3,791 research outputs found
The Vacuum Structure and Spectrum of N=2 Supersymmetric SU(N) Gauge Theory
We present an exact description of the metric on the moduli space of vacua
and the spectrum of massive states for four dimensional N=2 supersymmetric
SU(n) gauge theories. The moduli space of quantum vacua is identified with the
moduli space of a special set of genus n-1 hyperelliptic Riemann surfaces.Comment: 11 pages, Revtex, 2 figures. Reference adde
Heat storage in alloy transformations
The feasibility of using metal alloys as thermal energy storage media was determined. The following major elements were studied: (1) identification of congruently transforming alloys and thermochemical property measurements; (2) development of a precise and convenient method for measuring volume change during phase transformation and thermal expansion coefficients; (3) development of a numerical modeling routine for calculating heat flow in cylindrical heat exchangers containing phase change materials; and (4) identification of materials that could be used to contain the metal alloys. Several eutectic alloys and ternary intermetallic phases were determined. A method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation from data obtained during one continuous experimental test. The method and apparatus are discussed and the experimental results are presented. The development of the numerical modeling method is presented and results are discussed for both salt and metal alloy phase change media
Methods of tropical optimization in rating alternatives based on pairwise comparisons
We apply methods of tropical optimization to handle problems of rating
alternatives on the basis of the log-Chebyshev approximation of pairwise
comparison matrices. We derive a direct solution in a closed form, and
investigate the obtained solution when it is not unique. Provided the
approximation problem yields a set of score vectors, rather than a unique (up
to a constant factor) one, we find those vectors in the set, which least and
most differentiate between the alternatives with the highest and lowest scores,
and thus can be representative of the entire solution.Comment: 9 pages, presented at the Annual Intern. Conf. of the German
Operations Research Society (GOR), Helmut Schmidt University Hamburg,
Germany, August 30 - September 2, 201
Unified model for network dynamics exhibiting nonextensive statistics
We introduce a dynamical network model which unifies a number of network
families which are individually known to exhibit -exponential degree
distributions. The present model dynamics incorporates static (non-growing)
self-organizing networks, preferentially growing networks, and (preferentially)
rewiring networks. Further, it exhibits a natural random graph limit. The
proposed model generalizes network dynamics to rewiring and growth modes which
depend on internal topology as well as on a metric imposed by the space they
are embedded in. In all of the networks emerging from the presented model we
find q-exponential degree distributions over a large parameter space. We
comment on the parameter dependence of the corresponding entropic index q for
the degree distributions, and on the behavior of the clustering coefficients
and neighboring connectivity distributions.Comment: 11 pages 8 fig
DISTRIBUTION OF THE LICHEN SPECIES CETRARIA ACULEATA IN HUNGARY
Cetraria aculeata became legally protected in Hungary in 2005. Though for several decades it was known from a few localities only, recently it turned out that it is more frequent than previously ascertained. However, its range of distribution is insufficiently known and the species is still regarded to be rare. The present assessment is based on its specimens from Hungary; the currently known data of occurrences are presented on an updated distribution map. The recent records from the Bakony Mts (Királyszentistván, Sóly), Mecsek Mts (Cserkút, Pécs) and the Velence Mts (Pázmánd) are new to Hungary, and the one from the Gödöllő Hills (Erdőkertes) turned to be a recent confirmation of Boros’ old record (1962) at Vácegres locality
Static Versus Dynamic Friction: The Role of Coherence
A simple model for solid friction is analyzed. It is based on tangential
springs representing interlocked asperities of the surfaces in contact. Each
spring is given a maximal strain according to a probability distribution. At
their maximal strain the springs break irreversibly. Initially all springs are
assumed to have zero strain, because at static contact local elastic stresses
are expected to relax. Relative tangential motion of the two solids leads to a
loss of coherence of the initial state: The springs get out of phase due to
differences in their sizes. This mechanism alone is shown to lead to a
difference between static and dynamic friction forces already. We find that in
this case the ratio of the static and dynamic coefficients decreases with
increasing relative width of the probability distribution, and has a lower
bound of 1 and an upper bound of 2.Comment: 10 pages, 2 figures, revtex
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