Soft X-ray Excess in the Coma Cluster from a Cosmic Axion Background

We show that the soft X-ray excess in the Coma cluster can be explained by a cosmic background of relativistic axions converting into photons in the cluster magnetic field. We provide a detailed self-contained review of the cluster soft X-ray excess, the proposed astrophysical explanations and the problems they face, and explain how a 0.1-1 keV axion background naturally arises at reheating in many string theory models of the early universe. We study the morphology of the soft excess by numerically propagating axions through stochastic, multi-scale magnetic field models that are consistent with observations of Faraday rotation measures from Coma. By comparing to ROSAT observations of the 0.2-0.4 keV soft excess, we find that the overall excess luminosity is easily reproduced for $g_{a\gamma\gamma} \sim 2 \times 10^{-13}$ GeV$^{-1}$. The resulting morphology is highly sensitive to the magnetic field power spectrum. For Gaussian magnetic field models, the observed soft excess morphology prefers magnetic field spectra with most power in coherence lengths on ${\cal O}(3 {\rm ~kpc})$ scales over those with most power on ${\cal O}(12 {\rm ~kpc})$ scales. Within this scenario, we bound the mean energy of the axion background to $50\, {\rm eV}\lesssim \langle E_a \rangle \lesssim 250\, {\rm eV}$, the axion mass to $m_a \lesssim 10^{-12}\,\hbox{eV}$, and derive a lower bound on the axion-photon coupling $g_{a\gamma\gamma} \gtrsim \sqrt{0.5/\Delta N_{\rm eff}}\, 1.4 \times 10^{-13}$ GeV$^{-1}$.Comment: 43 pages, 11 figure

Implementing Quantum Gates by Optimal Control with Doubly Exponential Convergence

We introduce a novel algorithm for the task of coherently controlling a quantum mechanical system to implement any chosen unitary dynamics. It performs faster than existing state of the art methods by one to three orders of magnitude (depending on which one we compare to), particularly for quantum information processing purposes. This substantially enhances the ability to both study the control capabilities of physical systems within their coherence times, and constrain solutions for control tasks to lie within experimentally feasible regions. Natural extensions of the algorithm are also discussed.Comment: 4+2 figures; to appear in PR

Principle of Fall Turf Management

Management of cool-season turfgrasses in the fall is mainly directed toward fertilization, broadleaf weed control and mowing. Fertilizer and weed control recommendations are made with great authority because of a good research base. Fall mowing height has not received as much attention, especially since mowing is often considered a curse by the end of along growing season. In the summer, Kentucky bluegrass and tall fescue turf is mowed high (3-4 inches) to insulate the sward against moisture and temperature stress and to prevent germination of light-sensitive seed of crabgrass and other warm-season annuals. In the fall, however, the mowing height should be lowered progressively. To understand the importance of mowing height one needs a basic knowledge of the growth of vegetative turfgrasses

The Sunyaev-Zel'dovich temperature of the intracluster medium

The relativistic Sunyaev-Zel'dovich (SZ) effect offers a method, independent of X-ray, for measuring the temperature of the intracluster medium (ICM) in the hottest systems. Here, using N-body/hydrodynamic simulations of three galaxy clusters, we compare the two quantities for a non-radiative ICM, and for one that is subject both to radiative cooling and strong energy feedback from galaxies. Our study has yielded two interesting results. Firstly, in all cases, the SZ temperature is hotter than the X-ray temperature and is within ten per cent of the virial temperature of the cluster. Secondly, the mean SZ temperature is less affected by cooling and feedback than the X-ray temperature. Both these results can be explained by the SZ temperature being less sensitive to the distribution of cool gas associated with cluster substructure. A comparison of the SZ and X-ray temperatures (measured for a sample of hot clusters) would therefore yield interesting constraints on the thermodynamic structure of the intracluster gas.Comment: This version accepted for publication in MNRAS following minor revisio

A phenomenological model of the superconducting state of the Bechgaard salts

We present a group theoretical analysis of the superconducting state of the Bechgaard salts, e.g., (TMTSF)_2PF_6 or (TMTSF)_2ClO_6. We show that there are eight symmetry distinct superconducting states. Of these only the (fully gapped, even frequency, p-wave, triplet) 'polar state' is consistent with the full range of the experiments on the Bechgaard salts. The gap of the polar state is d(k) (psi_uk,0,0), where psi_uk may be any odd parity function that is translationally invariant.Comment: 4 pages, no figure

Responding to cybercrime: Results of a comparison between community members and police personnel

Advancements in information technology are sources of both opportunity and vulnerability for citizens. Previous research indicates that there are significant challenges for police in investigating cybercrime, that community expectations about police responses are based largely on media representations, and that victims experience high levels of frustration and stigmatisation. This paper examines the views of the Australian community and law enforcement officers about the policing of cybercrime. Results suggest that police personnel are more likely to view cybercrime as serious, and community members are more likely to ascribe blame to victims. Results also indicate a discrepancy between police and community members in their views of the efficacy of police responses. These discrepancies contribute to public dissatisfaction. Therefore, the paper covers some general strategies for short-and long-term cybercrime prevention

Kinetics and Mechanisms of Oxidation of Hemoprotein Model Compounds

The kinetics of reaction of oxyheme complexes with dithionite ion and with deoxyheme were studied. Because rates of autooxidation of oxyheme complexes were inversly proportional to oxygen pressure and proportional to the square of the total heme concentration, it was concluded that the reaction proceeds through Heme- 00-Heme as suggested by Cohen and Caughey. The direct reaction of dithionite ion with oxyheme complexes accords with the Fe+o 2- · formulation of the iron-oxygen bond

Kinetics and Mechanisms of Oxidation of Hemoprotein Model Compounds

The kinetics of reaction of oxyheme complexes with dithionite ion and with deoxyheme were studied. Because rates of autooxidation of oxyheme complexes were inversly proportional to oxygen pressure and proportional to the square of the total heme concentration, it was concluded that the reaction proceeds through Heme- 00-Heme as suggested by Cohen and Caughey. The direct reaction of dithionite ion with oxyheme complexes accords with the Fe+o 2- · formulation of the iron-oxygen bond

Domain Wall Spin Dynamics in Kagome Antiferromagnets

We report magnetization and neutron scattering measurements down to 60 mK on a new family of Fe based kagome antiferromagnets, in which a strong local spin anisotropy combined with a low exchange path network connectivity lead to domain walls intersecting the kagome planes through strings of free spins. These produce unfamiliar slow spin dynamics in the ordered phase, evolving from exchange-released spin-flips towards a cooperative behavior on decreasing the temperature, probably due to the onset of long-range dipolar interaction. A domain structure of independent magnetic grains is obtained that could be generic to other frustrated magnets.Comment: 5 pages, 4 figure

Nonperturbative Effects in Quarkonia Associated with Large Orders in Perturbation Theory

We show that the perturbation series for quarkonia energies diverges at large orders. This results in a perturbative ambiguity in the energy that scales as e^(-1/a*Lambda) where a is the Bohr radius of quarkonium and Lambda is the QCD scale parameter. This ambiguity is associated with a nonperturbative contribution to the energy from distances of order 1/Lambda and greater. This contribution is separate from that of the gluon condensate.Comment: 6 pages, 2 figure