4,107 research outputs found
Continuum Singularities of a Mean Field Theory of Collisions
Consider a complex energy for a -particle Hamiltonian and let
be any wave packet accounting for any channel flux. The time independent
mean field (TIMF) approximation of the inhomogeneous, linear equation
consists in replacing by a product or Slater
determinant of single particle states This results, under the
Schwinger variational principle, into self consistent TIMF equations
in single particle space. The method is a
generalization of the Hartree-Fock (HF) replacement of the -body homogeneous
linear equation by single particle HF diagonalizations
We show how, despite strong nonlinearities in this mean
field method, threshold singularities of the {\it inhomogeneous} TIMF equations
are linked to solutions of the {\it homogeneous} HF equations.Comment: 21 pages, 14 figure
Variational solution of the Yang-Mills Schr\"odinger equation in Coulomb gauge
The Yang-Mills Schr\"odinger equation is solved in Coulomb gauge for the
vacuum by the variational principle using an ansatz for the wave functional,
which is strongly peaked at the Gribov horizon. A coupled set of
Schwinger-Dyson equations for the gluon and ghost propagators in the Yang-Mills
vacuum as well as for the curvature of gauge orbit space is derived and solved
in one-loop approximation. We find an infrared suppressed gluon propagator, an
infrared singular ghost propagator and a almost linearly rising confinement
potential.Comment: 24 pages, revtex, 13 figure
On the temporal Wilson loop in the Hamiltonian approach in Coulomb gauge
We investigate the temporal Wilson loop using the Hamiltonian approach to
Yang-Mills theory. In simple cases such as the Abelian theory or the
non-Abelian theory in (1+1) dimensions, the known results can be reproduced
using unitary transformations to take care of time evolution. We show how
Coulomb gauge can be used for an alternative solution if the exact ground state
wave functional is known. In the most interesting case of Yang-Mills theory in
(3+1) dimensions, the vacuum wave functional is not known, but recent
variational approaches in Coulomb gauge give a decent approximation. We use
this formulation to compute the temporal Wilson loop and find that the Wilson
and Coulomb string tension agree within our approximation scheme. Possible
improvements of these findings are briefly discussed.Comment: 24 pages, 4 eps-figures; new version matches published on
The role of center vortices in Gribov's confinement scenario
The connection of Gribov's confinement scenario in Coulomb gauge with the
center vortex picture of confinement is investigated. For this purpose we
assume a vacuum wave functional which models the infrared properties of the
theory and in particular shows strict confinement, i.e. an area law of the
Wilson loop. We isolate the center vortex content of this wave functional by
standard lattice methods and investigate their contributions to various static
propagators of the Hamilton approach to Yang-Mills theory in Coulomb gauge. We
find that the infrared properties of these quantities, in particular the
infrared divergence of the ghost form factor, are dominated by center vortices.Comment: 18 pages, 5 figure
Application of recombinant TAF3 PHD domain instead of anti-H3K4me3 antibody
BACKGROUND: Histone posttranslational modifications (PTMs) represent a focal point of chromatin regulation. The genome-wide and locus-specific distribution and the presence of distinct histone PTMs is most commonly examined with the application of histone PTM-specific antibodies. In spite of their central role in chromatin research, polyclonal antibodies suffer from disadvantages like batch-to-batch variability and insufficient documentation of their quality and specificity. RESULTS: To mitigate some of the pitfalls of using polyclonal antibodies against H3K4me3, we successfully validated the application of a recombinant TAF3 PHD domain as anti-H3K4me3 affinity reagent in peptide array, western blot and ChIP-like experiments coupled with qPCR and deep sequencing. CONCLUSIONS: The successful addition of the TAF3 PHD domain to the growing catalog of recombinant affinity reagents for histone PTMs could help to improve the reproducibility, interpretation and cross-laboratory validation of chromatin data. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13072-016-0061-9) contains supplementary material, which is available to authorized users
From Bruges to Venice 1: Towards a common structure for international physical and rehabilitation medicine congresses
The chiral quark condensate and pion decay constant in nuclear matter at next-to-leading order
Making use of the recently developed chiral power counting for the physics of
nuclear matter [1,2], we evaluate the in-medium chiral quark condensate up to
next-to-leading order for both symmetric nuclear matter and neutron matter. Our
calculation includes the full in-medium iteration of the leading order local
and one-pion exchange nucleon-nucleon interactions. Interestingly, we find a
cancellation between the contributions stemming from the quark mass dependence
of the nucleon mass appearing in the in-medium nucleon-nucleon interactions.
Only the contributions originating from the explicit quark mass dependence of
the pion mass survive. This cancellation is the reason of previous observations
concerning the dominant role of the long-range pion contributions and the
suppression of short-range nucleon-nucleon interactions. We find that the
linear density contribution to the in-medium chiral quark condensate is only
slightly modified for pure neutron matter by the nucleon-nucleon interactions.
For symmetric nuclear matter the in-medium corrections are larger, although
smaller compared to other approaches due to the full iteration of the lowest
order nucleon-nucleon tree-level amplitudes. Our calculation satisfies the
Hellmann-Feynman theorem to the order worked out. Also we address the problem
of calculating the leading in-medium corrections to the pion decay constant. We
find that there are no extra in-medium corrections that violate the
Gell-Mann-Oakes-Renner relation up to next-to-leading order.Comment: 21 pages, 9 figure
Energy evolution in time-dependent harmonic oscillator
The theory of adiabatic invariants has a long history, and very important
implications and applications in many different branches of physics,
classically and quantally, but is rarely founded on rigorous results. Here we
treat the general time-dependent one-dimensional harmonic oscillator, whose
Newton equation cannot be solved in general. We
follow the time-evolution of an initial ensemble of phase points with sharply
defined energy at time and calculate rigorously the distribution of
energy after time , which is fully (all moments, including the
variance ) determined by the first moment . For example,
, and all
higher even moments are powers of , whilst the odd ones vanish
identically. This distribution function does not depend on any further details
of the function and is in this sense universal. In ideal
adiabaticity , and the variance is
zero, whilst for finite we calculate , and for the
general case using exact WKB-theory to all orders. We prove that if is of class (all derivatives up to and including the order
are continuous) , whilst for class it is known to be exponential .Comment: 26 pages, 5 figure
Foraminiferal Evidence of Late Holocene Sea-Level Change and Amerindian Site Distribution at Montague Harbour, British Columbia
Foraminiferal and sedimentological analysis of an underwater stratigraphie section from an Amerindian habitation site at Montague Harbour, British Columbia has further documented late Holocene sea level changes. It appears that part of the documented transgression was caused by tectonic subsidence of the area (Event 1 at approx. 3500 calendar years BP and Event 2 sometime before 1100 calendar years BP) and was recognized in the stratigraphie record by rapid environmental changes. The environmental changes caused by rapid shifts in water depth were recognized through sedimentological and foraminiferal evidence. The tectonic subsidence events, coupled with gentle late Holocene transgression, caused the breaching of Montague Harbour's northwestern channel. The breaching of the channel improved water circulation and increased salinity within the harbour. The salinity changes are reflected in the shift from a low salinity Cribroelphidium excavatum (Terquem, 1876) phenotype "clavata" dominated biofacies (1) at the base of the section to a higher salinity Buccella tenerrima (Bandy, 1950) and Elphidiella hannai (Cushman and Grant, 1927) dominated biofacies (2) at the top. These sea-level changes would have eventually forced local Amerindian settlements inland. The 14C dating of wood and shell, indicates that the recovery of archaeological remains of the Charles culture (ca.6500-3200 years BP) requires investigation in deeper waters.L'analyse des foraminifères et des sédiments d'une coupe stratigraphique sous-marine d'un habitat amérindien a permis d'accroître les connaissances sur les changements du niveau marin. Il semble qu'une partie de la transgression connue ait été causée par une subsidence de nature tectonique (1er épisode vers 3500 cal. BP et 2e épisode un peu avant 1100 cal. BP) qui a entraîné des changements environnementaux rapides consignés dans la stratigraphie. Les sédiments et les foraminifères ont en effet enregistré les changements rapides de la profondeur de l'eau. Les épisodes de subsidence, accompagnés par une transgression modérée à l'Holocène supérieur, ont provoqué la formation d'une brèche dans le chenal nord-ouest du Montague Harbour, qui a facilité la circulation des eaux et fait augmenter la salinité à l'intérieur du havre. Ce changement de salinité s'est manifesté par le remplacement du biofaciès (1) de faible salinité dominé par Cribroelphidium excavatum (Terquem, 1876) type « clavata », à la base de la coupe, par le biofaciès (2) de forte salinité dominé par Bucella tenerrima (Bandy, 1950) et Elphidiella hannai (Cushman et Grant, 1927) au sommet. Les changements du niveau marin ont forcé les Amérindiens à déménager vers l'intérieur. La datation au 14C sur bois et coquille montre que la récupération de vestiges archéologiques de la culture Charles (ca 6500-3200 BP) devra se faire en eaux plus profondes.Die Foraminiferen- und Sediment-Analyse eines stratigraphischen Unterwasserabschnitts von einer Indianer-Siedlung am Montague Harbour, British Columbia, hat weitere Belege ùber Meeresniveauwechsel im spàten Holozàn geliefert. Es scheint, daB ein Teil der dokumentierten Transgression durch tekton-ische Senkung des Gebiets verursacht wurde (Ereignis 1 urn circa 3500 Kalenderjahre v.u.Z. und Ereignis 2 irgendwann vor 1100 Kalenderjahren v.u.Z.) und in dem stratigraphischen Beleg durch rasche Umweltverànderungen kenntlich wurde. Die durch schnelle Wechsel der Wassertiefe verursachten Umweltverànderungen sind durch Sediment- und Foraminiferen-Belege aufgezeichnet worden. Die Episoden tektonischer Senkung verursachten zusammen mit einer sanften Transgression im spàten Holozàn die Bildung einer Bresche im nordwestlichen Kanal von Montague Harbour. Die Bresche im Kanal verbesserte die Wasserzirkulation und erhôhte den SaIzgehalt im Hafen. Die Verànderungen im Salzgehalt spiegeln sich im Wechsel von einer Biofazies (1) mit einem niedrigen Salzgehalt beherrscht von Cribroelphidium excavatum (Terquem, 1876) des Phânotypus "clavata" an der Basis des Schnittes, zu einer Biofazies (2) mit hôherem Salzgehalt, beherrscht von Bucella tenerrima (Bandy, 1950) und Elphidiella hannai (Cushman und Grant, 1927) an der Spitze. Diese Meeresniveau-Wechsel haben wohl die ôrtlichen indianischen Siedlungen gezwungen, landeinwàrts zu Ziehen. Die '4C-Datierung von HoIz und Muscheln zeigt, daB das Auffinden von archàologischen Spuren der Charles-Kultur (ca. 6500-3200 Jahre v.u.Z.) eine Suche in tieferen Wassern erfordert
On scale symmetry breaking and confinement in D=3 models
Within the framework of the gauge-invariant, but path-dependent, variables
formalism, we study the connection between scale symmetry breaking and
confinement in three-dimensional gluodynamics. We explicitly show that the
static potential profile contains a linear potential, leading to the
confinement of static charges. Also, we establish a new type of equivalence
among different three-dimensional effective theories.Comment: 6 pages, references adde
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