8,770 research outputs found
Trigonometric Parallaxes of Massive Star Forming Regions: III. G59.7+0.1 and W 51 IRS2
We report trigonometric parallaxes for G59.7+0.1 and W 51 IRS2, corresponding
to distances of 2.16^{+0.10}_{-0.09} kpc and 5.1^{+2.9}_{-1.4} kpc,
respectively. The distance to G59.7+0.1 is smaller than its near kinematic
distance and places it between the Carina-Sagittarius and Perseus spiral arms,
probably in the Local (Orion) spur. The distance to W 51 IRS2, while subject to
significant uncertainty, is close to its kinematic distance and places it near
the tangent point of the Carina-Sagittarius arm. It also agrees well with a
recent estimate based on O-type star spectro/photometry. Combining the
distances and proper motions with observed radial velocities gives the full
space motions of the star forming regions. We find modest deviations of 5 to 10
km/s from circular Galactic orbits for these sources, both counter to Galactic
rotation and toward the Galactic center.Comment: 16 pages, 6 figures; to appear in the Astrophysical Journa
Exponential inequalities for martingales and asymptotic properties of the free energy of directed polymers in random environment
The objective of the present paper is to establish exponential large
deviation inequalities, and to use them to show exponential concentration
inequalities for the free energy of a polymer in general random environment,
its rate of convergence, and an expression of its limit value in terms of those
of some multiplicative cascades.Comment: 25 page
Boundaries of Siegel Disks: Numerical Studies of their Dynamics and Regularity
Siegel disks are domains around fixed points of holomorphic maps in which the maps are locally linearizable (i.e., become a rotation under an appropriate change of coordinates which is analytic in a neighborhood of the origin). The dynamical behavior of the iterates of the map on the boundary of the Siegel disk exhibits strong scaling properties which have been intensively studied in the physical and mathematical literature. In the cases we study, the boundary of the Siegel disk is a Jordan curve containing a critical point of the map (we consider critical maps of different orders), and there exists a natural parametrization which transforms the dynamics on the boundary into a rotation. We compute numerically this parameterization and use methods of harmonic analysis to compute the global Holder regularity of the parametrization for different maps and rotation numbers. We obtain that the regularity of the boundaries and the scaling exponents are universal numbers in the sense of renormalization theory (i.e., they do not depend on the map when the map ranges in an open set), and only depend on the order of the critical point of the map in the boundary of the Siegel disk and the tail of the continued function expansion of the rotation number. We also discuss some possible relations between the regularity of the parametrization of the boundaries and the corresponding scaling exponents. (C) 2008 American Institute of Physics.NSFMathematic
Language Models as a Service: Overview of a New Paradigm and its Challenges
Some of the most powerful language models currently are proprietary systems,
accessible only via (typically restrictive) web or software programming
interfaces. This is the Language-Models-as-a-Service (LMaaS) paradigm. In
contrast with scenarios where full model access is available, as in the case of
open-source models, such closed-off language models present specific challenges
for evaluating, benchmarking, and testing them. This paper has two goals: on
the one hand, we delineate how the aforementioned challenges act as impediments
to the accessibility, replicability, reliability, and trustworthiness of LMaaS.
We systematically examine the issues that arise from a lack of information
about language models for each of these four aspects. We conduct a detailed
analysis of existing solutions and put forth a number of considered
recommendations, and highlight the directions for future advancements. On the
other hand, it serves as a comprehensive resource for existing knowledge on
current, major LMaaS, offering a synthesized overview of the licences and
capabilities their interfaces offer
Modules of Abelian integrals and Picard-Fuchs systems
We give a simple proof of an isomorphism between the two
-modules: the module of relative cohomologies and the module of Abelian integrals corresponding to a regular at
infinity polynomial in two variables. Using this isomorphism, we prove
existence and deduce some properties of the corresponding Picard-Fuchs system.Comment: A separate section discusses Fuchsian properties of the Picard-Fuchs
system, Morse condition exterminated. Few errors were correcte
Modelling Circumbinary Gas Flows in Close T Tauri Binaries
Young close binaries open central gaps in the surrounding circumbinary
accretion disc, but the stellar components may still gain mass from gas
crossing through the gap. It is not well understood how this process operates
and how the stellar components are affected by such inflows. Our main goal is
to investigate how gas accretion takes place and evolves in close T Tauri
binary systems. In particular, we model the accretion flows around two close T
Tauri binaries, V4046 Sgr and DQ Tau, both showing periodic changes in emission
lines, although their orbital characteristics are very different. In order to
derive the density and velocity maps of the circumbinary material, we employ
two-dimensional hydrodynamic simulations with a locally isothermal equation of
state. The flow patterns become quasi-stable after a few orbits in the frame
co-rotating with the system. Gas flows across the circumbinary gap through the
co-rotating Lagrangian points, and local circumstellar discs develop around
both components. Spiral density patterns develop in the circumbinary disc that
transport angular momentum efficiently. Mass is preferentially channelled
towards the primary and its circumstellar disc is more massive than the disc
around the secondary. We also compare the derived density distribution to
observed line profile variability. The line profile variability tracing the gas
flows in the central cavity shows clear similarities with the corresponding
observed line profile variability in V4046 Sgr, but only when the local
circumstellar disc emission was excluded. Closer to the stars normal
magnetospheric accretion may dominate while further out the dynamic accretion
process outlined here dominates. Periodic changes in the accretion rates onto
the stars can explain the outbursts of line emission observed in eccentric
systems such as DQ Tau.Comment: Accepted for publication in MNRA
On the Number of Zeros of Abelian Integrals: A Constructive Solution of the Infinitesimal Hilbert Sixteenth Problem
We prove that the number of limit cycles generated by a small
non-conservative perturbation of a Hamiltonian polynomial vector field on the
plane, is bounded by a double exponential of the degree of the fields. This
solves the long-standing tangential Hilbert 16th problem. The proof uses only
the fact that Abelian integrals of a given degree are horizontal sections of a
regular flat meromorphic connection (Gauss-Manin connection) with a
quasiunipotent monodromy group.Comment: Final revisio
Hadronic Regge Trajectories: Problems and Approaches
We scrutinized hadronic Regge trajectories in a framework of two different
models --- string and potential. Our results are compared with broad spectrum
of existing theoretical quark models and all experimental data from PDG98. It
was recognized that Regge trajectories for mesons and baryons are not straight
and parallel lines in general in the current resonance region both
experimentally and theoretically, but very often have appreciable curvature,
which is flavor-dependent. For a set of baryon Regge trajectories this fact is
well described in the considered potential model. The standard string models
predict linear trajectories at high angular momenta J with some form of
nonlinearity at low J.Comment: 15 pages, 9 figures, LaTe
Theory of Circle Maps and the Problem of One-Dimensional Optical Resonator with a Periodically Moving Wall
We consider the electromagnetic field in a cavity with a periodically
oscillating perfectly reflecting boundary and show that the mathematical theory
of circle maps leads to several physical predictions. Notably, well-known
results in the theory of circle maps (which we review briefly) imply that there
are intervals of parameters where the waves in the cavity get concentrated in
wave packets whose energy grows exponentially. Even if these intervals are
dense for typical motions of the reflecting boundary, in the complement there
is a positive measure set of parameters where the energy remains bounded.Comment: 34 pages LaTeX (revtex) with eps figures, PACS: 02.30.Jr, 42.15.-i,
42.60.Da, 42.65.Y
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