1,289 research outputs found

    A homomorphism between link and XXZ modules over the periodic Temperley-Lieb algebra

    Full text link
    We study finite loop models on a lattice wrapped around a cylinder. A section of the cylinder has N sites. We use a family of link modules over the periodic Temperley-Lieb algebra EPTL_N(\beta, \alpha) introduced by Martin and Saleur, and Graham and Lehrer. These are labeled by the numbers of sites N and of defects d, and extend the standard modules of the original Temperley-Lieb algebra. Beside the defining parameters \beta=u^2+u^{-2} with u=e^{i\lambda/2} (weight of contractible loops) and \alpha (weight of non-contractible loops), this family also depends on a twist parameter v that keeps track of how the defects wind around the cylinder. The transfer matrix T_N(\lambda, \nu) depends on the anisotropy \nu and the spectral parameter \lambda that fixes the model. (The thermodynamic limit of T_N is believed to describe a conformal field theory of central charge c=1-6\lambda^2/(\pi(\lambda-\pi)).) The family of periodic XXZ Hamiltonians is extended to depend on this new parameter v and the relationship between this family and the loop models is established. The Gram determinant for the natural bilinear form on these link modules is shown to factorize in terms of an intertwiner i_N^d between these link representations and the eigenspaces of S^z of the XXZ models. This map is shown to be an isomorphism for generic values of u and v and the critical curves in the plane of these parameters for which i_N^d fails to be an isomorphism are given.Comment: Replacement of "The Gram matrix as a connection between periodic loop models and XXZ Hamiltonians", 31 page

    Paradiso como proyecto político

    Get PDF
    Rather than being apolitical, José Lezama's Paradiso conceives the political at another level, in an aesthetic realm of friendship and conviviality set up by writing. The posthumous second volume of Paradiso, Oppiano Licario, is brought into an analysis of the literary republic of friendship postulated as an alternative to the heroic nationalist politics of the Cuban Revolution

    Validity of the Adiabatic Approximation

    Full text link
    We analyze the validity of the adiabatic approximation, and in particular the reliability of what has been called the "standard criterion" for validity of this approximation. Recently, this criterion has been found to be insufficient. We will argue that the criterion is sufficient only when it agrees with the intuitive notion of slowness of evolution of the Hamiltonian. However, it can be insufficient in cases where the Hamiltonian varies rapidly but only by a small amount. We also emphasize the distinction between the adiabatic {\em theorem} and the adiabatic {\em approximation}, two quite different although closely related ideas.Comment: 4 pages, 1 figur

    El doble del bárbaro: Joserramón Meléndes

    Get PDF
    This exegesis of the book Contraqelarre (2010) by Puerto Rican poet Joserramón Melendes argues that his writing challenges the aesthetic sovereignty of Western Modernism precisely by 'doubling' it and thus inoculating it with his difference as a marginal, 'uncivilized' Caribbean writer

    Using 21-cm absorption surveys to measure the average HI spin temperature in distant galaxies

    Full text link
    We present a statistical method for measuring the average HI spin temperature in distant galaxies using the expected detection yields from future wide-field 21cm absorption surveys. As a demonstrative case study we consider a simulated all-southern-sky survey of 2-h per pointing with the Australian Square Kilometre Array Pathfinder for intervening HI absorbers at intermediate cosmological redshifts between z=0.4z = 0.4 and 11. For example, if such a survey yielded 10001000 absorbers we would infer a harmonic-mean spin temperature of T‾spin∼100\overline{T}_\mathrm{spin} \sim 100K for the population of damped Lyman α\alpha (DLAs) absorbers at these redshifts, indicating that more than 5050 per cent of the neutral gas in these systems is in a cold neutral medium (CNM). Conversely, a lower yield of only 100 detections would imply T‾spin∼1000\overline{T}_\mathrm{spin} \sim 1000K and a CNM fraction less than 1010 per cent. We propose that this method can be used to provide independent verification of the spin temperature evolution reported in recent 21cm surveys of known DLAs at high redshift and for measuring the spin temperature at intermediate redshifts below z≈1.7z \approx 1.7, where the Lyman-α\alpha line is inaccessible using ground-based observatories. Increasingly more sensitive and larger surveys with the Square Kilometre Array should provide stronger statistical constraints on the average spin temperature. However, these will ultimately be limited by the accuracy to which we can determine the HI column density frequency distribution, the covering factor and the redshift distribution of the background radio source population.Comment: 11 pages, 9 figures, 1 table. Proof corrected versio

    Por un comunismo literario

    Get PDF
    Draws on Jean-Luc Nancy's essay on "literary Communism" in order to relate contemporary literary criticism to the critique of the communist failure in the twentieth century and the posing a of a non-immanent and non-transcendental, non-Utopian literary politics
    • …