Universal equilibrium distribution after a small quantum quench

A sudden change of the Hamiltonian parameter drives a quantum system out of equilibrium. For a finite-size system, expectations of observables start fluctuating in time without converging to a precise limit. A new equilibrium state emerges only in probabilistic sense, when the probability distribution for the observables expectations over long times concentrate around their mean value. In this paper we study the full statistic of generic observables after a small quench. When the quench is performed around a regular (i.e. non-critical) point of the phase diagram, generic observables are expected to be characterized by Gaussian distribution functions (``good equilibration''). Instead, when quenching around a critical point a new universal double-peaked distribution function emerges for relevant perturbations. Our analytic predictions are numerically checked for a non-integrable extension of the quantum Ising model.Comment: 4 pages, 2 figure

The CorDis Corpus Mark-up and Related Issues

CorDis is a large, XML, TEI-conformant, POS-tagged, multimodal, multigenre corpus representing a significant portion of the political and media discourse on the 2003 Iraqi conflict. It was generated from different sub-corpora which had been assembled by various research groups, ranging from official transcripts of Parliamentary sessions, both in the US and the UK, to the transcripts of the Hutton Inquiry, from American and British newspaper coverage of the conflict to White House press briefings and to transcriptions of American and British TV news programmes. The heterogeneity of the data, the specificity of the genres and the diverse discourse analytical purposes of different groups had led to a wide range of coding strategies being employed to make textual and meta-textual information retrievable. The main purpose of this paper is to show the process of harmonisation and integration whereby a loose collection of texts has become a stable architecture. The TEI proved a valid instrument to achieve standardisation of mark-up. The guidelines provide for a hierarchical organisation which gives the corpus a sound structure favouring replicability and enhancing the reliability of research. In discussing some examples of the problems encountered in the annotation, we will deal with issues like consistency and re-usability, and will examine the constraints imposed on data handling by specific research objectives. Examples include the choice to code the same speakers in different ways depending on the various (institutional) roles they may assume throughout the corpus, the distinction between quotations of spoken or written discourse and quotations read aloud in the course of a spoken text, and the segmentation of portions of news according to participants interaction and use of camera/voiceover

Wet Refractivity tomographic reconstruction over small areas using an ad-hoc GPS receivers network

One of the most attractive scientific issues in the use of GNSS (Global Navigation Satellite System) signal from a meteorological point of view, is the retrieval of high resolution tropospheric water vapour maps. The real-time (or quasi real-time) knowledge of such distributions could be very useful for several applications, from operative meteorology to atmospheric modeling. Moreover, the exploitation of wet refractivity field reconstruction techniques can be used for atmospheric delay compensation purposes and, as a very promising activity, it could be applied for example to calibrate SAR or Interferometric-SAR (In-SAR) observations for land remote sensing. This is in fact one of the objectives of the European Space Agency project METAWAVE (Mitigation of Electromagnetic Transmission errors induced by Atmospheric Water vapour Effects), in which several techniques were investigated and results were compared to identify a strategy to remove the contribution of water vapour induced propagation delays in In-SAR products. Within this project, the tomographic reconstruction of three dimensional wet refractivity fields on a small atmospheric volume (16km x 20 km x 10 km height, from 2 km to 4 km horizontal resolution and 1 km vertical resolution), was performed considering real tropospheric delays observations acquired by a GNSS network (9 dual frequency GPS receivers) deployed over Como area (Italy), during 12-18 October, 2008. Acquired L1 and L2 carrier phase observations have been processed in terms of hourly averaged Zenith Wet Delays. These vertical informations have been mapped along the correspondent line of sights (by up-sampling at 30 second sample times the 15 minutes GPS satellites positions obtained from IGS files) and inverted using a tomographic procedure. The used algorithm performs a first reconstruction (namely, the tomographic pre-processing) based on generalized inversion mechanisms, in order to define a low resolution first guess for the following step. This second step inverts GPS observables using a more refined algebraic tomographic reconstruction algorithm, in order to improve both vertical and horizontal resolution. Despite limitations due to the network design, internal consistency tests prove the efficiency of the adopted tomographic approach: the rms of the difference between reconstructed and GNSS observed Zenith Wet Delays (ZWD) are in the order of 4 mm. A good agreement is also observed between our ZWDs and corresponding delays obtained by vertically integrating independent wet refractivity fields, taken by co-located meteorological analysis. Finally, during the observing period, reconstructed vertical wet refractivity profiles evolution reveals water vapour variations induced by simple cloud covering. Even if our main goal was to demonstrate the effectiveness in adopting tomographic reconstruction procedures for the evaluation of propagation delays inside water vapour fields, the actual water vapour vertical variability and its evolution with time is well reproduced, demonstrating also the effectiveness of the inferred 3D wet refractivity fields. Even if results obtained were satisfactory, limitations due to the observation geometry, to the GNSS propagation delay information extraction form observables and to the applied tomographic technique will be highlighted, in order to trace the road-map toward future improvements in this challenging fiel