745 research outputs found
Compact jets as probes for sub-parsec scale regions in AGN
Compact relativistic jets in active galactic nuclei offer an effective tool
for investigating the physics of nuclear regions in galaxies. The emission
properties, dynamics, and evolution of jets in AGN are closely connected to the
characteristics of the central supermassive black hole, accretion disk and
broad-line region in active galaxies. Recent results from studies of the
nuclear regions in several active galaxies with prominent outflows are reviewed
in this contribution.Comment: AASLaTeX, 5 pages, 4 figures. Accepted in Astrophysics and Space
Scienc
The structure and properties of a hypoeutectic silumin subjected to complex electron–ion-plasma processing
The layer-by-layer analysis of structural–phase states and tribological properties of hypoeutectic АК10М2Н-type silumin at the depth up to 170 μm after the complex processing is carried out by the state-of-the-art methods of physical materials science. It involves the electroexplosion alloying with titanium and yttrium-oxide powder in different ratios followed by electron-beam processing.Методами сучасного фізичного матеріалознавства проведено пошарову аналізу структурно-фазових станів і трибологічних властивостей доевтектичного силуміну марки АК10М2Н на глибині до 170 мкм після комплексного оброблення. Воно полягало в електропідривному леґуванні титаном і порошком оксиду ітрію в різних співвідношеннях з подальшим електронно-пучковим обробленням.Методами современного физического материаловедения проведён послойный анализ структурно-фазовых состояний и трибологических свойств доэвтектического силумина марки АК10М2Н на глубине до 170 мкм после комплексной обработки. Она заключалась в электровзрывном легировании титаном и порошком оксида иттрия в разных соотношениях с последующей электронно-пучковой обработкой
Microstructure and properties of hypoeutectic silumin treated by high-current pulsed electron beams
The structural-phase states, microhardness, and tribological properties of hypoeutectic silumin after electron-beam treatment are studied by the methods of contemporary physical materials science. The object of the study is hypoeutectic АК10М2Н-type silumin containing 87.88 wt.% of Al and 11.1 wt.% of Si as the base components.Методами сучасного фізичного матеріалознавства досліджено структурно-фазові стани, мікротвердість і трибологічні властивості доевтектичного силуміну після електронно-пучкового оброблення. Об єктом дослідження був доевтектичний силумін марки АК10М2Н із вмістом 87,88 ваг.% Al й 11,1 ваг.% Si як головних компонентів.Методами современного физического материаловедения исследованы структурнофазовые состояния, микротв рдость и трибологические свойства доэвтектического силумина после электронно-пучковой обработки. Объектом исследования являлся доэвтектический силумин марки АК10М2Н с содержанием 87,88 вес.% Al и 11,1 вес.% Si как главных компонентов
A note on N=4 supersymmetric mechanics on K\"ahler manifolds
The geometric models of N=4 supersymmetric mechanics with
(2d.2d)_{\DC}-dimensional phase space are proposed, which can be viewed as
one-dimensional counterparts of two-dimensional N=2 supersymmetric sigma-models
by Alvarez-Gaum\'e and Freedman. The related construction of supersymmetric
mechanics whose phase space is a K\"ahler supermanifold is considered. Also,
its relation with antisymplectic geometry is discussed.Comment: 4 pages, revte
Nuclear structure corrections to gyromagnetic factor of the bound lepton
In the framework of the quasipotential method the covariant expression for
the two-particle vertex operator is obtained. The nuclear structure corrections
of orders (Z\alpha)^4, (Z\alpha)^5 including recoil effects to gyromagnetic
factors of the bound electron and muon are calculated. Numerical value of the
contribution of order (Z\alpha)^5 is obtained by means of the dipole
parameterization for the nuclear charge form factor in the range of the nuclear
charges Z=7-32.Comment: Talk presented on poster session of the Bogolubov Conference
"Problems of Theoretical and Mathematical Physics", Moscow-Dubna, September
2-6, 2004, 14 pages, 2 figure
Long-range attraction between particles in dusty plasma and partial surface tension of dusty phase boundary
Effective potential of a charged dusty particle moving in homogeneous plasma
has a negative part that provides attraction between similarly charged dusty
particles. A depth of this potential well is great enough to ensure both
stability of crystal structure of dusty plasma and sizable value of surface
tension of a boundary surface of dusty region. The latter depends on the
orientation of the surface relative to the counter-ion flow, namely, it is
maximal and positive for the surface normal to the flow and minimal and
negative for the surface along the flow. For the most cases of dusty plasma in
a gas discharge, a value of the first of them is more than sufficient to ensure
stability of lenticular dusty phase void oriented across the counter-ion flow.Comment: LATEX, REVTEX4, 7 pages, 6 figure
Pion and sigma meson properties in a relativistic quark model
A variety of strong and electroweak interaction properties of the pion and
the light scalar sigma meson are computed in a relativistic quark model. Under
the assumption that the resulting coupling of these mesons to the constituent
quarks is identical, the sigma meson mass is determined as M_sigma=385.4 MeV.
We discuss in detail the gauging of the non-local meson-quark interaction and
calculate the electromagnetic form factor of the pion and the form factors of
the pi(0) -> gamma gamma and sigma -> gamma gamma processes. We obtain explicit
expressions for the relevant form factors and evaluate the leading and
next-to-leading orders for large Euclidean photon virtualities. Turning to the
decay properties of the sigma we determine the width of the electromagnetic
sigma -> gamma gamma transition and discuss the strong decay sigma -> pi pi. In
a final step we compute the nonleptonic decays D -> sigma pi and B -> sigma pi
relevant for the possible observation of the sigma meson. All our results are
compared to available experimental data and to results of other theoretical
studies.Comment: 46 page
The B-Meson Distribution Amplitude in QCD
The B-meson distribution amplitude is calculated using QCD sum rules. In
particular we obtain an estimate for the integral relevant to exclusive
B-decays \lambda_B = 460 \pm 110 MeV at the scale 1 GeV. A simple QCD-motivated
parametrization of the distribution amplitude is suggested.Comment: 17 pages, 8 figures, Latex styl
Cyclotron effective masses in layered metals
Many layered metals such as quasi-two-dimensional organic molecular crystals
show properties consistent with a Fermi liquid description at low temperatures.
The effective masses extracted from the temperature dependence of the magnetic
oscillations observed in these materials are in the range, m^*_c/m_e \sim 1-7,
suggesting that these systems are strongly correlated. However, the ratio
m^*_c/m_e contains both the renormalization due to the electron-electron
interaction and the periodic potential of the lattice. We show that for any
quasi-two-dimensional band structure, the cyclotron mass is proportional to the
density of states at the Fermi energy. Due to Luttinger's theorem, this result
is also valid in the presence of interactions. We then evaluate m_c for several
model band structures for the \beta, \kappa, and \theta families of
(BEDT-TTF)_2X, where BEDT-TTF is bis-(ethylenedithia-tetrathiafulvalene) and X
is an anion. We find that for \kappa-(BEDT-TTF)_2X, the cyclotron mass of the
\beta-orbit, m^{*\beta}_c, is close to 2 m^{*\alpha}_c, where m^{*\alpha}_c is
the effective mass of the \alpha- orbit. This result is fairly insensitive to
the band structure details. For a wide range of materials we compare values of
the cyclotron mass deduced from band structure calculations to values deduced
from measurements of magnetic oscillations and the specific heat coefficient.Comment: 12 pages, 3 eps figure
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