2,437 research outputs found
What is the Geometry of Superspace ?
We investigate certain properties of the Wheeler-DeWitt metric (for constant
lapse) in canonical General Relativity associated with its non-definite nature.
Contribution to the conference on Mach's principle: "From Newtons Bucket to
Quantum Gravity", July 26-30 1993, Tuebingen, GermanyComment: 10 pages, Plain Te
Motives for choosing university and specialty applicants Ukraine (for example, students NTU "KPI")
Стаття присвячена аналізу портрета абітурієнта НТУ "ХПІ", де, крім визначення мотивів професійного вибору, самооцінки особистих здібностей, розглядаються і основні цілі навчання в НТУ "ХПІ". У статті підкреслюється, що проблема професійного самовизначення стояла перед молоддю завжди, а сьогодні вона особливо актуальна, тому що сучасні умови ринку праці ведуть до того, що більшість випускників не мають ясної життєвої перспективи. Аналізуються мотиви отримання абітурієнтами вищої освіти, мотивація вступу до НТУ "ХПІ", мотиви вибору спеціальності, період формування професійного інтересу. Проаналізовано мотиви професійного вибору абітурієнтів; період формування інтересу молодих людей до обраної спеціальності (процес самовизначення, коли здійснено вибір спеціальності, ВНЗ); специфіку вибору ВНЗ (яким за рахунком був ХПІ, хто допоміг визначитися з вибором); уявлення про процес навчання в університеті; відповідність уявлень про навчання в університеті реаліям університетського життя.This article analyzes portrait applicant NTU "KPI", where in addition to determining the reasons professional choice, self-personal skills, and discusses the main goals of training at NTU "KPI". The article highlights the problem of professional self -determination was always the youth, and today it is particularly urgent because the current labor market conditions lead to the fact that most graduates do not have a clear life perspective. Analyzed the motives of applicants receiving higher education, motivation admission to NTU "KPI" motives choice of specialty, during the formation of professional interest. Analyzed the motives of professional selection of applicants; during the formation of young people's interest to the chosen profession (the process of self-selection made when specialty Universities); the specific choice of university (how the account was HPI, who helped to choose); understanding of the learning process at the university; line ideas about university studies realities of university life
The profile of an emission line from relativistic outflows around a black hole
Recent observations show strong evidence for the presence of Doppler-shifted
emission lines in the spectrum of both black hole candidates and active
galactic nuclei. These lines are likely to originate from relativistic outflows
(or jets) in the vicinity of the central black hole. Consequently, the profile
of such a line should be distorted by strong gravitational effects near the
black hole, as well as special relativistic effects. In this paper, we present
results from a detailed study on how each process affects the observed line
profile. We found that the profile is sensitive to the intrinsic properties of
the jets (Lorentz factor, velocity profile, and emissivity law), as well as to
the spin of the black hole and the viewing angle (with respect to the axis of
the jets). More specifically, in the case of approaching jets, an intrisically
narrow line (blue-shifted) is seen as simply broadened at small viewing angles,
but it shows a doubly peaked profile at large viewing angles for extreme Kerr
black holes (due to the combination of gravitational focusing and Doppler
effects); the profile is always singly peaked for Schwarzschild black holes.
For receding jets, however, the line profile becomes quite complicated owing to
complicated photon trajectories. To facilitate comparison with observations, we
searched a large parameter space to derive representative line profiles. We
show the results and discuss how to use emission lines as a potential tool for
probing the inner region of a black hole jet system.Comment: 16 pages in emulateapj style, 11 figure
Stability properties of black holes in self-gravitating nonlinear electrodynamics
We analyze the dynamical stability of black hole solutions in
self-gravitating nonlinear electrodynamics with respect to arbitrary linear
fluctuations of the metric and the electromagnetic field. In particular, we
derive simple conditions on the electromagnetic Lagrangian which imply linear
stability in the domain of outer communication. We show that these conditions
hold for several of the regular black hole solutions found by Ayon-Beato and
Garcia.Comment: 15 pages, no figure
Quantum Monte Carlo study of the one-dimensional Holstein model of spinless fermions
The Holstein model of spinless fermions interacting with dispersionless
phonons in one dimension is studied by a Green's function Monte Carlo
technique. The ground state energy, first fermionic excited state, density wave
correlations, and mean lattice displacement are calculated for lattices of up
to 16 sites, for one fermion per two sites, i.e., a half-filled band. Results
are obtained for values of the fermion hopping parameter of ,
, and where is the phonon frequency. At a finite
fermion-phonon coupling there is a transition from a metallic phase to an
insulating phase in which there is charge-density-wave order. Finite size
scaling is found to hold in the metallic phase and is used to extract the
coupling dependence of the Luttinger liquid parameters, and ,
the velocity of charge excitations and the correlation exponent, respectively.
For free fermions () and for strong coupling () our
results agree well with known analytic results. For and
our results are inconsistent with the metal-insulator transition being a
Kosterlitz-Thouless transition.\\Comment: 16 pages of ReVTeX, 11 figures in uuencoded compressed tar file.
Minor changes to text. Our results are inconsistent with the metal-insulator
transition studied being a Kosterlitz-Thouless transition. The figures are
now in the correct order. To appear in Physical Review B, April 15, 199
The Schroedinger Problem, Levy Processes Noise in Relativistic Quantum Mechanics
The main purpose of the paper is an essentially probabilistic analysis of
relativistic quantum mechanics. It is based on the assumption that whenever
probability distributions arise, there exists a stochastic process that is
either responsible for temporal evolution of a given measure or preserves the
measure in the stationary case. Our departure point is the so-called
Schr\"{o}dinger problem of probabilistic evolution, which provides for a unique
Markov stochastic interpolation between any given pair of boundary probability
densities for a process covering a fixed, finite duration of time, provided we
have decided a priori what kind of primordial dynamical semigroup transition
mechanism is involved. In the nonrelativistic theory, including quantum
mechanics, Feyman-Kac-like kernels are the building blocks for suitable
transition probability densities of the process. In the standard "free" case
(Feynman-Kac potential equal to zero) the familiar Wiener noise is recovered.
In the framework of the Schr\"{o}dinger problem, the "free noise" can also be
extended to any infinitely divisible probability law, as covered by the
L\'{e}vy-Khintchine formula. Since the relativistic Hamiltonians
and are known to generate such laws, we focus on
them for the analysis of probabilistic phenomena, which are shown to be
associated with the relativistic wave (D'Alembert) and matter-wave
(Klein-Gordon) equations, respectively. We show that such stochastic processes
exist and are spatial jump processes. In general, in the presence of external
potentials, they do not share the Markov property, except for stationary
situations. A concrete example of the pseudodifferential Cauchy-Schr\"{o}dinger
evolution is analyzed in detail. The relativistic covariance of related waveComment: Latex fil
Neonectria liriodendri sp. nov., the main causal agent of black foot disease of grapevines
Black foot disease is a serious disease of grapevine crops in most areas
where vines are grown. Mainly two species of Cylindrocarpon, C.
destructans and C. macrodidymum, are associated with this
disease. Recent studies have revealed a tremendous molecular variation within
the former but only slight molecular variation within the latter, indicating
that C. destructans presents a complex of several species The present
study elucidates the taxonomic status of C. destructans-like isolates
associated with black foot disease of grapevines. Grapevine isolates were
studied morphologically, subjected to DNA analyses of their ITS and partial
β-tubulin genes, and were mated in all combinations in vitro.
Cylindrocarpon destructans strains isolated from grapevines in Europe
and South Africa appeared morphologically and genetically identical, and had
identical ITS and partial β-tubulin gene sequences. Phylogenetic analyses
placed these strains in a clade closely related but clearly distinct from
other clades with C. destructans-like anamorphs obtained from various
herbaceous or woody hosts. Only the ex-type strain of Cylindrocarpon
liriodendri had identical sequences to strains isolated from grapevines,
and could also not be distinguished by morphological characters. The grapevine
isolates are therefore reidentified here as Cylindrocarpon
liriodendri. Cylindrocarpn liriodendri formed perithecia in
heterothallic conditions and the holomorph of this species is described as
Neonectria liriodendri sp. nov. Neonectria liriodendri is
genetically distinct from the ex-type strain of Neonectria
radicicola, which originated from Cyclamen in Sweden. Both
ex-type strains also differ from at least two other clades comprising
additional C. destructans-like strains. Many of these strains
originated from Panax sp., which is the host of the type of C.
destructans. Our phylogenetic analyses indicate that C.
destructans is not the anamorph of N. radicicola and that N.
liriodendri, N. radicicola and several C.
destructans-like taxa may have evolved independently within the same
phylogenetic species complex
Achene slime content in some taxa of Matricaria L. (Asteraceae)
The achenes of Matricaria aurea and two varieties of M. chamomilla (var. chamomilla and var. recutita) have slime cells on the surface and they are characterized by slime envelope formation during hydration. The slime in these taxa is composed of pectins and cellulose. The slime could play important role in the distribution and colonisation of new habitats in Matricaria taxa
Tomato: a crop species amenable to improvement by cellular and molecular methods
Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures.
In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
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