25,207 research outputs found
On the renormalization of the Polyakov loop
We discuss a non-perturbative renormalization of n-point Polyakov loop
correlation functions by explicitly introducing a renormalization constant for
the Polyakov loop operator on a lattice deduced from the short distance
properties of 2-point correlators. We calculate this constant for the
SU(3)gauge theory.Comment: 5 pages, 1 figure, To appear in the proceedings of Workshop on Strong
and Electroweak Matter (SEWM 2002), Heidelberg, Germany, 2-5 Oct 200
Embedding the Zee-Wolfenstein neutrino mass matrix in an SO(10) x A4 GUT scenario
We consider renormalizable SO(10) Yukawa interactions and put the three
fermionic 16-plets into the 3-dimensional irreducible A_4 representation.
Scanning the possible A_4 representation assignments to the scalars, we find a
unique case which allows to accommodate the down-quark and charged-lepton
masses. Assuming type II seesaw dominance, we obtain a viable scenario with the
Zee-Wolfenstein neutrino mass matrix, i.e., the Majorana mass matrix with a
vanishing diagonal. Contributions from the charged-lepton mass matrix resolve
the well-known problems with lepton mixing arising from the vanishing diagonal.
In our scenario, fermion masses and mixings are well reproduced for both normal
and inverted neutrino mass spectra, and b-tau Yukawa unification and definite
predictions for the effective mass in neutrinoless double-beta decay are
obtained.Comment: 19 pages, 3 figures, v2: final version for Phys. Rev.
Dagstuhl Reports : Volume 1, Issue 2, February 2011
Online Privacy: Towards Informational Self-Determination on the Internet (Dagstuhl Perspectives Workshop 11061) : Simone Fischer-HĂŒbner, Chris Hoofnagle, Kai Rannenberg, Michael Waidner, Ioannis Krontiris and Michael Marhöfer Self-Repairing Programs (Dagstuhl Seminar 11062) : Mauro PezzĂ©, Martin C. Rinard, Westley Weimer and Andreas Zeller Theory and Applications of Graph Searching Problems (Dagstuhl Seminar 11071) : Fedor V. Fomin, Pierre Fraigniaud, Stephan Kreutzer and Dimitrios M. Thilikos Combinatorial and Algorithmic Aspects of Sequence Processing (Dagstuhl Seminar 11081) : Maxime Crochemore, Lila Kari, Mehryar Mohri and Dirk Nowotka Packing and Scheduling Algorithms for Information and Communication Services (Dagstuhl Seminar 11091) Klaus Jansen, Claire Mathieu, Hadas Shachnai and Neal E. Youn
Gribov Copies in the Minimal Landau Gauge: the Influence on Gluon and Ghost Propagators
We study the influence of Gribov copies on gluon and ghost propagators,
evaluated numerically in pure SU(2) lattice gauge theory in the minimal Landau
gauge. Simulations are done at four different values of (namely
= 0, 0.8, 1.6 and 2.7) and for volumes up to (up to at =
1.6). For the gluon propagator, Gribov noise seems to be of the order of
magnitude of the numerical accuracy, even at very small values of the coupling
. On the contrary, for the ghost propagator, Gribov noise is clearly
observable for the three values of in the strong-coupling regime. In
particular, data corresponding to the minimal Landau gauge are always smaller
than those obtained in a generic Landau gauge. This result can be qualitatively
explained.Comment: 19 pages, including three figures; minor modifications following
referee's suggestions. ZiF-MS-16/97 preprint. To appear in Nucl.Phys.
Towards Optimal Degree-distributions for Left-perfect Matchings in Random Bipartite Graphs
Consider a random bipartite multigraph with left nodes and right nodes. Each left node has random right
neighbors. The average left degree is fixed, . We ask
whether for the probability that has a left-perfect matching it is
advantageous not to fix for each left node but rather choose it at
random according to some (cleverly chosen) distribution. We show the following,
provided that the degrees of the left nodes are independent: If is an
integer then it is optimal to use a fixed degree of for all left
nodes. If is non-integral then an optimal degree-distribution has the
property that each left node has two possible degrees, \floor{\Delta} and
\ceil{\Delta}, with probability and , respectively, where
is from the closed interval and the average over all equals
\ceil{\Delta}-\Delta. Furthermore, if and is
constant, then each distribution of the left degrees that meets the conditions
above determines the same threshold that has the following
property as goes to infinity: If then there exists a
left-perfect matching with high probability. If then there
exists no left-perfect matching with high probability. The threshold
is the same as the known threshold for offline -ary cuckoo
hashing for integral or non-integral
Critical behaviour and Scaling functions for the three-dimensional O(6) spin model with external field
We numerically investigate the three-dimensional O(6) model on 12^3 to 120^3
lattices. From Binder's cumulant at vanishing magnetic field we obtain the
critical coupling J_c=1.42865(5) and verify this value with the \chi^2-method.
The universal value of Binder's cumulant at this point is
g_r(J_c)=-1.94456(10). At the critical coupling we find the critical exponents
\nu=0.818(5), \beta=0.425(2) and \gamma=1.604(6) from a finite size scaling
analysis. We also determine the finite-size-scaling function on the critical
line and the equation of state. Our O(6)-result for the equation of state is
compared to the Ising, O(2) and O(4) results.Comment: 5 pages, 4 figures, To appear in the proceedings of Workshop on
Strong and Electroweak Matter (SEWM 2002), Heidelberg, Germany, 2-5 Oct 200
The Nonabelian Screening Potential Beyond the Leading Order
The nonabelian screening potential is calculated in the temporal axial gauge.
The Slavnov-Taylor identity is used to construct the three-gluon vertex
function from the inverse gluon propagator. After solving the Schwinger - Dyson
equation beyond leading order we find that the obtained momentum dependence of
the gluon self-energy at high temperature does not correspond to an attractive
QCD - Debye potential, but instead it is repulsive and power behaved () at large distance.Comment: 10 pages, LATEX, ( 1 figure not included), BI-TP 94/0
Resistenter Ălrettich zur Regulierung von Wurzelgallennematoden im ökologischen Landbau
Der Wurzelgallennematode Meloidogyne hapla ist einer der bedeutenden Schaderreger im ökologischen Anbau von FeldgemĂŒse und Kartoffeln. Untersuchungen innerhalb dieses Forschungsvorhabens bestĂ€tigten die teils hohen Besatzdichten mit M. hapla auf ökologisch bewirtschafteten Betrieben. Faktoren wie weite Fruchtfolge, hoher Anteil an Leguminosen, GemĂŒse und HackfrĂŒchte (Wirtspflanzen) bei gleichzeitig geringem Anteil an Getreide (schlechte Wirtspflanzen) in der Fruchtfolge, kurze Brachezeiten sowie oftmals unzureichende Unkrautregulierung bedeuten ein fast kontinuierliches Vorhandensein an Wirtspflanzen fĂŒr bestimmte pflanzenparasitĂ€re Nematoden, insbesondere fĂŒr M. hapla. Mit Ausnahme der im ökologischen Landbau unerwĂŒnschten Schwarzbrache sind derzeit keine Verfahren zur gezielten BekĂ€mpfung von M. hapla im ökologischen Landbau praktisch anwendbar.
Zur Information der Landwirte und Anbauberater ĂŒber diesen Schaderreger wurde zu Beginn des Forschungsvorhabens ein Faltblatt zu M. hapla erstellt und verteilt. In dem Forschungsvorhaben wurde dann untersucht, inwieweit durch Anbau gering anfĂ€lliger ZwischenfrĂŒchte eine Befallsreduzierung von M. hapla erzielt werden kann. Die Untersuchungen konzentrierten sich auf Ălrettich, da bekannt war, dass Einzelpflanzen einiger Sorten hoch resistent gegenĂŒber diesem Schaderreger sind. Die in der beschreibenden Sortenliste 2002 aufgefĂŒhrten Ălrettichsorten wurden hinsichtlich ihrer AnfĂ€lligkeit fĂŒr M. hapla charakterisiert.
Die geringste AnfĂ€lligkeit gegenĂŒber M. hapla zeigte die Sorte 'Commodore' mit einem Pf/Pi = 0,14. Die befallsreduzierende Wirkung dieser Sorte bezĂŒglich M. hapla konnte in Kleinparzellenversuchen bestĂ€tigt werden. Bei hohem Ausgangsbesatz wurde die Besatzdichte von M. hapla um 96 % reduziert. Durch Einarbeitung des Pflanzenaufwuchses konnte die befallsreduzierende Wirkung von Ălrettich sogar noch gesteigert werden. Feldversuche auf zwei ökologisch wirtschaftenden Betrieben in Niedersachsen im Jahr 2003 bestĂ€tigten die geringe AnfĂ€lligkeit von Ălrettich 'Commodore' gegenĂŒber M. hapla.
In dem Forschungsvorhaben wurden wichtige AnsÀtze und Möglichkeiten zur Abwehr von Wurzelgallennematoden im ökologischen Landbau erarbeitet, die durch das BMVEL weiter verfolgt werden sollten. Eine fachliche Information der Landwirte sowie eine intensive Förderung der Resistenzforschung stehen dabei an erster Stelle
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