Cosmological meaning of the gravitational gauge group

It is shown that among the R+beta S^{abc}S_{abc} models, only the one with beta=1/2 has nonvanishing torsion effect in the Robertson--Walker universe filled with a spin fluid, where S_{abc} denotes torsion. Moreover, the torsion effect in that model is found to be able to replace the big-bang singularity by a big bounce. Furthermore, we find that the model can be obtained under a Kaluza--Klein-like ansatz, by assuming that the gravitational gauge group is the de Sitter group.Comment: 9 pages. arXiv admin note: substantial text overlap with arXiv:1402.365

Free Deterministic Equivalents for the Analysis of MIMO Multiple Access Channel

In this paper, a free deterministic equivalent is proposed for the capacity analysis of the multi-input multi-output (MIMO) multiple access channel (MAC) with a more general channel model compared to previous works. Specifically, a MIMO MAC with one base station (BS) equipped with several distributed antenna sets is considered. Each link between a user and a BS antenna set forms a jointly correlated Rician fading channel. The analysis is based on operator-valued free probability theory, which broadens the range of applicability of free probability techniques tremendously. By replacing independent Gaussian random matrices with operator-valued random variables satisfying certain operator-valued freeness relations, the free deterministic equivalent of the considered channel Gram matrix is obtained. The Shannon transform of the free deterministic equivalent is derived, which provides an approximate expression for the ergodic input-output mutual information of the channel. The sum-rate capacity achieving input covariance matrices are also derived based on the approximate ergodic input-output mutual information. The free deterministic equivalent results are easy to compute, and simulation results show that these approximations are numerically accurate and computationally efficient.Comment: 26 pages, 7 figures, Accepted by IEEE Transactions on Information Theor

Playing Stackelberg Opinion Optimization with Randomized Algorithms for Combinatorial Strategies

From a perspective of designing or engineering for opinion formation games in social networks, the "opinion maximization (or minimization)" problem has been studied mainly for designing subset selecting algorithms. We furthermore define a two-player zero-sum Stackelberg game of competitive opinion optimization by letting the player under study as the first-mover minimize the sum of expressed opinions by doing so-called "internal opinion design", knowing that the other adversarial player as the follower is to maximize the same objective by also conducting her own internal opinion design. We propose for the min player to play the "follow-the-perturbed-leader" algorithm in such Stackelberg game, obtaining losses depending on the other adversarial player's play. Since our strategy of subset selection is combinatorial in nature, the probabilities in a distribution over all the strategies would be too many to be enumerated one by one. Thus, we design a randomized algorithm to produce a (randomized) pure strategy. We show that the strategy output by the randomized algorithm for the min player is essentially an approximate equilibrium strategy against the other adversarial player

The development of advanced creep constitutive equations for high chromium steel P91 at low stress range

Diffusion dominates the creep deformation at low stress range for high chromium steel P91. Brittle creep fracture is caused by cavity nucleation, growth and coalescence of cavities and large precipitates (Laves phase and M23C6) at grain boundary under low stress range. At low stress range, a linear relation between strain at failure and different stresses has been described. Moreover, the minimum strain rate is also proportional to the different stresses