Mass Spectrum and Bounds on the Couplings in Yukawa Models With Mirror-Fermions

The $\rm SU(2)_L\otimes SU(2)_R$ symmetric Yukawa model with mirror-fermions in the limit where the mirror-fermion is decoupled is studied both analytically and numerically. The bare scalar self-coupling $\lambda$ is fixed at zero and infinity. The phase structure is explored and the relevant phase transition is found to be consistent with a second order one. The fermionic mass spectrum close to that transition is discussed and a first non-perturbative estimate of the influence of fermions on the upper and lower bounds on the renormalized scalar self-coupling is given. Numerical results are confronted with perturbative predictions.Comment: 7 (Latex) page

Fracture of a viscous liquid

When a viscous liquid hits a pool of liquid of same nature, the impact region is hollowed by the shock. Its bottom becomes extremely sharp if increasing the impact velocity, and we report that the curvature at that place increases exponentially with the flow velocity, in agreement with a theory by Jeong and Moffatt. Such a law defines a characteristic velocity for the collapse of the tip, which explains both the cusp-like shape of this region, and the instability of the cusp if increasing (slightly) the impact velocity. Then, a film of the upper phase is entrained inside the pool. We characterize the critical velocity of entrainment of this phase and compare our results with recent predictions by Eggers

Effect of an InP/In0.53_{0.53}Ga0.47_{0.47}As Interface on Spin-orbit Interaction in In0.52_{0.52}Al0.48_{0.48}As/In0.53_{0.53}Ga0.47_{0.47}As Heterostructures

We report the effect of the insertion of an InP/In$_{0.53}$Ga$_{47}$As Interface on Rashba spin-orbit interaction in In$_{0.52}$Al$_{0.48}$As/In$_{0.53}$Ga$_{0.47}$As quantum wells. A small spin split-off energy in InP produces a very intriguing band lineup in the valence bands in this system. With or without this InP layer above the In$_{0.53}$Ga$_{47}$As well, the overall values of the spin-orbit coupling constant $\alpha$ turned out to be enhanced or diminished for samples with the front- or back-doping position, respectively. These experimental results, using weak antilocalization analysis, are compared with the results of the $\mathbf{k\cdot p}$ theory. The actual conditions of the interfaces and materials should account for the quantitative difference in magnitude between the measurements and calculations.Comment: Submitted for publication; v2 to adjust Eq.6; v3 to correct the figure file name; v4, a revised version accepted for publication in Phys. Rev.

Numerical simulation of heavy fermions in an SU(2)_L x SU(2)_R symmetric Yukawa model

An exploratory numerical study of the influence of heavy fermion doublets on the mass of the Higgs boson is performed in the decoupling limit of a chiral $\rm SU(2)_L \otimes SU(2)_R$ symmetric Yukawa model with mirror fermions. The behaviour of fermion and boson masses is investigated at infinite bare quartic coupling on $4^3 \cdot 8$, $6^3 \cdot 12$ and $8^3 \cdot 16$ lattices. A first estimate of the upper bound on the renormalized quartic coupling as a function of the renormalized Yukawa-coupling is given.Comment: 15 pp + 11 Figures appended as Postscript file

Toward a Deterministic Model of Planetary Formation IV: Effects of Type-I Migration

In a further development of a deterministic planet-formation model (Ida & Lin 2004), we consider the effect of type-I migration of protoplanetary embryos due to their tidal interaction with their nascent disks. During the early embedded phase of protostellar disks, although embryos rapidly emerge in regions interior to the ice line, uninhibited type-I migration leads to their efficient self-clearing. But, embryos continue to form from residual planetesimals at increasingly large radii, repeatedly migrate inward, and provide a main channel of heavy element accretion onto their host stars. During the advanced stages of disk evolution (a few Myr), the gas surface density declines to values comparable to or smaller than that of the minimum mass nebula model and type-I migration is no longer an effective disruption mechanism for mars-mass embryos. Over wide ranges of initial disk surface densities and type-I migration efficiency, the surviving population of embryos interior to the ice line has a total mass several times that of the Earth. With this reservoir, there is an adequate inventory of residual embryos to subsequently assemble into rocky planets similar to those around the Sun. But, the onset of efficient gas accretion requires the emergence and retention of cores, more massive than a few M_earth, prior to the severe depletion of the disk gas. The formation probability of gas giant planets and hence the predicted mass and semimajor axis distributions of extrasolar gas giants are sensitively determined by the strength of type-I migration. We suggest that the observed fraction of solar-type stars with gas giant planets can be reproduced only if the actual type-I migration time scale is an order of magnitude longer than that deduced from linear theories.Comment: 32 pages, 8 figures, 1 table, accepted for publication in Ap

Oxygen superstructures throughout the phase diagram of (Y,Ca)Ba2Cu3O6+x\bf (Y,Ca)Ba_2 Cu_3 O_{6+x}

Short-range lattice superstructures have been studied with high-energy x-ray diffuse scattering in underdoped, optimally doped, and overdoped $\rm (Y,Ca)Ba_2 Cu_3 O_{6+x}$. A new four-unit-cell superstructure was observed in compounds with $x\sim 0.95$. Its temperature, doping, and material dependence was used to attribute its origin to short-range oxygen vacancy ordering, rather than electronic instabilities in the $\rm CuO_2$ layers. No significant diffuse scattering is observed in YBa$_2$Cu$_4$O$_{8}$. The oxygen superstructures must be taken into account when interpreting spectral anomalies in $\rm (Y,Ca)Ba_2 Cu_3 O_{6+x}$