B(0)-B(0) mixing in unquenched lattice QCD.

We present an unquenched lattice calculation for the B(0)-B(0) transition amplitude. The calculation, carried out at an inverse lattice spacing 1/a=2.22(4) GeV, incorporates two flavors of dynamical quarks described by the O(a)-improved Wilson fermion action and heavy quarks described by nonrelativistic QCD. Particular attention is paid to the uncertainty that arises from the chiral extrapolation, especially the effect of pion loops, for light quarks, which we find could be sizable for the leptonic decay constant, whereas it is small for the B parameters. We obtain f(B(d))=191(10)(+12-22) MeV, f(B(s))/f(B(d))=1.13(3)(+13-2), B(B(d))(m(b))=0.836(27)(+56-62), B(B(s))/B(B(d))=1.017(16)(+56-17), and xi=1.14(3)(+13-2), where the first error is statistical, and the second is systematic, including uncertainties due to chiral extrapolation, finite lattice spacing, heavy quark expansion, and perturbative operator matching.

Resurrection of grand unified theory baryogenesis.

A "new" scenario is proposed for baryogenesis. We show that the delayed decay of colored Higgs particles in grand unified theories may generate an excess baryon number of the empirically desired amount, if the mass of the heaviest neutrino is in the range 0.02 eV

Dynamical quark effects on light quark masses

Light quark masses are calculated in lattice QCD with two degenerate flavors of dynamical quarks. The calculations are made with improved actions with lattice spacing a = 0.22-0.11 fm. In the continuum limit we find m(M&Smacr;)(ud)(2 GeV) = 3.44(+0.14)(-0.22) MeV using the pi and rho meson masses as physical input, and m(M&Smacr;)(s)(2 GeV) = 88(+4)(-6) MeV or 90(+5)(-11) MeV with the K or straight phi meson mass as additional input. The quoted errors represent statistical and systematic combined, the latter including those from continuum and chiral extrapolations, and from renormalization factors. Compared to quenched results, two flavors of dynamical quarks reduce quark masses by about 25%.

Limits on neutrino mass from cosmic structure formation

We consider the effect of three species of neutrinos with nearly degenerate mass on the cosmic structure formation in a low-matter-density universe within a hierarchical clustering scenario with a flat Gaussian initial perturbation spectrum. The matching condition for fluctuation powers at the COBE scale and at the cluster scale leads to a strong upper limit on neutrino mass. For a flat universe with matter density parameter Omega = 0.3, we obtain m(nu)<0.6 eV for the Hubble constant H0<80 km s(-1) Mpc(-1). Allowing for the more generous parameter space limited by Omega<0.4, H0<80 km s(-1) Mpc(-1) and age t(0)>11.5 Gyr, the limit is 0.9 eV.

Quenched light hadron spectrum

We present results of a large-scale simulation for the flavor nonsinglet light hadron spectrum in quenched lattice QCD with the Wilson quark action. Hadron masses are calculated at four values of lattice spacing in the range a approximately 0.1-0.05 fm on lattices with a physical extent of 3 fm at five quark masses corresponding to m(pi)/m(rho) approximately 0.75-0.4. The calculated spectrum in the continuum limit shows a systematic deviation from experiment, though the magnitude of deviation is contained within 11%. Results for decay constants and light quark masses are also reported.

The Missing Link: Early Methane ("T") Dwarfs in the Sloan Digital Sky Survey.

We report the discovery of three cool brown dwarfs that fall in the effective temperature gap between the latest L dwarfs currently known, with no methane absorption bands in the 1-2.5 µm range, and the previously known methane (T) dwarfs, whose spectra are dominated by methane and water. The newly discovered objects were detected as very red objects in the Sloan Digital Sky Survey imaging data and have JHK colors between the red L dwarfs and the blue Gl 229B-like T dwarfs. They show both CO and CH(4) absorption in their near-infrared spectra in addition to H(2)O, with weaker CH(4) absorption features in the H and K bands than those in all other methane dwarfs reported to date. Due to the presence of CH(4) in these bands, we propose that these objects are early T dwarfs. The three form part of the brown dwarf spectral sequence and fill in the large gap in the overall spectral sequence from the hottest main-sequence stars to the coolest methane dwarfs currently known.

The Discovery of a High-Redshift Quasar without Emission Lines from Sloan Digital Sky Survey Commissioning Data.

We report observations of a luminous unresolved object at redshift z=4.62, with a featureless optical spectrum redward of the Lyalpha forest region, discovered from Sloan Digital Sky Survey commissioning data. The redshift is determined by the onset of the Lyalpha forest at lambda approximately 6800 Å and a Lyman limit system at lambda=5120 Å. A strong Lyalpha absorption system with weak metal absorption lines at z=4.58 is also identified in the spectrum. The object has a continuum absolute magnitude of -26.6 at 1450 Å in the rest frame (h0=0.5, q0=0.5) and therefore cannot be an ordinary galaxy. It shows no radio emission (the 3 sigma upper limit of its flux at 6 cm is 60 µJy), indicating a radio-to-optical flux ratio at least as small as that of the radio-weakest BL Lacertae objects known. It is also not linearly polarized to a 3 sigma upper limit of 4% in the observed I band. Therefore, it is either the most distant BL Lac object known to date, with very weak radio emission, or a new type of unbeamed quasar, whose broad emission line region is very weak or absent.

The history of the galaxies.

Astronomical observations now reach far enough back in time, in enough depth and detail, to reveal the history of galaxies since their formation. The early Universe contained a network of gas clouds that filled much of the space between the young galaxies, where stars were forming at a high rate. Since then, intergalactic space has been swept clean, and galaxies have continued to convert the dwindling supply of gas slow into stars.

Kinematics and thermodynamics of a folding heteropolymer.

In order to elucidate the folding dynamics of protein, we have carried out numerical simulations of a heteropolymer model of self-interacting random chains. We find that folding propensity depends strongly on sequence and that both folding and nonfolding sequences exist. Furthermore we show that folding is a two-step process: the transition from coil state to unique folded state takes place through a globule phase. In addition to the continuous coil-globule transition, there exists an abrupt transition that separates the unique folded state from the globule state and ensures the stability of the native state.