost dressing function and the quark-ghost scattering amplitude. This latter quantity satisfies its own, previously unexplored, dynamical equation, which may be decomposed into individual integral equations for its various form factors. In particular, the scalar form factor is obtained from an approximate version of the “one-loop dressed” integral equation, and its numerical impact turns out to be rather considerable. The detailed numerical analysis of the resulting gap equation reveals that the constituent quark mass obtained is about 300 MeV, while fermions in the adjoint representation acquire a mass in the range of (750-962) MeV.
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Szilner, S. et al, & Gadea, A. (2011). Interplay between single-particle and collective excitations in argon isotopes populated by transfer reactions. Phys. Rev. C, 84(1), 014325–7pp.
Abstract: New gamma transitions have been identified in argon isotopes in (40)Ar + (208)Pb multiple transfer reactions by exploiting, in a fragment-gamma measurement, the new generation of magnetic spectrometers based on trajectory reconstruction coupled to large gamma arrays. The coupling of single-particle degrees of freedom to nuclear vibration quanta was discussed. The interpretation of the newly observed states within a particle-phonon coupling picture was used to consistently follow, via their excitation energies, the evolution of collectivity in odd Ar isotopes. The proposed level schemes are supported by the results of sd-pf shell-model calculations, which have been also employed to evaluate the strength functions of the populated states.
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Constantinou, M., Dimopoulos, P., Frezzotti, R., Jansen, K., Gimenez, V., Lubicz, V., et al. (2011). B-K-parameter from N-f=2 twisted mass lattice QCD. Phys. Rev. D, 83(1), 014505–20pp.
Abstract: We present an unquenched N-f = 2 lattice computation of the B-K parameter which controls K-0 – (K) over bar (0) oscillations. A partially quenched setup is employed with two maximally twisted dynamical (sea) light Wilson quarks, and valence quarks of both the maximally twisted and the Osterwalder-Seiler variety. Suitable combinations of these two kinds of valence quarks lead to a lattice definition of the B-K parameter which is both multiplicatively renormalizable and O(a) improved. Employing the nonperturbative RI-MOM scheme, in the continuum limit and at the physical value of the pion mass we get B-K(RGI) = 0.729 +/- 0.030, a number well in line with the existing quenched and unquenched determinations.
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