3,829 research outputs found
Dynamical Measurements of the Young Upper Scorpius Triple NTTS 155808-2219
The young, low-mass, triple system NTTS 155808-2219 (ScoPMS 20) was
previously identified as a ~17-day period single-lined spectroscopic binary
with a tertiary component at 0.21 arcseconds. Using high-resolution infrared
spectra, acquired with NIRSPEC on Keck II, both with and without adaptive
optics, we measured radial velocities of all three components. Reanalysis of
the single-lined visible light observations, made from 1987 to 1993, also
yielded radial velocity detections of the three stars. Combining visible light
and infrared data to compute the orbital solution produces orbital parameters
consistent with the single-lined solution and a mass ratio of q = 0.78 +/- 0.01
for the SB. We discuss the consistency between our results and previously
published data on this system, our radial-velocity analysis with both observed
and synthetic templates, and the possibility that this system is eclipsing,
providing a potential method for the determination of the stars' absolute
masses. Over the ~20 year baseline of our observations, we have measured the
acceleration of the SB's center-of-mass in its orbit with the tertiary.
Long-term, adaptive optics imaging of the tertiary will eventually yield
dynamical data useful for component mass estimates.Comment: 6 Tables, 8 Figures, updated to match published tex
Strong uniqueness for stochastic evolution equations with unbounded measurable drift term
We consider stochastic evolution equations in Hilbert spaces with merely
measurable and locally bounded drift term and cylindrical Wiener noise. We
prove pathwise (hence strong) uniqueness in the class of global solutions. This
paper extends our previous paper (Da Prato, Flandoli, Priola and M. Rockner,
Annals of Prob., published online in 2012) which generalized Veretennikov's
fundamental result to infinite dimensions assuming boundedness of the drift
term. As in our previous paper pathwise uniqueness holds for a large class, but
not for every initial condition. We also include an application of our result
to prove existence of strong solutions when the drift is only measurable,
locally bounded and grows more than linearly.Comment: The paper will be published in Journal of Theoretical Probability.
arXiv admin note: text overlap with arXiv:1109.036
Cubature on Wiener space in infinite dimension
We prove a stochastic Taylor expansion for SPDEs and apply this result to
obtain cubature methods, i. e. high order weak approximation schemes for SPDEs,
in the spirit of T. Lyons and N. Victoir. We can prove a high-order weak
convergence for well-defined classes of test functions if the process starts at
sufficiently regular initial values. We can also derive analogous results in
the presence of L\'evy processes of finite type, here the results seem to be
new even in finite dimension. Several numerical examples are added.Comment: revised version, accepted for publication in Proceedings Roy. Soc.
Analysis of equilibrium states of Markov solutions to the 3D Navier-Stokes equations driven by additive noise
We prove that every Markov solution to the three dimensional Navier-Stokes
equation with periodic boundary conditions driven by additive Gaussian noise is
uniquely ergodic. The convergence to the (unique) invariant measure is
exponentially fast.
Moreover, we give a well-posedness criterion for the equations in terms of
invariant measures. We also analyse the energy balance and identify the term
which ensures equality in the balance.Comment: 32 page
Dimension-independent Harnack inequalities for subordinated semigroups
Dimension-independent Harnack inequalities are derived for a class of
subordinate semigroups. In particular, for a diffusion satisfying the
Bakry-Emery curvature condition, the subordinate semigroup with power
satisfies a dimension-free Harnack inequality provided ,
and it satisfies the log-Harnack inequality for all Some
infinite-dimensional examples are also presented
Adjoint bi-continuous semigroups and semigroups on the space of measures
For a given bi-continuous semigroup T on a Banach space X we define its
adjoint on an appropriate closed subspace X^o of the norm dual X'. Under some
abstract conditions this adjoint semigroup is again bi-continuous with respect
to the weak topology (X^o,X). An application is the following: For K a Polish
space we consider operator semigroups on the space C(K) of bounded, continuous
functions (endowed with the compact-open topology) and on the space M(K) of
bounded Baire measures (endowed with the weak*-topology). We show that
bi-continuous semigroups on M(K) are precisely those that are adjoints of a
bi-continuous semigroups on C(K). We also prove that the class of bi-continuous
semigroups on C(K) with respect to the compact-open topology coincides with the
class of equicontinuous semigroups with respect to the strict topology. In
general, if K is not Polish space this is not the case
The GL 569 Multiple System
We report the results of high spectral and angular resolution infrared
observations of the multiple system GL 569 A and B that were intended to
measure the dynamical masses of the brown dwarf binary believed to comprise GL
569 B. Our analysis did not yield this result but, instead, revealed two
surprises. First, at age ~100 Myr, the system is younger than had been reported
earlier. Second, our spectroscopic and photometric results provide support for
earlier indications that GL 569 B is actually a hierarchical brown dwarf triple
rather than a binary. Our results suggest that the three components of GL 569 B
have roughly equal mass, ~0.04 Msun.Comment: 29 pages, 10 figures, accepted for publication in the Astrophysical
Journal; minor corrections to Section 5.1; changed typo in 6.
Use of Perylene Diimides in Synthetic Photochemistry
Perylene diimides (PDIs) are valuable organic chromophores that stand out for their outstanding optical and redox properties. Owing to these features, PDIs have emerged as prominent dyes capable of acting as photocatalysts for numerous relevant organic transformations. This Minireview highlights the recent advances in the application of PDIs in organic photocatalysis. The various mechanistic pathways of the photo-reduction reaction of aryl halides, recently proposed in independent studies, are discussed with an eye to unsolved challenges and forward-looking opportunities regarding the use of PDIs within this field
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