PSR 0943+10: a bare strange star?

Recent work by Rankin & Deshpande strongly suggests that there exist strong ``micro-storms'' rotating around the magnetic axis of the 1.1s pulsar PSR 0943+10. Such a feature hints that most probably the large-voltage vacuum gap proposed by Ruderman & Sutherland (RS) does exist in the pulsar polar cap. However, there are severe arguments against the formation of the RS-type gap in pulsars, since the binding energies of both the Fe ions and the electrons in a neutron star's surface layer is too small to prevent thermionic ejection of the particles from the surface. Here we propose that PSR 0943+10 (probably also most of the other ``drifting'' pulsars) might be bare strange stars rather than normal neutron stars, in which the ``binding energy'' at the surface is merely infinity either for the case of ``pulsar'' or ``anti-pulsar''. It is further proposed that identifying a drifting pulsar as an anti-pulsar is the key criterion to distinguish strange stars from neutron stars.Comment: 4 pages, no figures, LaTeX, accepted 1999 July 9 by ApJ Letter

A Hessenberg Markov chain for fast fibre delay line length optimization

In this paper we present an approach to compute the invariant vector of the N + 1 state Markov chain P presented in (Rogiest et al., Lecture Notes in Computer Science, NET-COOP 2007 Special Issue, pp. 4465:185-194) to determine the loss rate of an FDL buffer consisting of N lines, by solving a related Hessenberg system (i.e., a Markov chain skip-free in one direction). This system is obtained by inserting additional time instants in the sample paths of P and allows us to compute the loss rate for various FDL lengths by solving a single system. This is shown to be especially effective in reducing the computation time of the heuristic LRA algorithm presented in (Lambert et al., Proc. NAEC 2005, pp. 545-555) to optimize the FDL lengths, where improvements of several orders of magnitude can be realized

On the Application of Gluon to Heavy Quarkonium Fragmentation Functions

We analyze the uncertainties induced by different definitions of the momentum fraction $z$ in the application of gluon to heavy quarkonium fragmentation function. We numerically calculate the initial $g \to J / \psi$ fragmentation functions by using the non-covariant definitions of $z$ with finite gluon momentum and find that these fragmentation functions have strong dependence on the gluon momentum $\vec{k}$. As $| \vec{k} | \to \infty$, these fragmentation functions approach to the fragmentation function in the light-cone definition. Our numerical results show that large uncertainties remains while the non-covariant definitions of $z$ are employed in the application of the fragmentation functions. We present for the first time the polarized gluon to $J/\psi$ fragmentation functions, which are fitted by the scheme exploited in this work.Comment: 11 pages, 7 figures;added reference for sec.

Magnetodielectric effect of Bi6Fe2Ti3O18 film under an ultra-low magnetic field

Good quality and fine grain Bi6Fe2Ti3O18 magnetic ferroelectric films with single-phase layered perovskite structure have been successfully prepared via metal organic decomposition (MOD) method. Results of low-temperature magnetocapacitance measurements reveal that an ultra-low magnetic field of 10 Oe can produce a nontrivial magnetodielectric (MD) response in zero-field-cooling condition, and the relative variation of dielectric constants in magnetic field is positive, i.e., MD=0.05, when T<55K, but negative with a maximum of MD=-0.14 when 55K<T<190K. The magnetodielectric effect appears a sign change at 55K, which is due to transition from antiferromagnetic to weak ferromagnetic; and vanishes abruptly around 190K, which is thought to be associated with order-disorder transition of iron ion at B site of perovskite structures. The ultra-low-field magnetodielectric behaviour of Bi6Fe2Ti3O18 film has been discussed in the light of quasi-two-dimension unique nature of local spin order in ferroelectric film. Our results allow expectation on low-cost applications of detectors and switches for extremely weak magnetic fields in a wide temperature range 55K-190K.Comment: 10 pages 4 figures, planned to submit to J. Phys.: Condensed Matte