The antiferromagnetic phi4 Model, II. The one-loop renormalization

It is shown that the four dimensional antiferromagnetic lattice phi4 model has the usual non-asymptotically free scaling law in the UV regime around the chiral symmetrical critical point. The theory describes a scalar and a pseudoscalar particle. A continuum effective theory is derived for low energies. A possibility of constructing a model with a single chiral boson is mentioned.Comment: To appear in Phys. Rev.

Quantum theta functions and Gabor frames for modulation spaces

Representations of the celebrated Heisenberg commutation relations in quantum mechanics and their exponentiated versions form the starting point for a number of basic constructions, both in mathematics and mathematical physics (geometric quantization, quantum tori, classical and quantum theta functions) and signal analysis (Gabor analysis). In this paper we try to bridge the two communities, represented by the two co--authors: that of noncommutative geometry and that of signal analysis. After providing a brief comparative dictionary of the two languages, we will show e.g. that the Janssen representation of Gabor frames with generalized Gaussians as Gabor atoms yields in a natural way quantum theta functions, and that the Rieffel scalar product and associativity relations underlie both the functional equations for quantum thetas and the Fundamental Identity of Gabor analysis.Comment: 38 pages, typos corrected, MSC class change

On the Cut-Off Prescriptions Associated with Power-Law Generalized Thermostatistics

We revisit the cut-off prescriptions which are needed in order to specify completely the form of Tsallis' maximum entropy distributions. For values of the Tsallis entropic parameter $q>1$ we advance an alternative cut-off prescription and discuss some of its basic mathematical properties. As an illustration of the new cut-off prescription we consider in some detail the $q$-generalized quantum distributions which have recently been shown to reproduce various experimental results related to high $T_c$ superconductors

Spin-dynamics simulations of the triangular antiferromagnetic XY model

Using Monte Carlo and spin-dynamics methods, we have investigated the dynamic behavior of the classical, antiferromagnetic XY model on a triangular lattice with linear sizes $L \leq 300$. The temporal evolutions of spin configurations were obtained by solving numerically the coupled equations of motion for each spin using fourth-order Suzuki-Trotter decompositions of exponential operators. From space- and time-displaced spin-spin correlation functions and their space-time Fourier transforms we obtained the dynamic structure factor $S({\bf q},w)$ for momentum ${\bf q}$ and frequency $\omega$. Below $T_{KT}$(Kosterlitz-Thouless transition), both the in-plane ($S^{xx}$) and the out-of-plane ($S^{zz}$) components of $S({\bf q},\omega)$ exhibit very strong and sharp spin-wave peaks. Well above $T_{KT}$, $S^{xx}$ and $S^{zz}$ apparently display a central peak, and spin-wave signatures are still seen in $S^{zz}$. In addition, we also observed an almost dispersionless domain-wall peak at high $\omega$ below $T_{c}$(Ising transition), where long-range order appears in the staggered chirality. Above $T_{c}$, the domain-wall peak disappears for all $q$. The lineshape of these peaks is captured reasonably well by a Lorentzian form. Using a dynamic finite-size scaling theory, we determined the dynamic critical exponent $z$ = 1.002(3). We found that our results demonstrate the consistency of the dynamic finite-size scaling theory for the characteristic frequeny $\omega_{m}$ and the dynamic structure factor $S({\bf q},\omega)$ itself.Comment: 8 pages, RevTex, 10 figures, submitted to PR

Ambulatory Estimation of Relative Foot Positions using Ultrasound

The recording of human movement is used for biomedical applications like physical therapy and sports training. Over the last few years inertial sensors have been proven to be a useful ambulatory alternative to traditional optical systems. An example of a successful application is the instrumented shoe, which contains two 6D force/moment sensors beneath the heel and the forefoot and two inertial sensors rigidly attached to the force/moment sensors [1]. These shoes can be used for ambulatory assessment of walking kinetics and kinematics. The relative position of the feet is currently not measured directly but estimated from double integration of feet accelerations. However, this method immediately leads to large position errors (drift) when the estimated inertial accelerations are inaccurate. In this study we investigated the ambulatory estimation of the relative positions of the feet using ultrasound transducers. On one shoe we mounted a 400PT120 Air Ultrasonic Ceramic Transducer (13 mm diameter, 10 mm height, 85º beam angle) sending a 40 kHz pulse to a similar transducer on the other shoe. Using the time of flight, the distance is estimated. Under static conditions a mean error of 5.7 ±0.8 mm was obtained over a range of 5 till 75 cm [2]. From this pilot study we concluded that the distance between the feet can be estimated ambulatory using small and low-cost ultrasound transducers. Future research includes the use of multiple transducers on each foot for a distance measure during different daily-life activities. Also the relative positions of the feet will be investigated by fusing the distance estimates with inertial sensor data

The antiferromagnetic phi4 Model, I. The Mean-field Solution

Certain higher dimensional operators of the lagrangian may render the vacuum inhomogeneous. A rather rich phase structure of the phi4 scalar model in four dimensions is presented by means of the mean-field approximation. One finds para- ferro- ferri- and antiferromagnetic phases and commensurate-incommensurate transitions. There are several particles described by the same quantum field in a manner similar to the species doubling of the lattice fermions. It is pointed out that chiral bosons can be introduced in the lattice regularized theory.Comment: To appear in Phys. Rev.

Testing one-body density functionals on a solvable model

There are several physically motivated density matrix functionals in the literature, built from the knowledge of the natural orbitals and the occupation numbers of the one-body reduced density matrix. With the help of the equivalent phase-space formalism, we thoroughly test some of the most popular of those functionals on a completely solvable model.Comment: Latex, 16 pages, 4 figure

The heart rate variability-derived Newborn Infant Parasympathetic Evaluation (NIPE (TM)) Index in pediatric surgical patients from 0 to 2 years under sevoflurane anesthesia

Abstract Background The heart rate variability‐derived Newborn Infant Parasympathetic Evaluation (NIPE™) Index is a continuous noninvasive tool to assess pain and discomfort in infants <2 years. Initial studies focused on pain monitoring in the neonatal intensive care unit environment. Aims The aim of this study was to investigate the performance of the NIPE in infants under sevoflurane anesthesia. The primary objective of this study was to compare the NIPE and heart rate as tools to help recognize the need for additional opioid drugs. Secondary objectives were the course of the NIPE and heart rate around specific standardized noxious procedural mile‐stones. Methods NIPE and heart rate values recorded during a 120 seconds interval before the anesthetist's decision to administer additional opioid due to the perceived insufficient antinociception and during a 120 seconds interval after drug administration were analyzed by means of a repeated measures ANOVA. The same analyses were performed for datasets around per protocol administration of morphine for postoperative analgesia, performance of a caudal block and surgical incision. Results In patients with a NIPE value <50, an additional opioid drug administration resulted in a rise of NIPE values, reaching a maximum increase of 5.1 (95% CI: 0.22‐9.99) units 120 seconds after drug administration (P = 0.041). There was no evidence of a change in heart rate during these two 120 seconds periods. Per protocol administration of morphine, caudal block, and surgical incision did not result in changes of the NIPE, which was around 65 units on these occasions, and heart rate. Conclusion In infants anesthetized with sevoflurane, NIPE values <50 might be indicative of insufficient antinociception. The results of this observational pilot study might suggest that the NIPE could be a better measure of the nociception/antinociception balance than heart rate

Artenvielfalt auf biologischen und nicht-biologischen Landwirtschaftsbetrieben in zehn europäischen Regionen

One of the aims of organic farming is the protection of biodiversity. In the EU FP7 project BioBio, we studied the effect of organic farming on species numbers at farm level on 169 randomly selected organic and non-organic farms with mostly low to medium intensity in ten European regions. Using a preferential sampling scheme based on habitat mapping, numbers of plants, earthworms, spiders and bees were assessed at farm level. A global analysis across the ten regions shows that organic farms have significantly higher numbers of plant and bee species than non-organic farms. The effect of organic farming on earthworm and spider species numbers are also positive but insignificant. The effects in absolute terms are small and much smaller than the variation between individual farms. Currently ongoing analyses aim at identifying the important driving factors for farmland biodiversity

Theoretical study of the optical conductivity of α′−NaV2O5\alpha'-NaV_2O_5

Using finite temperature diagonalization techniques it is shown that the quarter-filled t-J-V model on a trellis lattice structure provides a quantitative explanation of the highly anisotropic optical conductivity of the $\alpha'-NaV_{2}O_{5}$ compound. The combined effects of the short-range Coulomb interaction and valence fluctuations of V-ions determine the main absorption and the fundamental gap. Inter-ladder hopping is necessary for the explanation of the anomalous in-gap absorption and generation of spectral weight at high energy. The role of valence fluctuations is explained in terms of the domain wall excitations of an anisotropic 2D Ising model in a transverse field close to criticality.Comment: 4 pages, 5 figure