Trapped Particle Stability for the Kinetic Stabilizer

A kinetically stabilized axially symmetric tandem mirror (KSTM) uses the momentum flux of low-energy, unconfined particles that sample only the outer end-regions of the mirror plugs, where large favorable field-line curvature exists. The window of operation is determined for achieving MHD stability with tolerable energy drain from the kinetic stabilizer. Then MHD stable systems are analyzed for stability of the trapped particle mode. This mode is characterized by the detachment of the central-cell plasma from the kinetic stabilizer region without inducing field-line bending. Stability of the trapped particle mode is sensitive to the electron connection between the stabilizer and the end plug. It is found that the stability condition for the trapped particle mode is more constraining than the stability condition for the MHD mode, and it is challenging to satisfy the required power constraint. Furthermore a severe power drain may arise from the necessary connection of low-energy electrons in the kinetic stabilizer to the central region

Silurian plutonism in the Trinity terrane (Neoproterozoic and Ordovician), Klamath Mountains, California, United States

New data indicate that the Trinity terrane of northern California is a polygenetic composite terrane rather than a single slice of oceanic lithosphere. We suggest approximately one third of the Trinity terrane consists of Silurian intrusive rocks that represent the roots of a previously unrecognized Silurian magmatic arc. Crosscutting relations and U‐Pb zircon isotopic data document at least one early Paleozoic deformation in the Trinity terrane of northern California. A ductile shear zone between Neoproterozoic metagabbro and Ordovician(?) harzburgite is intruded by the Upper Silurian China Mountain pluton. This evidence indicates a major early Paleozoic shear zone formed in the eastern Klamath Mountains after the Middle Ordovician but prior to Late Silurian plutonism

Revised Phase Diagram of the Gross-Neveu Model

We confirm earlier hints that the conventional phase diagram of the discrete chiral Gross-Neveu model in the large N limit is deficient at non-zero chemical potential. We present the corrected phase diagram constructed in mean field theory. It has three different phases, including a kink-antikink crystal phase. All transitions are second order. The driving mechanism for the new structure of baryonic matter in the Gross-Neveu model is an Overhauser type instability with gap formation at the Fermi surface.Comment: Revtex, 12 pages, 15 figures; v2: Axis labelling in Fig. 9 correcte

Q-stars in extra dimensions

We study q-stars with global and local U(1) symmetry in extra dimensions in asymptotically anti de Sitter or flat spacetime. The behavior of the mass, radius and particle number of the star is quite different in 3 dimensions, but in 5, 6, 8 and 11 dimensions is similar to the behavior in 4.Comment: 18 pages, to appear in Phys. Rev.

Non-Universal Power Law of the "Hall Scattering Rate" in a Single-Layer Cuprate Bi_{2}Sr_{2-x}La_{x}CuO_{6}

In-plane resistivity \rho_{ab}, Hall coefficient, and magnetoresistance (MR) are measured in a series of high-quality Bi_{2}Sr_{2-x}La_{x}CuO_{6} crystals with various carrier concentrations, from underdope to overdope. Our crystals show the highest T_c (33 K) and the smallest residual resistivity ever reported for Bi-2201 at optimum doping. It is found that the temperature dependence of the Hall angle obeys a power law T^n with n systematically decreasing with increasing doping, which questions the universality of the Fermi-liquid-like T^2 dependence of the "Hall scattering rate". In particular, the Hall angle of the optimally-doped sample changes as T^{1.7}, not as T^2, while \rho_{ab} shows a good T-linear behavior. The systematics of the MR indicates an increasing role of spin scattering in underdoped samples.Comment: 4 pages, 5 figure

Frustration and the Kondo effect in heavy fermion materials

The observation of a separation between the antiferromagnetic phase boundary and the small-large Fermi surface transition in recent experiments has led to the proposal that frustration is an important additional tuning parameter in the Kondo lattice model of heavy fermion materials. The introduction of a Kondo (K) and a frustration (Q) axis into the phase diagram permits us to discuss the physics of heavy fermion materials in a broader perspective. The current experimental situation is analysed in the context of this combined "QK" phase diagram. We discuss various theoretical models for the frustrated Kondo lattice, using general arguments to characterize the nature of the $f$-electron localization transition that occurs between the spin liquid and heavy Fermi liquid ground-states. We concentrate in particular on the Shastry--Sutherland Kondo lattice model, for which we establish the qualitative phase diagram using strong coupling arguments and the large-$N$ expansion. The paper closes with some brief remarks on promising future theoretical directions.Comment: To appear in a special issue of JLT

Extracting the rho-omega mixing amplitude from the pion form-factor

We re-examine and extend a recent analysis which showed that the rho-omega mixing amplitude cannot be unambiguously extracted from the pion electromagnetic form-factor in a model independent way. In particular, we focus on the argument that the extraction is sensitive to the presence of any intrinsic omega_I -> 2pi coupling. Our extended analysis confirms the original conclusion, with only minor, quantitative differences. The extracted mixing amplitude is shown to be sensitive to both the intrinsic coupling omega_I -> 2pi and to the value assumed for the mass of the neutral rho meson.Comment: 11 pages, publication details added to title pag

Kondo effect in coupled quantum dots: a Non-crossing approximation study

The out-of-equilibrium transport properties of a double quantum dot system in the Kondo regime are studied theoretically by means of a two-impurity Anderson Hamiltonian with inter-impurity hopping. The Hamiltonian, formulated in slave-boson language, is solved by means of a generalization of the non-crossing approximation (NCA) to the present problem. We provide benchmark calculations of the predictions of the NCA for the linear and nonlinear transport properties of coupled quantum dots in the Kondo regime. We give a series of predictions that can be observed experimentally in linear and nonlinear transport measurements through coupled quantum dots. Importantly, it is demonstrated that measurements of the differential conductance ${\cal G}=dI/dV$, for the appropriate values of voltages and inter-dot tunneling couplings, can give a direct observation of the coherent superposition between the many-body Kondo states of each dot. This coherence can be also detected in the linear transport through the system: the curve linear conductance vs temperature is non-monotonic, with a maximum at a temperature $T^*$ characterizing quantum coherence between both Kondo states.Comment: 20 pages, 17 figure

Interference in interacting quantum dots with spin

We study spectral and transport properties of interacting quantum dots with spin. Two particular model systems are investigated: Lateral multilevel and two parallel quantum dots. In both cases different paths through the system can give rise to interference. We demonstrate that this strengthens the multilevel Kondo effect for which a simple two-stage mechanism is proposed. In parallel dots we show under which conditions the peak of an interference-induced orbital Kondo effect can be split.Comment: 8 pages, 8 figure

Magnetotransport in the Normal State of La1.85Sr0.15Cu(1-y)Zn(y)O4 Films

We have studied the magnetotransport properties in the normal state for a series of La1.85Sr0.15Cu(1-y)Zn(y)O4 films with values of y, between 0 and 0.12. A variable degree of compressive or tensile strain results from the lattice mismatch between the substrate and the film, and affects the transport properties differently from the influence of the zinc impurities. In particular, the orbital magnetoresistance (OMR) varies with y but is strain-independent. The relations for the resistivity and the Hall angle and the proportionality between the OMR and tan^2 theta are followed about 70 K. We have been able to separate the strain and impurity effects by rewriting the above relations, where each term is strain-independent and depends on y only. We also find that changes in the lattice constants give rise to closely the same fractional changes in other terms of the equation.The OMR is more strongly supressed by the addition of impurities than tan^2 theta. We conclude that the relaxation ratethat governs Hall effect is not the same as for the magnetoresistance. We also suggest a correspondence between the transport properties and the opening of the pseudogap at a temperature which changes when the La-sr ratio changes, but does not change with the addition of the zinc impurities