19,252 research outputs found

    The Euro changeover and price adjustments in Italy

    Get PDF
    By estimating a staggered price model over the period 1980q1-2010q2, this paper documents that, after the euro changeover, Italian retailers have increased the number of price adjustments, which has translated into a higher inflation rate, with a detrimental effect on the competitiveness of the Italian economy

    Orbit decidability and the conjugacy problem for some extensions of groups

    Full text link
    Given a short exact sequence of groups with certain conditions, 1→F→G→H→11\to F\to G\to H\to 1, we prove that GG has solvable conjugacy problem if and only if the corresponding action subgroup A⩽Aut(F)A\leqslant Aut(F) is orbit decidable. From this, we deduce that the conjugacy problem is solvable, among others, for all groups of the form Z2⋊Fm\mathbb{Z}^2\rtimes F_m, F2⋊FmF_2\rtimes F_m, Fn⋊ZF_n \rtimes \mathbb{Z}, and Zn⋊AFm\mathbb{Z}^n \rtimes_A F_m with virtually solvable action group A⩽GLn(Z)A\leqslant GL_n(\mathbb{Z}). Also, we give an easy way of constructing groups of the form Z4⋊Fn\mathbb{Z}^4\rtimes F_n and F3⋊FnF_3\rtimes F_n with unsolvable conjugacy problem. On the way, we solve the twisted conjugacy problem for virtually surface and virtually polycyclic groups, and give an example of a group with solvable conjugacy problem but unsolvable twisted conjugacy problem. As an application, an alternative solution to the conjugacy problem in Aut(F2)Aut(F_2) is given

    SR-FTiR microscopy and FTIR imaging in the earth sciences

    Full text link
    During the last decades, several books have been devoted to the application of spectroscopic methods in mineralogy. Several short courses and meetings have addressed particular aspects of spectroscopy, such as the analysis of hydrous components in minerals and Earth materials. In these books, complete treatment of the infrared theory and practical aspects of instrumentation and methods, along with an exhaustive list of references, can be found. The present chapter is intended to cover those aspects of infrared spectroscopy that have been developed in the past decade and are not included in earlier reviews such as Volume 18 of Reviews in Mineralogy. These new topics involve primarily: (1) the use of synchrotron radiation (SR), which, although not a routine method, is now rather extensively applied in infrared studies, in particular those requiring ultimate spatial and time resolution and the analysis of extremely small samples (a few tens of micrometers); (2) the development of imaging techniques also for foreseen time resolved studies of geo-mineralogical processes and environmental studies.Comment: 36 pages, 24 figures - Reviews in Mineralogy & Geochemistry - Vol. 78 (2013) in pres

    Modelling the closest double degenerate system RXJ0806.3+1527 and its decreasing period

    Full text link
    In the hypothesis that the 5.4m binary RXJ0806.3+1527 consists of a low mass helium white dwarf (donor) transferring mass towards its more massive white dwarf companion (primary), we consider as possible donors white dwarfs which are the result of common envelope evolution occurring when the helium core mass of the progenitor giant was still very small (~ 0.2Msun), so that they are surrounded by a quite massive hydrogen envelope (~1/100Msun or larger), and live for a very long time supported by proton--proton burning. Mass transfer from such low mass white dwarfs very probably starts during the hydrogen burning stage, and the donor structure will remain dominated by the burning shell until it loses all the hydrogen envelope and begins transferring helium. We model mass transfer from these low mass white dwarfs, and show that the radius of the donor decreases while they shed the hydrogen envelope. This radius behavior, which is due to the fact that the white dwarf is not fully degenerate, has two important consequences on the evolution of the binary: 1) the orbital period decreases, with a timescale consistent with the period decrease of the binary RXJ0806.3+1527; 2) the mass transfer rate is a factor of about 10 smaller than from a fully degenerate white dwarf, easing the problem connected with the small X-ray luminosity of this object. The possibility that such evolution describes the system RXJ0806.3+1527 is also consistent with the possible presence of hydrogen in the optical spectrum of the star, whose confirmation would become a test of the model.Comment: 13 pages, 4 figures, accepted for publication on ApJ, main journa
    • …