Of Higgs, Unitarity and other Questions

On the verge of conclusive checks on the Standard Model by the LHC, we discuss some of the basic assumptions. The reason for this analysis stems from a recent proposal of an Electroweak Model based on a nonlinearly realized gauge group SU(2) X U(1), where, in the perturbative approximation, there is no Higgs boson. The model enjoys the Slavnov-Taylor identities and therefore the perturbative unitarity. On the other hand, it is commonly believed that the existence of the Higgs boson is entangled with the property of unitarity, when high energy processes are considered. The argument is based mostly on the Froissart bound and on the Equivalence Theorem. In this talk we briefly review some of our objections on the validity of such arguments. Some open questions are pointed out, in particular on the limit of zero mass for the vector mesons and on the fate of the longitudinal polarizations.Comment: 23 pages, 1 figure, presented by Ruggero Ferrari at the International Conference "Gauge Fields. Yesterday, Today, Tomorrow" in honor of A.A. Slavnov. Moscow, January 19-24 201

Heavy top renormalon contribution to fermion propagators

We study resummed perturbative contributions due to a heavy top-quark. These renormalon contributions are evaluated for fermion propagators. Results for the top-quark width are given. Estimates of non-perturbative uncertainties are made on the \rho-parameter using different schemes of dealing with the Landau-pole. For the physical top-quark mass the effects are negligible.Comment: 30 pages, 14 figures, 1 table; v2: Ref.19 added, typos corrected, final version published in PR

Resummed corrections to the \rho parameter due to a finite width of the top quark

We perform an all-order calculation of the \rho parameter in a simplified framework, where the top propagator can be calculated exactly. Special emphasis is placed on the question of gauge invariance and the treatment of non-perturbative cut-off effects.Comment: 21 pages, 4 figures, 1 table, typos corrected, final version published by Phys. Rev.

The Algebra of Physical Observables in Nonlinearly Realized Gauge Theories

We classify the physical observables in spontaneously broken nonlinearly realized gauge theories in the recently proposed loopwise expansion governed by the Weak Power-Counting (WPC) and the Local Functional Equation. The latter controls the non-trivial quantum deformation of the classical nonlinearly realized gauge symmetry, to all orders in the loop expansion. The Batalin-Vilkovisky (BV) formalism is used. We show that the dependence of the vertex functional on the Goldstone fields is obtained via a canonical transformation w.r.t. the BV bracket associated with the BRST symmetry of the model. We also compare the WPC with strict power-counting renormalizability in linearly realized gauge theories. In the case of the electroweak group we find that the tree-level Weinberg relation still holds if power-counting renormalizability is weakened to the WPC condition.Comment: 20 pages, 1 figur

A Massive Yang-Mills Theory based on the Nonlinearly Realized Gauge Group

We propose a subtraction scheme for a massive Yang-Mills theory realized via a nonlinear representation of the gauge group (here SU(2)). It is based on the subtraction of the poles in D-4 of the amplitudes, in dimensional regularization, after a suitable normalization has been performed. Perturbation theory is in the number of loops and the procedure is stable under iterative subtraction of the poles. The unphysical Goldstone bosons, the Faddeev-Popov ghosts and the unphysical mode of the gauge field are expected to cancel out in the unitarity equation. The spontaneous symmetry breaking parameter is not a physical variable. We use the tools already tested in the nonlinear sigma model: hierarchy in the number of Goldstone boson legs and weak power-counting property (finite number of independent divergent amplitudes at each order). It is intriguing that the model is naturally based on the symmetry SU(2)_L local times SU(2)_R global. By construction the physical amplitudes depend on the mass and on the self-coupling constant of the gauge particle and moreover on the scale parameter of the radiative corrections. The Feynman rules are in the Landau gauge.Comment: 44 pages, 1 figure, minor changes, final version accepted by Phys. Rev.

Distance statistics in large toroidal maps

We compute a number of distance-dependent universal scaling functions characterizing the distance statistics of large maps of genus one. In particular, we obtain explicitly the probability distribution for the length of the shortest non-contractible loop passing via a random point in the map, and that for the distance between two random points. Our results are derived in the context of bipartite toroidal quadrangulations, using their coding by well-labeled 1-trees, which are maps of genus one with a single face and appropriate integer vertex labels. Within this framework, the distributions above are simply obtained as scaling limits of appropriate generating functions for well-labeled 1-trees, all expressible in terms of a small number of basic scaling functions for well-labeled plane trees.Comment: 24 pages, 9 figures, minor corrections, new added reference

Bandgap behavior and singularity of the domain-induced light scattering through the pressure-induced ferroelectric transition in relaxor ferroelectric A(x)Ba(1-x)Nb(2)O(6) (A: Sr,Ca)

[EN] In this letter, we have investigated the electronic structure of A(x)Ba(1-x)Nb(2)O(6) relaxor ferroelectrics on the basis of optical absorption spectroscopy in unpoled single crystals with A = Sr and Ca under high pressure. The direct character of the fundamental transition could be established by fitting Urbach's rule to the photon energy dependence of the absorption edge yielding bandgaps of 3.44(1) eV and 3.57(1) eV for A = Sr and Ca, respectively. The light scattering by ferroelectric domains in the pre-edge spectral range has been studied as a function of composition and pressure. After confirming with x-ray diffraction the occurrence of the previously observed ferroelectric to paraelelectric phase transition at 4 GPa, the light scattering produced by micro-and nano-ferroelectric domains at 3.3 eV in Ca0.28Ba0.72Nb2O6 has been probed. The direct bandgap remains virtually constant under compression with a drop of only 0.01 eV around the phase transition. Interestingly, we have also found that light scattering by the polar nanoregions in the paraelectric phase is comparable to the dispersion due to ferroelectric microdomains in the ferroelectric state. Finally, we have obtained that the bulk modulus of the ferroelectric phase of Ca0.28Ba0.72Nb2O6 is B-0 = 222(9) GPa. Published by AIP Publishing.J.R.-F. acknowledges the Spanish MINECO for the Juan de la Cierva (IJCI-2014-20513) Program and Dr. Bayarjargal from the Goethe-Universitat Frankfurt for providing the CBN28 samples. This work was supported by Spanish MINECO under Grant No. MAT2016-75586-C4-1-P/2-P. The high pressure x-ray diffraction experiments were performed at MSPD beamline at ALBA Synchrotron (Project 2016021588) with the collaboration of ALBA staff.Ruiz-Fuertes, J.; Gomis, O.; Segura, A.; Bettinelli, M.; Burianek, M.; Muehlberg, M. (2018). Bandgap behavior and singularity of the domain-induced light scattering through the pressure-induced ferroelectric transition in relaxor ferroelectric A(x)Ba(1-x)Nb(2)O(6) (A: Sr,Ca). Applied Physics Letters. 112(4). https://doi.org/10.1063/1.5012111S112

Lifting the Gribov ambiguity in Yang-Mills theories

We propose a new one-parameter family of Landau gauges for Yang-Mills theories which can be formulated by means of functional integral methods and are thus well suited for analytic calculations, but which are free of Gribov ambiguities and avoid the Neuberger zero problem of the standard Faddeev-Popov construction. The resulting gauge-fixed theory is perturbatively renormalizable in four dimensions and, for what concerns the calculation of ghost and gauge field correlators, it reduces to a massive extension of the Faddeev-Popov action. We study the renormalization group flow of this theory at one-loop and show that it has no Landau pole in the infrared for some - including physically relevant - range of values of the renormalized parameters.Comment: 8 pages, 1 figure; published version (PLB), minor corrections, references adde

Living with Gitelman disease: an insight into patients' daily experiences

Background Gitelman disease presents with musculoskeletal complaints and fatigue. Surprisingly, there is no clear-cut correlation between biochemical abnormalities and symptoms. Methods Starting from the hypothesis that the way patients comprehend their illness within their sociocultural frameworks reflects on their way of adapting to it, this study investigated how adult patients experience the disease in everyday life. We conducted a qualitative analysis based on interviews with 12 patients. Interviews were audio recorded, fully transcribed and analyzed using the constant comparative method described by Strauss and Corbin. Results A typology of the experiences emerged from the data and was tested on each transcript with an explicit search for disconfirming cases. Patients fell into four main groups: (i) those considering Gitelman disease a disabling illness, (ii) those considering it a normalized illness, (iii) those considering it a different normality and (iv) those considering it an episodic disability. Each pattern of experience was characterized by particular (i) ways of interpreting symptoms (ii) ways of managing Gitelman disease in everyday life, (iii) general lifestyles and (iv) risks for the patient's psychosocial life. Conclusions These findings suggest that health care providers should take advantage of considering patients' own perception of the disease in order to adjust the care and advice provide