Stability of a Charged Particle Beam in a Resistive Plasma Channel

A self-focusing of a coasting relativistic beam in a plasma channel that is confined by an external magnetic field is studied as a means of reconditioning the beam emerging from a beam injector [a radio frequency quadrupole (RFQ)] for a linac. A detailed study of the beam stability in the self-focused beam has been carried out. In order to explain beam filaments and the resistive hose instability in a unified way, we treat all the azimuthal modes in the derivation of the dispersion relation in a finite plasma channel that exhibit many unstable modes, which are classified by Weinberg's scheme [Steven Weinberg, J. Math. 8, 614 (1967)].Comment: A useful study for the development of radiation or neutron sources for diagnostics in material scienc

Atomic Theory of the Two-fluid Model: Broken Gauge Symmetry in Bose-Einstein condensation

We discuss the collective excitations in a spatially inhomogeneous (cylindrically symmetric) Bose-Einstein condensation (BEC) at low temperature ($T \ll T_{\lambda}$). The main result is the dispersion relation for a (first) sound wave that is obtained by describing the perturbation as a Lagrangian coordinate. The dispersion curve is in good agreement with the Bogoliubov phonon spectrum $\omega=c k$, where $k=k_{\theta}=m/r$, the wave number and $c=[4 \pi a \rho \hbar^{2}]^{1/2}/M$, the speed of first sound. Based on Bohm's quantum theory, a spontaneously broken gauge symmetry in a quantum fluid is discussed in terms of the quantum fluctuation-dissipation, from which it is shown that the symmetry breaking takes place at the free surface of BEC in an external field.Comment: 20 pages plus one figur

Quantum Hamilton-Jacobi Equation and Broken Symmetry in Hydrodynamics of Liquid Helium II

Based on the quantum theory of Bohm and the phase coherence along with the mean field of Penrose and Onsager, it is shown that a free surface of He II behaves like a classical fluid. The broken symmetry of a macroscopic Bose system at the free surface in an external field is discussed in terms of the quantum fluctuations-dissipation. First, we apply this peculiarly universal behavior to explain a breakdown of superfluidity at a vortex core. Secondly, we resolve a long standing puzzle with Landau's two-fluid model on a free surface of a rotating He II in a gravitational field.Comment: 15 pages and no figure

Atomic Theory of Collective Excitations in Bose-Einstein Condensation and Spontaneously Broken Gauge Symmetry

A theory of collective excitations in Bose-Einstein condensation in a trap is developed based on the quantum Hamilton-Jacobi equation of Bohm and the phase coherence along with the idea of off-diagonal long range order of Penrose and Onsager. First, we show that a free surface behaves like a normal fluid - a breakdown of superfluidity. Second, inside the free surface it is shown that the spectrum of phonons is of the form $\omega=ck$ scaled with the external potential, where the speed of (first) sound, $c=[4\pi a\rho\hbar^{2}]^{1/2}/M$ and $k$ is the wave number. Third, in the limit $a\to 0$, the hard spheres in the Bose-Einstein condensation collapse to a close-packed classical lattice with the zero-point vibrational motion about fixed points.Comment: total 16 pages, including 1 figur

The Galactic distribution of magnetic fields in molecular clouds and HII regions

{Magnetic fields exist on all scales in our Galaxy. There is a controversy about whether the magnetic fields in molecular clouds are preserved from the permeated magnetic fields in the interstellar medium (ISM) during cloud formation. We investigate this controversy using available data in the light of the newly revealed magnetic field structure of the Galactic disk obtained from pulsar rotation measures (RMs).} % {We collected measurements of the magnetic fields in molecular clouds, including Zeeman splitting data of OH masers in clouds and OH or HI absorption or emission lines of clouds themselves.} % {The Zeeman data show structures in the sign distribution of the line-of-sight component of the magnetic field. Compared to the large-scale Galactic magnetic fields derived from pulsar RMs, the sign distribution of the Zeeman data shows similar large-scale field reversals. Previous such examinations were flawed in the over-simplified global model used for the large-scale magnetic fields in the Galactic disk.} % {We conclude that the magnetic fields in the clouds may still ``remember'' the directions of magnetic fields in the Galactic ISM to some extent, and could be used as complementary tracers of the large-scale magnetic structure. More Zeeman data of OH masers in widely distributed clouds are required.}Comment: Typo fixed in this new versio

Reply to comment on "Doping Driven (π,0\pi,0) Nesting and Magnetic Properties of Fe1+x_{1+x}Te Superconductors"

Inclusion of correlation effects affects quantitatively the agreement with experiment as far as the value of energy shift and the level of doping is concerned, and our original statement that nesting at ($\pi$,0) can be responsible for magnetic behavior of FeTe is hereby reinstated

Probing gravitational lensing of the CMB with SDSS-IV quasars

We study the cross-correlation between the Planck cosmic microwave background (CMB) lensing convergence map and the extended-Baryon Oscillation Spectroscopic Survey (e-BOSS) quasar overdensity obtained from the Sloan Digital Sky Survey (SDSS) IV, in the redshift range 0.9 < z < 2.2. We detect the CMB lensing convergence–quasar cross-power spectrum at 5.4σ significance. The cross-power spectrum provides a quasar clustering bias measurement that is expected to be particularly robust against systematic effects. The redshift distribution of the quasar sample has a median redshift z ≈ 1.55, and an effective redshift about 1.51. The best-fitting bias of the quasar sample is b q = 2.43 ± 0.45, corresponding to a host halo mass of log 10 h − 1MM = 12.54 +−00 .. 2536 . This is broadly consistent with the previous literature on quasars with a similar redshift range and selection. Since our constraint on the bias comes from the cross-correlation between quasars and CMB lensing, we expect it to be robust to a wide range of possible systematic effects that may contaminate the autocorrelation of quasars. We checked for a number of systematic effects from both CMB lensing and quasar overdensity, and found that all systematics are consistent with null within 2σ. The data are not sensitive to a possible scale dependence of the bias at present, but we expect that as the number of quasars increases [in future surveys such as Dark Energy Spectroscopic Instrument (DESI)], it is likely that strong constraints on the scale dependence of the bias can be obtained

Violation of Kohler's rule by the magnetoresistance of a quasi-two-dimensional organic metal

The interlayer magnetoresistance of the quasi-two-dimensional metal $\alpha$-(BEDT-TTF)$_2$KHg(SCN)$_4$ is considered. In the temperature range from 0.5 to 10 K and for fields up to 10 tesla the magnetoresistance has a stronger temperature dependence than the zero-field resistance. Consequently Kohler's rule is not obeyed for any range of temperatures or fields. This means that the magnetoresistance cannot be described in terms of semiclassical transport on a single Fermi surface with a single scattering time. Possible explanations for the violations of Kohler's rule are considered, both within the framework of semi-classical transport theory and involving incoherent interlayer transport. The issues considered are similar to those raised by the magnetotransport of the cuprate superconductors.Comment: 5 pages, RevTeX + epsf, 2 figures. Slightly revised version to appear in Physical Review B, May 15, 199

Occupation Numbers of a Half-Filled Landau Level

We demonstrate that a theory of the edge of a half-filled Landau level recently proposed by Lee and Wen predicts results for the edge occupation number similar to those of a variational trial wave function proposed previously by us. We treat Lee and Wen's edge action of a half-filled Landau level within the framework of bosonization theory, and show that the momentum occupation numbers are determined by a product of two Green's functions, one charged and one neutral. In the bulk region ($k<0$) we find a linear occupation profile, $n_k \propto A+Bk$, while in the tail region ($k>0$) it is exponentially decaying over the range k\sim\Ln, the momentum cutoff for neutral mode. We find a good fit with the numerical results for occupation numbers

Transverse and in-plane modification of superconductivity and electronic structure in the quasi-two dimensional organic conductor κ\kappa --(BEDT-TTF)2_{2}Cu(SCN)2_{2} by uniaxial stress

We have employed uniaxial stress along the principal axes of the quasi-two dimensional organic superconductor $\kappa$--(BEDT-TTF)$_{2}$Cu(SCN)$_{2}$. The lattice anisotropy is thereby altered, with corresponding changes in the intermolecular transfer energies. The effect of uniaxial stress on the superconducting transition temperature $T_{c}$ and critical field $B_{c2}$ is found to be anisotropic.There is an indication of an increase in $T_{c}$ and $B_{c2}$ for in-plane stress, but both parameters decrease rapidly for transverse (inter-plane) stress. Magnetotransport studies reveal stress-induced changes in the Fermi surface through the observation of the Shubnikov de Haas oscillations. The stress dependence of a resistive anomaly in the magnetoresistance, which is associated with the critical field $B_{c2}$, is also investigated. We discuss the experimental findings in the context of recent phenomenological and theoretical treatments of quasi-two dimensional systems where the anisotropic triangular lattice Hubbard model has been used to treat two-dimensional superconductors.Comment: 10 pages, two tables, 14 figure