Stability of the aligned state of ^3He-A in a superflow

The stability of the equilibrium orientation of l parallel or antiparallel to a counterflow is studied both dynamically and statically. In contrast to the recent work of Hall and Hook (1977) - who, it is shown, use incorrect dynamical equations - the equilibrium is found to be stable in the Ginzburg-Landau regime. At lower temperatures an instability should develop

Hadron-Hadron Interactions from Nf=2+1+1N_f=2+1+1 Lattice QCD: isospin-2 ππ\pi\pi scattering length

We present results for the $I=2$ $\pi\pi$ scattering length using $N_f=2+1+1$ twisted mass lattice QCD for three values of the lattice spacing and a range of pion mass values. Due to the use of Laplacian Heaviside smearing our statistical errors are reduced compared to previous lattice studies. A detailed investigation of systematic effects such as discretisation effects, volume effects, and pollution of excited and thermal states is performed. After extrapolation to the physical point using chiral perturbation theory at NLO we obtain $M_\pi a_0=-0.0442(2)_\mathrm{stat}(^{+4}_{-0})_\mathrm{sys}$.Comment: Edited for typos, overhauled figures, more detailed comparison to existing lattice result

Photoproduction of pentaquark cascades from nucleons

The cross sections for production of pentaquark $\Xi^+_5$ from the reaction $\gamma p\to K^0K^0\Xi^+_5$ and $\Xi^{--}_5$ from the reaction $\gamma n\to K^+K^+\Xi^{--}_5$ are evaluated in a hadronic model that includes their couplings to both $\Sigma\bar K$ and $\Sigma\bar K^*$. With these coupling constants determined from the empirical $\pi NN(1710)$ and $\rho NN(1710)$ coupling constants by assuming that $\Xi^+_5$, $\Xi^{--}_5$, and N(1710) belong to the same antidecuplet of spin 1/2 and positive parity, and using form factors at strong interaction vertices similar to those for pentaquark $\Theta^+$ production in photonucleon reactions, we obtain a cross section of about 0.03-0.6 nb for the reaction $\gamma p\to K^0K^0\Xi^+_5$ and about 0.1-0.6 nb for the reaction $\gamma n\to K^+K^+\Xi^{--}_5$ at photon energy $E_\gamma=4.5$ GeV, depending on the value of the coupling constant $g_{K^*\Sigma\Xi_5}$.Comment: 14 pages, 5 figure

I=2 Pion scattering length with improved actions on anisotropic lattices

$\pi\pi$ scattering length in the I=2 channel is calculated within quenched approximation using improved gauge and improved Wilson fermion actions on anisotropic lattices. The results are extrapolated towards the chiral, infinite volume and continuum limit. This result improves our previous result on the scattering length. In the chiral, infinite volume and continuum limit, we obtain $a^{(2)}_0m_\pi=-0.0467(45)$, which is consistent with the result from Chiral Perturbation Theory, the experiment and results from other lattice calculations.Comment: 7 pages, 2 figures, typeset wit elsart.cl

Representations and classification of traveling wave solutions to Sinh-G{\"o}rdon equation

Two concepts named atom solution and combinatory solution are defined. The classification of all single traveling wave atom solutions to Sinh-G{\"o}rdon equation is obtained, and qualitative properties of solutions are discussed. In particular, we point out that some qualitative properties derived intuitively from dynamic system method aren't true. In final, we prove that our solutions to Sinh-G{\"o}rdon equation include all solutions obtained in the paper[Fu Z T et al, Commu. in Theor. Phys.(Beijing) 2006 45 55]. Through an example, we show how to give some new identities on Jacobian elliptic functions.Comment: 12 pages. accepted by Communications in theoretical physics (Beijing

Cross sections for pentaquark baryon production from protons in reactions induced by hadrons and photons

Using hadronic Lagrangians that include the interaction of pentaquark $\Theta^+$ baryon with $K$ and $N$, we evaluate the cross sections for its production from meson-proton, proton-proton, and photon-proton reactions near threshold. With empirical coupling constants and form factors, the predicted cross sections are about 1.5 mb in kaon-proton reactions, 0.1 mb in rho-nucleon reactions, 0.05 mb in pion-nucleon reactions, 20 $\mu$b in proton-proton reactions, and 40 nb in photon-proton reactions.Comment: 14 pages, 7 figure