Effects of the low lying Dirac modes on excited hadrons in lattice QCD

Chiral symmetry breaking in Quantum Chromodynamics is associated with the low lying spectral modes of the Dirac operator according to the Banks-Casher relation. Here we study how removal of a variable number of low lying modes from the valence quark sector affects the masses of the ground states and first excited states of baryons and mesons in two flavor lattice QCD.Comment: 6 pages, 2 figures. Contribution to proceedings of "Excited QCD 2012", May 6-12, 2012, Peniche, Portuga

More effects of Dirac low-mode removal

In previous studies we have shown that hadrons, except for a pion, survive the removal of the lowest lying Dirac eigenmodes from the valence quark propagators. The low-modes are tied to the dynamical breaking of chiral symmetry and we found chiral symmetry to be restored by means of matching masses of chiral partners, like, e.g., the vector and axial vector currents. Here we investigate the influence of removing the lowest part of the Dirac spectrum on the locality of the Dirac operator. Moreover, we analyze the influence of low-mode truncation on the quark momenta and thereupon on the hadron spectrum and, finally, introduce a reweighting scheme to extend the truncation to the sea quark sector.Comment: 7pages, 4 figures. Proceedings of the 31st International Symposium on Lattice Field Theory, July 29 - August 3, 2013, Mainz, German

Adaptation of renal ammonia production in the diabetic ketoacidotic rat

Adaptation of renal ammonia production in the diabetic ketoacidotic rat. Renal ammonia production was measured in diabetic, ketoacidotic rats. Rats were made diabetic by the i.v. injection of streptozotocin (150mg/kg of body wt). They were maintained on insulin for 1 week. Ketoacidosis was induced by withdrawing insulin for 3 days. At that time, blood and kidney ketone body (D-β-hydroxybutyrate and acetoacetate) levels were markedly elevated (approx. 6mM), and plasma total carbon dioxide concentration was strongly depressed (approx. 11mM). Renal ammonia production (ammonia released into renal vein plus that excreted in the urine) was stimulated sevenfold by the diabetic ketoacidosis. In a separate study, we examined the effects of ketone bodies on renal ammonia production in ammonium-chloride-induced acidotic, nondiabetic rats. Infusion of β-hydroxybutyrate had no significant effect on either urinary ammonia excretion (at relatively constant urinary pH), total renal ammonia production, or renal glutamine extraction. In vitro studies showed that β-hydroxybutyrate (4.0mM) markedly inhibited (61%) conversion ofL-glutamine (0.6mM) to ammonia by renal cortical slices prepared from normal rats. Inhibition was greatly reduced with slices prepared from kidneys of acidotic (ammonium-chloride-induced or diabetic ketoacidosis) rats. These results indicate that (1) renal ammonia production is markedly stimulated in diabetic ketoacidosis, and (2) in contrast to findings previously obtained by others in the acidotic dog, ketone bodies do not appear to inhibit renal ammonia production in vivo and only weakly in vitro in the acidotic rat.Adaptation de la production rénale d'ammoniac chez le rat diabétique en acidocétose. La production rénale d'ammoniaque a été mesurée chez le rat diabétique en acidocétose. Les rats ont été rendus diabétiques par une injection i.v. de streptozotocine (150 mg/kg body wt) et traités par l'insuline pendant une semaine. L'acidocétose a été déclenchée par la suppresion de l'insuline pendant trois jours. A ce moment, les concentrations sanguines et rénales de corps cétoniques (D-β-hydroxybutyrate et acéto-acétate) étaient très augmentées (approximativement 6mM) et le CO2 total du plasma très abaissé (approximativement 11mM). La production rénale d'ammoniac (ammoniac de la veine rénale plus ammoniaque de l'urine) était multipliée par 7. Dans un protocole différent, nous avons étudié les effets des corps cétoniques sur la production rénale d'ammoniac chez des rats non diabétiques, en acidose parle chlorure d'ammonium. La perfusion de β-hydroxybutyrate n'a eu d'effet significatif ni sur l'excétion urinaire d'ammoniaque (à pH relativement constant), ni sur la production rénale d'ammoniac ou l'extraction rénale de la glutamine. Des études in vitro ont montré que le β-hydroxybutyrate (4,0mM) inhibe de façon importante (61%) la conversion de laL-glutamine (0,6mM) en ammoniac par les tranches de cortex de rein préparées à partir de rats normaux. L'inhibition est moindre avec des tranches préparées à partir de rats en acidose (chlorure d'ammonium ou acidocétose diabétique). Ces résultats indiquent que (1) la production rénale d'ammoniac est fortement stimulée au cours de l'acidocétose diabétique et, (2) contrairement aux résultats obtenus par d'autres chez le chien en acidose, les corps cétoniques ne paraissent pas inhiber la production rénale d'ammoniac in vivo, et seulement faiblement in vitro, chez le rat en acidose

Symmetries of hadrons after unbreaking the chiral symmetry

We study hadron correlators upon artificial restoration of the spontaneously broken chiral symmetry. In a dynamical lattice simulation we remove the lowest lying eigenmodes of the Dirac operator from the valence quark propagators and study evolution of the hadron masses obtained. All mesons and baryons in our study, except for a pion, survive unbreaking the chiral symmetry and their exponential decay signals become essentially better. From the analysis of the observed spectroscopic patterns we conclude that confinement still persists while the chiral symmetry is restored. All hadrons fall into different chiral multiplets. The broken U(1)_A symmetry does not get restored upon unbreaking the chiral symmetry. We also observe signals of some higher symmetry that includes chiral symmetry as a subgroup. Finally, from comparison of the \Delta - N splitting before and after unbreaking of the chiral symmetry we conclude that both the color-magnetic and the flavor-spin quark-quark interactions are of equal importance.Comment: 12 pages, 14 figures; final versio

Forschungsfeld Kulturpolitik – eine Kartierung von Theorie und Praxis

Zwanzig Jahre lang hat Wolfgang Schneider als ordentlicher Professor für Kulturpolitik und als Direktor die Geschicke des Instituts für Kulturpolitik der Universität Hildesheim gelenkt. Im Zentrum stand dabei von Anfang an, Theorie und Praxis miteinander zu denken und zu gestalten. Zahlreiche Forschungsprojekte wurden im Laufe der Zeit von ihm initiiert und betreut – immer auf der Suche nach den Anknüpfungspunkten und der Rückbindung der wissenschaftlichen Erkenntnisse an Kulturpolitik und die Künste. Dieses Buch versammelt Beiträge von akademischen Weggefährt*innen, insbesondere von ehemaligen und aktuellen Doktorand*innen, und will damit eine Kartierung der Themenfelder und Perspektiven einer Hildesheimer Kulturpolitikwissenschaft vornehmen. Es versteht sich in diesem Sinne als Teil von Grundlagenforschung zur Kulturpolitik aus diversen Perspektiven eines kleinen Faches und als Impuls dieses Forschungsfeld weiterzudenken