Haldane charge conjecture in one-dimensional multicomponent fermionic cold atoms

A Haldane conjecture is revealed for spin-singlet charge modes in 2N-component fermionic cold atoms loaded into a one-dimensional optical lattice. By means of a low-energy approach and DMRG calculations, we show the emergence of gapless and gapped phases depending on the parity of $N$ for attractive interactions at half-filling. The analogue of the Haldane phase of the spin-1 Heisenberg chain is stabilized for N=2 with non-local string charge correlation, and pseudo-spin 1/2 edge states. At the heart of this even-odd behavior is the existence of a spin-singlet pseudo-spin $N/2$ operator which governs the low-energy properties of the model for attractive interactions and gives rise to the Haldane physics.Comment: 4 pages, 4 figure

Competing orders in one-dimensional half-filled multicomponent fermionic cold atoms: The Haldane-charge conjecture

We investigate the nature of the Mott-insulating phases of half-filled 2N-component fermionic cold atoms loaded into a one-dimensional optical lattice. By means of conformal field theory techniques and large-scale DMRG calculations, we show that the phase diagram strongly depends on the parity of $N$. First, we single out charged, spin-singlet, degrees of freedom, that carry a pseudo-spin ${\cal S}=N/2$ allowing to formulate a Haldane conjecture: for attractive interactions, we establish the emergence of Haldane insulating phases when $N$ is even, whereas a metallic behavior is found when $N$ is odd. We point out that the $N=1,2$ cases do \emph{not} have the generic properties of each family. The metallic phase for $N$ odd and larger than 1 has a quasi-long range singlet pairing ordering with an interesting edge-state structure. Moreover, the properties of the Haldane insulating phases with even $N$ further depend on the parity of N/2. In this respect, within the low-energy approach, we argue that the Haldane phases with N/2 even are not topologically protected but equivalent to a topologically trivial insulating phase and thus confirm the recent conjecture put forward by Pollmann {\it et al.} [Pollmann {\it et al.}, arXiv:0909.4059 (2009)].Comment: 25 pages, 20 figure

Equilibrium onions?

We demonstrate the possibility of a stable equilibrium multi-lamellar ("onion") phase in pure lamellar systems (no excess solvent) due to a sufficiently negative Gaussian curvature modulus. The onion phase is stabilized by non-linear elastic moduli coupled to a polydisperse size distribution (Apollonian packing) to allow space-filling without appreciable elastic distortion. This model is compared to experiments on copolymer-decorated lamellar surfactant systems, with reasonable qualitative agreement

Force distribution in a scalar model for non-cohesive granular material

We study a scalar lattice model for inter-grain forces in static, non-cohesive, granular materials, obtaining two primary results. (i) The applied stress as a function of overall strain shows a power law dependence with a nontrivial exponent, which moreover varies with system geometry. (ii) Probability distributions for forces on individual grains appear Gaussian at all stages of compression, showing no evidence of exponential tails. With regard to both results, we identify correlations responsible for deviations from previously suggested theories.Comment: 16 pages, 9 figures, Submitted to PR

Numbers do not tell the whole story: gender and medicine in Portugal

Despite a progressive increase in the number of women in medicine, gender inequalities remain. This article presents a study analyzing the gender dynamics of tokenism in the medical field in Portugal, through the experiences of male specialists in female areas and female specialists in male areas and through their strategies for coping with such situations. We conducted individual, semi-structured interviews with nine female doctors and eight male doctors aged between 32 and 62 years old. Results show the links between tokenism dynamics and gender asymmetry in medicine, putting female tokens at a disadvantage in relation to male tokens. Token positions occasionally produce gender arrangements but, all things considered, do not transform female and male positions either in the medical field or in the private sphere. We conclude that tokenism contributes to maintaining the gender social order.info:eu-repo/semantics/acceptedVersio

Permeability of self-affine rough fractures

The permeability of two-dimensional fractures with self-affine fractal roughness is studied via analytic arguments and numerical simulations. The limit where the roughness amplitude is small compared with average fracture aperture is analyzed by a perturbation method, while in the opposite case of narrow aperture, we use heuristic arguments based on lubrication theory. Numerical simulations, using the lattice Boltzmann method, are used to examine the complete range of aperture sizes, and confirm the analytic arguments.Comment: 11 pages, 9 figure

Conformal Mapping on Rough Boundaries II: Applications to bi-harmonic problems

We use a conformal mapping method introduced in a companion paper to study the properties of bi-harmonic fields in the vicinity of rough boundaries. We focus our analysis on two different situations where such bi-harmonic problems are encountered: a Stokes flow near a rough wall and the stress distribution on the rough interface of a material in uni-axial tension. We perform a complete numerical solution of these two-dimensional problems for any univalued rough surfaces. We present results for sinusoidal and self-affine surface whose slope can locally reach 2.5. Beyond the numerical solution we present perturbative solutions of these problems. We show in particular that at first order in roughness amplitude, the surface stress of a material in uni-axial tension can be directly obtained from the Hilbert transform of the local slope. In case of self-affine surfaces, we show that the stress distribution presents, for large stresses, a power law tail whose exponent continuously depends on the roughness amplitude

ELEVATED SERUM LEVELS OF TNF SOLUBLE RECEPTORS IN PATIENTS WITH POSITIVE ANTI-NEUTROPHIL CYTOPLASMIC ANTIBODIES

ANCA are found in various systemic vasculitis and are supposed to play a role in the pathogenesis of the disease, in cooperation with other factors such as cytokines. A total of 36 ANCA-positive and 10 ANCA-negative serum samples were analysed for the presence of TNF soluble receptors (TNF-sR), which are shed from the surface of activated cells and may act as TNF inhibitors. Of the ANCA-positive samples, 67% had elevated TNF-sR75 and 72% had elevated TNF-sR55 compared to ANCA-negative specimens (mean [S.E.] 18.7 [17.3] vs 3.6 [1.5] and 10.5 [9.7] vs 1.9 [0.7] ng/ml, P<0.01). Elevation of TNF-sR in patients with ANCA suggests that cytokines and their inhibitors are involved in the pathogenesis of ANCA-associated autoimmune disease

Frictionless bead packs have macroscopic friction, but no dilatancy

The statement of the title is shown by numerical simulation of homogeneously sheared packings of frictionless, nearly rigid beads in the quasistatic limit. Results coincide for steady &#64258;ows at constant shear rate &#947; in the limit of small &#947; and static approaches, in which packings are equilibrated under growing deviator stresses. The internal friction angle &#981;, equal to 5.76 $\pm$ 0.22 degrees in simple shear, is independent on the average pressure P in the rigid limit. It is shown to stem from the ability of stable frictionless contact networks to form stress-induced anisotropic fabrics. No enduring strain localization is observed. Dissipation at the macroscopic level results from repeated network rearrangements, like the e&#64256;ective friction of a frictionless slider on a bumpy surface. Solid fraction &#934; remains equal to the random close packing value &#8771; 0.64 in slowly or statically sheared systems. Fluctuations of stresses and volume are observed to regress in the large system limit, and we conclude that the same friction law for simple shear applies in the large psystem limit if normal stress or density is externally controlled. De&#64257;ning the inertia number as I = &#947; m/(aP), with m the grain mass and a its diameter, both internal friction coe&#64259;cient $\mu$&#8727; = tan &#981; and volume 1/&#934; increase as powers of I in the quasistatic limit of vanishing I, in which all mechanical properties are determined by contact network geometry. The microstructure of the sheared material is characterized with a suitable parametrization of the fabric tensor and measurements of connectivity and coordination numbers associated with contacts and near neighbors.Comment: 19 pages. Additional technical details may be found in v