13961120
Space- and ground-based pulsation data of η bootis explained with stellar models including turbulence
The space telescope MOSTis now providing us with extremely accurate low-frequency p-mode oscillation data for the starBoo. We demonstrate in this paper that these data, when combined with ground-based measurements ofthehigh-frequencyp-modespectrum,canbereproducedwithstellarmodelsthatincludetheeffectsofturbulence in their outer layers.Withoutturbulence, thel ¼ 0modes ofour models deviatefromeithertheground-basedorthe space data by about 1.5-4 � Hz. This discrepancy can be completely removed by including turbulence in the models, and we can exactly match 12 out of 13 MOST frequencies that we identified as l ¼ 0 modes, in addition to 13 out of 21 ground-based frequencies within their observational 2 � tolerances. The better agreement between model frequencies and observed frequencies depends for the most part on the turbulent kinetic energy that was taken from a three-dimensional convection simulation for the Sun.
117219942
Calculation of Solar P-mode Oscillation Frequency Splittings Based on a Two-dimensional Solar Model
We compute the p-mode oscillation frequencies and frequency splittings that arise in a two-dimensional model of the Sun that contains toroidal magnetic fields in its interior.
16866447
Interpreting Helioseismic Structure Inversion Results of Solar Active Regions
Helioseismic techniques such as ring-diagram analysis have often been used to determine the subsurface structural differences between solar active and quiet regions. Results obtained by inverting the frequency differences between the regions are usually interpreted as the sound-speed differences between them. These in turn are used as a measure of temperature and magnetic-field strength differences between the two regions. In this paper we first show that the “sound-speed” difference obtained from inversions is actually a combination of sound-speed difference and a magnetic component. Hence, the inversion result is not directly related to the thermal structure. Next, using solar models that include magnetic fields, we develop a formulation to use the inversion results to infer the differences in the magnetic and thermal structures between active and quiet regions. We then apply our technique to existing structure inversion results for different pairs of active and quiet regions. We find that the effect of magnetic fields is strongest in a shallow region above 0.985R⊙ and that the strengths of magnetic-field effects at the surface and in the deeper (r<0.98R⊙) layers are inversely related (i.e., the stronger the surface magnetic field the smaller the magnetic effects in the deeper layers, and vice versa). We also find that the magnetic effects in the deeper layers are the strongest in the quiet regions, consistent with the fact that these are basically regions with weakest magnetic fields at the surface. Because the quiet regions were selected to precede or follow their companion active regions, the results could have implications about the evolution of magnetic fields under active regions.
14227222
Two-Dimensional Stellar Evolution Code Including Arbitrary Magnetic Fields. II. Precision Improvement and Inclusion of Turbulence and Rotation
In the second paper of this series we pursue two objectives. First, in order to make the code more sensitive to small effects, we remove many approximations made in Paper I. Second, we include turbulence and rotation in the two-dimensional framework. The stellar equilibrium is described by means of a set of five differential equations, with the introduction of a new dependent variable, namely the perturbation to the radial gravity, that is found when the nonradial effects are considered in the solution of the Poisson equation. Following the scheme of the first paper, we write the equations in such a way that the two-dimensional effects can be easily disentangled. The key concept introduced in this series is the equipotential surface. We use the underlying cause-effect relation to develop a recurrence relation to calculate the equipotential surface functions for uniform rotation, differential rotation, rotation-like toroidal magnetic fields, and turbulence. We also develop a more precise code to numerically solve the two-dimensional stellar structure and evolution equations based on the equipotential surface calculations. We have shown that with this formulation we can achieve the precision required by observations by appropriately selecting the convergence criterion. Several examples are presented to show that the method works well. Since we are interested in modeling the effects of a dynamo-type field on the detailed envelope structure and global properties of the Sun, the code has been optimized for short timescales phenomena (down to 1 yr). The time dependence of the code has so far been tested exclusively to address such problems.
118681206
Solar Models with Revised Abundance
We present new solar models in which we use the latest low abundances and further include the effects of rotation, magnetic fields, and extra-mixing processes. We assume that the extra-element mixing can be treated as a diffusion process, with the diffusion coefficient depending mainly on the solar internal configuration of rotation and magnetic fields. We find that such models can well reproduce the observed solar rotation profile in the radiative region. Furthermore, the proposed models can match the seismic constraints better than the standard solar models, also when these include the latest abundances, but neglect the effects of rotation and magnetic fields.
10120589
The nonhomologous nature of solar diameter variations
We show in this Letter that the changes of the solar diameter in response to variations of large-scale magnetic fields and turbulence are not homologous. For the best current model, the variation at the photospheric level is over 1000 times larger than the variation at a depth of 5 Mm, which is about the level at which f-mode solar oscillations determine diameter variations. This model is supported by observations that indicate larger diameter changes for high-degree f-modes than for low-degree f-modes, since the energy of the former is concentrated at shallower layers than the latter.
119255736
Determining Nuclear Form factor for Detection of Dark Matter in Relativistic Mean Field Theory
In this work, we derive the nuclear form factor for the spin-independent collision between the WIMPs and nucleus in terms of the relativistic mean field (RMF) theory. Comparison with the traditional form factors which are commonly used in literature is given and it is found that our results are slightly above that of the 2PF model by 4% to 8%, but deviate from the Helm form factor by 15% to 25% for the whole recoil energy spectrum of 0 ~ 100 keV. Moreover, taking Xe and Ge as examples, we show the dependence of the form factor on the recoil energy.
122970197
Multijet production in neutral current deep inelastic scattering at HERA and determination of alpha(s)
Multijet production rates in neutral current deep inelastic scattering (DIS) have been measured in the range of exchanged boson virtualities 10<Q2<5000 GeV2. The data were taken at the ep collider HERA with centre-of-mass energy using the ZEUS detector and correspond to an integrated luminosity of 82.2 pb-1. Jets were identified in the Breit frame using the kT cluster algorithm in the longitudinally invariant inclusive mode. Measurements of differential multijet cross sections are presented as functions of jet transverse energy , pseudorapidity and Q2 with and . Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant αs(MZ), determined from the ratio of the trijet to dijet cross sections, is .
117833563
A Library of Lick/IDS Indices for Binary Stellar Populations
Using EPS we present 13 refined Lick/IDS absorption-line indices for an extensive set of instantaneous-burst binary stellar populations (BSPs) at high resolution (0.3 \AA) of various age and metallicity (1-15Gyr, 0.004-0.03), and 38 indices at intermediate resolution (3 \AA). These indices are obtained by two methods: (1) obtain them by using the empirical fitting functions (FFs method); (2) measure them directly from the synthetic spectra (DC method). Together with our previous paper a database of Lick/IDS spectral absorption-line indices for BSPs at high and intermediate resolutions is provided. This set of indices includes 21 indices of Worthey et al., four Balmer indices defined by Worthey & Ottaviani and 13 indices with the new passband definitions of Trager et al. The full set of synthetic indices and the integrated pseudo-continuum are listed in the Appendix, which is only available online or from our website (this http URL com/), or on request from the first author. Moreover, the ISEDs can be obtained from our website. 
We compare the synthetic Lick/IDS indices obtained by FFs method and those by DC method, and find that the discrepancies are significant: Ca4455 (index 6), Fe4668 (8), Mg_b (13), Fe5709 (17), NaD (19), TiO_1 (20) and TiO_2 (21, except for Z=0.02) in the W94 system, Ca4455^T (6^T), C_2 4668^T (8^T), NaD^T (19^T), TiO_1^T (20^T) and TiO_2^T (21^T, except for Z=0.02) in the T98 system obtained by DC method are less (bluer) than the corresponding ones obtained by FFs method for all metallicities. Ca4227 (index 3), Fe5782 (18),Ca4227^T (3^T) and Fe5782^T (18^T) are greater at Z=0.03 and become to be bluer at Z=0.004, Fe5709^T (17^T) index is less at Z=0.03 and becomes to be redder at Z=0.004 than the corresponding ones obtained by FFs method.
55053994
Galaxy Formation & Dark Matter Modelling in the Era of the Square Kilometre Array
Theoretical galaxy formation models are an established and powerful tool for interpreting the astrophysical significance of observational data, particularly galaxy surveys. Such models have been utilised with great success by optical surveys such as 2dFGRS and SDSS, but their application to radio surveys of cold gas in galaxies has been limited. In this chapter we describe recent developments in the modelling of the cold gas properties in the models, and how these developments are essential if they are to be applied to cold gas surveys of the kind that will be carried out with the SKA. By linking explicitly a galaxy's star formation rate to the abundance of molecular hydrogen in the galaxy rather than cold gas abundance, as was assumed previously, the latest models reproduce naturally many of the global atomic and molecular hydrogen properties of observed galaxies. We review some of the key results of the latest models and highlight areas where further developments are necessary. We discuss also how model predictions can be most accurately compared with observational data, what challenges we expect when creating synthetic galaxy surveys in the SKA era, and how the SKA can be used to test models of dark matter.
117840720
Top Quark Production at the Tevatron Collider
Top quark physics has been a rich testing ground for the standard model since the top quark discovery in 1995. The large mass of top quark suggests that it could play a special role in searches for new phenomena. In this paper I provide an overview of recent top quark production cross section measurements from both CDF and D0 collaborations and also some new physics searches done in the top quark sector.