18,754 research outputs found
Root asymptotics of spectral polynomials for the Lame operator
The study of polynomial solutions to the classical Lam\'e equation in its
algebraic form, or equivalently, of double-periodic solutions of its
Weierstrass form has a long history. Such solutions appear at integer values of
the spectral parameter and their respective eigenvalues serve as the ends of
bands in the boundary value problem for the corresponding Schr\"odinger
equation with finite gap potential given by the Weierstrass -function on
the real line. In this paper we establish several natural (and equivalent)
formulas in terms of hypergeometric and elliptic type integrals for the density
of the appropriately scaled asymptotic distribution of these eigenvalues when
the integer-valued spectral parameter tends to infinity. We also show that this
density satisfies a Heun differential equation with four singularities.Comment: final version, to appear in Commun. Math. Phys.; 13 pages, 3 figures,
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La movilización como comunicación: Una contribución latinoamericana al estudio de los movimientos sociales
Many scholars have noted the lack of interdisciplinary dialogue and research between the areas of
social movements studies and that of media and
communications. While social movement studies fail
to fully analyse media practices and communicative
processes in relation to mobilization, in media and
communication the social and political aspects of
mobilization are seldom taken into account when
analysing communication in social movements. This
apparent lack of dialogue is presented in the paper
as a consequence of north-centred theorization in
the fields of social movement studies and media and
communication, which is addressed by spelling out
the contribution of Latin American communication
scholarship and a view of mobilization as anchored in
communication.Muchos académicos han observado la ausencia
de diálogo interdisciplinario entre los estudios
de los movimientos sociales y de los medios y la
comunicación. Mientras que los estudios de los
movimientos sociales no analizan de manera integral
las prácticas mediáticas y los procesos comunicacionales en relación con la movilización, los estudios
de medios y comunicación raras veces toman en
cuenta los aspectos socio-políticos cuando analizan
la comunicación en los movimientos sociales. Este
artículo plantea esa aparente falta de diálogo como una
consecuencia de una teorización eurocéntrica, explica
en detalle la contribución de los estudios latinoamericanos de la comunicación, y propone una visión de la
movilización centrada en la comunicación
ALMA follows streaming of dense gas down to 40 pc from the supermassive black hole in NGC1097
We present a kinematic analysis of the dense molecular gas in the central 200
parsecs of the nearby galaxy NGC1097, based on Cycle 0 observations with the
Atacama Large Millimeter/sub-millimeter Array (ALMA). We use the HCN(4-3) line
to trace the densest interstellar molecular gas, and quantify its kinematics,
and estimate an inflow rate for the molecular gas. We find a striking
similarity between the ALMA kinematic data and the analytic spiral inflow model
that we have previously constructed based on ionized gas velocity fields on
larger scales. We are able to follow dense gas streaming down to 40 pc distance
from the supermassive black hole in this Seyfert 1 galaxy. In order to fulfill
marginal stability, we deduce that the dense gas is confined to a very thin
disc, and we derive a dense gas inflow rate of 0.09 Msun/yr at 40 pc radius.
Combined with previous values from the Ha and CO gas, we calculate a combined
molecular and ionized gas inflow rate of 0.2 Msun/yr at 40 pc distance from the
central supermassive black hole of NGC1097.Comment: Accepted for Publication in the ApJ Letter
On total reality of meromorphic functions
We show that if a meromorphic function of degree at most four on a real
algebraic curve of an arbitrary genus has only real critical points then it is
conjugate to a real meromorphic function after a suitable projective
automorphism of the image.Comment: 13 page
Scalelength of disc galaxies
We have derived disk scale lengths for 30374 non-interacting disk galaxies in
all five SDSS bands. Virtual Observatory methods and tools were used to define,
retrieve, and analyse the images for this unprecedentedly large sample
classified as disk/spiral galaxies in the LEDA catalogue. Cross correlation of
the SDSS sample with the LEDA catalogue allowed us to investigate the variation
of the scale lengths for different types of disk/spiral galaxies. We further
investigat asymmetry, concentration, and central velocity dispersion as
indicators of morphological type, and are able to assess how the scale length
varies with respect to galaxy type. We note however, that the concentration and
asymmetry parameters have to be used with caution when investigating type
dependence of structural parameters in galaxies. Here, we present the scale
length derivation method and numerous tests that we have carried out to
investigate the reliability of our results. The average r-band disk scale
length is 3.79 kpc, with an RMS dispersion of 2.05 kpc, and this is a typical
value irrespective of passband and galaxy morphology, concentration, and
asymmetry. The derived scale lengths presented here are representative for a
typical galaxy mass of , and the RMS dispersion
is larger for more massive galaxies. Distributions and typical trends of scale
lengths have also been derived in all the other SDSS bands with linear
relations that indicate the relation that connect scale lengths in one passband
to another. Such transformations could be used to test the results of
forthcoming cosmological simulations of galaxy formation and evolution of the
Hubble sequence.Comment: Accepter for publication in MNRAS (15 pages, 15 figures, and 3
tables
New Multiplier Sequences via Discriminant Amoebae
In their classic 1914 paper, Polya and Schur introduced and characterized two
types of linear operators acting diagonally on the monomial basis of R[x],
sending real-rooted polynomials (resp. polynomials with all nonzero roots of
the same sign) to real-rooted polynomials. Motivated by fundamental properties
of amoebae and discriminants discovered by Gelfand, Kapranov, and Zelevinsky,
we introduce two new natural classes of polynomials and describe diagonal
operators preserving these new classes. A pleasant circumstance in our
description is that these classes have a simple explicit description, one of
them coinciding with the class of log-concave sequences.Comment: 11 pages, 6 figures. Submitted for publicatio
Classification of Finite Dimensional Modular Lie Superalgebras with Indecomposable Cartan Matrix
Finite dimensional modular Lie superalgebras over algebraically closed fields
with indecomposable Cartan matrices are classified under some technical, most
probably inessential, hypotheses. If the Cartan matrix is invertible, the
corresponding Lie superalgebra is simple otherwise the quotient of the derived
Lie superalgebra modulo center is simple (if its rank is greater than 1).
Eleven new exceptional simple modular Lie superalgebras are discovered. Several
features of classic notions, or notions themselves, are clarified or
introduced, e.g., Cartan matrix, several versions of restrictedness in
characteristic 2, Dynkin diagram, Chevalley generators, and even the notion of
Lie superalgebra if the characteristic is equal to 2. Interesting phenomena in
characteristic 2: (1) all simple Lie superalgebras with Cartan matrix are
obtained from simple Lie algebras with Cartan matrix by declaring several (any)
of its Chevalley generators odd; (2) there exist simple Lie superalgebras whose
even parts are solvable. The Lie superalgebras of fixed points of automorphisms
corresponding to the symmetries of Dynkin diagrams are also listed and their
simple subquotients described
Assessing lidar-based classification schemes for polar stratospheric clouds based on 16 years of measurements at Esrange, Sweden
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License CC BY-NC-ND 3.0 https://creativecommons.org/licenses/by-nc-nd/3.0/, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.Lidar measurements of polar stratospheric clouds (PSCs) are commonly analyzed in classification schemes that apply the backscatter ratio and the particle depolarization ratio. This similarity of input data suggests comparable results of different classification schemes - despite measurements being performed with a variety of mostly custom-made instruments. Based on a time series of 16 years of lidar measurements at Esrange (68°N, 21°E), Sweden, we show that PSC classification differs substantially depending on the applied scheme. The discrepancies result from varying threshold values of lidar-derived parameters used to define certain PSC types. The resulting inconsistencies could impact the understanding of long-term PSC observations documented in the literature. We identify two out of seven considered classification schemes that are most likely to give reliable results and should be used in future lidar-based studies. Using polarized backscatter ratios gives the advantage of increased contrast for observations of weakly backscattering and weakly depolarizing particles. Improved confidence in PSC classification can be achieved by a more comprehensive consideration of the effect of measurement uncertainties. The particle depolarization ratio is the key to a reliable identification of different PSC types. Hence, detailed information on the calibration of the polarization-sensitive measurement channels should be provided to assess the findings of a study. Presently, most PSC measurements with lidar are performed at 532 nm only. The information from additional polarization-sensitive measurements in the near infrared could lead to an improved PSC classification. Coincident lidar-based temperature measurements at PSC level might provide useful information for an assessment of PSC classification. Key Points Assessment of PSC classification schemes Statistical analysis of PSC observations Recommendations for lidar-based PSC studiesPeer reviewe
Articulation rate in Swedish child-directed speech increases as a function of the age of the child even when surprisal is controlled for
In earlier work, we have shown that articulation rate in Swedish
child-directed speech (CDS) increases as a function of the age of the child,
even when utterance length and differences in articulation rate between
subjects are controlled for. In this paper we show on utterance level in
spontaneous Swedish speech that i) for the youngest children, articulation rate
in CDS is lower than in adult-directed speech (ADS), ii) there is a significant
negative correlation between articulation rate and surprisal (the negative log
probability) in ADS, and iii) the increase in articulation rate in Swedish CDS
as a function of the age of the child holds, even when surprisal along with
utterance length and differences in articulation rate between speakers are
controlled for. These results indicate that adults adjust their articulation
rate to make it fit the linguistic capacity of the child.Comment: 5 pages, Interspeech 201
The Extremely Young Star Cluster Population In Haro 11
We have performed a deep multi-band photometric analysis of the star cluster
population of Haro 11. This starburst galaxy (log L_FUV = 10.3 L_sun) is
considered a nearby analogue of Lyman break galaxies (LBGs) at high redshift.
The study of the numerous star clusters in the systems is an effective way to
investigate the formation and evolution of the starburst phase. In fact, the
SED fitting models have revealed a surprisingly young star cluster population,
with ages between 0.5 and 40 Myr, and estimated masses between 10^3 and 10^7
solar masses. An independent age estimation has been done with the EW(Halpha)
analysis of each cluster. This last analysis has confirmed the young ages of
the clusters. We noticed that the clusters with ages between 1 and 10 Myr show
a flux excess in H (NIC3/F160W) and/or I (WFPC2/F814W) bands with respect to
the evolutionary models. Once more Haro 11 represents a challenge to our
understanding.Comment: 4 pages, 3 figures. To appear in the proceedings of "Galaxy Wars:
Stellar Populations and Star Formation in Interacting Galaxies" (Tennessee,
July 09
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