Low relaxation rate in a low-Z alloy of iron

The longest relaxation time and sharpest frequency content in ferromagnetic precession is determined by the intrinsic (Gilbert) relaxation rate \emph{$G$}. For many years, pure iron (Fe) has had the lowest known value of $G=\textrm{57 Mhz}$ for all pure ferromagnetic metals or binary alloys. We show that an epitaxial iron alloy with vanadium (V) possesses values of $G$ which are significantly reduced, to 35$\pm$5 Mhz at 27% V. The result can be understood as the role of spin-orbit coupling in generating relaxation, reduced through the atomic number $Z$.Comment: 14 pages, 4 figure

Relativistic Multiple Scattering Theory and the Relativistic Impulse Approximation

It is shown that a relativistic multiple scattering theory for hadron-nucleus scattering can be consistently formulated in four-dimensions in the context of meson exchange. We give a multiple scattering series for the optical potential and discuss the differences between the relativistic and non-relativistic versions. We develop the relativistic multiple scattering series by separating out the one boson exchange term from the rest of the Feynman series. However this particular separation is not absolutely necessary and we discuss how to include other terms. We then show how to make a three-dimensional reduction for hadron-nucleus scattering calculations and we find that the relative energy prescription used in the elastic scattering equation should be consistent with the one used in the free two-body t-matrix involved in the optical potential. We also discuss what assumptions are involved in making a Dirac Relativistic Impulse Approximation (RIA).Comment: 20 pages, 9 figures, Accepted for publication in Journal of Physics

Io and Europa Atmosphere Detection through Jovian Mutual Events Scott Degenhardt International Occultation Timing Association (IOTA) 2112 Maple Leaf

Abstract Approximately every 6 years the orbital plane of the Jovian moons turns edge on from earth's line of sight giving us the opportunity to time the eclipses and occultations arising from this geometry known as Jupiter Mutual Events (JME). These timings help to refine the residuals in the orbital elements of Jovian moons. While taking several tens of minutes of wing data surrounding an occultation by Io in 2009 during that JME cycle, an anomaly was detected in the lightcurve prior to and following the actual occultation. Analysis of this anomaly led to the hypothesis that it was the result of atmospheric extinction of the light from the occulted moon by the atmosphere of Io. The same anomaly was then found when Europa was the occulting body. Occultations by Ganymede showed no dimming anomaly. Eleven observers from 4 countries contributed 53 data sets for 28 individual events in an observing program for the study of this phenomenon. This paper will detail the results including camera response, observing method, reduction method, and atmospheric extinction detection. The atmospheric extinction hypothesis is supported by several independent methods which will also be detailed. Derived atmospheric models will be presented including a noted asymmetry

Relativistic calculations of pionic and kaonic atoms hyperfine structure

We present the relativistic calculation of the hyperfine structure in pionic and kaonic atoms. A perturbation method has been applied to the Klein-Gordon equation to take into account the relativistic corrections. The perturbation operator has been obtained \textit{via} a multipole expansion of the nuclear electromagnetic potential. The hyperfine structure of pionic and kaonic atoms provide an additional term in the quantum electrodynamics calculation of the energy transition of these systems. Such a correction is required for a recent measurement of the pion mass

Modeling core collapse supernovae in 2 and 3 dimensions with spectral neutrino transport

The overwhelming evidence that the core collapse supernova mechanism is inherently multidimensional, the complexity of the physical processes involved, and the increasing evidence from simulations that the explosion is marginal presents great computational challenges for the realistic modeling of this event, particularly in 3 spatial dimensions. We have developed a code which is scalable to computations in 3 dimensions which couples PPM Lagrangian with remap hydrodynamics [1], multigroup, flux-limited diffusion neutrino transport [2], with many improvements), and a nuclear network [3]. The neutrino transport is performed in a ray-by-ray plus approximation wherein all the lateral effects of neutrinos are included (e.g., pressure, velocity corrections, advection) except the transport. A moving radial grid option permits the evolution to be carried out from initial core collapse with only modest demands on the number of radial zones. The inner part of the core is evolved after collapse along with the rest of the core and mantle by subcycling the lateral evolution near the center as demanded by the small Courant times. We present results of 2-D simulations of a symmetric and an asymmetric collapse of both a 15 and an 11 M progenitor. In each of these simulations we have discovered that once the oxygen rich material reaches the shock there is a synergistic interplay between the reduced ram pressure, the energy released by the burning of the shock heated oxygen rich material, and the neutrino energy deposition which leads to a revival of the shock and an explosion.Comment: 10 pages, 3 figure

Integrability and chaos: the classical uncertainty

In recent years there has been a considerable increase in the publishing of textbooks and monographs covering what was formerly known as random or irregular deterministic motion, now named by the more fashionable term of deterministic chaos. There is still substantial interest in a matter that is included in many graduate and even undergraduate courses on classical mechanics. Based on the Hamiltonian formalism, the main objective of this article is to provide, from the physicist's point of view, an overall and intuitive review of this broad subject (with some emphasis on the KAM theorem and the stability of planetary motions) which may be useful to both students and instructors.Comment: 24 pages, 10 figure

Genetic and migratory evidence for sympatric spawning of tropical pacific eels from Vanuatu

The spawning areas of tropical anguillid eels in the South Pacific are poorly known, and more information about their life histories is needed to facilitate conservation. We genetically characterized 83 out of 84 eels caught on Gaua Island (Vanuatu) and tagged 8 eels with pop-up satellite transmitters. Based on morphological evidence, 32 eels were identified as Anguilla marmorata, 45 as A. megastoma and 7 as A. obscura. Thirteen of these eels possessed a mitochondrial DNA sequence (control region, 527 bp) or nuclear haplotype (GTH2b, 268 bp) conflicting with their species designation. These individuals also had multi-locus genotypes (6 microsatellite loci) intermediate between the species, and 9 of these eels further possessed heterozygote genotypes at species-diagnostic nuclear single nucleotide polymorphisms (SNPs). We classified these individuals as possibly admixed between A. marmorata and A. megastoma. One A. marmorata and one A. megastoma migrated 634 and 874 km, respectively, towards the border between the South Equatorial Current and the South Equatorial Counter Current. Both species descended from around 200 m depth at night to 750 m during the day. Lunar cycle affected the upper limit of migration depths of both species. The tags remained attached for 3 and 5 mo and surfaced <300 km from the pop-up location of a previously tagged A. marmorata. A salinity maximum at the pop-up locations corresponding to the upper nighttime eel migration depths may serve as a seamark of the spawning area. The similar pop-up locations of both species and the evidence for admixture suggest that these tropical eels share a sympatric spawning area

Leptonic μ \mu - and τ \tau -decays: mass effects, polarization effects and O(α) O(\alpha) radiative corrections

We calculate the radiative corrections to the unpolarized and the four polarized spectrum and rate functions in the leptonic decay of a polarized $\mu$ into a polarized electron. The new feature of our calculation is that we keep the mass of the final state electron finite which is mandatory if one wants to investigate the threshold region of the decay. Analytical results are given for the energy spectrum and the polar angle distribution of the final state electron whose longitudinal and transverse polarization is calculated. We also provide analytical results on the integrated spectrum functions. We analyze the $m_e \to 0$ limit of our general results and investigate the quality of the $m_e \to 0$ approximation. In the $m_e \to 0$ case we discuss in some detail the role of the $O(\alpha)$ anomalous helicity flip contribution of the final electron which survives the $m_e \to 0$ limit. The results presented in this 0203048 also apply to the leptonic decays of polarized $\tau$-leptons for which we provide numerical results.Comment: 39 pages, 11 postscript figures added. Updated version. Four references added. A few text improvements. Final version to appear in Phys.Rev.

Judgments of learning index relative confidence, not subjective probability

The underconfidence-with-practice (UWP) effect is a common finding in calibration studies concerned with judgments of learning (JOLs) elicited on a percentage scale. The UWP pattern is present when, in a procedure consisting of multiple study-test cycles, mean scale JOLs underestimate mean recall performance on cycle 2 and beyond. Although this pattern is present both for items recalled and unrecalled on the preceding cycle, to date research has concentrated mostly on the sources of UWP for the latter type of items. The present study aimed at bridging this gap. In three experiments, we examined calibration on the third of three cycles. The results of Experiment 1 demonstrated the typical pattern of higher recall and scale JOLs for previously recalled items compared to unrecalled ones. More important, they also revealed that even though the UWP effect was found for both items previously recalled once and twice, its magnitude was greater for the former class of items. Experiments 2 and 3, which employed a binary betting task and a binary 0/100% JOL task, respectively, demonstrated that people can accurately predict future recall for previously recalled items with binary decisions. In both experiments, the UWP effect was absent both for items recalled once and twice. We suggest that the sensitivity of scale JOLs, but not binary judgments, to the number of previous recall successes strengthens the claim of Hanczakowski, Zawadzka, Pasek, and Higham (2013) that scale JOLs reflect confidence in, rather than the subjective probability of, future recall

Pulsar spin-velocity alignment from single and binary neutron star progenitors

The role of binary progenitors of neutron stars in the apparent distribution of space velocities and spin-velocity alignment observed in young pulsars is studied. A Monte-Carlo synthesis of pulsar population from single and binary stars with different assumptions about the NS natal kick model (direction distribution, amplitude, and kick reduction in binary progenitors which experienced mass exchange due to Roche lobe overflow with initial masses on the main sequence from the range 8-11 $M_\odot$) is performed. The calculated spin-velocity alignment distributions are compared with observational data obtained from radio polarization measurements. The observed space velocity of pulsars is found to be mostly shaped by the natal kick velocity form and its amplitude; the fraction of binaries is not important here for reasonably large kicks. The distribution of kick direction relative to the spin axis during the formation of a NS is found to affect strongly the spin-velocity correlation of pulsars. Comparison with observed pulsar spin-velocity angles favours a sizeable fraction of binary progenitors and the kick-spin angle $\sim 5-20^\circ$. The form of the initial binary mass ratio distribution does not affect our results.Comment: 20 pages, 8 figures; Submitted to MNRA