1,156 research outputs found
Right-handed lepton mixings at the LHC
We study how the elements of the leptonic right-handed mixing matrix can be
determined at the LHC in the minimal Left-Right symmetric extension of the
standard model. We do it by explicitly relating them with physical quantities
of the Keung-Senjanovi\'c process and the lepton number violating decays of the
right doubly charged scalar. We also point out that the left and right doubly
charged scalars can be distinguished at the LHC, without measuring the
polarization of the final state leptons coming from their decays.Comment: 12 pages, 6 figures, discussion in section III expanded and
sharpened, one appendix added, updated reference
Spike trains statistics in Integrate and Fire Models: exact results
We briefly review and highlight the consequences of rigorous and exact
results obtained in \cite{cessac:10}, characterizing the statistics of spike
trains in a network of leaky Integrate-and-Fire neurons, where time is discrete
and where neurons are subject to noise, without restriction on the synaptic
weights connectivity. The main result is that spike trains statistics are
characterized by a Gibbs distribution, whose potential is explicitly
computable. This establishes, on one hand, a rigorous ground for the current
investigations attempting to characterize real spike trains data with Gibbs
distributions, such as the Ising-like distribution, using the maximal entropy
principle. However, it transpires from the present analysis that the Ising
model might be a rather weak approximation. Indeed, the Gibbs potential (the
formal "Hamiltonian") is the log of the so-called "conditional intensity" (the
probability that a neuron fires given the past of the whole network). But, in
the present example, this probability has an infinite memory, and the
corresponding process is non-Markovian (resp. the Gibbs potential has infinite
range). Moreover, causality implies that the conditional intensity does not
depend on the state of the neurons at the \textit{same time}, ruling out the
Ising model as a candidate for an exact characterization of spike trains
statistics. However, Markovian approximations can be proposed whose degree of
approximation can be rigorously controlled. In this setting, Ising model
appears as the "next step" after the Bernoulli model (independent neurons)
since it introduces spatial pairwise correlations, but not time correlations.
The range of validity of this approximation is discussed together with possible
approaches allowing to introduce time correlations, with algorithmic
extensions.Comment: 6 pages, submitted to conference NeuroComp2010
http://2010.neurocomp.fr/; Bruno Cessac
http://www-sop.inria.fr/neuromathcomp
Resummation in QFT with Meijer G-functions
We employ a recent resummation method to deal with divergent series, based on
the Meijer G-function, which gives access to the non-perturbative regime of any
QFT from the first few known coefficients in the perturbative expansion. Using
this technique, we consider in detail the model where we estimate the
non-perturbative function and prove that its asymptotic behavior
correctly reproduces instantonic effects calculated using semiclassical
methods. After reviewing the emergence of the renormalons in this theory, we
also speculate on how one can resum them. Finally, we resum the
non-perturbative function of abelian and non-abelian gauge-fermion
theories and analyze the behavior of these theories as a function of the number
of fermion flavors. While in the former no fixed points are found, in the
latter, a richer phase diagram is uncovered and illustrated by the regions of
confinement, large-distance conformality, and asymptotic safety.Comment: 22 pages, 10 figures, final version with minor changes, as accepted
in NP
Time-reversal symmetry violation in several Lepton-Flavor-Violating processes
We compute a T-odd triple vector correlation for the decay and the conversion process. We find simple results
in terms of the CP violating phases of the effective Hamiltonians. Then we
focus on the minimal Left-Right symmetric extension of the Standard Model,
which can lead to an appreciable correlation. We show that under rather general
assumptions, this correlation can be used to discriminate between Parity or
Charge-conjugation as the discrete Left-Right symmetry.Comment: 22 pages, 5 figures. Comments added. Sections 5 and 6 expanded.
Appendices A and B expanded, accepted for publication in JHE
La réforme des forces de police au Canada : les tensions entre la sécurité des citoyens, les libertés fondamentales et le fédéralisme
Cet article envisage les politiques en matière de sécurité citoyenne et la réforme des forces de police au Canada pendant les 25 dernières années. La Charte canadienne des droits et libertés a établi dans l’article 7 la garantie à la « sécurité de la personne ». La poursuite de cette garantie a supposé, d’une part, une tension entre la décentralisation, le désengagement de l’État et le rôle de la police et, d’autre part, une tension entre son mandat de préserver l’ordre public, entendu comme la sauvegarde de l’État, et la protection des citoyens. Même si ces tensions se révèlent problématiques, elles n’ont pas empêché que le Canada soit un pays sûr dont le taux de criminalité est bas et où règne un important sentiment de sécurité parmi les citoyens.This article looks at policies concerning citizen security and reform among Canada's police forces during the last twenty-five years. Article 7 of the Canadian Charter of Rights and Freedoms established a guarantee of "security of the person". Pursuit of this guarantee has supposed, on one hand, a tension between decentralization, withdrawal of the State, and the role of police, and on the other hand, a tension between the Charter's mandate to preserve public order, understood as the safeguard of the State, and the protection of citizens. Even if revealed as problematic, these tensions did not prevent Canada from being a confident country with low crime rates and a heightened sense of security among its citizens
Phenomenology of the right-handed lepton mixings at the LHC in LR symmetric theory and the Time-Reversal symmetry violation in the \ub5 --> e\u3d2 decay and \ub5 --> e conversion process
We study how the elements of the leptonic right-handed mixing matrix can be determined at the LHC in the minimal Left-Right symmetric extension of the standard model. We do it by explicitly relating them with physical quantities of the Keung-Senjanovi\'c process and the lepton number violating decays of the right doubly charged scalar. We also point out that the left and right doubly charged scalars can be distinguished at the LHC, without measuring the polarization of the final state leptons coming from their decays.
Then we study time reversal symmetry violation in the decay and the conversion process and compute a T-odd triple vector correlation for the
decay and the conversion process,
finding simple results in terms of the CP violating phases of the effective
Hamiltonians. Finally we focus on the minimal Left-Right symmetric extension of
the
Standard Model, which is a complete model of neutrino masses that can lead to an appreciable correlation. We show that under
rather general assumptions, this correlation can be used to discriminate between
Parity or Charge-conjugation as the discrete Left-Right
symmetry
A consistent quantum field theory from dimensional reduction
We incorporate the concept of dimensional reduction at high energies within
the perturbative formulation of quantum field theory. In this new framework,
space and momentum integrations are modified by a weighting function
incorporating an effective mass energy associated with the dimensional
reduction scale. We quantize the theory within canonical formalism. We then
show that it can be made finite in perturbation theory, free of renormalon
ambiguities, and with better analytic behavior for infinitesimal coupling
constant compared to standard quantum field theory. The new approach reproduces
the known results at low energies. One key feature of this class of models is
that the coupling constant always reaches a fixed point in the ultraviolet
region, making the models ultra-violet complete.Comment: to appear in J. Phys. A Math. Theo
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