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Direct Formation of Structural Components Using a Martian Soil Simulant.
Martian habitats are ideally constructed using only locally available soils; extant attempts to process structural materials on Mars, however, generally require additives or calcination. In this work we demonstrate that Martian soil simulant Mars-1a can be directly compressed at ambient into a strong solid without additives, highlighting a possible aspect of complete Martian in-situ resource utilization. Flexural strength of the compact is not only determined by the compaction pressure but also significantly influenced by the lateral boundary condition of processing loading. The compression loading can be applied either quasi-statically or through impact. Nanoparticulate iron oxide (npOx), commonly detected in Martian regolith, is identified as the bonding agent. Gas permeability of compacted samples was measured to be on the order of 10-16 m2, close to that of solid rocks. The compaction procedure is adaptive to additive manufacturing
Strong stability of Nash equilibria in load balancing games
We study strong stability of Nash equilibria in the load balancing games of m (m >= 2) identical servers, in which every job chooses one of the m servers and each job wishes to minimize its cost, given by the
workload of the server it chooses.
A Nash equilibrium (NE) is a strategy profile that is resilient to unilateral deviations. Finding an NE in such a game is simple. However, an NE assignment is not stable against coordinated deviations of several jobs, while a strong Nash equilibrium (SNE) is. We study how well an
NE approximates an SNE.
Given any job assignment in a load balancing game, the improvement ratio (IR) of a deviation of a job is defined as the ratio between the pre-and post-deviation costs. An NE is said to be a ρ-approximate SNE (ρ >= 1) if there is no coalition of jobs such that each job of the coalition
will have an IR more than ρ from coordinated deviations of the coalition.
While it is already known that NEs are the same as SNEs in the 2-server load balancing game, we prove that, in the m-server load balancing game for any given m >= 3, any NE is a (5=4)-approximate SNE, which together with the lower bound already established in the literature implies that the approximation bound is tight. This closes the final gap in the literature on the study of approximation of general NEs to SNEs in the load balancing games. To establish our upper bound, we apply with novelty a powerful graph-theoretic tool
Magic wavelengths for the 6s^2\,^1S_0-6s6p\,^3P_1^o transition in ytterbium atom
The static and dynamic electric-dipole polarizabilities of the 6s^2\,^1S_0
and 6s6p\,^3P_1^o states of Yb are calculated by using the relativistic ab
initio method. Focusing on the red detuning region to the
6s^2\,^1S_0-6s6p\,^3P_1^o transition, we find two magic wavelengths at
1035.7(2) nm and 612.9(2) nm for the 6s^2\,^1S_0-6s6p\,^3P_1^o, M_J=0
transition and three magic wavelengthes at 1517.68(6) nm, 1036.0(3) nm and
858(12) nm for the 6s^2\,^1S_0-6s6p\,^3P_1^o, M_J=\pm1 transitions. Such
magic wavelengths are of particular interest for attaining the
state-insensitive cooling, trapping, and quantum manipulation of neutral Yb
atom.Comment: 13 pages, 3 figure
The Gamow-Teller Resonance in Finite Nuclei in the Relativistic Random Phase Approximation
Gamow-Teller(GT) resonances in finite nuclei are studied in a fully
consistent relativistic random phase approximation (RPA) framework. A
relativistic form of the Landau-Migdal contact interaction in the spin-isospin
channel is adopted. This choice ensures that the GT excitation energy in
nuclear matter is correctly reproduced in the non-relativistic limit. The GT
response functions of doubly magic nuclei Ca, Zr and Pb
are calculated using the parameter set NL3 and =0.6 . It is found that
effects related to Dirac sea states account for a reduction of 6-7 % in the GT
sum rule.Comment: 9 pages, 1 figur
Warped Brane worlds in Critical Gravity
We investigate the brane models in arbitrary dimensional critical gravity
presented in [Phys. Rev. Lett. 106, 181302 (2011)]. For the model of the thin
branes with codimension one, the Gibbons-Hawking surface term and the junction
conditions are derived, with which the analytical solutions for the flat, AdS,
and dS branes are obtained at the critical point of the critical gravity. It is
found that all these branes are embedded in an AdS spacetime, but, in
general, the effective cosmological constant of the AdS
spacetime is not equal to the naked one in the critical gravity,
which can be positive, zero, and negative. Another interesting result is that
the brane tension can also be positive, zero, or negative, depending on the
symmetry of the thin brane and the values of the parameters of the theory,
which is very different from the case in general relativity. It is shown that
the mass hierarchy problem can be solved in the braneworld model in the
higher-derivative critical gravity. We also study the thick brane model and
find analytical and numerical solutions of the flat, AdS, and dS branes. It is
find that some branes will have inner structure when some parameters of the
theory are larger than their critical values, which may result in resonant KK
modes for some bulk matter fields. The flat branes with positive energy density
and AdS branes with negative energy density are embedded in an -dimensional
AdS spacetime, while the dS branes with positive energy density are embedded in
an -dimensional Minkowski one.Comment: 14 pages, 7 figures, updated version, accepted by EPJ
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