29,937 research outputs found
Statistical stability and limit laws for Rovella maps
We consider the family of one-dimensional maps arising from the contracting
Lorenz attractors studied by Rovella. Benedicks-Carleson techniques were used
by Rovella to prove that there is a one-parameter family of maps whose
derivatives along their critical orbits increase exponentially fast and the
critical orbits have slow recurrent to the critical point. Metzger proved that
these maps have a unique absolutely continuous ergodic invariant probability
measure (SRB measure).
Here we use the technique developed by Freitas and show that the tail set
(the set of points which at a given time have not achieved either the
exponential growth of derivative or the slow recurrence) decays exponentially
fast as time passes. As a consequence, we obtain the continuous variation of
the densities of the SRB measures and associated metric entropies with the
parameter. Our main result also implies some statistical properties for these
maps.Comment: 1 figur
An ALMA study of the Orion Integral Filament : I. Evidence for narrow fibers in a massive cloud
© 2018 ESO. Reproduced with permission from Astronomy & Astrophysics. Content in the UH Research Archive is made available for personal research, educational, and non-commercial purposes only. Unless otherwise stated, all content is protected by copyright, and in the absence of an open license, permissions for further re-use should be sought from the publisher, the author, or other copyright holder.Aim. We have investigated the gas organization within the paradigmatic Integral Shape Filament (ISF) in Orion in order to decipher whether or not all filaments are bundles of fibers. Methods. We combined two new ALMA Cycle 3 mosaics with previous IRAM 30m observations to produce a high-dynamic range N 2H + (1-0) emission map of the ISF tracing its high-density material and velocity structure down to scales of 0.009 pc (or ~2000 AU). Results. From the analysis of the gas kinematics, we identify a total of 55 dense fibers in the central region of the ISF. Independently of their location in the cloud, these fibers are characterized by transonic internal motions, lengths of ~0.15 pc, and masses per unit length close to those expected in hydrostatic equilibrium. The ISF fibers are spatially organized forming a dense bundle with multiple hub-like associations likely shaped by the local gravitational potential. Within this complex network, the ISF fibers show a compact radial emission profile with a median FWHM of 0.035 pc systematically narrower than the previously proposed universal 0.1 pc filament width. Conclusions. Our ALMA observations reveal complex bundles of fibers in the ISF, suggesting strong similarities between the internal substructure of this massive filament and previously studied lower-mass objects. The fibers show identical dynamic properties in both low- and high-mass regions, and their widespread detection in nearby clouds suggests a preferred organizational mechanism of gas in which the physical fiber dimensions (width and length) are self-regulated depending on their intrinsic gas density. Combining these results with previous works in Musca, Taurus, and Perseus, we identify a systematic increase of the surface density of fibers as a function of the total mass per-unit-length in filamentary clouds. Based on this empirical correlation, we propose a unified star-formation scenario where the observed differences between low- and high-mass clouds, and the origin of clusters, emerge naturally from the initial concentration of fibers.Peer reviewedFinal Published versio
Dynamics and Constraints of the Massive Gravitons Dark Matter Flat Cosmologies
We discuss the dynamics of the universe within the framework of Massive
Graviton Dark Matter scenario (MGCDM) in which gravitons are geometrically
treated as massive particles. In this modified gravity theory, the main effect
of the gravitons is to alter the density evolution of the cold dark matter
component in such a way that the Universe evolves to an accelerating expanding
regime, as presently observed. Tight constraints on the main cosmological
parameters of the MGCDM model are derived by performing a joint likelihood
analysis involving the recent supernovae type Ia data, the Cosmic Microwave
Background (CMB) shift parameter and the Baryonic Acoustic Oscillations (BAOs)
as traced by the Sloan Digital Sky Survey (SDSS) red luminous galaxies. The
linear evolution of small density fluctuations is also analysed in detail. It
is found that the growth factor of the MGCDM model is slightly different
() from the one provided by the conventional flat CDM
cosmology. The growth rate of clustering predicted by MGCDM and CDM
models are confronted to the observations and the corresponding best fit values
of the growth index () are also determined. By using the expectations
of realistic future X-ray and Sunyaev-Zeldovich cluster surveys we derive the
dark-matter halo mass function and the corresponding redshift distribution of
cluster-size halos for the MGCDM model. Finally, we also show that the Hubble
flow differences between the MGCDM and the CDM models provide a halo
redshift distribution departing significantly from the ones predicted by other
DE models. These results suggest that the MGCDM model can observationally be
distinguished from CDM and also from a large number of dark energy
models recently proposed in the literature.Comment: Accepted for publication in Physical Review D (12 pages, 4 figures
Unparticle inspired corrections to the Gravitational Quantum Well
We consider unparticle inspired corrections of the type
to the Newtonian potential in the context of the
gravitational quantum well. The new energy spectrum is computed and bounds on
the parameters of these corrections are obtained from the knowledge of the
energy eigenvalues of the gravitational quantum well as measured by the GRANIT
experiment.Comment: Revtex4 file, 4 pages, 2 figures and 1 table. Version to match the
one published at Physical Review
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