890 research outputs found
Multi-particle quantum chaos in tilted optical lattices
We show that, in the parameter regime of state of the art experiments on Bose
Einstein Condensates loaded into optical lattices, the energy spectrum of the
1D Bose-Hubbard model amended by a static field exhibits unambiguous signatures
of quantum chaos. In the dynamics, this leads to the irreversible decay of
Bloch oscillations.Comment: 3 pages, 3 figur
Genericity of blackhole formation in the gravitational collapse of homogeneous self-interacting scalar fields
The gravitational collapse of a wide class of self-interacting homogeneous
scalar fields models is analyzed. The class is characterized by certain general
conditions on the scalar field potential, which, in particular, include both
asymptotically polynomial and exponential behaviors. Within this class, we show
that the generic evolution is always divergent in a finite time, and then make
use of this result to construct radiating star models of the Vaidya type. It
turns out that blackholes are generically formed in such models.Comment: 18 pages, 4 figure
Thirty years of the heart as an endocrine organ: physiological role and clinical utility of cardiac natriuretic hormones
Thirty years ago, De Bold et al. ( 20 ) reported that atrial extracts contain some biologically active peptides, which promote a rapid and massive diuresis and natriuresis when injected in rats. It is now clear that the heart also exerts an endocrine function and in this way plays a key role in the regulation of cardiovascular and renal systems. The aim of this review is to discuss some recent insights and still-debated findings regarding the cardiac natriuretic hormones (CNHs) produced and secreted by cardiomyocytes (i.e., atrial natriuretic peptide and B-type natriuretic peptide). The functional status of the CNH system depends not only on the production/secretion of CNHs by cardiomyocytes but also on both the peripheral activation of circulating inactive precursor of natriuretic hormones and the transduction of the hormone signal by specific receptors. In this review, we will discuss the data supporting the hypothesis that the production and secretion of CNHs is the result of a complex integration among mechanical, chemical, hemodynamic, humoral, ischemic, and inflammatory inputs. The cross talk among endocrine function, adipose tissue, and sex steroid hormones will be discussed more in detail, considering the clinically relevant relationships linking together cardiovascular risk, sex, and body fat development and distribution. Finally, we will review the pathophysiological role and the clinical relevance of both peripheral maturation of the precursor of B-type natriuretic peptides and hormone signal transduction . </jats:p
Sufficient condition for Blackhole formation in spherical gravitational collapse
A sufficient condition for the validity of Cosmic Censorship in spherical
gravitational collapse is formulated and proved. The condition relies on an
attractive mathematical property of the apparent horizon, which holds if
''minimal'' requirements of physical reasonableness are satisfied by the matter
model.Comment: 5 pages, LaTeX2
Quantum Chaos in the Bose-Hubbard model
We present a numerical study of the spectral properties of the 1D
Bose-Hubbard model. Unlike the 1D Hubbard model for fermions, this system is
found to be non-integrable, and exhibits Wigner-Dyson spectral statistics under
suitable conditions.Comment: 4 pages, 4 figure
A Morse-theoretical analysis of gravitational lensing by a Kerr-Newman black hole
Consider, in the domain of outer communication of a Kerr-Newman black hole, a
point (observation event) and a timelike curve (worldline of light source).
Assume that the worldline of the source (i) has no past end-point, (ii) does
not intersect the caustic of the past light-cone of the observation event, and
(iii) goes neither to the horizon nor to infinity in the past. We prove that
then for infinitely many positive integers k there is a past-pointing lightlike
geodesic of (Morse) index k from the observation event to the worldline of the
source, hence an observer at the observation event sees infinitely many images
of the source. Moreover, we demonstrate that all lightlike geodesics from an
event to a timelike curve in the domain of outer communication are confined to
a certain spherical shell. Our characterization of this spherical shell shows
that in the Kerr-Newman spacetime the occurrence of infinitely many images is
intimately related to the occurrence of centrifugal-plus-Coriolis force
reversal.Comment: 14 pages, 2 figures; REVTEX; submitted to J. Math. Phy
Applicability of a forecasting chain in a different morphological environment in Italy
International audienceThe operational meteo-hydrological forecasting chain of the Liguria Region (NW Italy) is applied to a different morphoclimatic environment, such as the Emilia Romagna Region (N Italy). Modification to the chain, both in models and in procedures, are introduced to overcome problems related to medium dimension catchments (A?1000km2), characterized by complex altimetry profiles and antropical interventions along the river. The main feature of the original operational procedure, that is the probabilistic approach, is maintained. Hydraulic hazard reduction through artificial reservoirs management is exploited with reference to a specific event occurred on the Reno basin (Emilia Romagna Region)
Gravitational lensing in spherically symmetric static spacetimes with centrifugal force reversal
In Schwarzschild spacetime the value of the radius coordinate is
characterized by three different properties: (a) there is a ``light sphere'',
(b) there is ``centrifugal force reversal'', (c) it is the upper limiting
radius for a non-transparent Schwarschild source to act as a gravitational lens
that produces infinitely many images. In this paper we prove a theorem to the
effect that these three properties are intimately related in {\em any}
spherically symmetric static spacetime. We illustrate the general results with
some examples including black-hole spacetimes and Morris-Thorne wormholes.Comment: 18 pages, 3 eps-figure
A hydrological analysis of the 4 November 2011 event in Genoa
On the 4 November 2011 a flash flood event hit the area of Genoa with dramatic consequences. Such an event represents, from the meteorological and hydrological perspective, a paradigm of flash floods in the Mediterranean environment. <br><br> The hydro-meteorological probabilistic forecasting system for small and medium size catchments in use at the Civil Protection Centre of Liguria region exhibited excellent performances for the event, by predicting, 24–48 h in advance, the potential level of risk associated with the forecast. It greatly helped the decision makers in issuing a timely and correct alert. <br><br> In this work we present the operational outputs of the system provided during the Liguria events and the post event hydrological modelling analysis that has been carried out accounting also for the crowd sourcing information and data. We discuss the benefit of the implemented probabilistic systems for decision-making under uncertainty, highlighting how, in this case, the multi-catchment approach used for predicting floods in small basins has been crucial
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