What are spin currents in Heisenberg magnets?

We discuss the proper definition of the spin current operator in Heisenberg magnets subject to inhomogeneous magnetic fields. We argue that only the component of the naive "current operator" J_ij S_i x S_j in the plane spanned by the local order parameters and is related to real transport of magnetization. Within a mean field approximation or in the classical ground state the spin current therefore vanishes. Thus, finite spin currents are a direct manifestation of quantum correlations in the system.Comment: 4 pages, 1 figure, published versio

Magnetic Monopoles, Center Vortices, Confinement and Topology of Gauge Fields

The vortex picture of confinement is studied. The deconfinement phase transition is explained as a transition from a phase in which vortices percolate to a phase of small vortices. Lattice results are presented in support of this scenario. Furthermore the topological properties of magnetic monopoles and center vortices arising, respectively, in Abelian and center gauges are studied in continuum Yang-Mills-theory. For this purpose the continuum analog of the maximum center gauge is constructed.Comment: talk given by H. Reinhardt on the Int. Workshop ``Hadrons 1999'', Coimbra, 10.-15. Sept. 199

Distance-generalized Core Decomposition

The $k$-core of a graph is defined as the maximal subgraph in which every vertex is connected to at least $k$ other vertices within that subgraph. In this work we introduce a distance-based generalization of the notion of $k$-core, which we refer to as the $(k,h)$-core, i.e., the maximal subgraph in which every vertex has at least $k$ other vertices at distance $\leq h$ within that subgraph. We study the properties of the $(k,h)$-core showing that it preserves many of the nice features of the classic core decomposition (e.g., its connection with the notion of distance-generalized chromatic number) and it preserves its usefulness to speed-up or approximate distance-generalized notions of dense structures, such as $h$-club. Computing the distance-generalized core decomposition over large networks is intrinsically complex. However, by exploiting clever upper and lower bounds we can partition the computation in a set of totally independent subcomputations, opening the door to top-down exploration and to multithreading, and thus achieving an efficient algorithm

Assessment of post-radiotherapy salivary glands

Salivary glands are usually irradiated during radiotherapy for head and neck cancers, which can lead to radiation-induced damage. Radiation-induced xerostomia (oral dryness) is the most common post-radiotherapy complication for head and neck cancer patients and can reduce the patient's quality of life. Accurate and efficient salivary gland assessment methods provide a better understanding of the cause and degree of xerostomia, and may help in patient management. At present, there are different methods for the assessment of salivary gland hypofunction; however, none of them are considered to be standard procedure. This article reviews the value of common methods in the assessment of post-radiotherapy salivary glands. © 2011 The British Institute of Radiology.link_to_subscribed_fulltex

Spectral gap of the totally asymmetric exclusion process at arbitrary filling

We calculate the spectral gap of the Markov matrix of the totally asymmetric simple exclusion process (TASEP) on a ring of L sites with N particles. Our derivation is simple and self-contained and extends a previous calculation that was valid only for half-filling. We use a special property of the Bethe equations for TASEP to reformulate them as a one-body problem. Our method is closely related to the one used to derive exact large deviation functions of the TASEP

QCD sum rules with finite masses

The concept of QCD sum rules is extended to bound states composed of particles with finite mass such as scalar quarks or strange quarks. It turns out that mass corrections become important in this context. The number of relevant corrections is analyzed in a systematic discussion of the IR- and UV-divergencies, leading in general to a finite number of corrections. The results are demonstrated for a system of two massless quarks and two heavy scalar quarks.Comment: 15 pages, including two pictures to be found in an extra file. Latex neads epsf.st

Comparison of body temperature measurements obtained with otic digital thermometer and mercury axillary and rectal thermometers in children under the age of five

Indexación: Web of Science; ScieloIntroducción: En los últimos años han aparecido nuevos métodos para medir la temperatura en niños, como el termómetro digital ótico. Siendo este un método más rápido para medir la temperatura y por lo tanto ideal para el servicio de urgencias, es necesario conocer su confiabilidad. Objetivo: Comparar los valores de temperatura corporal que entrega el termómetro ótico digital con los termómetros de mercurio axilar y rectal. Pacientes y Método: Se efectuó la medición de la temperatura en 50 pacientes menores de 5 años elegidos al azar, que consultaron en el Servicio de Urgencia del Hospital de Niños y Cunas de Viña del Mar. Se les midió la temperatura con un termómetro digital ótico al lado izquierdo y derecho, y las temperaturas axilar derecha y rectal con termómetros de mercurio. EL análisis de los resultados se efectuó en el grupo estudiado, separado en dos grupos, menores y mayores de 6 meses. Resultados: Los resultados entre ambos subgrupos fueron los mismos. La temperatura media rectal obtenida fue 0,414°C más alta que la media ótica derecha (p < 0,001) y 0,438°C más alta que la temperatura media ótica izquierda (p < 0,001). Conclusión: El termómetro ótico digital entrega una temperatura significativamente más baja que la que entregan los termómetros de mercurio axilar y rectal.Background: In recent years, otic thermometers to measure body temperature in children have become increasingly popular as they reflect changes in body temperature sooner than other thermometers. The have become valuable assets in hospital emergency rooms; however, their accuracy and reliability need further studies. Objective: To compare corporal temperature readings between an otic thermometer and mercury axillary and rectal thermometers. Patients and Method: 50 patients under the age of 5, who were treated at the emergency room of our hospital, were randomly chosen to participate in this study. Temperature was measured on their right and left ears using an otic thermometer, and their rectal and right axillary temperature was taken using mercury thermometers. Patients were separated into 2 subgroups for comparison, children under and over 6 months old. Results: The results between the 2 subgroups were very similar. The average temperature obtained by rectal thermometers was 0.414°C higher than the average right-ear temperature (p < 0.001) and 0.438°c higher than the average left-ear temperature (p < 0.001). Conclusion: The otic thermometer's reading is significantly lower than the one obtained using mercury rectal and axillary thermometers.http://ref.scielo.org/72p3g

Current Distribution and random matrix ensembles for an integrable asymmetric fragmentation process

We calculate the time-evolution of a discrete-time fragmentation process in which clusters of particles break up and reassemble and move stochastically with size-dependent rates. In the continuous-time limit the process turns into the totally asymmetric simple exclusion process (only pieces of size 1 break off a given cluster). We express the exact solution of master equation for the process in terms of a determinant which can be derived using the Bethe ansatz. From this determinant we compute the distribution of the current across an arbitrary bond which after appropriate scaling is given by the distribution of the largest eigenvalue of the Gaussian unitary ensemble of random matrices. This result confirms universality of the scaling form of the current distribution in the KPZ universality class and suggests that there is a link between integrable particle systems and random matrix ensembles.Comment: 11 page

Measuring hadron properties at finite temperature

We estimate the numbers and mass spectra of observed lepton and kaon pairs produced from $\phi$ meson decays in the central rapidity region of an Au+Au collision at lab energy 11.6 GeV/nucleon. The following effects are considered: possible mass shifts, thermal broadening due to collisions with hadronic resonances, and superheating of the resonance gas. Changes in the dilepton mass spectrum may be seen, but changes in the dikaon spectrum are too small to be detectable.Comment: 9 pages (revtex), 3 figures (uuencoded postscript