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Are currency crises self-fulfilling? The case of Argentina
This paper analyzes the 2002 Argentine crisis using the Jeanne and Masson (2000)
model with sunspots. Testing this model empirically through a Markov-switching model
suggests that self-sulfilling prophecies is a reasonable explanation for the devaluation of
the peso
Testing Verlinde's emergent gravity in early-type galaxies
Verlinde derived gravity as an emergent force from the information flow,
through two-dimensional surfaces and recently, by a priori postulating the
entanglement of information in 3D space, he derived the effect of the
gravitational potential from dark matter (DM) as the entropy displacement of
dark energy by baryonic matter. In Emergent Gravity (EG) this apparent DM
depends only on the baryonic mass distribution and the present-day value of the
Hubble parameter. In this paper we test the EG proposition, formalized by
Verlinde for a spherical and isolated mass distribution, using the central
velocity dispersion, and the light distribution in a sample of 4260
massive and local early-type galaxies (ETGs) from the SPIDER sample. Our
results remain unaltered if we consider the sample of 807 roundest field
galaxies. We derive the predictions by EG for the stellar mass-to-light ratio
(M/L) and the Initial Mass Function (IMF), and compare them with the same
inferences derived from a) DM-based models, b) MOND and c) stellar population
models. We demonstrate that, consistently with a classical Newtonian framework
with a DM halo component, or alternative theories of gravity as MOND, the
central dynamics can be fitted if the IMF is assumed non-universal. The results
can be interpreted with a IMF lighter than a standard Chabrier at low-,
and bottom-heavier IMFs at larger . We find lower, but still
acceptable, stellar M/L in EG theory, if compared with the DM-based NFW model
and with MOND. The results from EG are comparable to what is found if the DM
haloes are adiabatically contracted and with expectations from spectral
gravity-sensitive features. If the strain caused by the entropy displacement
would be not maximal, as adopted in the current formulation, then the dynamics
of ETGs could be reproduced with larger M/L. (abridged)Comment: 12 pages, 2 figures, submitted to MNRAS. The updated manuscript
presents significantly altered conclusions, after discovering an internal bug
in an older version of the Mathematica package, leading to incorrect
numerical results when calculating the derivatives of Gamma function
On and Beyond Egor Letov: Rock and Punk Music from (Soviet) Siberia
Nell'articolo si esamina il ruolo giocato dai fenomeni musicali dell'underground siberiano nello sviluppo della musica rock e punk in Russia, prestando particolare attenzione al profilo di Egor Letov e alle sue attività artistiche. L'analisi viene collocata nel quadro più ampio degli studi relativi alla musica rock russa e alla cultura underground sovietica in generale, nonché si approfondisce il contesto siberiano della tarda epoca sovietica
MOND and IMF variations in early-type galaxies from ATLAS3D
MOdified Newtonian dynamics (MOND) represents a phenomenological alternative
to dark matter (DM) for the missing mass problem in galaxies and clusters of
galaxies. We analyze the central regions of a local sample of
early-type galaxies from the survey, to see if the data can be
reproduced without recourse to DM. We estimate dynamical masses in the MOND
context through Jeans analysis, and compare to stellar masses
from stellar population synthesis. We find that the observed stellar
mass--velocity dispersion relation is steeper than expected assuming MOND with
a fixed stellar initial mass function (IMF) and a standard value for the
acceleration parameter . Turning from the space of observables to
model space, a) fixing the IMF, a universal value for cannot be
fitted, while, b) fixing and leaving the IMF free to vary, we find
that it is "lighter" (Chabrier-like) for low-dispersion galaxies, and "heavier"
(Salpeter-like) for high dispersions. This MOND-based trend matches inferences
from Newtonian dynamics with DM, and from detailed analysis of spectral
absorption lines, adding to the converging lines of evidence for a
systematically-varying IMF.Comment: 6 pages, 3 figures, accepted for publication on MNRAS Letters, typos
corrected and further references adde
Colour and stellar population gradients in galaxies
We discuss the colour, age and metallicity gradients in a wide sample of
local SDSS early- and late-type galaxies. From the fitting of stellar
population models we find that metallicity is the main driver of colour
gradients and the age in the central regions is a dominant parameter which
rules the scatter in both metallicity and age gradients. We find a consistency
with independent observations and a set of simulations. From the comparison
with simulations and theoretical considerations we are able to depict a general
picture of a formation scenario.Comment: 4 pages, 4 figures. Proceedings of 54th Congresso Nazionale della
SAIt, Napoli 4-7 May 201
Calibration of a rainfall-runoff model using radar and raingauge data
International audienceSince raingauges give pointwise measurements the small scale variability of rainfall fields leads to biases on the estimation for the rainfall over the whole basin. In this context meteorological radars have several advantages since a single site is able to obtain coverage over a wide area with high temporal and spatial resolution. The purpose of this study is to compare the capability of the two different measurement systems in order to give correct input to drive rainfall-runoff models. Therefore a geomorphological model was calibrated, using firstly raingauge data and secondly radar rainfall estimates, for the Treja river basin. In this way it is possible to determine different sets of parameters and the influence of measurement system in hydrological modelling. The results shown that radar rainfall data is able to improve significantly hydrographs reconstructions
Rainfall thresholds and flood warning: an operative case study
Abstract. An operative methodology for rainfall thresholds definition is illustrated, in order to provide at critical river section optimal flood warnings. Threshold overcoming could produce a critical situation in river sites exposed to alluvial risk and trigger the prevention and emergency system alert. The procedure for the definition of critical rainfall threshold values is based both on the quantitative precipitation observed and the hydrological response of the basin. Thresholds values specify the precipitation amount for a given duration that generates a critical discharge in a given cross section and are estimated by hydrological modelling for several scenarios (e.g.: modifying the soil moisture conditions). Some preliminary results, in terms of reliability analysis (presence of false alarms and missed alarms, evaluated using indicators like hit rate and false alarm rate) for the case study of Mignone River are presented
KiDS0239-3211: A new gravitational quadruple lens candidate
We report the discovery of a candidate to quadrupole gravitationally lensed
system KiDS0239-3211 based on the public data release 3 of the KiDS survey and
machine learning techniques
Evolution of the Mass-Metallicity relations in passive and star-forming galaxies from SPH-cosmological simulations
We present results from SPH-cosmological simulations, including
self-consistent modelling of SN feedback and chemical evolution, of galaxies
belonging to two clusters and twelve groups. We reproduce the mass-metallicity
(ZM) relation of galaxies classified in two samples according to their
star-forming activity, as parametrized by their sSFR, across a redshift range
up to z=2.
Its slope shows irrelevant evolution in the passive sample, being steeper in
groups than in clusters. However, the sub-sample of high-mass passive galaxies
only is characterized by a steep increase of the slope with redshift, from
which it can be inferred that the bulk of the slope evolution of the ZM
relation is driven by the more massive passive objects. (...ABRIDGED...)
The ZM relation for the star-forming sample reveals an increasing scatter
with redshift, indicating that it is still being built at early epochs. The
star-forming galaxies make up a tight sequence in the SFR-M_* plane at high
redshift, whose scatter increases with time alongside with the consolidation of
the passive sequence. We also confirm the anti-correlation between sSFR and
stellar mass, pointing at a key role of the former in determining the galaxy
downsizing, as the most significant means of diagnostics of the star formation
efficiency. Likewise, an anti-correlation between sSFR and metallicity can be
established for the star-forming galaxies, while on the contrary more active
galaxies in terms of simple SFR are also metal-richer.
We discuss these results in terms of the mechanisms driving the evolution
within the high- and low-mass regimes at different epochs: mergers,
feedback-driven outflows and the intrinsic variation of the star formation
efficiency.Comment: Emended list of author
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