Dynamical Electroweak Symmetry Breaking in SO(5)xU(1) Gauge-Higgs Unification with Top and Bottom Quarks

An SO(5)xU(1) gauge-Higgs unification model in the Randall-Sundrum warped space with top and bottom quarks is constructed. Additional fermions on the Planck brane make exotic particles heavy by effectively changing boundary conditions of bulk fermions from those determined by orbifold conditions. Gauge couplings of a top quark multiplet trigger electroweak symmetry breaking by the Hosotani mechanism, simultaneously giving a top quark the observed mass. The bottom quark mass is generated by combination of brane interactions and the Hosotani mechanism, where only one ratio of brane masses is relevant when the scale of brane masses is much larger than the Kaluza-Klein scale (\sim 1.5 TeV). The Higgs mass is predicted to be 49.9 (53.5) GeV for the warp factor 10^{15} (10^{17}). The Wilson line phase turns out \pi/2 and the Higgs couplings to W and Z vanish so that the LEP2 bound for the Higgs mass is evaded. In the flat spacetime limit the electroweak symmetry is unbroken.Comment: 35 pages, 2 figures. A few corrections are mad

Xenopus NM23-X4 regulates retinal gliogenesis through interaction with p27Xic1

Background. In Xenopus retinogenesis, p27Xic1, a Xenopus cyclin dependent kinase inhibitor, functions as a cell fate determinant in both gliogenesis and neurogenesis in a context dependent manner. This activity is essential for co-ordination of determination and cell cycle regulation. However, very little is known about the mechanism regulating the context dependent choice between gliogenesis versus neurogenesis. Results. We have identified NM23-X4, a NM23 family member, as a binding partner of p27Xic1. NM23-X4 is expressed at the periphery of the ciliary marginal zone of the Xenopus retina and the expression overlaps with p27Xic1 at the central side. Our in vivo functional analysis in Xenopus retina has shown that knockdown of NM23-X4 activates gliogenesis. Furthermore, co-overexpression of NM23-X4 with p27Xic1 results in the inhibition of p27Xic1-mediated gliogenesis, through direct interaction of NM23-X4 with the amino-terminal side of p27Xic1. This inhibitory effect on gliogenesis requires serine-150 and histidine-148, which correspond to the important residues for the kinase activities of NM23 family members. Conclusion. This study demonstrates that NM23-X4 functions as an inhibitor of p27Xic1-mediated gliogenesis in Xenopus retina and suggests that this activity contributes to the proper spatio-temporal regulation of gliogenesis

Phase diagram at finite temperature and quark density in the strong coupling limit of lattice QCD for color SU(3)

We study the phase diagram of quark matter at finite temperature (T) and finite chemical potential (mu) in the strong coupling limit of lattice QCD for color SU(3). We derive an analytical expression of the effective free energy as a function of T and mu, including baryon effects. The finite temperature effects are evaluated by integrating over the temporal link variable exactly in the Polyakov gauge with anti-periodic boundary condition for fermions. The obtained phase diagram shows the first order phase transition at low temperatures and the second order phase transition at high temperatures separated by the tri-critical point in the chiral limit. Baryon has effects to reduce the effective free energy and to extend the hadron phase to a larger mu direction at low temperatures.Comment: 18 pages, 10 figure

Non-resonant direct p- and d-wave neutron capture by 12C

Discrete gamma-rays from the neutron capture state of 13C to its low-lying bound states have been measured using pulsed neutrons at En = 550 keV. The partial capture cross sections have been determined to be 1.7+/-0.5, 24.2+/-1.0, 2.0+/-0.4 and 1.0+/-0.4 microb for the ground (1/2-), first (1/2+), second (3/2-) and third (5/2+) excited states, respectively. From a comparison with theoretical predictions based on the non-resonant direct radiative capture mechanism, we could determine the spectroscopic factor for the 1/2+ state to be 0.80 +/- 0.04, free from neutron-nucleus interaction ambiguities in the continuum. In addition we have detected the contribution of the non-resonant d-wave capture component in the partial cross sections for transitions leading to the 1/2- and 3/2- states. While the s-wave capture dominates at En < 100 keV, the d-wave component turns out to be very important at higher energies. From the present investigation the 12C(n,gamma)13C reaction rate is obtained for temperatures in the range 10E+7 - 10E+10 K.Comment: Accepted for publication in Phys. Rev. C. - 16 pages + 8 figure

Cosmogenic 11C production and sensitivity of organic scintillator detectors to pep and CNO neutrinos

Several possible background sources determine the detectability of pep and CNO solar neutrinos in organic liquid scintillator detectors. Among such sources, the cosmogenic 11C nuclide plays a central role. 11C is produced underground in reactions induced by the residual cosmic muon flux. Experimental data available for the effective cross section for 11C by muons indicate that 11C will be the dominant source of background for the observation of pep and CNO neutrinos. 11C decays are expected to total a rate 2.5 (20) times higher than the combined rate of pep and CNO neutrinos in Borexino (KamLAND) in the energy window preferred for the pep measurement, between 0.8 and 1.3 MeV. This study examines the production mechanism of 11C by muon-induced showers in organic liquid scintillators with a novel approach: for the first time, we perform a detailed ab initio calculation of the production of a cosmogenic nuclide, 11C, taking into consideration all relevant production channels. Results of the calculation are compared with the effective cross sections measured by target experiments in muon beams. This paper also discusses a technique for reduction of background from 11C in organic liquid scintillator detectors, which allows to identify on a one-by-one basis and remove from the data set a large fraction of 11C decays. The background reduction technique hinges on an idea proposed by Martin Deutsch, who suggested that a neutron must be ejected in every interaction producing a 11C nuclide from 12C. 11C events are tagged by a three-fold coincidence with the parent muon track and the subsequent neutron capture on protons.Comment: 11 pages, 6 figures; added one section detailing comparison with previous estimates; added reference

Normal levels of p27Xic1 are necessary for somite segmentation and determining pronephric organ size

The Xenopus laevis cyclin dependent kinase inhibitor p27Xic1 has been shown to be involved in exit from the cell cycle and differentiation of cells into a quiescent state in the nervous system, muscle tissue, heart and retina. We show that p27Xic1 is expressed in the developing kidney in the nephrostomal regions. Using over-expression and morpholino oligonucleotide (MO) knock-down approaches we show normal levels of p27Xic1 regulate pronephros organ size by regulating cell cycle exit. Knock-down of p27Xic1 expression using a MO prevented myogenesis, as previously reported; an effect that subsequently inhibits pronephrogenesis. Furthermore, we show that normal levels of p27Xic1 are required for somite segmentation also through its cell cycle control function. Finally, we provide evidence to suggest correct paraxial mesoderm segmentation is not necessary for pronephric induction in the intermediate mesoderm. These results indicate novel developmental roles for p27Xic1, and reveal its differentiation function is not universally utilised in all developing tissues

Spectroscopic factors for bound s-wave states derived from neutron scattering lengths

A simple and model-independent method is described to derive neutron single-particle spectroscopic factors of bound s-wave states in $^{A+1}Z = ^{A}Z \otimes n$ nuclei from neutron scattering lengths. Spectroscopic factors for the nuclei ^{13}C, ^{14}C, ^{16}N, ^{17}O, ^{19}O, ^{23}Ne, ^{37}Ar, and ^{41}Ar are compared to results derived from transfer experiments using the well-known DWBA analysis and to shell model calculations. The scattering length of ^{14}C is calculated from the ^{15}C_{g.s.} spectroscopic factor.Comment: 9 pages (uses revtex), no figures, accepted for publication in PRC, uuencoded tex-files and postscript-files available at ftp://is1.kph.tuwien.ac.at/pub/ohu/Thermal.u

Antiferromagnetic spintronics

Antiferromagnetic materials are magnetic inside, however, the direction of their ordered microscopic moments alternates between individual atomic sites. The resulting zero net magnetic moment makes magnetism in antiferromagnets invisible on the outside. It also implies that if information was stored in antiferromagnetic moments it would be insensitive to disturbing external magnetic fields, and the antiferromagnetic element would not affect magnetically its neighbors no matter how densely the elements were arranged in a device. The intrinsic high frequencies of antiferromagnetic dynamics represent another property that makes antiferromagnets distinct from ferromagnets. The outstanding question is how to efficiently manipulate and detect the magnetic state of an antiferromagnet. In this article we give an overview of recent works addressing this question. We also review studies looking at merits of antiferromagnetic spintronics from a more general perspective of spin-ransport, magnetization dynamics, and materials research, and give a brief outlook of future research and applications of antiferromagnetic spintronics.Comment: 13 pages, 7 figure