5,412 research outputs found
Longer aftershocks duration in extensional tectonic settings
Aftershocks number decay through time, depending on several parameters peculiar to each seismogenic regions, including mainshock magnitude, crustal rheology, and stress changes along
the fault. However, the exact role of these parameters in controlling the duration of the aftershock sequence is still unknown. Here, using two methodologies, we show that the tectonic setting primarily controls the duration of aftershocks. On average and for a given mainshock magnitude (1) aftershock sequences are longer and (2) the number of earthquakes is greater in extensional tectonic settings than in contractional ones. We interpret this difference as related to the different type of energy dissipated during earthquakes. In detail, (1) a joint effect of gravitational forces and pure elastic stress release governs extensional earthquakes, whereas (2) pure elastic stress release controls contractional earthquakes. Accordingly, normal faults operate in favour of gravity, preserving inertia for a longer period and seismicity lasts until gravitational equilibrium is reached. Vice versa, thrusts act against gravity, exhaust their inertia faster and the elastic energy dissipation is buffered by the gravitational force. Hence, for seismic sequences of comparable magnitude and rheological parameters, aftershocks last longer in extensional settings because gravity favours the collapse of the hangingwall volumes
Dynamical evolution of V-type photometric candidates in the outer Main-belt
V-type asteroids, characterized by two absorption bands at 1.0 and 2.0 , are usually thought to be portions of the crust of differentiated or
partially differentiated bodies. Most V-type asteroids are found in the inner
main belt and are thought to be current or past members of the Vesta dynamical
family. Recently, several V-type photometric candidates have been identified in
the central and outer main belt.
While the dynamical evolution of V-type photometric candidates in the central
main belt has been recently investigated, less attention has been given to the
orbital evolution of basaltic material in the outer main belt as a whole. Here
we identify known and new V-type photometric candidates in this region, and
study their orbital evolution under the effect of gravitational and
non-gravitational forces. A scenario in which a minimum of three local sources,
possibly associated with the parent bodies of (349) Dembowska, (221) Eos, and
(1459) Magnya, could in principle explain the current orbital distribution of
V-type photometric candidates in the region.Comment: This paper has 6 figures and 1 table. Accepted for publication in
MNRAS. arXiv admin note: text overlap with arXiv:1401.633
Quantum Dynamics of the Taub Universe in a Generalized Uncertainty Principle framework
The implications of a Generalized Uncertainty Principle on the Taub
cosmological model are investigated. The model is studied in the ADM reduction
of the dynamics and therefore a time variable is ruled out. Such a variable is
quantized in a canonical way and the only physical degree of freedom of the
system (related to the Universe anisotropy) is quantized by means of a modified
Heisenberg algebra. The analysis is performed at both classical and quantum
level. In particular, at quantum level, the motion of wave packets is
investigated. The two main results obtained are as follows. i) The classical
singularity is probabilistically suppressed. The Universe exhibits a stationary
behavior and the probability amplitude is peaked in a determinate region. ii)
The GUP wave packets provide the right behavior in the establishment of a
quasi-isotropic configuration for the Universe.Comment: 10 pages, 4 figures; v2: section added, to appear on PR
I Want To Remember
I want to remember
crawling into bed beside you
the way I remember
reading a poem aloud for the first time. ~excerpt from poe
Null test for interactions in the dark sector
Since there is no known symmetry in Nature that prevents a non-minimal
coupling between the dark energy (DE) and cold dark matter (CDM) components,
such a possibility constitutes an alternative to standard cosmology, with its
theoretical and observational consequences being of great interest. In this
paper we propose a new null test on the standard evolution of the dark sector
based on the time dependence of the ratio between the CDM and DE energy
densities which, in the standard CDM scenario, scales necessarily as
. We use the latest measurements of type Ia supernovae, cosmic
chronometers and angular baryonic acoustic oscillations to reconstruct the
expansion history using model-independent Machine Learning techniques, namely,
the Linear Model formalism and Gaussian Processes. We find that while the
standard evolution is consistent with the data at level, some
deviations from the CDM model are found at low redshifts, which may be
associated with the current tension between local and global determinations of
.Comment: 15 pages, 12 figure
Accurate Modeling of Weak Lensing with the sGL Method
We revise and extend the stochastic approach to cumulative weak lensing
(hereafter the sGL method) first introduced in Ref. [1]. Here we include a
realistic halo mass function and density profiles to model the distribution of
mass between and within galaxies, galaxy groups and galaxy clusters. We also
introduce a modeling of the filamentary large-scale structures and a method to
embed halos into these structures. We show that the sGL method naturally
reproduces the weak lensing results for the Millennium Simulation. The strength
of the sGL method is that a numerical code based on it can compute the lensing
probability distribution function for a given inhomogeneous model universe in a
few seconds. This makes it a useful tool to study how lensing depends on
cosmological parameters and its impact on observations. The method can also be
used to simulate the effect of a wide array of systematic biases on the
observable PDF. As an example we show how simple selection effects may reduce
the variance of observed PDF, which could possibly mask opposite effects from
very large scale structures. We also show how a JDEM-like survey could
constrain the lensing PDF relative to a given cosmological model. The updated
turboGL code is available at turboGL.org.Comment: PRD style: 20 pages, 10 figures; replaced to match the improved
version accepted for publication in PRD. The updated turboGL code can be
downloaded at http://www.turbogl.org
Optical spectra of solids obtained by time-dependent density-functional theory with the jellium-with-gap model exchange-correlation kernel
Within the framework of ab initio time-dependent density-functional theory
(TD-DFT), we propose a static approximation to the exchange-correlation kernel
based on the jellium-with-gap model. This kernel accounts for electron-hole
interactions and it is able to address both strongly bound excitons and weak
excitonic effects. TD-DFT absorption spectra of several bulk materials (both
semiconductor and insulators) are reproduced in very good agreement with the
experiments and with a low computational cost.Comment: 5 pages, 3 figures, 1 tabl
Relay I trapped radiation measurements
Radiation measurements of geomagnetically trapped electrons by instruments on Relay I satellite in 196
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