pinecone/core-2020-05-10-deduplication huggingface dataset:
Models of Individual Blue Stragglers

This chapter describes the current state of models of individual blue
stragglers. Stellar collisions, binary mergers (or coalescence), and partial or
ongoing mass transfer have all been studied in some detail. The products of
stellar collisions retain memory of their parent stars and are not fully mixed.
Very high initial rotation rates must be reduced by an unknown process to allow
the stars to collapse to the main sequence. The more massive collision products
have shorter lifetimes than normal stars of the same mass, while products
between low mass stars are long-lived and look very much like normal stars of
their mass. Mass transfer can result in a merger, or can produce another binary
system with a blue straggler and the remnant of the original primary. The
products of binary mass transfer cover a larger portion of the colour-magnitude
diagram than collision products for two reasons: there are more possible
configurations which produce blue stragglers, and there are differing
contributions to the blended light of the system. The effects of rotation may
be substantial in both collision and merger products, and could result in
significant mixing unless angular momentum is lost shortly after the formation
event. Surface abundances may provide ways to distinguish between the formation
mechanisms, but care must be taking to model the various mixing mechanisms
properly before drawing strong conclusions. Avenues for future work are
outlined.Comment: Chapter 12, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Blue Stragglers in Globular Clusters: Observations, Statistics and
  Physics

This chapter explores how we might use the observed {\em statistics} of blue
stragglers in globular clusters to shed light on their formation. This means we
will touch on topics also discussed elsewhere in this book, such as the
discovery and implications of bimodal radial distributions and the "double
sequences" of blue stragglers that have recently been found in some clusters.
However, we will focus particularly on the search for a "smoking gun"
correlation between the number of blue stragglers in a given globular cluster
and a physical cluster parameter that would point towards a particular
formation channel. As we shall see, there is little evidence for an intrinsic
correlation between blue straggler numbers and stellar collision rates, even in
dense cluster cores. On the other hand, there is a clear correlation between
blue straggler numbers and the total (core) mass of the cluster. This would
seem to point towards a formation channel involving binaries, rather than
dynamical encounters. However, the correlation between blue straggler numbers
and actual binary numbers - which relies on recently determined empirical
binary fractions - is actually weaker than that with core mass. We explain how
this surprising result may be reconciled with a binary formation channel if
binary fractions depend almost uniquely on core mass. If this is actually the
case, it would have significant implications for globular cluster dynamics more
generally.Comment: Chapter 13, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Blue Stragglers in Clusters and Integrated Spectral Properties of
  Stellar Populations

Blue straggler stars are the most prominent bright objects in the
colour-magnitude diagram of a star cluster that challenges the theory of
stellar evolution. Star clusters are the closest counterparts of the
theoretical concept of simple stellar populations (SSPs) in the Universe. SSPs
are widely used as the basic building blocks to interpret stellar contents in
galaxies. The concept of an SSP is a group of coeval stars which follows a
given distribution in mass, and has the same chemical property and age. In
practice, SSPs are more conveniently made by the latest stellar evolutionary
models of single stars. In reality, however, stars can be more complicated than
just single either at birth time or during the course of evolution in a typical
environment. Observations of star clusters show that there are always exotic
objects which do not follow the predictions of standard theory of stellar
evolution. Blue straggler stars (BSSs), as discussed intensively in this book
both observationally and theoretically, are very important in our context when
considering the integrated spectral properties of a cluster, or a simple
stellar population. In this chapter, we are going to describe how important the
contribution of BSSs is to the total light of a cluster.Comment: Chapter 14, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Blue Straggler Stars: Early Observations that Failed to Solve the
  Problem

In this chapter, I describe early ideas on blue stragglers, and various
observations (some published, some not) that promised but failed to resolve the
question of their origin. I review the data and ideas that were circulating
from Allan Sandage's original discovery in 1953 of "anomalous blue stars" in
the globular cluster M3, up until about 1992, when what seems to have been the
only previous meeting devoted to Blue Straggler Stars (BSSs) was held at the
Space Telescope Science Institute.Comment: Chapter 2, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
The Blue Stragglers of the Old Open Cluster NGC 188

The old (7 Gyr) open cluster NGC 188 has yielded a wealth of astrophysical
insight into its rich blue straggler population. Specifically, the NGC 188 blue
stragglers are characterized by: A binary frequency of 80% for orbital periods
less than $10^4$ days;Typical orbital periods around 1000 days;Typical
secondary star masses of 0.5 M$_{\odot}$; At least some white dwarf companion
stars; Modestly rapid rotation; A bimodal radial spatial distribution;
Dynamical masses greater than standard stellar evolution masses (based on
short-period binaries); Under-luminosity for dynamical masses (short-period
binaries). Extensive $N$-body modeling of NGC 188 with empirical initial
conditions reproduces the properties of the cluster, and in particular the
main-sequence solar-type binary population. The current models also reproduce
well the binary orbital properties of the blue stragglers, but fall well short
of producing the observed number of blue stragglers. This deficit could be
resolved by reducing the frequency of common-envelope evolution during Roche
lobe overflow. Both the observations and the $N$-body models strongly indicate
that the long-period blue-straggler binaries - which dominate the NGC 188 blue
straggler population - are formed by asymptotic-giant (primarily) and red-giant
mass transfer onto main sequence stars. The models suggest that the few
non-velocity-variable blue stragglers formed from mergers or collisions.
Several remarkable short-period double-lined binaries point to the importance
of subsequent dynamical exchange encounters, and provide at least one example
of a likely collisional origin for a blue straggler.Comment: Chapter 3, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Blue Straggler Stars in Globular Clusters: a powerful tool to probe the
  internal dynamical evolution of stellar systems

This chapter presents an overview of the main observational results obtained
to date about Blue Straggler Stars (BSSs) in Galactic Globular Clusters (GCs).
The BSS specific frequency, radial distribution, chemical composition and
rotational properties are presented and discussed in the framework of using
this stellar population as probe of GC internal dynamics. In particular, the
shape of the BSS radial distribution has been found to be a powerful tracer of
the dynamical age of stellar systems, thus allowing the definition of the first
empirical "dynamical clock".Comment: Chapter 5, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
The Blue Straggler Population in Dwarf Galaxies

In this chapter I review the recent developments regarding the study of Blue
Stragglers (BSS) in dwarf galaxies. The loose density environment of dwarf
galaxies resembles that of the Galactic Halo, hence it is natural to compare
their common BSS properties. At the same time, it is unescapable to compare
with the BSS properties in Galactic Globular clusters, which constitute the
reference point for BSS studies. Admittedly, the literature on BSS in dwarf
galaxies is not plentiful. The limitation is mostly due to the large distance
to even the closest dwarf galaxies. Nevertheless, recent studies have allowed a
deeper insight on the BSS photometric properties that are worth examining.Comment: Chapter 6, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Mass Transfer by Stellar Wind

I review the process of mass transfer in a binary system through a stellar
wind, with an emphasis on systems containing a red giant. I show how wind
accretion in a binary system is different from the usually assumed Bondi-Hoyle
approximation, first as far as the flow's structure is concerned, but most
importantly, also for the mass accretion and specific angular momentum loss.
This has important implications on the evolution of the orbital parameters. I
also discuss the impact of wind accretion, on the chemical pollution and change
in spin of the accreting star. The last section deals with observations and
covers systems that most likely went through wind mass transfer: barium and
related stars, symbiotic stars and central stars of planetary nebulae (CSPN).
The most recent observations of cool CSPN progenitors of barium stars, as well
as of carbon-rich post-common envelope systems, are providing unique
constraints on the mass transfer processes.Comment: Chapter 7, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Binary Evolution: Roche Lobe Overflow and Blue Stragglers

One of the principal mechanisms that is responsible for the origin of blue
stragglers is mass transfer that takes place while one of the binary companions
overfills its Roche lobe. In this Chapter, we overview the theoretical
understanding of mass transfer via Roche lobe overflow: classification, how
both the donor and of the accretor respond to the mass transfer on different
timescales (adiabatic response, equilibrium response, superadiabatic response,
time-dependent response) for different types of their envelopes (convective and
radiative). These responses, as well as the assumption on how liberal the
process is, are discussed in terms of the stability of the ensuing mass
transfer. The predictions of the theory of mass transfer via Roche lobe
overflow are then briefly compared with the observed mass-transferring systems
with both degenerate and non-degenerate donors. We conclude with the discussion
which cases of mass transfer and which primordial binaries could be responsible
for blue stragglers formation via Roche lobe overflow, as well as how this can
be enhanced for blue stragglers formed in globular clusters.Comment: Chapter 8, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Formation Channels for Blue Straggler Stars

In this chapter we consider two formation channels for blue straggler stars:
1) the merger of two single stars via a collision, and 2) those produced via
mass transfer within a binary. We review how computer simulations show that
stellar collisions are likely to lead to relatively little mass loss and are
thus effective in producing a young population of more-massive stars. The
number of blue straggler stars produced by collisions will tend to increase
with cluster mass. We review how the current population of blue straggler stars
produced from primordial binaries decreases with increasing cluster mass. This
is because exchange encounters with third, single stars in the most massive
clusters tend to reduce the fraction of binaries containing a primary close to
the current turn-off mass. Rather, their primaries tend to be somewhat more
massive and have evolved off the main sequence, filling their Roche lobes in
the past, often converting their secondaries into blue straggler stars (but
more than 1 Gyr or so ago and thus they are no longer visible today as blue
straggler stars).Comment: Chapter 9, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
  Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Hand gesture recognition for human computer interaction: a comparative study of different image features

Hand gesture recognition for human computer interaction, being a
natural way of human computer interaction, is an area of active research in
computer vision and machine learning. This is an area with many different possible
applications, giving users a simpler and more natural way to communicate
with robots/systems interfaces, without the need for extra devices. So, the primary
goal of gesture recognition research is to create systems, which can identify
specific human gestures and use them to convey information or for device
control. For that, vision-based hand gesture interfaces require fast and extremely
robust hand detection, and gesture recognition in real time. In this study
we try to identify hand features that, isolated, respond better in various situations
in human-computer interaction. The extracted features are used to train a
set of classifiers with the help of RapidMiner in order to find the best learner. A
dataset with our own gesture vocabulary consisted of 10 gestures, recorded
from 20 users was created for later processing. Experimental results show that
the radial signature and the centroid distance are the features that when used
separately obtain better results, with an accuracy of 91% and 90,1% respectively
obtained with a Neural Network classifier. These to methods have also
the advantage of being simple in terms of computational complexity, which
make them good candidates for real-time hand gesture recognition
Query-competitive algorithms for cheapest set problems under uncertainty

Considering the model of computing under uncertainty where element weights are uncertain but can be obtained at a cost by query operations, we study the problem of identifying a cheapest (minimum-weight) set among a given collection of feasible sets using a minimum number of queries of element weights. For the general case we present an algorithm that makes at most d·OPT+d queries, where d is the maximum cardinality of any given set and OPT is the optimal number of queries needed to identify a cheapest set. For the minimum multi-cut problem in trees with d terminal pairs, we give an algorithm that makes at most d·OPT+1 queries. For the problem of computing a minimum-weight base of a given matroid, we give an algorithm that makes at most 2·OPT queries, generalizing a known result for the minimum spanning tree problem. For each of our algorithms we give matching lower bounds.Peer-reviewedPost-print39th International Symposium, MFCS 2014, Budapest, Hungary, August 25-29, 2014. In Proceedings, Part I
A reconfigurations analogue of Brooks’ theorem.

Let G be a simple undirected graph on n vertices with maximum degree Δ. Brooks’ Theorem states that G has a Δ-colouring unless G is a complete graph, or a cycle with an odd number of vertices. To recolour G is to obtain a new proper colouring by changing the colour of one vertex. We show that from a k-colouring, k > Δ, a Δ-colouring of G can be obtained by a sequence of O(n 2) recolourings using only the original k colours unless\ud
G is a complete graph or a cycle with an odd number of vertices, or\ud
k = Δ + 1, G is Δ-regular and, for each vertex v in G, no two neighbours of v are coloured alike.\ud
We use this result to study the reconfiguration graph R k (G) of the k-colourings of G. The vertex set of R k (G) is the set of all possible k-colourings of G and two colourings are adjacent if they differ on exactly one vertex. It is known that\ud
if k ≤ Δ(G), then R k (G) might not be connected and it is possible that its connected components have superpolynomial diameter,\ud
if k ≥ Δ(G) + 2, then R k (G) is connected and has diameter O(n 2).\ud
We complete this structural classification by settling the missing case:\ud
if k = Δ(G) + 1, then R k (G) consists of isolated vertices and at most one further component which has diameter O(n 2).\ud
We also describe completely the computational complexity classification of the problem of deciding whether two k-colourings of a graph G of maximum degree Δ belong to the same component of R k (G) by settling the case k = Δ(G) + 1. The problem is\ud
O(n 2) time solvable for k = 3,\ud
PSPACE-complete for 4 ≤ k ≤ Δ(G),\ud
O(n) time solvable for k = Δ(G) + 1,\ud
O(1) time solvable for k ≥ Δ(G) + 2 (the answer is always yes)
Intersection graphs of L-shapes and segments in the plane.

An L-shape is the union of a horizontal and a vertical segment with a common endpoint. These come in four rotations: ⌊,⌈,⌋ and ⌉. A k-bend path is a simple path in the plane, whose direction changes k times from horizontal to vertical. If a graph admits an intersection representation in which every vertex is represented by an ⌊, an ⌊ or ⌈, a k-bend path, or a segment, then this graph is called an ⌊-graph, ⌊,⌈-graph, B k -VPG-graph or SEG-graph, respectively. Motivated by a theorem of Middendorf and Pfeiffer [Discrete Mathematics, 108(1):365–372, 1992], stating that every ⌊,⌈-graph is a SEG-graph, we investigate several known subclasses of SEG-graphs and show that they are ⌊-graphs, or B k -VPG-graphs for some small constant k. We show that all planar 3-trees, all line graphs of planar graphs, and all full subdivisions of planar graphs are ⌊-graphs. Furthermore we show that all complements of planar graphs are B 19-VPG-graphs and all complements of full subdivisions are B 2-VPG-graphs. Here a full subdivision is a graph in which each edge is subdivided at least once
On the Complexity of List Ranking in the Parallel External Memory Model

We study the problem of list ranking in the parallel external memory (PEM)
model. We observe an interesting dual nature for the hardness of the problem
due to limited information exchange among the processors about the structure of
the list, on the one hand, and its close relationship to the problem of
permuting data, which is known to be hard for the external memory models, on
the other hand.
  By carefully defining the power of the computational model, we prove a
permuting lower bound in the PEM model. Furthermore, we present a stronger
\Omega(log^2 N) lower bound for a special variant of the problem and for a
specific range of the model parameters, which takes us a step closer toward
proving a non-trivial lower bound for the list ranking problem in the
bulk-synchronous parallel (BSP) and MapReduce models. Finally, we also present
an algorithm that is tight for a larger range of parameters of the model than
in prior work
Knocking out P_k-free graphs.

A parallel knock-out scheme for a graph proceeds in rounds in each of which each surviving vertex eliminates one of its surviving neighbours. A graph is KO-reducible if there exists such a scheme that eliminates every vertex in the graph. The Parallel Knock-Out problem is to decide whether a graph G is KO-reducible. This problem is known to be NP-complete and has been studied for several graph classes since MFCS 2004. We show that the problem is NP-complete even for split graphs, a subclass of P 5-free graphs. In contrast, our main result is that it is linear-time solvable for P 4-free graphs (cographs)
A Tight Lower Bound on Certificate Complexity in Terms of Block
  Sensitivity and Sensitivity

Sensitivity, certificate complexity and block sensitivity are widely used
Boolean function complexity measures. A longstanding open problem, proposed by
Nisan and Szegedy, is whether sensitivity and block sensitivity are
polynomially related. Motivated by the constructions of functions which achieve
the largest known separations, we study the relation between 1-certificate
complexity and 0-sensitivity and 0-block sensitivity.
  Previously the best known lower bound was $C_1(f)\geq \frac{bs_0(f)}{2
s_0(f)}$, achieved by Kenyon and Kutin. We improve this to $C_1(f)\geq \frac{3
bs_0(f)}{2 s_0(f)}$. While this improvement is only by a constant factor, this
is quite important, as it precludes achieving a superquadratic separation
between $bs(f)$ and $s(f)$ by iterating functions which reach this bound. In
addition, this bound is tight, as it matches the construction of Ambainis and
Sun up to an additive constant.Comment: 12 page
Forbidden induced subgraphs and the price of connectivity for feedback vertex set.

Let fvs(G) and cfvs(G) denote the cardinalities of a minimum feedback vertex set and a minimum connected feedback vertex set of a graph G, respectively. For a graph class G, the price of connectivity for feedback vertex set (poc-fvs) for G is defined as the maximum ratio cfvs(G)/fvs(G) over all connected graphs G in G. It is known that the poc-fvs for general graphs is unbounded. We study the poc-fvs for graph classes defined by a finite family H of forbidden induced subgraphs. We characterize exactly those finite families H for which the poc-fvs for H-free graphs is bounded by a constant. Prior to our work, such a result was only known for the case where |H|=1
Vision based referee sign language recognition system for the RoboCup MSL league

In RoboCup Middle Size league (MSL) the main referee uses assisting technology, controlled by a second referee, to support him, in particular for conveying referee decisions for robot players with the help of a wireless communication system.
In this paper a vision-based system is introduced, able to interpret dynamic and static gestures of the referee, thus eliminating the need for a second one. The referee's gestures are interpreted by the system and sent directly to the Referee Box, which sends the proper commands to the robots. The system is divided into four modules: a real time hand tracking and feature extraction, a SVM (Support Vector Machine) for static hand posture identification, an HMM (Hidden Markov Model) for dynamic unistroke hand gesture recognition, and a FSM (Finite State Machine) to control the various system states transitions. The experimental results showed that the system works very reliably, being able to recognize the combination of gestures and hand postures in real-time. For the hand posture recognition, with the SVM model trained with the selected features, an accuracy of 98,2% was achieved. Also, the system has many advantages over the current implemented one, like avoiding the necessity of a second referee, working on noisy environments, working on wireless jammed situations. This system is easy to implement and train and may be an inexpensive solution
Modular development of mobile robots with open source hardware and software components

Prototyping and engineering robot hardware and low-level control often require time and efforts thus subtracted to core research activities, such as SLAM or planning algorithms development, which need a working, reliable, platform to be evaluated in a real world scenario. In this paper, we present Rapid Robot Prototyping (R2P), an open source, hardware and software architecture for the rapid prototyping of robotic applications, where off-the-shelf embedded modules (e.g., sensors, actuators, and controllers) are combined together in a plug-and-play fashion, enabling the implementation of a complex system in a simple and modular way. R2P makes people involved in robotics, from researchers and designers to students and hobbyists, dramatically reduce the time and efforts required to build a robot prototype