Groups whose cyclic subgroups have bounded permutability properties

It follows from classical results of Neumann and Macdonald that a group G has finite commuator subgroup if and only if either the normalizers of cyclic subgroups of G have boundedly finite indices or cyclic subgroups of G have bounded indices in their normal closures. In this paper, groups with a similar condition are considered, when normality is replaced by permutability.      

Universality of One-Dimensional Fermi Systems,II. The Luttinger Liquid Structure

We complete the proof started in Benfatto et al. (2014) of the universal Luttinger liquid relations for a general model of spinning fermions on a lattice, by making use of the Ward identities due to asymptotically emerging symmetries. This is done by introducing an effective model verifying extra symmetries and by relating its critical exponents to those of the fermion lattice gas by suitable fine tuning of the parameters.     

Surface studies of novel hydrophobic active carbons

The efficient adsorption of toxic organic species from humid airstreams by active carbons is impeded by the competitive adsorption of water vapour which, at low values of p/p^s, occurs at specific (polar) adsorption sites located at the edges of the carbon layer-planes and at in-plane defects. At higher pressures, adsorption in micropores and mesopores also occurs. The concentration of polar adsorption sites therefore determines the hydrophilicity of the carbon structure and their accelerated formation, by exposure to air and water vapour, is also responsible for the ‘ageing’ of active carbons. Overall, the adsorption of water reduces the volume of porosity available for the adsorption of target species and the hydrophilic nature of active carbons is recognized as a major barrier to their effective use in many applications.We present here results for the adsorption of nitrogen, organic and water vapours by a hydrophobic respirator granular active carbon produced by the thermal treatment of a base carbon, to desorb polar oxygen groups, followed by use of a plasma enhanced chemical vapour deposition (PECVD) treatment to apply a hydrophobic, fluorine containing, surface nanolayer. We show that at equivalent %RH values the treated carbon adsorbs significantly less water compared to an untreated (control) carbon and that the treatment does not reduce the levels of open porosity or impede the adsorption of a range of organic vapours at ambient temperatures. Preliminary evidence for the presence, after treatment, of constrictions at pore entrances which act as molecular gates is also presented. The treated carbon (after ageing for 6 weeks at 80%RH) is shown to have greater adsorptivity than an untreated base carbon toward hexane present in a humid (80%RH) airstream. This results in a 39% increase in break-through time. These hydrophobic properties persist one year after manufacture. The mechanism leading to the modified water adsorption properties is the partial desorption of polar oxygen sites followed by deposition at the external carbon surfaces of hydrophobic plasma polymer species. This reduces the polar surface free energy of the carbon and hence the amount of water adsorption occurring by the primary mechanism. This in turn retards the diffusion of water molecules into the micropores and leads to lower adsorption volumes at higher pressures.     

Optical properties determination at 10.6 μm of thin semiconducting layers

An optical characterization of thin semiconducting multilayers in the infrared range, using a combination ofm-lines and reflection spectroscopy techniques is exposed. Such a method, non-destructive, allows to determine the thickness and the refractive index of each component of a multilayer multimodal planar waveguide.     

First measurement of the rho spectral function in high-energy nuclear collisions

We report on a precision measurement of low-mass muon pairs in 158 AGeV indium-indium collisions at the CERN SPS. A significant excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size of 360,000 dimuons and the good mass resolution of about 2% allow us to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum is consistent with a dominant contribution from pi+pi- -->rho -->mu+mu- annihilation. The associated space-time averaged spectral function shows a strong broadening, but essentially no shift in mass. This may rule out theoretical models linking hadron masses directly to the chiral condensate.     

Tunneling mediated by 2D+1 conical waves in a 1D lattice

The propagation of 2D+1 wave packets in 1D band gap systems shows that the interplay of periodicity and nonlinearity leads to the spontaneous formation of fast and slow conical localized waves. Such nonlinear tunneling has features that differ on the two edges of the band gap and it is characterized by the competition of bullets and nonlinear X waves.     

On a class of metahamiltonian groups

A group is metahamiltonian if all its non-abelian subgroups are normal. It is known that any infinite (generalized) soluble group whose proper subgroups are metahamiltonian is itself metahamiltonian. Moreover, it turns out that the study of soluble groups whose infinite proper subgroups are metahamiltonian can be reduced to the case of a finite extension of a central subgroup of type $p^\infty $ for some prime $p$ . A classification of metahamiltonian groups in this latter class is given.     

A unifying approach to the regularization of Fourier polynomials

In a previous paper [4] the following problem was considered:find, in the class of Fourier polynomials of degree n, the one which minimizes the functional: (0.1) $$J^* [F_n ,\sigma ] = \left\| {f - F_n } \right\|^2 + \sum\limits_{r = 1}^\infty {\frac{{\sigma ^r }}{{r!}}} \left\| {F_n^{(r)} } \right\|^2$$ , where ∥·∥ is theL ² norm,F _n ^(r) is therth derivative of the Fourier polynomialF _n (x), andf(x) is a given function with Fourier coefficientsc _k . It was proved that the optimal polynomial has coefficientsc _k ^* given by (0.2) $$c_k^* = c_k e^{ - \sigma k^2 } ; k = 0, \pm ,..., \pm n$$ . In this paper we consider the more general functional (0.3) $$\hat J[F_n ,\sigma _r ] = \left\| {f - F_n } \right\|^2 + \sum\limits_{r = 1}^\infty {\sigma _r \left\| {F_n^{(r)} } \right\|^2 }$$ , which reduces to (0.1) forσ _r =σ ^r /r!. We will prove that the classical sigma-factor method for the regularization of Fourier polynomials may be obtained by minimizing the functional (0.3) for a particular choice of the weightsσ _r . This result will be used to propose a motivated numerical choice of the parameterσ in (0.1).     

Dynamical iteration schemes for multiscale simulation in nanoelectronics

In this paper we present the spatial discretization of the thermal element model for coupled electrothermal simulation introduced in [1] with a suitable multiscale Finite Element scheme. The structure of the local matrices for the the thermal element is presented in detail and some preliminary numerical results are reported. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)