131,260 research outputs found
Markoff-Rosenberger triples with Fibonacci components
No full textWe characterize the solutions of the Markoff-Rosenberger equation
a x2 + b y2 + c z2 = d x y z
with a,b,c,d ∈ ℤ, gcd(a,b)=gcd(a,c)=gcd(b,c)=1 and a,b,c | d, for which (x,y,z)=(Fi,Fj,Fk), where Fn denotes the n-th Fibonacci number for any integer n≥ 0
Integral Hasse principle and strong approximation for Markoff surfaces
No full textWe study the failure of the integral Hasse principle and strong approximationfor Markoff surfaces, as studied by Ghosh and Sarnak, using the Brauer-Maninobstruction.<br
Nombres de Markoff et catégories inclinées amassées
No full textOn introduit une famille de modules, appelés modules de Marlcoff, engendrée par un procédé itératif semblable à la mutation des objects inclinants dans une catégorie amassée. On montre que ces modules ont une structure combinatoire similaire à celle des mots de Christoffel. En outre, on construit une bijection entre l'ensemble des triplets de modules de Markoff et l'ensemble des triplets de Markoff propres. Ceci nous permet de reformuler la conjecture d'unicité des nombres de Markoff dans un cadre algébrique. Dans la deuxième partie, on étudie les dimensions projectives de la restriction des foncteurs [Special characters omitted.] HomC (-, X ) à une sous-catégorie contravariantement finie et rigide d'une catégorie triangulée [Special characters omitted.] C . On montre que la dimension projective de [Special characters omitted.] HomC (-, X )[Special characters omitted.] T est au plus un si et seulement si il n'existe aucun morphisme non nul entre objets de [Special characters omitted.] T [1] qui se factorise par X , lorsque X appartient à une certaine sous-catégorie convenable de [Special characters omitted.] C . Par conséquent, on obtient une caractérisation des objets de dimension projective infinie dans la catégorie des foncteurs contravariants de présentation finie sur une sous-catégorie inclinante amassée de [Special characters omitted.] C . [symboles non conformes
An improvement of the Minkowski bound for real quadratic orders using the Markoff theorem
No full textAbstractUsing the Markoff theorem on indefinite binary quadratic forms it is shown that every element of the class group of any real quadratic order of discriminant d has an ideal of norm less than or equal to 1+⌊d3⌋. This bound is best possible as there are quadratic orders of discriminant d which have ideal classes where the least norm is 1+⌊d3⌋. These discriminants are explicitly given and their connection to the Markoff conjecture is highlighted
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Unity in diversity: Constraints on jet/disk geometry and radiative processes in stellar black holes via modeling broadband SEDs
No full textState transitions in X-ray binaries are manifestations of instabilities in the accretion in/outflow. Therefore, time dependence in the energetics must to be taken into account to understand such transitions. However, most spectral models assume a static, steady-state scenario, and therefore work well only when the source is either in the hard state or in the soft state. For example, a compact jet model, coupled with a T~R(-3/4) accretion disk and a thermal blackbody (see e.g. (Markoff et al. 2005) for a description of the model), has been successfully used to model broadband spectra of several X-ray binaries in the hard state, but not the intermediate states. With the long-term goal to study time dependence, we present new results of studying quasi-simultaneous broadband data from radio to X-rays for GX 339-4 and J1118+480 in the hard X-ray state, using the jet model, to constrain system geometry and emission processes, which will in turn serve as starting points for the time-dependent models
Reproduction package for the paper "Correlating spectral and timing properties in the evolving jet of themicro blazar MAXI J1836-194"
No full textBasic reproduction package for the paper in the title; it contains all the necessary information and scripts required to replicate the results and plots, minus the proprietary code used (which can be found on github on request).</span
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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