2,052 research outputs found
Uniqueness of infrared asymptotics in Landau gauge Yang-Mills theory
We uniquely determine the infrared asymptotics of Green functions in Landau
gauge Yang-Mills theory. They have to satisfy both,
Dyson-Schwinger equations and functional renormalisation group equations.
Then, consistency fixes the relation between the infrared power laws of these
Green functions. We discuss consequences for the interpretation of recent
results from lattice QCD.Comment: 24 pages, 8 figure
An unconditional experimental test of Nonclassicality
We theoretically introduce and experimentally demonstrate the realization of
a nonclassicality test that allows for arbitrarily low detection efficiency
without invoking any extra assumptions as independence of the devices. Our test
and its implementation is set in a prepare-and-measure scenario with an upper
limit on the communication capacity of the channel through which the systems
are communicated. The essence for our novel test is the use of two preparation
and two measurement devices, which are randomly paired in each round. Our work
opens up the possibility of experimental realizations of device independent
protocols with current off-the-shelf technology
QCD critical region and higher moments for three flavor models
One of the distinctive feature of the QCD phase diagram is the possible
emergence of a critical endpoint. The critical region around the critical point
and the path dependency of the critical exponents is investigated within
effective chiral (2+1)-flavor models with and without Polyakov-loops. Results
obtained in no-sea mean-field approximations where a divergent vacuum part in
the fermion-loop contribution is neglected, are confronted to the renormalized
ones. Furthermore, the modifications caused by the back-reaction of the matter
fluctuations on the pure Yang-Mills system are discussed. Higher order,
non-Gaussian moments of event-by-event distributions of various particle
multiplicities are enhanced near the critical point and could serve as a probe
to determine its location in the phase diagram. By means of a novel derivative
technique higher order generalized quark-number susceptibilities are calculated
and their sign structure in the phase diagram is analyzed.Comment: 12 pages, 11 figures. Final PRD version (references and one more
equation added
Can filamentary accretion explain the orbital poles of the Milky Way satellites?
Several scenarios have been suggested to explain the phase-space distribution
of the Milky Way (MW) satellite galaxies in a disc of satellites (DoS). To
quantitatively compare these different possibilities, a new method analysing
angular momentum directions in modelled data is presented. It determines how
likely it is to find sets of angular momenta as concentrated and as close to a
polar orientation as is observed for the MW satellite orbital poles. The method
can be easily applied to orbital pole data from different models. The observed
distribution of satellite orbital poles is compared to published angular
momentum directions of subhalos derived from six cosmological state-of-the-art
simulations in the Aquarius project. This tests the possibility that
filamentary accretion might be able to naturally explain the satellite orbits
within the DoS. For the most likely alignment of main halo and MW disc spin,
the probability to reproduce the MW satellite orbital pole properties turns out
to be less than 0.5 per cent in Aquarius models. Even an isotropic distribution
of angular momenta has a higher likelihood to produce the observed
distribution. The two Via Lactea cosmological simulations give results similar
to the Aquarius simulations. Comparing instead with numerical models of
galaxy-interactions gives a probability of up to 90 per cent for some models to
draw the observed distribution of orbital poles from the angular momenta of
tidal debris. This indicates that the formation as tidal dwarf galaxies in a
single encounter is a viable, if not the only, process to explain the
phase-space distribution of the MW satellite galaxies.Comment: 14 pages, 4 figures, 3 tables. Accepted for publication in MNRA
Shuttle payload S-band communications system
The Shuttle payload S-band communications system design, operational capabilities, and performance are described in detail. System design requirements, overall system and configuration and operation, and laboratory/flight test results are presented. Payload communications requirements development is discussed in terms of evolvement of requirements as well as the resulting technical challenges encountered in meeting the initial requirements. Initial design approaches are described along with cost-saving initiatives that subsequently had to be made. The resulting system implementation that was finally adopted is presented along with a functional description of the system operation. A description of system test results, problems encountered, how the problems were solved, and the system flight experience to date is presented. Finally, a summary of the advancements made and the lessons learned is discussed
The Phase Structure of the Polyakov--Quark-Meson Model
The relation between the deconfinement and chiral phase transition is
explored in the framework of an Polyakov-loop-extended two-flavor quark-meson
(PQM) model. In this model the Polyakov loop dynamics is represented by a
background temporal gauge field which also couples to the quarks. As a novelty
an explicit quark chemical potential and N_f-dependence in the Polyakov loop
potential is proposed by using renormalization group arguments. The behavior of
the Polyakov loop as well as the chiral condensate as function of temperature
and quark chemical potential is obtained by minimizing the grand canonical
thermodynamic potential of the system. The effect of the Polyakov loop dynamics
on the chiral phase diagram and on several thermodynamic bulk quantities is
presented.Comment: 13 pages, 12 figures, RevTex4; discussion of mu-dependence extended,
references added, version to be published in PR
Molecular phylogeny of common cibicidids and related rotaliida (foraminifera) based on small subunit rDNA sequences
To infer the phylogenetic relationships of cibicidids, we obtained small subunit ribosomal DNA (SSU rDNA) sequences of six common cibicidid morphospecies. In view of our results, the placement of cibicidids in different superfamilies, the distinction between planoconvex Cibicides and biconvex Cibicidoides, and the erection of genera such as Fontbotia and Lobatula are unjustified. Moreover, the superfamily Planorbulinacea, in which cibicidids are often placed, is polyphyletic and coiling mode cannot be used as a major taxonomic criterion. Our data suggest that all cibicidids examined here could be classified in one unique family, the Cibicididae, that includes Melonis, Hanzawaia, Cibicides (for C. refulgens), and Cibicidoides for the other five morphospecies studied (C. kullenbergi, C. lobatulus, C. pachyderma, C. ungerianus, and C. wuellerstorfi). Among the six sampled morphospecies, Cibicides refulgens is least closely related to any of the other cibicidids and forms a clade consisting of two different species, Cibicides sp. and C. refulgens clearly separated by geography (Antarctic and Mediterranean, respectively). The morphospecies Cibicidoides kullenbergi and C. pachyderma form a single clade representing the same species. The three other species, Cibicidoides lobatulus, C. ungerianus, and C. wuellerstorfi are closely related. Cibicidoides lobatulus possibly comprises two genetically distinct populations, one in the Mediterranean and the other in the North Atlantic
Renormalization group flows for gauge theories in axial gauges
Gauge theories in axial gauges are studied using Exact Renormalisation Group flows. We introduce a background field in the infrared regulator, but not in the gauge fixing, in contrast to the usual background field gauge. It is shown how heat-kernel methods can be used to obtain approximate solutions to the flow and the corresponding Ward identities. Expansion schemes are discussed, which are not applicable in covariant gauges. As an application, we derive the one-loop effective action for covariantly constant field strength, and the one-loop beta-function for arbitrary regulator
Quasi-local rotating black holes in higher dimension: geometry
With a help of a generalized Raychaudhuri equation non-expanding null
surfaces are studied in arbitrarily dimensional case. The definition and basic
properties of non-expanding and isolated horizons known in the literature in
the 4 and 3 dimensional cases are generalized. A local description of horizon's
geometry is provided. The Zeroth Law of black hole thermodynamics is derived.
The constraints have a similar structure to that of the 4 dimensional spacetime
case. The geometry of a vacuum isolated horizon is determined by the induced
metric and the rotation 1-form potential, local generalizations of the area and
the angular momentum typically used in the stationary black hole solutions
case.Comment: 32 pages, RevTex
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