275 research outputs found
Black hole-neutron star mergers: effects of the orientation of the black hole spin
The spin of black holes in black hole-neutron star (BHNS) binaries can have a
strong influence on the merger dynamics and the postmerger state; a wide
variety of spin magnitudes and orientations are expected to occur in nature. In
this paper, we report the first simulations in full general relativity of BHNS
mergers with misaligned black hole spin. We vary the spin magnitude from a/m=0
to a/m=0.9 for aligned cases, and we vary the misalignment angle from 0 to 80
degrees for a/m=0.5. We restrict our study to 3:1 mass ratio systems and use a
simple Gamma-law equation of state. We find that the misalignment angle has a
strong effect on the mass of the postmerger accretion disk, but only for angles
greater than ~ 40 degrees. Although the disk mass varies significantly with
spin magnitude and misalignment angle, we find that all disks have very similar
lifetimes ~ 100ms. Their thermal and rotational profiles are also very similar.
For a misaligned merger, the disk is tilted with respect to the final black
hole's spin axis. This will cause the disk to precess, but on a timescale
longer than the accretion time. In all cases, we find promising setups for
gamma-ray burst production: the disks are hot, thick, and hyperaccreting, and a
baryon-clear region exists above the black hole.Comment: 15 pages, 13 figure
Life cycle assessment of a stormwater sanitation system with vertical flow constructed wetlands (ADEPTE project)
(Almost) efficient information transmission in elections
We study a model in which two parties compete by announcing their policies, after receiving conditionally independent private signals about the true state of the world. Parties are both office- and policy-motivated. Our model can explain radically different policy positions, even when parties receive identical signals and have unbiased preferences. This holds in an asymmetric equilibrium in which both parties reveal their private information to the voters and the implemented policy is (almost) first-best for all possible realizations of parties’ signals. In this equilibrium, one party adopts extreme and the other one moderate policy positions
Multichannel coupling with supersymmetric quantum mechanics and exactly-solvable model for Feshbach resonance
A new type of supersymmetric transformations of the coupled-channel radial
Schroedinger equation is introduced, which do not conserve the vanishing
behavior of solutions at the origin. Contrary to usual transformations, these
``non-conservative'' transformations allow, in the presence of thresholds, the
construction of potentials with coupled scattering matrices from uncoupled
potentials. As an example, an exactly-solvable potential matrix is obtained
which provides a very simple model of Feshbach-resonance phenomenon.Comment: 10 pages, 2 figure
Innovations and technological comebacks
Motivated by the comeback of the vinyl, we explore the idea that the success of a third-generation technology (digital music) can have adverse effects on the second generation (CD) but positive effects on the first one (vinyl). This phenomenon arises in a market if the process of innovation is not transitive. In particular, we identify a condition such that the second generation completely substitutes the first one, the third generation completely substitutes the second one, but the first and the third generations have enough complementarities to coexist. Beyond the case of music industry, our model has implications on product positioning and product design
High occurrence of new particle formation events at the Maïdo high-altitude observatory (2150 m), Réunion (Indian Ocean)
This study aims to report and
characterise the frequent new particle formation (NPF) events observed at the
Maïdo observatory, Réunion, a Southern Hemisphere site located at
2150 m (a.s.l.) and surrounded by the Indian Ocean. From May 2014 to December
2015, continuous aerosol measurements were made using both a differential
mobility particle sizer (DMPS) and an air ion spectrometer (AIS) to
characterise the NPF events down to the lowest particle-size scale. Carbon
monoxide (CO) and black carbon (BC) concentrations were monitored, as well as
meteorological parameters, in order to identify the conditions that were
favourable to the occurrence of nucleation in this specific environment. We
point out that the annual NPF frequency average (65 %) is one of the
highest reported so far. Monthly averages show a bimodal variation in the NPF
frequency, with a maximum observed during transition periods (autumn and
spring). A high yearly median particle growth rate (GR) of 15.16 nm h−1
is also measured showing a bimodal seasonal variation with maxima observed in
July and November. Yearly medians of 2 and 12 nm particle formation rates
(J2 and J12) are 0.858 and 0.508 cm−3 s−1, respectively,
with a seasonal variation showing a maximum during winter, that correspond to
low temperature and RH typical of the dry season, but also to high BC
concentrations. We show that the condensation sink exceeds a threshold value
(1.04×10−3 s−1) with a similar seasonal variation than
the one of the NPF event frequency, suggesting that the occurrence of the NPF
process might be determined by the availability of condensable vapours, which
are likely to be transported together with pre-existing particles from lower
altitudes.</p
Evolution of Spin Direction of Accreting Magnetic Protostars and Spin-Orbit Misalignment in Exoplanetary Systems
Recent observations have shown that in many exoplanetary systems the spin
axis of the parent star is misaligned with the planet's orbital axis. These
have been used to argue against the scenario that short-period planets migrated
to their present-day locations due to tidal interactions with their natal
discs. However, this interpretation is based on the assumption that the spins
of young stars are parallel to the rotation axes of protostellar discs around
them. We show that the interaction between a magnetic star and its
circumstellar disc can (but not always) have the effect of pushing the stellar
spin axis away from the disc angular momentum axis toward the perpendicular
state and even the retrograde state. Planets formed in the disc may therefore
have their orbital axes misaligned with the stellar spin axis, even before any
additional planet-planet scatterings or Kozai interactions take place. In
general, magnetosphere--disc interactions lead to a broad distribution of the
spin--orbit angles, with some systems aligned and other systems misaligned.Comment: 10 pages, 5 figures. Comments/clarifications and a new figure (Fig.3)
are added. To be published in MNRA
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