Search results for "Background"
showing 10 items of 556 documents
Pinch technique to all orders
2002
The generalization of the pinch technique to all orders in perturbation theory is presented. The effective Green's functions constructed with this procedure are singled out in a unique way through the full exploitation of the underlying Becchi-Rouet-Stora-Tyutin symmetry. A simple all-order correspondence between the pinch technique and the background field method in the Feynman gauge is established. Comment: 10 pages, 4 figures; one reference added, typos corrected; final version to match the pubblished one
One-loop renormalization of Resonance Chiral Theory: scalar and pseudoscalar resonances
2005
We consider the Resonance Chiral Theory with one multiplet of scalar and pseudoscalar resonances, up to bilinear couplings in the resonance fields, and evaluate its beta-function at one-loop with the use of the background field method. Thus we also provide the full set of operators that renormalize the theory at one loop and render it finite.
The QCD Axion and Gravitational Waves in light of NANOGrav results
2020
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration has recently reported strong evidence for a stochastic process affecting the 12.5 yr dataset of pulsar timing residuals. We show that the signal can be interpreted in terms of a stochastic gravitational wave background emitted from a network of axionic strings in the early Universe. The spontaneous breaking of the Peccei-Quinn symmetry originate the axionic string network and the QCD axion, the dark matter particle in the model. We explore a non-standard cosmological model driven by an exotic scalar field $\phi$ which evolves under the influence of a self-interacting potential; the axion field starts t…
Effective gluon mass and infrared fixed point in QCD
2007
We report on a special type of solutions for the gluon propagator of pure QCD, obtained from the corresponding non-linear Schwinger-Dyson equation formulated in the Feynman gauge of the background field method. These solutions reach a finite value in the deep infrared and may be fitted using a massive propagator, with the crucial characteristic that the effective ``mass'' employed depends on the momentum transfer. Specifically, the gluon mass falls off as the inverse square of the momentum, as expected from the operator-product expansion. In addition, one may define a dimensionless quantity, which constitutes the generalization in a non-Abelian context of the universal QED effective charge.…
Neutrino Mass Ordering from Oscillations and Beyond: 2018 Status and Future Prospects
2018
The ordering of the neutrino masses is a crucial input for a deep understanding of flavor physics, and its determination may provide the key to establish the relationship among the lepton masses and mixings and their analogous properties in the quark sector. The extraction of the neutrino mass ordering is a data-driven field expected to evolve very rapidly in the next decade. In this review, we both analyze the present status and describe the physics of subsequent prospects. Firstly, the different current available tools to measure the neutrino mass ordering are described. Namely, reactor, long-baseline (accelerator and atmospheric) neutrino beams, laboratory searches for beta and neutrinol…
New method for determining the quark-gluon vertex
2014
We present a novel nonperturbative approach for calculating the form factors of the quark-gluon vertex, in a general covariant gauge. The key ingredient of this method is the exact all-order relation connecting the conventional quark-gluon vertex with the corresponding vertex of the background field method, which is Abelian-like. When this latter relation is combined with the standard gauge technique, supplemented by a crucial set of transverse Ward identities, it allows the approximate determination of the nonperturbative behavior of all twelve form factors comprising the quark-gluon vertex, for arbitrary values of the momenta. The actual implementation of this procedure is carried out in …
Inflation, quantum fields, and CMB anisotropies
2009
Revert field Inflationary cosmology has proved to be the most successful at predicting the properties of the anisotropies observed in the cosmic microwave background (CMB). In this essay we show that quantum field renormalization significantly influences the generation of primordial perturbations and hence the expected measurable imprint of cosmological inflation on the CMB. However, the new predictions remain in agreement with observation, and in fact favor the simplest forms of inflation. In the near future, observations of the influence of gravitational waves from the early universe on the CMB will test our new predictions.
Radiative Improvement of the Lattice Nonrelativistic QCD Action Using the Background Field Method and Application to the Hyperfine Splitting of Quark…
2011
We present the first application of the background field method to nonrelativistic QCD (NRQCD) on the lattice in order to determine the one-loop radiative corrections to the coefficients of the NRQCD action in a manifestly gauge-covariant manner. The coefficients of the $\mathbit{\ensuremath{\sigma}}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{B}$ term in the NRQCD action and the four-fermion spin-spin interaction are computed at the one-loop level; the resulting shift of the hyperfine splitting of bottomonium is found to bring the lattice predictions in line with experiment.
LA PARTICIÓN FOCO–TRASFONDO EN LAS ORACIONES INTERROGATIVAS DEL CATALÁN Y DEL ESPAÑOL: ESTUDIO DE CORPUS
2018
El catalán y el español expresan la partición foco-trasfondo (FR) de forma muy diferente (Villalba, 2007, 2011, Leonetti 2011, Planas-Morales y Villalba, 2015), especialmente en las oraciones interrogativas, en las cuales el catalán permite la dislocación a la derecha (DD) del trasfondo, en lugar de la omisión (recuperable por el clítico o la concordancia). Además, el español nunca expresa el trasfondo con la DD, sino que lo representa in situ. En esta comunicación, presentamos un estudio comparativo de corpus que demuestra que la partición FR de las oraciones interrogativas genera diferencias microparamétricas Catalan and Spanish express the focus-background (FB) partition of sentence in a…