Microscopic Model versus Systematic Low-Energy Effective Field Theory for a Doped Quantum Ferromagnet

We consider a microscopic model for a doped quantum ferromagnet as a test case for the systematic low-energy effective field theory for magnons and holes, which is constructed in complete analogy to the case of quantum antiferromagnets. In contrast to antiferromagnets, for which the effective field theory approach can be tested only numerically, in the ferromagnetic case both the microscopic and the effective theory can be solved analytically. In this way the low-energy parameters of the effective theory are determined exactly by matching to the underlying microscopic model. The low-energy behavior at half-filling as well as in the single- and two-hole sectors is described exactly by the systematic low-energy effective field theory. In particular, for weakly bound two-hole states the effective field theory even works beyond perturbation theory. This lends strong support to the quantitative success of the systematic low-energy effective field theory method not only in the ferromagnetic but also in the physically most interesting antiferromagnetic case.Comment: 34 pages, 1 figur

Praxisüberprüfung und Optimierung von Peronospora- und Oidiumbekämpfungsmaßnahmen im ökologischen Weinbau - Alternativen zum Einsatz von Kupfer und Schwefel

Aus langjährigen Erfahrungen und der kontinuierlichen Zusammenarbeit zwischen den Herstellerfirmen, den beteiligten Betrieben und den Lehr- und Versuchsanstalten sowie ECO-CONSULT als wissenschaftlicher Koordinator der Versuchsdurchführung, wurden in den Untersuchungsjahren 2002/2003 auf drei Standorten (Trier, Landau und Korb) Versuche zur Peronosporabekämpfung sowie auf einem Standort (Korb) Versuche zur Bekämpfung von Oidium angelegt. Die Auswahl der eingesetzten Mittel ergab sich aus dem aktuellen Stand der Zulassung von Pflanzenstärkungs- Schutzmittel sowie Neu- und Weiterentwicklungen der Firmen., so dass immer die aktuellsten Präparate für die Praxis getestet werden. Durch diese enge Zusammenarbeit ist es möglich die Ergebnisse unmittelbar sowohl in der Beratung (Field days, Beraterinformation) wie auch in der Weiterentwicklung und Kommerzialisierung durch die Firmen einzusetzen. Ergebnisse Die Witterungs- und Infektionsbedingungen für Peronospora waren im Versuchsjahr 2002 extrem günstig für das Auftreten der Peronospora. Schon sehr früh traten erste Befallssymptome an den Blättern als Ölflecke auf. Die Hauptinfektionszeit lag um die Blüte sowie im Zeitraum Fruchtansatz bis Erbsengröße der Beeren. In der unbehandelten Kontrolle waren schon früh annähernd alle Trauben befallen. Es zeigt sich, dass unter den unterschiedlichen Bedingungen die eingesetzten Versuchspräparate sowohl gute als auch unzureichende Wirkung hatten. Ein direkter Vergleich ist daher sehr schwierig. Dennoch zeigt sich, dass je nach Befallssituation die Varianten 9 x Kupfer in einer Gesamtkupferaufwandmenge von 3 kg die gleiche Wirkung zeigte wie die Präparate MYCO-SIN VIN, Ulmasud und Ulmasud VP. Im Versuchsjahr 2003 trat nur zu Beginn der Blütezeit vereinzelt Peronospora auf. Infolge der Witterungsbedingungen kam es zu keinem stärkeren Befall. In der Versuchsanlage Trier trat, wie auch insgesamt im Anbaugebiet, verstärkt Schwarzfäule auf. Bei der Bonitur zeigten sich positive Ergebnisse bei den Präparaten: Frutogard, Phyto-Algin Super sowie MYCO-SIN VIN. Der Wirkungsgrad lag gegenüber der reinen Schwefelbehandlung bei über 60%. Oidium trat in den beiden Versuchsjahren nur zum Ende der Vegetation an den Blättern auf. Neben Botrytis wurde in der Versuchsanlage Landau Nussdorf Weingut Rummel zusätzlich noch auf Sauerfäule sowie Penicillium bonitiert. Penicillium ist ein tertiärer Schwäche – Fäulnisparasit, der sich zusammen mit Botrytis auf den Trauben ansiedelt. Penicillium stellte in den letzten Jahren zusammen mit Sauerfäule eine nicht unerhebliche Beeinträchtigung des Lesegutes und somit auch der Weinqualität dar. Bei der Bonitur ergaben sch vergleichsweise geringe Befallswerte, die sich aber nach den anschließenden Niederschlägen deutlich verstärkten. Die Befallswerte lagen zwischen 12 und 26%. Ebenso ist das Auftreten von Sauerfäule zwischen den Boniturergebnissen deutlich angestiegen. Der Befall lag bei 40%. Die Variante Ulmasud VP zeigte sowohl im Befall durch Botrytis, Penicillium wie auch Essigsäure die geringsten Befallswerte. Gerade im Befall mit Penicillium und Essigsäure waren die Unterschiede zwar statistisch nicht ab zu sichern aber doch um 50% geringer als in der Variante OekoFluid

Constraint Effective Potential of the Staggered Magnetization in an Antiferromagnet

We employ an improved estimator to calculate the constraint effective potential of the staggered magnetization in the spin $\tfrac{1}{2}$ quantum Heisenberg model using a loop-cluster algorithm. The first and second moment of the probability distribution of the staggered magnetization are in excellent agreement with the predictions of the systematic low-energy magnon effective field theory. We also compare the Monte Carlo data with the universal shape of the constraint effective potential of the staggered magnetization and study its approach to the convex effective potential in the infinite volume limit. In this way the higher-order low-energy parameter $k_0$ is determined from a fit to the numerical data

Optimisation of downy mildew (Plasmopara viticola) control in organic viticulture with low copper doses, new copper formulations and plant strengtheners, results of four years of on farm research

In three different wine growing regions in Germany, due to weather and infection conditions several fungicide (copper formulations) and plant strengtheners (Myco-Sin VIN®, Kendal®, Frutogard ®) applications against downy mildew are required in order to obtain satisfactory disease control. Results of the four years of on farm trials confirmed good efficacy of the copper based substances like copper hydroxide, partly in combination with two or three applications of potassium phosphonate, new copper-hydroxide formulation or copper oxychloride used in a low doses of copper and alternative products like Myco-Sin-VIN® (clay with high aluminium content) in combination with Kendal® ( plant extract)

Systematic Effective Field Theory Investigation of Spiral Phases in Hole-Doped Antiferromagnets on the Honeycomb Lattice

Motivated by possible applications to the antiferromagnetic precursor of the high-temperature superconductor Na$_x$CoO$_2\cdot$yH$_2$O, we use a systematic low-energy effective field theory for magnons and holes to study different phases of doped antiferromagnets on the honeycomb lattice. The effective action contains a leading single-derivative term, similar to the Shraiman-Siggia term in the square lattice case, which gives rise to spirals in the staggered magnetization. Depending on the values of the low-energy parameters, either a homogeneous phase with four or a spiral phase with two filled hole pockets is energetically favored. Unlike in the square lattice case, at leading order the effective action has an accidental continuous spatial rotation symmetry. Consequently, the spiral may point in any direction and is not necessarily aligned with a lattice direction.Comment: 10 pages, 6 figure

The effect of electron-electron correlation on the attoclock experiment

We investigate multi-electron effects in strong-field ionization of Helium using a semi-classical model that, unlike other commonly used theoretical approaches, takes into account electron-electron correlation. Our approach has an additional advantage of allowing to selectively switch off different contributions from the parent ion (such as the remaining electron or the nuclear charge) and thereby investigate in detail how the final electron angle in the attoclock experiment is influenced by these contributions. We find that the bound electron exerts a significant effect on the final electron momenta distribution that can, however, be accounted for by an appropriately selected mean field. Our results show excellent agreement with other widely used theoretical models done within a single active electron approximation

Assessment of Physical Activity Patterns in Adolescent Patients With Anorexia Nervosa and Their Effect on Weight Gain

(1) Background: Altered physical activity (PA) affects weight recovery in anorexia nervosa (AN) patients. The study aimed to objectively characterize PA patterns and their effect on weight trajectory in adolescent AN patients. (2) Methods: PA was assessed in 47 patients on admission to inpatient treatment, in n = 25 of these patients again 4 weeks after discharge (follow-up, FU), as well as in 20 adolescent healthy controls using the Sense Wear™ armband. The following PA categories were defined by metabolic equivalent (MET) ranges: sedentary behavior (SB), light (LPA), moderate (MPA), vigorous (VPA), and high-level PA (HLPA= MPA + VPA). (3) Results: LPA on admission was significantly higher in AN patients than in controls (103 vs. 55 min/d, p < 0.001), and LPA in AN decreased over time to 90 min/d (p = 0.006). Patients with higher admission LPA (n = 12) still had elevated LPA at FU (p = 0.003). High admission LPA was associated with a higher inpatient BMI percentage gain (ΔBMI%; 18.2% ± 10.0% vs. 12.0% ± 9.7%, p = 0.037) but with a loss of ΔBMI% at FU (-2.3% ± 3.6% vs. 0.8% ± 3.6%, p = 0.045). HLPA at baseline was associated with a lower inpatient ΔBMI% (p = 0.045). (4) Conclusion: Elevated LPA in AN patients decreased after inpatient treatment, and PA patterns had an impact on weight trajectory

Exact Insulating and Conducting Ground States of a Periodic Anderson Model in Three Dimensions

We present a class of exact ground states of a three-dimensional periodic Anderson model at 3/4 filling. Hopping and hybridization of d and f electrons extend over the unit cell of a general Bravais lattice. Employing novel composite operators combined with 55 matching conditions the Hamiltonian is cast into positive semidefinite form. A product wave function in position space allows one to identify stability regions of an insulating and a conducting ground state. The metallic phase is a non-Fermi liquid with one dispersing and one flat band.Comment: 4 pages, 3 figure

Spiral phases and two-particle bound states from a systematic low-energy effective theory for magnons, electrons, and holes in an antiferromagnet

We have constructed a systematic low-energy effective theory for hole- and electron-doped antiferromagnets, where holes reside in momentum space pockets centered at $(\pm\frac{\pi}{2a},\pm\frac{\pi}{2a})$ and where electrons live in pockets centered at $(\frac{\pi}{a},0)$ or $(0,\frac{\pi}{a})$. The effective theory is used to investigate the magnon-mediated binding between two holes or two electrons in an otherwise undoped system. We derive the one-magnon exchange potential from the effective theory and then solve the corresponding two-quasiparticle Schr\"odinger equation. As a result, we find bound state wave functions that resemble $d_{x^2-y^2}$-like or $d_{xy}$-like symmetry. We also study possible ground states of lightly doped antiferromagnets.Comment: 2 Pages; Proc. of SCES'07, Housto

Radiative corrections to the pressure and the one-loop polarization tensor of massless modes in SU(2) Yang-Mills thermodynamics

We compute the one-loop polarization tensor $\Pi$ for the on-shell, massless mode in a thermalized SU(2) Yang-Mills theory being in its deconfining phase. Postulating that SU(2)$_{\tiny{CMB}}\stackrel{\tiny{today}}=U(1)_Y$, we discuss $\Pi$'s effect on the low-momentum part of the black-body spectrum at temperatures $\sim 2... 4$ $T_{\tiny{CMB}}$ where $T_{\tiny{CMB}}\sim 2.73$K. A table-top experiment is proposed to test the above postulate. As an application, we point out a possible connection with the stability of dilute, cold, and old innergalactic atomic hydrogen clouds. We also compute the two-loop correction to the pressure arising from the instantaneous massless mode in unitary-Coulomb gauge, which formerly was neglected, and present improved estimates for subdominant corrections.Comment: 25 pages, 17 figs, v4: consequences of a modification of the evolution equation for the effectice coupling implemented, no qualitative change of the physic