Quadratic forms, generalized Hamming weights of codes and curves with many points

We use the relations between quadrics, trace codes and algebraic curves to construct algebraic curves over finite fields with many points and to compute generalized Hamming weights of codes.Comment: 14 pages, Plain Te

Electromagnons and instabilities in magnetoelectric materials with non-collinear spin orders

We show that strong electromagnon peaks can be found in absorption spectra of non-collinear magnets exhibiting a linear magnetoelectric effect. The frequencies of these peaks coincide with the frequencies of antiferromagnetic resonances and the ratio of the spectral weights of the electromagnon and antiferromagnetic resonance is related to the ratio of the static magnetoelectric constant and magnetic susceptibility. Using a Kagome lattice antiferromagnet as an example, we show that frustration of spin ordering gives rise to magnetoelastic instabilities at strong spin-lattice coupling, which transform a non-collinear magnetoelectric spin state into a collinear multiferroic state with a spontaneous electric polarization and magnetization. The Kagome lattice antiferromagnet also shows a ferroelectric incommensurate-spiral phase, where polarization is induced by the exchange striction mechanism.Comment: 9 pages, 4 figure

Size distribution of embryos produced by crystal-rod contacts

We performed contact nucleation experiments on the (010) face of potassium hydrogen phthalate (KAP) crystals growing in a stagnant supersaturated aqueous solution and determined - after a given growth time t - (ex situ) the crystal size distribution (CSD) of the secondary nuclei (which at t = 0 are called "embryos") by using a scanning electron microscope (SEM). The origin of the secondary nuclei could clearly be revealed (damage to the crystal surface). The CSD can be fitted with a log-normal distribution which is typical for many powders obtained by grinding. Minimum size and mean size can be quantitatively understood by elementary fracture mechanics

Constant Q and a fractal, stratifed Earth

Frequency dependent measurements of the quality factor Q typically show a constant behaviour for low frequencies and a positive power law dependence for higher frequencies. In particular, the constant Q pattern is usually explained using intrinsic attenuation models due to anelasticity with either a single or multiple superposed relaxation mechanisms - each with a particular resonance peak. However, in this study, I show using wave localisation theory that a constant Q may also be due to apparent attenuation due to scattering losses. Namely, this phenomenon occurs if the Earth displays fractal characteristics. Moreover, if fractal characteristics exist over a limited range of scales only, even an absorption band can be created - in accordance with observations. This indicates that it may be very difficult to distinguish between intrinsic and scattering attenuation on the basis of frequency dependent measurements of the quality factor only

A comparison of the fast timing behaviour of 4U 1705-44 to that of 4U 1608-52 and Cyg X-1

We studied the fast timing behaviour of the atoll source 4U 1705-44 using the entire EXOSAT dataset, four observations covering a total of 230,000 seconds of 1-20 keV spectral and timing data. In one of the observations, 4U 1705-44 was in a low intensity "island" state and had an unusually hard spectrum. The fast timing analysis of this hard island state shows a power spectrum very similar to that of black hole candidates in the "low state", with a flat-topped band-limited noise component that gradually steepens towards higher frequency. We perform for the first time a quantitative comparison of the timing behaviour of an atoll source in the hard island state (4U 1705-44) with that of a black hole candidate in the low state (Cygnus X-1). We also compare the power spectrum of 4U 1705-44 in the hard island state with those of the atoll source 4U 1608-52 in a similar state as reported by Yoshida et al. (1993). Our results confirm that there are similarities between the fast timing behaviour of the hard island states of these atoll sources and the low state of black hole candidates, yet we also find significant differences in power spectral parameters; the power spectra of the neutron star systems have a lower rms amplitude and are less steep. We find a trend among the neutron star power spectral properties, in the sense that the lower the centroid frequency of the fitted Lorentzian is, the higher its fractional rms amplitude, and the steeper the continuum underneath it. We propose a new method to fit the power spectra of Cyg X-1 and other black hole candidates in the low state, that provides a significantly better fit than previous models.Comment: Accepted for publication in A&A 7 pages 4 figure

Beyond Marble, Medicants & Myth: Epidaurus' History, Material Culture, Purpose and Place in the Greater Mediterranean Area

'The most famous of sanctuaries of Asclepius had their origin from Epidaurus’, Pausanias writes in his Hellados Periegesis (‘Description of Greece’). All across the Aegean and beyond, word of the salutary reputation of Epidaurian divinity had spread. And as tales of Epidaurus’ sanctuary of Asclepius travelled the lands and crossed the seas, so did the urge to ensure that the Epidaurian success formula was, as we say, coming soon to a place near you. So we know Epidaurus had managed to make a name for itself: all the way from the Argolid Peninsula to Asia Minor and the shores of Northern Africa. But what exactly had led to its rise in prominence? What about Epidaurus allowed for it to transcend its local cult-status? And how did its celebrated reputation and meaning change across places and time? What, in other words, is the story of what is often simply referred to as the sanctuary of Asclepius at Epidaurus

A ‘Grooming Chamber’ For Antisemitism

If Jewish Bolsheviks could put an end to the imperial rule of the Romanovs, could they pose a threat to the vision of a Third Reigh? A question the German National Socialists are likely to have asked themselves before and on the eve of plotting the rise of the Nazi regime. After all, Europe had had a long-standing relationship with blaming the Jews for the world’s miseries. A relationship Germany was ready to refuel, as indicated by German Field Marshal Walter von Reichenau, when he stated that ‘the most essential aim of war against the Jewish-bolshevistic system is a complete destruction of their means of power and the elimination of Asiatic influence from the European culture.’ But the German fears of Jewish interference with their great scheme for Europe’s future, must surely have been inspired by more than just the age-old conspiratorial allegation that Jews were the main forces behind world politics. As such, this essay will seek to inspect the apparent rise of antisemitic fears at the time, and put a case forward to show how religion played into all this

Divine Leadership and The Ruler Cult in Roman and Contemporary Times

Seeing how the idea of the ‘ruler cult’ and the necessary ‘myth-making’ to establish it exists to this day, as seen with the regime of a 21st century dictator like Kim Jong-il, it would be most interesting to see what parallels exist between cases of divine leadership and what we might learn about our contemporary cult rulers when looking at the dynamics of the two-millennia-old cult of the deified Emperor Augustus. As such, I have formulated a central question that focuses on the reign of Divus Augustus, and in doing so provides opportunity to extrapolate from it new insights in similar but contemporary figures of leadership. A clear case of 'to understand motives in the present, one must look at actions in the past.