10,418 research outputs found

    Coordinate representation for non Hermitian position and momentum operators

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    In this paper we undertake an analysis of the eigenstates of two non self-adjoint operators q^\hat q and p^\hat p similar, in a suitable sense, to the self-adjoint position and momentum operators q^0\hat q_0 and p^0\hat p_0 usually adopted in ordinary quantum mechanics. In particular we discuss conditions for these eigenstates to be {\em biorthogonal distributions}, and we discuss few of their properties. We illustrate our results with two examples, one in which the similarity map between the self-adjoint and the non self-adjoint is bounded, with bounded inverse, and the other in which this is not true. We also briefly propose an alternative strategy to deal with q^\hat q and p^\hat p, based on the so-called {\em quasi *-algebras}.Comment: Accepted in Proceedings of the Royal Society

    Constraints on anomalous gauge couplings from present LEP1 and future LEP2, BNL data

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    We analyze, in a rather general model where anomalous triple gauge couplings are present, the visible effects in Rb_b (measured at LEP1), in W pair production (to be measured at LEP2) and in the muon anomalous magnetic moment (to be measured at BNL). From the combination of the three experiments a remarkable improvement on the pure LEP2 constraints is obtained.Comment: 10 pages and 6 figures. e-mail: [email protected]

    The Hadronic Contribution to the Muon g−2g-2 from Hadron Production in Initial State Radiation Events at the e+e−e^+ e^- Collider DAΦ\PhiNE

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    A relevant reduction of the theoretical uncertainty on the muon anomalous magnetic moment, dominated by the error on the leading hadronic contribution aμha^{\rm h}_\mu, would come from a new precise measurement of the cross section of e+e−e^+e^- annihilation into hadrons (σh\sigma_h) below 1~GeV. An experimental approach to the evaluation of the dispersion integral defining aμha^{\rm h}_\mu is proposed here as an alternative to the conventional method based on the interpolation of different measurements of σh\sigma_h performed with a center of mass energy scan. The wide occurrence of hadron production, at variable q2q^2, in the initial state radiation (ISR) events at the high luminosity ϕ−\phi-factory DAΦ\PhiNE suggests to redefine the dispersion integral in terms of the differential cross section for e+e−→hadrons+γISRe^+e^-\rightarrow hadrons + \gamma_{\rm ISR}. The feasibility of such measurement, which can be performed without the need of dedicated run conditions and with the benefit of the full luminosity of the machine, is discussed. The required precision is shown to be easily achieved thanks to the resolutions and performances of the KLOE detector

    An interoperable ICT tool for asset and maintenance management -Advances in research –

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    Asset and maintenance management needs to store and use much information about the behaviour over time of different building materials, products and components. Service life planning and data capitalization from facility management are only the first steps for an efficient asset management because it is necessary to develop specific ICT tools for life cycle data use and sharing. Managing information related with actual maintenance works and inspection activity (condition assessment) allow handling Building Information Systems and this is fundamental in order to fit the reliability and service life evaluations for maintenance planning. For this reason, an ongoing research activity is developing some methods and tools for Service Life Planning and Management, which can be easily integrated by maintenance data to be used during planning, design, facility and maintenance activities. The aim is to develop an interoperable Life Cycle Management System (LCMS) platform where this kind of data are available and where different stakeholders can store and share information about building and constructed assets. The interoperable LCMS platform can be then used on actual maintenance works management to demonstrate the benefit as for economic (Life Cycle Costs) and environmental achievements (Life Cycle Assessment). This operation has been done according to the international standard for service life planning of building and constructed asset procedures ISO 15686, in particular in conformity with the fifth part on Life-cycle Costing, which allows a cost analysis of the entire building life cycle (maintenance included). Eventually, this ICT-tool is being developed using the standard IFC (Industrial Foundation Classes) of IAI (International Alliance for Interoperability) to define Building Information Models (BIM). In particular, interoperability will be guarantee by sharing file .ifcxml and therefore using eXtensible Mark-up Language (XML). Service life data, maintenance information, costs and each parameter for sustainability have in fact to be matched with Building Information Models attributes, upgrading BIM objects themselves in case of lack of some attributes. This database will be accessible online from a web platform, which is thought to become an interactive footbridge among different stakeholders. As the quantity of collected information will be huge, there are different views of the database according to the stakeholder profile: the aim is to facilitate its use, filtering only useful data for the considered stakeholder, but leaving the possibility to search, visualize and, possibly, modify any other information of the database. Hereafter the advances in research to structure this database and to enhance existing methods and tools for Life Cycle management are described

    Bounds on universal new physics effects from fermion-antifermion production at LEP2

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    We consider lepton-antilepton annihilation into a fermion-antifermion pair at variable c.m. energy. We propose for this process a simple parametrization of the virtual effects of the most general model of new physics of \underline{universal} type. This parametrization is based on a recent approach, that uses the experimental results of LEP1, SLC as theoretical input. It introduces \underline{three} functions whose energy dependence is argued to be smooth and, in first approximation, negligible. A couple of representative models of new physics are considered, as a support of the previous claim. Explicit bounds are then derived for this type of new physics from the available LEP2 data, and a discussion is given of the relevance in this respect of the different experimental measurements. The method is then extended to treat the case of two particularly simple models of {\it non universal} type, for which it is possible to draw analogous conclusions.Comment: 15 pages, 3 tables and 4 figures. e-mail: [email protected]

    Van der Waals and resonance interactions between accelerated atoms in vacuum and the Unruh effect

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    We discuss different physical effects related to the uniform acceleration of atoms in vacuum, in the framework of quantum electrodynamics. We first investigate the van der Waals/Casimir-Polder dispersion and resonance interactions between two uniformly accelerated atoms in vacuum. We show that the atomic acceleration significantly affects the van der Waals force, yielding a different scaling of the interaction with the interatomic distance and an explicit time dependence of the interaction energy. We argue how these results could allow for an indirect detection of the Unruh effect through dispersion interactions between atoms. We then consider the resonance interaction between two accelerated atoms, prepared in a correlated Bell-type state, and interacting with the electromagnetic field in the vacuum state, separating vacuum fluctuations and radiation reaction contributions, both in the free-space and in the presence of a perfectly reflecting plate. We show that nonthermal effects of acceleration manifest in the resonance interaction, yielding a change of the distance dependence of the resonance interaction energy. This suggests that the equivalence between temperature and acceleration does not apply to all radiative properties of accelerated atoms. To further explore this aspect, we evaluate the resonance interaction between two atoms in non inertial motion in the coaccelerated (Rindler) frame and show that in this case the assumption of an Unruh temperature for the field is not required for a complete equivalence of locally inertial and coaccelerated points of views.Comment: 8 pages, Proceedings of the Eighth International Workshop DICE 2016 Spacetime - Matter - Quantum Mechanic

    Effect of boundaries on vacuum field fluctuations and radiation-mediated interactions between atoms

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    In this paper we discuss and review several aspects of the effect of boundary conditions and structured environments on dispersion and resonance interactions involving atoms or molecules, as well as on vacuum field fluctuations. We first consider the case of a perfect mirror, which is free to move around an equilibrium position and whose mechanical degrees of freedom are treated quantum mechanically. We investigate how the quantum fluctuations of the mirror's position affect vacuum field fluctuations for both a one-dimensional scalar and electromagnetic field, showing that the effect is particularly significant in the proximity of the moving mirror. This result can be also relevant for possible gravitational effects, since the field energy density couples to gravity. We stress that this interaction-induced modification of the vacuum field fluctuations can be probed through the Casimir-Polder interaction with a polarizable body, thus allowing to detect the effect of the mirror's quantum position fluctuations. We then consider the effect of an environment such as an isotropic photonic crystal or a metallic waveguide, on the resonance interaction between two entangled identical atoms, one excited and the other in the ground state. We discuss the strong dependence of the resonance interaction with the relative position of the atomic transition frequency with the gap of the photonic crystal in the former case, and with the cut-off frequency of waveguide in the latter.Comment: 8 pages, 2 figures, Proceedings of the Eighth International Workshop DICE 2016 Spacetime - Matter - Quantum Mechanic

    Recent advances in the genetics of idiopathic pulmonary fibrosis

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    Purpose of reviewGenetics contributes substantially to the susceptibility to idiopathic pulmonary fibrosis (IPF). Genetic studies in sporadic and familial disease have identified several IPF-associated variants, mainly in telomere-related and surfactant protein genes.Here, we review the most recent literature on genetics of IPF and discuss how it may contribute to disease pathogenesis.Recent findingsRecent studies implicate genes involved in telomere maintenance, host defence, cell growth, mammalian target of rapamycin signalling, cell-cell adhesion, regulation of TGF-& beta; signalling and spindle assembly as biological processes involved in the pathogenesis of IPF. Both common and rare genetic variants contribute to the overall risk of IPF; however, while common variants (i.e. polymorphisms) account for most of the heritability of sporadic disease, rare variants (i.e. mutations), mainly in telomere-related genes, are the main contributors to the heritability of familial disease. Genetic factors are likely to also influence disease behaviour and prognosis. Finally, recent data suggest that IPF shares genetic associations - and probably some pathogenetic mechanisms - with other fibrotic lung diseases.Common and rare genetic variants are associated with susceptibility and prognosis of IPF. However, many of the reported variants fall in noncoding regions of the genome and their relevance to disease pathobiology remains to be elucidated
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