The geometric order of stripes and Luttinger liquids

It is argued that the electron stripes as found in correlated oxides have to do with an unrecognized form of order. The manifestation of this order is the robust property that the charge stripes are at the same time anti-phase boundaries in the spin system. We demonstrate that the quantity which is ordering is sublattice parity, referring to the geometric property of a bipartite lattice that it can be subdivided in two sublattices in two different ways. Re-interpreting standard results of one dimensional physics, we demonstrate that the same order is responsible for the phenomenon of spin-charge separation in strongly interacting one dimensional electron systems. In fact, the stripe phases can be seen from this perspective as the precise generalization of the Luttinger liquid to higher dimensions. Most of this paper is devoted to a detailed exposition of the mean-field theory of sublattice parity order in 2+1 dimensions. Although the quantum-dynamics of the spin- and charge degrees of freedom is fully taken into account, a perfect sublattice parity order is imposed. Due to novel order-out-of-disorder physics, the sublattice parity order gives rise to full stripe order at long wavelength. This adds further credibility to the notion that stripes find their origin in the microscopic quantum fluctuations and it suggests a novel viewpoint on the relationship between stripes and high Tc superconductivity.Comment: 29 pages, 14 figures, 1 tabl

Spin motive forces due to magnetic vortices and domain walls

We study spin motive forces, i.e, spin-dependent forces, and voltages induced by time-dependent magnetization textures, for moving magnetic vortices and domain walls. First, we consider the voltage generated by a one-dimensional field-driven domain wall. Next, we perform detailed calculations on field-driven vortex domain walls. We find that the results for the voltage as a function of magnetic field differ between the one-dimensional and vortex domain wall. For the experimentally relevant case of a vortex domain wall, the dependence of voltage on field around Walker breakdown depends qualitatively on the ratio of the so-called $\beta$-parameter to the Gilbert damping constant, and thus provides a way to determine this ratio experimentally. We also consider vortices on a magnetic disk in the presence of an AC magnetic field. In this case, the phase difference between field and voltage on the edge is determined by the $\beta$ parameter, providing another experimental method to determine this quantity.Comment: 8 pages, 9 figures, submitted to PR

Systematic Density Expansion of the Lyapunov Exponents for a Two-dimensional Random Lorentz Gas

We study the Lyapunov exponents of a two-dimensional, random Lorentz gas at low density. The positive Lyapunov exponent may be obtained either by a direct analysis of the dynamics, or by the use of kinetic theory methods. To leading orders in the density of scatterers it is of the form $A_{0}\tilde{n}\ln\tilde{n}+B_{0}\tilde{n}$, where $A_{0}$ and $B_{0}$ are known constants and $\tilde{n}$ is the number density of scatterers expressed in dimensionless units. In this paper, we find that through order $(\tilde{n}^{2})$, the positive Lyapunov exponent is of the form $A_{0}\tilde{n}\ln\tilde{n}+B_{0}\tilde{n}+A_{1}\tilde{n}^{2}\ln\tilde{n} +B_{1}\tilde{n}^{2}$. Explicit numerical values of the new constants $A_{1}$ and $B_{1}$ are obtained by means of a systematic analysis. This takes into account, up to $O(\tilde{n}^{2})$, the effects of {\it all\/} possible trajectories in two versions of the model; in one version overlapping scatterer configurations are allowed and in the other they are not.Comment: 12 pages, 9 figures, minor changes in this version, to appear in J. Stat. Phy

Resonant Impurity States in the D-Density-Wave Phase

We study the electronic structure near impurities in the d-density-wave (DDW) state, a possible candidate phase for the pseudo-gap region of the high-temperature superconductors. We show that the local DOS near a non-magnetic impurity in the DDW state is {\it qualitatively} different from that in a superconductor with $d_{x^2-y^2}$-symmetry. Since this result is a robust feature of the DDW phase, it can help to identify the nature of the two different phases recently observed by scanning tunneling microscopy experiments in the superconducting state of underdoped Bi-2212 compounds

Cochrane corner: Is integrated disease management for patients with COPD effective?

Patients with COPD experience respiratory symptoms, impairments of daily living and recurrent exacerbations. The aim of integrated disease management (IDM) is to establish a programme of different components of care (ie, self-management, exercise, nutrition) in which several healthcare providers (ie, nurses, general practitioners, physiotherapists, pulmonologists) collaborate to provide efficient and good quality of care. The aim of this Cochrane systematic review was to evaluate the effectiveness of IDM on quality of life, exercise tolerance and exacerbation related outcomes. Searches for all available evidence were carried out in various databases. Included randomised controlled trials (RCTs) consisted of interventions with multidisciplinary (≥2 healthcare providers) and multitreatment (≥2 components) IDM interventions with duration of at least 3 months. Two reviewers independently searched, assessed and extracted data of all RCTs. A total of 26 RCTs were included, involving 2997 patients from 11 different countries with a followup varying from 3 to 24 months. In all 68% of the patients were men, with a mean age of 68 years and a mean forced expiratory volume in 1 s (FEV1) predicted value of 44.3%. Patients treated with an IDM programme improved significantly on quality of life scores and reported a clinically relevant improvement of 44 m on 6 min walking distance, compared to controls. Furthermore, the number of patients with ≥1 respiratory related hospital admission reduced from 27 to 20 per 100 patients. Duration of hospitalisation decreased significantly by nearly 4 days

Influence of the interelectrode distance on the production of nanoparticles by means of atmospheric pressure inert gas DC glow discharge

This work is aimed at investigating the influence of the inter-electrode spacing on the production rate and size of nanoparticles generated by evaporating a cathode on an atmospheric pressure dc glow discharge. Experiments are conducted in the configuration of two vertically aligned cylindrical electrodes in upward coaxial flow with copper as a consumable cathode and nitrogen as a carrier gas. A constant current of 0.5 A is delivered to the electrodes and the inter-electrode distance spanned from 0.5 to 10 mm. Continuous stable nanoparticle production is attained by optimal coaxial flow convection cooling of the cathode. Both the particle production rate and the primary particle size increase with the inter-electrode spacing up to nearly 5 mm and strongly decrease with an increasing inter-electrode distance beyond 5 mm. Production rates in the range of 1 mg h-1 of very small nanoparticles

Field induced d_x^2-y^2+id_xy state in d-density-wave metals

We argue that the d_{xy} component of the order parameter can be generated to form the d_x^2-y^2+id_xy-density wave state by the external magnetic field. The driving force for this transition is the coupling of the magnetic field with the orbital magnetism. The fully gapped particle spectrum and the magnetically active collective mode of the condensate are discussed as a possible signature of the d+id' density wave state.Comment: 5 pages, 2 color figure

Hidden order in bosonic gases confined in one dimensional optical lattices

We analyze the effective Hamiltonian arising from a suitable power series expansion of the overlap integrals of Wannier functions for confined bosonic atoms in a 1d optical lattice. For certain constraints between the coupling constants, we construct an explicit relation between such an effective bosonic Hamiltonian and the integrable spin-$S$ anisotropic Heisenberg model. Therefore the former results to be integrable by construction. The field theory is governed by an anisotropic non linear $\sigma$-model with singlet and triplet massive excitations; such a result holds also in the generic non-integrable cases. The criticality of the bosonic system is investigated. The schematic phase diagram is drawn. Our study is shedding light on the hidden symmetry of the Haldane type for one dimensional bosons.Comment: 5 pages; 1 eps figure. Revised version, to be published in New. J. Phy

Geometry and the Hidden Order of Luttinger Liquids: the Universality of Squeezed Space

We present the case that Luttinger liquids are characterized by a form of hidden order which is similar, but distinct in some crucial regards, to the hidden order characterizing spin-1 Heisenberg chains. We construct a string correlator for the Luttinger liquid which is similar to the string correlator constructed by den Nijs and Rommelse for the spin chain. From a geometric prespective on the so-called `squeezed space' construction, we demonstrate that the physics at long wavelength can be reformulated in terms of a $Z_2$ gauge theory. Peculiarly, the normal spin chain lives at infinite gauge coupling where it is characterized by deconfinement. We identify the microscopic conditions required for confinement thereby identifying a novel phase of the spin-chain. We demonstrate that the Luttinger liquid can be approached in the same general framework. The difference from the spin chain is that the gauge sector is critical in the sense that the Luttinger liquid is at the phase boundary where the $Z_2$ local symmetry emerges. We evaluate the string correlator analytically and show that the squeezed space structure is present both for the strongly coupled Hubbard model and the non-interacting fermion gas. These structures are hard-wired in the mathematical structure of bosonization and this becomes obvious by considering string correlators. Numerical results are presented for the string correlator using a non-abelian version of the density matrix renormalization group algorithm, confirming in detail the expectations following from the theory. We conclude with some observations regarding the generalization of bosonization to higher dimensions.Comment: 24 pages, 14 eps figures, Revtex