Decay of weak turbulence

Weak turbulence fields generated by single and multiple stage grids covering Reynolds numbers between 7 and 70 showing decay of energy spectr

Anomalous Light Scattering by Topological PT{\mathcal{PT}}-symmetric Particle Arrays

Robust topological edge modes may evolve into complex-frequency modes when a physical system becomes non-Hermitian. We show that, while having negligible forward optical extinction cross section, a conjugate pair of such complex topological edge modes in a non-Hermitian $\mathcal{PT}$-symmetric system can give rise to an anomalous sideway scattering when they are simultaneously excited by a plane wave. We propose a realization of such scattering state in a linear array of subwavelength resonators coated with gain media. The prediction is based on an analytical two-band model and verified by rigorous numerical simulation using multiple-multipole scattering theory. The result suggests an extreme situation where leakage of classical information is unnoticeable to the transmitter and the receiver when such a $\mathcal{PT}$-symmetric unit is inserted into the communication channel.Comment: 16 pages, 8 figure

Analysis and control of bifurcation and chaos in averaged queue length in TCP/RED model

This paper studies the bifurcation and chaos phenomena in averaged queue length in a developed Transmission Control Protocol (TCP) model with Random Early Detection (RED) mechanism. Bifurcation and chaos phenomena are nonlinear behaviour in network systems that lead to degradation of the network performance. The TCP/RED model used is a model validated previously. In our study, only the average queue size k q − is considered, and the results are based on analytical model rather than actual measurements. The instabilities in the model are studied numerically using the conventional nonlinear bifurcation analysis. Extending from this bifurcation analysis, a modified RED algorithm is derived to prevent the observed bifurcation and chaos regardless of the selected parameters. Our modification is for the simple scenario of a single RED router carrying only TCP traffic. The algorithm neither compromises the throughput nor the average queuing delay of the system

Quasinormal modes prefer supersymmetry ?

One ambiguity in loop quantum gravity is the appearance of a free parameter which is called Immirzi parameter. Recently Dreyer has argued that this parameter may be fixed by considering the quasinormal mode spectrum of black holes, while at the price of changing the gauge group to SO(3) rather than the original one SU(2). Physically such a replacement is not quite natural or desirable. In this paper we study the relationship between the black hole entropy and the quasi normal mode spectrum in the loop quantization of N=1 supergravity. We find that a single value of the Immirzi parameter agrees with the semiclassical expectations as well. But in this case the lowest supersymmetric representation dominates, fitting well with the result based on statistical consideration. This suggests that, so long as fermions are included in the theory, supersymemtry may be favored for the consistency of the low energy limit of loop quantum gravity.Comment: 3 page

Striped Magnetic Ground State of the Kagome Lattice in Fe4Si2Sn7O16

We have experimentally identified a new magnetic ground state for the kagome lattice, in the perfectly hexagonal Fe2+ (3d6, S = 2) compound Fe4Si2Sn7O16. Representational symmetry analysis of neutron diffraction data shows that below T_N = 3.5 K, the spins on 2/3 of the magnetic ions order into canted antiferromagnetic chains, separated by the remaining 1/3 which are geometrically frustrated and show no long-range order down to at least T = 0.1 K. Moessbauer spectroscopy confirms that there is no static order on the latter 1/3 of the magnetic ions - i.e., they are in a liquid-like rather than a frozen state - down to at least 1.65 K. A heavily Mn-doped sample Fe1.45Mn2.55Si2Sn7O16 has the same magnetic structure. Although the propagation vector q = (0, 1/2 , 1/2 ) breaks hexagonal symmetry, we see no evidence for magnetostriction in the form of a lattice distortion within the resolution of our data. We discuss the relationship to partially frustrated magnetic order on the pyrochlore lattice of Gd2Ti2O7, and to theoretical models that predict symmetry breaking ground states for perfect kagome lattices.Comment: 5 pages, 5 figure

Holographic Formulation of Quantum Supergravity

We show that ${\cal N}=1$ supergravity with a cosmological constant can be expressed as constrained topological field theory based on the supergroup $Osp(1|4)$. The theory is then extended to include timelike boundaries with finite spatial area. Consistent boundary conditions are found which induce a boundary theory based on a supersymmetric Chern-Simons theory. The boundary state space is constructed from states of the boundary supersymmetric Chern-Simons theory on the punctured two sphere and naturally satisfies the Bekenstein bound, where area is measured by the area operator of quantum supergravity.Comment: 30 pages, no figur

Barite co-precipitation of arsenic and chromium anions for the treatment of fracking wastewater

Hydraulic fracturing, also known as fracking, produces wastewater that contains hazardous ions such as arsenic, strontium, and chromium. In order to remove these toxic contaminants, Na2SO4 can be added to fracking wastewater to form Barite (BaSO4). During this process, ions such as Arsenic and Chromium will incorporate into the solid phase. In this work, we examined the coprecipitation of Arsenic and Chromium anions into Barite. We have created simulations of this precipitate formation in fracking wastewater treatments and have used this for Arsenic, Chromium, and Barium. A 1:1 ratio of BaCl2 to Na2SO4 at saturation indices of 2.19, 2.89, 3.49 for BaSO4 were used for experimentation. We conducted two more experiment sets at 1.0 M NaCl to analyze the effect of salinity with the same experiment concentration and an adjusted concentration to result in identical saturation indices. Na2SO4 was added to the simulated fracking wastewater. X-ray fluorescence was conducted to analyze the concentrations of Chromium, Arsenic, and Barium in precipitated solids. Fracking wastewater solutions that are undersaturated with respect to BaCrO4 have undetectable levels of Chromium. For experiments that are oversaturated with respect to Barium Chromate, the Chromium concentration increases as NaCrO4 (M) increases with and without NaCl. Arsenic incorporation into Barite somewhat correlates with HAsO42- but is complicated by competition with CrO42-. As BaSO4 saturation index increases, Chromium incorporation decreases. Arsenic incorporation also increases with BaSO4 saturation index until a threshold is reached, likely due to competition with Chromium. Increased NaCl leads to Barite particles that are more concentrated in Chromium and Arsenic. These results have implications for how competing anions are affected during the treatment of fracking wastewater using co-precipitation