13,294 research outputs found
Coreness of Cooperative Games with Truncated Submodular Profit Functions
Coreness represents solution concepts related to core in cooperative games,
which captures the stability of players. Motivated by the scale effect in
social networks, economics and other scenario, we study the coreness of
cooperative game with truncated submodular profit functions. Specifically, the
profit function is defined by a truncation of a submodular function
: if and
otherwise, where is a given threshold. In this paper, we
study the core and three core-related concepts of truncated submodular profit
cooperative game. We first prove that whether core is empty can be decided in
polynomial time and an allocation in core also can be found in polynomial time
when core is not empty. When core is empty, we show hardness results and
approximation algorithms for computing other core-related concepts including
relative least-core value, absolute least-core value and least average
dissatisfaction value
Viscosity and thermal conductivity effects at first-order phase transitions in heavy-ion collisions
Effects of viscosity and thermal conductivity on the dynamics of first-order
phase transitions are studied. The nuclear gas-liquid and hadron-quark
transitions in heavy-ion collisions are considered. We demonstrate that at
non-zero thermal conductivity, , onset of spinodal instabilities
occurs on an isothermal spinodal line, whereas for instabilities
take place at lower temperatures, on an adiabatic spinodal.Comment: invited talk at 6th International Workshop on Critical Point and
Onset of Deconfinment (CPOD2010), Dubna, August 22-28, 201
Discovery of a binary AGN in the ultraluminous infrared galaxy NGC 6240 using Chandra
Ultraluminous infrared galaxies (ULIRGs) are outstanding due to their huge
luminosity output in the infrared, which is predominantly powered by super
starbursts and/or hidden active galactic nuclei (AGN). NGC 6240 is one of the
nearest ULIRGs and is considered a key representative of its class.
Here, we report the first high-resolution imaging spectroscopy of NGC 6240 in
X-rays. The observation, performed with the ACIS-S detector aboard the Chandra
X-ray observatory, led to the discovery of two hard nuclei, coincident with the
optical-IR nuclei of NGC 6240. The AGN character of both nuclei is revealed by
the detection of absorbed hard, luminous X-ray emission and two strong neutral
Fe_K_alpha lines. In addition, extended X-ray emission components are present,
changing their rich structure in dependence of energy. The close correlation of
the extended emission with the optical Halpha emission of NGC 6240, in
combination with the softness of its spectrum, clearly indicates its relation
to starburst-driven superwind activity.Comment: ApJ Letters in press, 7 colour figures included; preprint and related
papers on NGC 6240 also available at http://www.xray.mpe.mpg.de/~skomossa
Properties of charge density waves in LaBaCuO
We report a comprehensive x-ray scattering study of charge density wave
(stripe) ordering in , for which the
superconducting is greatly suppressed. Strong superlattice reflections
corresponding to static ordering of charge stripes were observed in this
sample. The structural modulation at the lowest temperature was deduced based
on the intensity of over 70 unique superlattice positions surveyed. We found
that the charge order in this sample is described with one-dimensional charge
density waves, which have incommensurate wave-vectors (0.23, 0, 0.5) and (0,
0.23, 0.5) respectively on neighboring planes. The structural
modulation due to the charge density wave order is simply sinusoidal, and no
higher harmonics were observed. Just below the structural transition
temperature, short-range charge density wave correlation appears, which
develops into a large scale charge ordering around 40 K, close to the spin
density wave ordering temperature. However, this charge ordering fails to grow
into a true long range order, and its correlation length saturates at , and slightly decreases below about 15 K, which may be due to the onset
of two-dimensional superconductivity.Comment: 11 pages, 9 figure
Ground-state properties of the one-dimensional electron liquid
We present calculations of the energy, pair-correlation function (PCF), static structure factor (SSF), and momentum density (MD) for the one-dimensional electron gas using the quantum Monte Carlo method. We are able to resolve peaks in the SSF at even-integer multiples of the Fermi wave vector, which grow as the coupling is increased. Our MD results show an increase in the effective Fermi wave vector as the interaction strength is raised in the paramagnetic harmonic wire; this appears to be a result of the vanishing difference between the wave functions of the paramagnetic and ferromagnetic systems. We have extracted the Luttinger liquid exponent from our MDs by fitting to data around kF, finding good agreement between the exponent of the ferromagnetic infinitely thin wire and the ferromagnetic harmonic wire
Impurity-induced stabilization of Luttinger liquid in quasi-one-dimensional conductors
It is shown theoretically that the Luttinger liquid phase in
quasi-one-dimensional conductors can exist in the presence of impurities in a
form of a collection of bounded Luttinger liquids. The conclusion is based upon
the observation by Kane and Fisher that a local impurity potential in Luttinger
liquid acts, at low energies, as an infinite barrier. This leads to a discrete
spectrum of collective charge and spin density fluctuations, so that interchain
hopping can be considered as a small parameter at temperatures below the
minimum excitation energy of the collective modes. The results are compared
with recent experimental observation of a Luttinger-liquid-like behavior in
thin NbSe and TaS wires.Comment: 11 pages, revtex, final version published in JETP Lett
Origin of Radio Emission from Nearby Low-Luminosity Active Galactic Nuclei
We use the observational data in radio, optical and X-ray wavebands, for a
sample of active galactic nuclei (AGNs) with measured black hole masses, to
explore the origin of radio emission from nearby low-luminosity active galactic
nuclei (LLAGNs). We find that the radio luminosities are higher than the
maximal luminosities expected from the ADAF model, for most sources in this
sample. This implies that the radio emission is dominantly from the jets in
these sources. The radio emission from a small fraction of the sources in this
sample can be explained by the ADAF model. However, comparing the observed
multi-band emission data with the spectra calculated for the ADAF or ADIOS
cases, we find that neither ADAF nor ADIOS models can reproduce the observed
multi-band emission simultaneously, with reasonable magnetic field strengths,
for these radio-weak sources. A variety of other possibilities are discussed,
and we suggest that the radio emission is probably dominated by jet emission
even in these radio-weak LLAGNs.Comment: 25 pages, some references were added, accepted for publication in Ap
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Macroporous smart hydrogels for fast-responsive piezoresistive chemical microsensors
Within this work we present the synthesis and characterization of a pH-sensitive macroporous p(AAm-co-AA) hydrogel with an interconnected channel structure to enhance diffusion of aqueous solutions. The hydrogel is characterized by SEM and mercury porosimetry. Furthermore, the hydrogel is successfully integrated into piezoresistive microsensors measuring the hydrogel swelling due to pH changes. A response time reduction of about 80% compared to sensors with conventional non-porous hydrogels is accomplished
Macroporous smart hydrogels for fast-responsive piezoresistive chemical microsensors
Within this work we present the synthesis and characterization of a pH-sensitive macroporous p(AAm-co-AA) hydrogel with an interconnected channel structure to enhance diffusion of aqueous solutions. The hydrogel is characterized by SEM and mercury porosimetry. Furthermore, the hydrogel is successfully integrated into piezoresistive microsensors measuring the hydrogel swelling due to pH changes. A response time reduction of about 80% compared to sensors with conventional non-porous hydrogels is accomplished
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