Quasi Periodic Oscillations in Low Mass X-Ray Binaries and Constraints on the Equation of State of Neutron Star Matter

Recently discovered quasi periodic oscillations in the X-ray brightness of low mass X-ray binaries are used to derive constraints on the mass of the neutron star component and the equation of state of neutron star matter. The observations are compared with models of rapidly rotating neutron stars which are calculated by means of an exact numerical method in full relativity. For the equations of state we select a broad collection of models representing different assumptions about the many-body structure and the complexity of the composition of super dense matter. The mass constraints differ from their values in the approximate treatment by \sim 10%. Under the assumption that the maximum frequency of the quasi periodic oscillations originates from the innermost stable orbit the mass of the neutron star is in the range: $M\sim 1.92-2.25 M_\odot$. Especially the quasi periodic oscillation in the Atoll-source 4U 1820-30 is only consistent with equations of state which are rather stiff at high densities which is explainable, so far, only with pure nucleonic/leptonic composition. This interpretation contradicts the hypothesis that the protoneutron star formed in SN 1987A collapsed to a black hole, since this would demand a maximum neutron star mass below $1.6 M_\odot$. The recently suggested identification of quasi periodic oscillations with frequencies around 10 Hz with the Lense-Thirring precession of the accretion disk is found to be inconsistent with the models studied in this work, unless it is assumed that the first overtone of the precession is observed.Comment: 12 pages including figures, to be published in MNRA

Melting of hexagonal skyrmion states in chiral magnets

Skyrmions are spiral structures observed in thin films of certain magnetic materials (Uchida et al 2006 Science 311 359–61). Of the phases allowed by the crystalline symmetries of these materials (Yi et al 2009 Phys. Rev. B 80 054416), only the hexagonally packed phases (SCh) have been observed. Here the melting of the SCh phase is investigated using Monte Carlo simulations. In addition to the usual measure of skyrmion density, chiral charge, a morphological measure is considered. In doing so it is shown that the low-temperature reduction in chiral charge is associated with a change in skyrmion profiles rather than skyrmion destruction. At higher temperatures, the loss of six-fold symmetry is associated with the appearance of elongated skyrmions that disrupt the hexagonal packing

Chiral Quark Model

In this talk I review studies of hadron properties in bosonized chiral quark models for the quark flavor dynamics. Mesons are constructed from Bethe--Salpeter equations and baryons emerge as chiral solitons. Such models require regularization and I show that the two--fold Pauli--Villars regularization scheme not only fully regularizes the effective action but also leads the scaling laws for structure functions. For the nucleon structure functions the present approach serves to determine the regularization prescription for structure functions whose leading moments are not given by matrix elements of local operators. Some numerical results are presented for the spin structure functions.Comment: Talk presented at the workshop QCD 2002, IIT Kanpur, Nov. 2002, 10 pages, proceedings style files include

Soliton Models for the Nucleon and Predictions for the Nucleon Spin Structure

In these lectures the three flavor soliton approach for baryons is reviewed. Effects of flavor symmetry breaking in the baryon wave--functions on axial current matrix elements are discussed. A bosonized chiral quark model is considered to outline the computation of spin dependent nucleon structure functions in the soliton picture.Comment: 12 pages, Lectures presented at the Advanced Study Institute Symmetry and Spin, Prague, 2001, to appear in the proceedings. References correcte

Universal amplitude-exponent relation for the Ising model on sphere-like lattices

Conformal field theory predicts finite-size scaling amplitudes of correlation lengths universally related to critical exponents on sphere-like, semi-finite systems $S^{d-1}\times\mathbb{R}$ of arbitrary dimensionality $d$. Numerical studies have up to now been unable to validate this result due to the intricacies of lattice discretisation of such curved spaces. We present a cluster-update Monte Carlo study of the Ising model on a three-dimensional geometry using slightly irregular lattices that confirms the validity of a linear amplitude-exponent relation to high precision.Comment: 6 pages, 2 figures, Europhys. Lett., in prin

Effect of irradiance, sucrose, and CO2 concentration on the growth of potato (Solanum tuberosum L.) in vitro

Growth measurements were taken of potato plantlets (Solanum tuberosum L.) cvs. Norland (NL), Denali (DN), and Kennebec (KN), grown in vitro. Studies were conducted in a growth chamber, with nodal explants grown for 21 days on Murashige and Skoog salts with either 0, 1, 2, or 3% sucrose and capped with loose-fitted Magenta 2-way caps that allowed approximately 2.25 air exchanges/hour. Plantlets were exposed to either 100 or 300 micro mol/sq m/s photosynthetic photon flux (PPF), and the growth chamber was maintained at either 400 or 4000 micro mol/mol CO2. Regardless of PPF, all cvs. that were grown at 4000 micro mol/mol CO2 showed significant increases in total plantlet dry weight (TDW) and shoot length (SL) when sucrose was omitted from the media, indicating an autotrophic response. At 400 micro mol/mol CO2, all cvs. showed an increase in TDW and SL with increasing sucrose under both PPF levels. Within any sucrose treatment, the highest TDW for all cvs. resulted from 300 micro mol/sq m/s PPF and 4000 micro mol/mol CO2 At 4000 micro mol/mol CO2, TDW showed no further increase with sucrose levels above 1% for cvs. NL and DN at both PPF levels, suggesting that sucrose levels greater than 1% may hinder growth when CO2 enrichment is used

Parton distributions in the chiral quark model: a continuum computation

We compute the parton distributions for the chiral quark model. We present a new technique for performing such computations based on Green functions. This approach avoids a discretization of the spectrum. It therefore does not need any smoothing procedures. The results are similar to those of other groups, however the distributions peak at smaller $x$.Comment: 19 pages, 8 Figures, LaTeX, some typos corrected, some additional comments in the conclusion

Nucleon Structure Functions from a Chiral Soliton in the Infinite Momentum Frame

We study the frame dependence of nucleon structure functions obtained within a chiral soliton model for the nucleon. Employing light cone coordinates and introducing collective coordinates together with their conjugate momenta, translational invariance of the solitonic quark fields (which describe the nucleon as a localized object) is restored. This formulation allows us to perform a Lorentz boost to the infinite momentum frame of the nucleon. The major result is that the Lorentz contraction associated with this boost causes the leading twist contribution to the structure functions to properly vanish when the Bjorken variable $x$ exceeds unity. Furthermore we demonstrate that for structure functions calculated in the valence quark approximation to the Nambu--Jona--Lasinio chiral soliton model the Lorentz contraction also has significant effects on the structure functions for moderate values of the Bjorken variable $x$.Comment: 16 pages, 1 figure, revised version to be published in Int. J. Mod. Phys.

Observations of meteoric material and implications for aerosol nucleation in the winter Arctic lower stratosphere derived from in situ particle measurements

Number concentrations of total and non-volatile aerosol particles with size diameters >0.01 μm as well as particle size distributions (0.4–23 μm diameter) were measured in situ in the Arctic lower stratosphere (10–20.5 km altitude). The measurements were obtained during the campaigns European Polar Stratospheric Cloud and Lee Wave Experiment (EUPLEX) and Envisat-Arctic-Validation (EAV). The campaigns were based in Kiruna, Sweden, and took place from January to March 2003. Measurements were conducted onboard the Russian high-altitude research aircraft Geophysica using the low-pressure Condensation Nucleus Counter COPAS (COndensation PArticle Counter System) and a modified FSSP 300 (Forward Scattering Spectrometer Probe). Around 18–20 km altitude typical total particle number concentrations nt range at 10–20 cm−3 (ambient conditions). Correlations with the trace gases nitrous oxide (N2O) and trichlorofluoromethane (CFC-11) are discussed. Inside the polar vortex the total number of particles >0.01 μm increases with potential temperature while N2O is decreasing which indicates a source of particles in the above polar stratosphere or mesosphere. A separate channel of the COPAS instrument measures the fraction of aerosol particles non-volatile at 250°C. Inside the polar vortex a much higher fraction of particles contained non-volatile residues than outside the vortex (~67% inside vortex, ~24% outside vortex). This is most likely due to a strongly increased fraction of meteoric material in the particles which is transported downward from the mesosphere inside the polar vortex. The high fraction of non-volatile residual particles gives therefore experimental evidence for downward transport of mesospheric air inside the polar vortex. It is also shown that the fraction of non-volatile residual particles serves directly as a suitable experimental vortex tracer. Nanometer-sized meteoric smoke particles may also serve as nuclei for the condensation of gaseous sulfuric acid and water in the polar vortex and these additional particles may be responsible for the increase in the observed particle concentration at low N2O. The number concentrations of particles >0.4 μm measured with the FSSP decrease markedly inside the polar vortex with increasing potential temperature, also a consequence of subsidence of air from higher altitudes inside the vortex. Another focus of the analysis was put on the particle measurements in the lowermost stratosphere. For the total particle density relatively high number concentrations of several hundred particles per cm3 at altitudes below ~14 km were observed in several flights. To investigate the origin of these high number concentrations we conducted air mass trajectory calculations and compared the particle measurements with other trace gas observations. The high number concentrations of total particles in the lowermost stratosphere are probably caused by transport of originally tropospheric air from lower latitudes and are potentially influenced by recent particle nucleation