22,780 research outputs found
Modelling Citation Networks
The distribution of the number of academic publications as a function of
citation count for a given year is remarkably similar from year to year. We
measure this similarity as a width of the distribution and find it to be
approximately constant from year to year. We show that simple citation models
fail to capture this behaviour. We then provide a simple three parameter
citation network model using a mixture of local and global search processes
which can reproduce the correct distribution over time. We use the citation
network of papers from the hep-th section of arXiv to test our model. For this
data, around 20% of citations use global information to reference recently
published papers, while the remaining 80% are found using local searches. We
note that this is consistent with other studies though our motivation is very
different from previous work. Finally, we also find that the fluctuations in
the size of an academic publication's bibliography is important for the model.
This is not addressed in most models and needs further work.Comment: 29 pages, 22 figure
Techniques for the realization of ultrareliable spaceborne computers Interim scientific report
Reliability tests on spaceborne digital computer
An Empirical Study of Finding Approximate Equilibria in Bimatrix Games
While there have been a number of studies about the efficacy of methods to
find exact Nash equilibria in bimatrix games, there has been little empirical
work on finding approximate Nash equilibria. Here we provide such a study that
compares a number of approximation methods and exact methods. In particular, we
explore the trade-off between the quality of approximate equilibrium and the
required running time to find one. We found that the existing library GAMUT,
which has been the de facto standard that has been used to test exact methods,
is insufficient as a test bed for approximation methods since many of its games
have pure equilibria or other easy-to-find good approximate equilibria. We
extend the breadth and depth of our study by including new interesting families
of bimatrix games, and studying bimatrix games upto size .
Finally, we provide new close-to-worst-case examples for the best-performing
algorithms for finding approximate Nash equilibria
Recommended from our members
Raman Line Shapes in Liquid and
The six fundamental bands of and , both as pure liquids and in solution with , have been studied in order to obtain information about the molecular rotational and vibrational dynamics. Emphasis was placed on the features of the spectra that can be interpreted independent of a particular model. An examination for Boltzmann asymmetry in the and E bands indicates that the former, being symmetric, are amenable to classical description, while the latter, being asymmetric, definitely require quantum mechanical interpretations. With respect to the validity of the assumption that rotation‐vibration coupling can be ignored, we give evidence of substantial coupling effects in a nondegenerate mode as well as in the doubly degenerate E modes. We emphasize that, in attempting to obtain dynamical information, several bands of any given liquid must be studied and compared in order to decide which can be used with confidence in a detailed analysis. The consistency of the rotational diffusion model for describing the tumbling motion of the methyl iodide molecules has been confirmed.Engineering and Applied Science
Relativistic three-body recombination with the QED vacuum
Electron-positron pair annihilation into a single photon is studied when a
second free electron is present. Focussing on the relativistic regime, we show
that the photon emitted in the three-lepton interaction may exhibit distinct
angular distributions and polarization properties. Moreover, the process can
dominate over two-photon annihilation in relativistic electron-positron plasmas
of few-MeV temperature. An analogy with three-body recombination of electrons
with ions is drawn.Comment: 5 pages, 4 figure
The Origin of the Electromagnetic Interaction in Einstein's Unified Field Theory with Sources
Einstein's unified field theory is extended by the addition of matter terms
in the form of a symmetric energy tensor and of two conserved currents. From
the field equations and from the conservation identities emerges the picture of
a gravoelectrodynamics in a dynamically polarizable Riemannian continuum.
Through an approximate calculation exploiting this dynamical polarizability it
is argued that ordinary electromagnetism may be contained in the theory.Comment: 8 pages. Misprint in eq. 15 correcte
Evidence of Skyrmion excitations about in n-Modulation Doped Single Quantum Wells by Inter-band Optical Transmission
We observe a dramatic reduction in the degree of spin-polarization of a
two-dimensional electron gas in a magnetic field when the Fermi energy moves
off the mid-point of the spin-gap of the lowest Landau level, . This
rapid decay of spin alignment to an unpolarized state occurs over small changes
to both higher and lower magnetic field. The degree of electron spin
polarization as a function of is measured through the magneto-absorption
spectra which distinguish the occupancy of the two electron spin states. The
data provide experimental evidence for the presence of Skyrmion excitations
where exchange energy dominates Zeeman energy in the integer quantum Hall
regime at
Techniques for the realization of ultrareliable spaceborne computers Interim scientific report
Error-free ultrareliable spaceborne computer
The Spin Holonomy Group In General Relativity
It has recently been shown by Goldberg et al that the holonomy group of the
chiral spin-connection is preserved under time evolution in vacuum general
relativity. Here, the underlying reason for the time-independence of the
holonomy group is traced to the self-duality of the curvature 2-form for an
Einstein space. This observation reveals that the holonomy group is
time-independent not only in vacuum, but also in the presence of a cosmological
constant. It also shows that once matter is coupled to gravity, the
"conservation of holonomy" is lost. When the fundamental group of space is
non-trivial, the holonomy group need not be connected. For each homotopy class
of loops, the holonomies comprise a coset of the full holonomy group modulo its
connected component. These cosets are also time-independent. All possible
holonomy groups that can arise are classified, and examples are given of
connections with these holonomy groups. The classification of local and global
solutions with given holonomy groups is discussed.Comment: 21 page
- …