9,571 research outputs found
Second fundamental form of the Prym map in the ramified case
In this paper we study the second fundamental form of the Prym map in the ramified case .
We give an expression of it in terms of the second fundamental form of the
Torelli map of the covering curves. We use this expression to give an upper
bound for the dimension of a germ of a totally geodesic submanifold, and hence
of a Shimura subvariety of , contained in the
Prym locus.Comment: To appear in Galois Covers, Grothendieck-Teichmueller Theory and
Dessins d'Enfants - Interactions between Geometry, Topology, Number Theory
and Algebra. Springer Proceedings in Mathematics & Statistics. arXiv admin
note: text overlap with arXiv:1711.0342
Single-species fragmentation: the role of density-dependent feedbacks
Internal feedbacks are commonly present in biological populations and can
play a crucial role in the emergence of collective behavior. We consider a
generalization of Fisher-KPP equation to describe the temporal evolution of the
distribution of a single-species population. This equation includes the
elementary processes of random motion, reproduction and, importantly, nonlocal
interspecific competition, which introduces a spatial scale of interaction.
Furthermore, we take into account feedback mechanisms in diffusion and growth
processes, mimicked through density-dependencies controlled by exponents
and , respectively. These feedbacks include, for instance, anomalous
diffusion, reaction to overcrowding or to rarefaction of the population, as
well as Allee-like effects. We report that, depending on the dynamics in place,
the population can self-organize splitting into disconnected sub-populations,
in the absence of environment constraints. Through extensive numerical
simulations, we investigate the temporal evolution and stationary features of
the population distribution in the one-dimensional case. We discuss the crucial
role that density-dependency has on pattern formation, particularly on
fragmentation, which can bring important consequences to processes such as
epidemic spread and speciation
Iatrogenic Cushing syndrome due to drug interaction between inhaled fluticasone and cobicistat
In this paper we report a case of iatrogenic Cushing syndrome due to a pharmacological interaction between fluticasone and cobicistat. Inhaled corticosteroids were previously thought to be safe, but increasing numbers of cases of iatrogenic Cushing syndrome are being reported, especially in patients taking cytochrome P450 inhibitors, including cobicistat. Although the drug interaction between cobicistat and fluticasone has been described elsewhere, to our knowledge we present one of the first descriptions of iatrogenic Cushing syndrome due to this pharmacological interaction
On some differential-geometric aspects of the Torelli map
In this note we survey recent results on the extrinsic geometry of the
Jacobian locus inside . We describe the second fundamental form
of the Torelli map as a multiplication map, recall the relation between totally
geodesic subvarieties and Hodge loci and survey various results related to
totally geodesic subvarieties and the Jacobian locus.Comment: To appear on Boll. UMI, special volume in memory of Paolo de
Bartolomei
Interplay between bending and stretching in carbon nanoribbons
We investigate the bending properties of carbon nanoribbons by combining
continuum elasticity theory and tight-binding atomistic simulations. First, we
develop a complete analysis of a given bended configuration through continuum
mechanics. Then, we provide by tight-binding calculations the value of the
bending rigidity in good agreement with recent literature. We discuss the
emergence of a stretching field induced by the full atomic-scale relaxation of
the nanoribbon architecture. We further prove that such an in-plane strain
field can be decomposed into a first contribution due to the actual bending of
the sheet and a second one due to edge effects.Comment: 5 pages, 6 figure
AE Aurigae: first detection of non-thermal X-ray emission from a bow shock produced by a runaway star
Runaway stars produce shocks when passing through interstellar medium at
supersonic velocities. Bow shocks have been detected in the mid-infrared for
several high-mass runaway stars and in radio waves for one star. Theoretical
models predict the production of high-energy photons by non-thermal radiative
processes in a number sufficiently large to be detected in X-rays. To date, no
stellar bow shock has been detected at such energies. We present the first
detection of X-ray emission from a bow shock produced by a runaway star. The
star is AE Aur, which was likely expelled from its birthplace by the encounter
of two massive binary systems and now is passing through the dense nebula IC
405. The X-ray emission from the bow shock is detected at 30" to the northeast
of the star, coinciding with an enhancement in the density of the nebula. From
the analysis of the observed X-ray spectrum of the source and our theoretical
emission model, we confirm that the X-ray emission is produced mainly by
inverse Compton upscattering of infrared photons from dust in the shock front.Comment: Accepted for publication in the Astrophysical Journal with number
ApJ, 757, L6. Four figure
Optical Spectroscopy of X-Mega targets in the Carina Nebula - VI. FO 15: a new O-Type double-lined eclipsing binary
We report the discovery of a new O-type double-lined spectroscopic binary
with a short orbital period of 1.4 days. We find the primary component of this
binary, FO 15, to have an approximate spectral type O5.5Vz, i.e. a
Zero-Age-Main-Sequence star. The secondary appears to be of spectral type
O9.5V. We have performed a numerical model fit to the public ASAS photometry,
which shows that FO 15 is also an eclipsing binary. We find an orbital
inclination of ~ 80 deg. From a simultaneous light-curve and radial velocity
solution we find the masses and radii of the two components to be 30 +/- 1 and
16 +/- 1 solar masses and 7.5 +/- 0.5 and 5.3 +/- 0.5 solar radii. These radii,
and hence also the luminosities, are smaller than those of normal O-type stars,
but similar to recently born ZAMS O-type stars. The absolute magnitudes derived
from our analysis locate FO 15 at the same distance as Eta Carinae. From
Chandra and XMM X-ray images we also find that there are two close X-ray
sources, one coincident with FO 15 and another one without optical counterpart.
This latter seems to be a highly variable source, presumably due to a
pre-main-sequence stellar neighbour of FO 15.Comment: 11 pages, 9 figures, 3 tables. Accepted for publication in MNRAS.
Higher resolution version available at
http://lilen.fcaglp.unlp.edu.ar/papers2006.htm
Segal-Bargmann-Fock modules of monogenic functions
In this paper we introduce the classical Segal-Bargmann transform starting
from the basis of Hermite polynomials and extend it to Clifford algebra-valued
functions. Then we apply the results to monogenic functions and prove that the
Segal-Bargmann kernel corresponds to the kernel of the Fourier-Borel transform
for monogenic functionals. This kernel is also the reproducing kernel for the
monogenic Bargmann module.Comment: 11 page
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