85 research outputs found
Exact Analysis of Level-Crossing Statistics for (d+1)-Dimensional Fluctuating Surfaces
We carry out an exact analysis of the average frequency
in the direction of positive-slope crossing of a given level
such that, , of growing surfaces in spatial
dimension . Here, is the surface height at time , and
is its mean value. We analyze the problem when the surface growth
dynamics is governed by the Kardar-Parisi-Zhang (KPZ) equation without surface
tension, in the time regime prior to appearance of cusp singularities (sharp
valleys), as well as in the random deposition (RD) model. The total number
of such level-crossings with positive slope in all the directions is then
shown to scale with time as for both the KPZ equation and the RD
model.Comment: 22 pages, 3 figure
Structures and waves in a nonlinear heat-conducting medium
The paper is an overview of the main contributions of a Bulgarian team of
researchers to the problem of finding the possible structures and waves in the
open nonlinear heat conducting medium, described by a reaction-diffusion
equation. Being posed and actively worked out by the Russian school of A. A.
Samarskii and S.P. Kurdyumov since the seventies of the last century, this
problem still contains open and challenging questions.Comment: 23 pages, 13 figures, the final publication will appear in Springer
Proceedings in Mathematics and Statistics, Numerical Methods for PDEs:
Theory, Algorithms and their Application
Hadrons with Charm and Beauty
By combining potential models and QCD spectral sum rules (QSSR), we discuss
the spectroscopy of the mesons and of the , and
baryons ( or ), the decay constant and the
(semi)leptonic decay modes of the meson. For the masses, the best
predictions come from potential models and read: ~MeV,
~MeV, ~GeV,
~GeV, ~GeV
and ~GeV. The decay constant is well determined from QSSR and leads to:
s.The uses of the vertex sum rules for the semileptonic decays of the
show that the -dependence of the form factors is much stronger than
predicted by vector meson dominance. It also predicts the almost equal strength
of about 0.30 sec for the semileptonic rates into
and J/. Besides these phenomenological results, we
also show explicitly how the Wilson coefficients of the and gluon condensates already contain the full
heavy quark- () and mixed- ()
condensate contributions in the OPE.}Comment: 32 pages, LaTeX, no changes in the 1994 paper, latex errors corrected
in 201
Properties of heavy quarkonia and B_c mesons in the relativistic quark model
The mass spectra and electromagnetic decay rates of charmonium, bottomonium
and B_c mesons are comprehensively investigated in the relativistic quark
model. The presence of only heavy quarks allows the expansion in powers of
their velocities. All relativistic corrections of order v^2/c^2, including
retardation effects and one-loop radiative corrections, are systematically
taken into account in the computations of the mass spectra. The obtained wave
functions are used for the calculation of radiative magnetic dipole (M1) and
electric dipole (E1) transitions. It is found that relativistic effects play a
substantial role. Their account and the proper choice of the Lorentz structure
of the quark-antiquark interaction in a meson is crucial for bringing
theoretical predictions in accord with experimental data. A detailed comparison
of the calculated decay rates and branching fractions with available
experimental data for radiative decays of charmonium and bottomonium is
presented. The possibilities to observe the currently missing spin-singlet S
and P states as well as D states in bottomonium are discussed. The results for
B_c masses and decays are compared with other quark model predictions.Comment: 31 pages, 2 figures, minor correction
Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets
The spins of ten stellar black holes have been measured using the
continuum-fitting method. These black holes are located in two distinct classes
of X-ray binary systems, one that is persistently X-ray bright and another that
is transient. Both the persistent and transient black holes remain for long
periods in a state where their spectra are dominated by a thermal accretion
disk component. The spin of a black hole of known mass and distance can be
measured by fitting this thermal continuum spectrum to the thin-disk model of
Novikov and Thorne; the key fit parameter is the radius of the inner edge of
the black hole's accretion disk. Strong observational and theoretical evidence
links the inner-disk radius to the radius of the innermost stable circular
orbit, which is trivially related to the dimensionless spin parameter a_* of
the black hole (|a_*| < 1). The ten spins that have so far been measured by
this continuum-fitting method range widely from a_* \approx 0 to a_* > 0.95.
The robustness of the method is demonstrated by the dozens or hundreds of
independent and consistent measurements of spin that have been obtained for
several black holes, and through careful consideration of many sources of
systematic error. Among the results discussed is a dichotomy between the
transient and persistent black holes; the latter have higher spins and larger
masses. Also discussed is recently discovered evidence in the transient sources
for a correlation between the power of ballistic jets and black hole spin.Comment: 30 pages. Accepted for publication in Space Science Reviews. Also to
appear in hard cover in the Space Sciences Series of ISSI "The Physics of
Accretion onto Black Holes" (Springer Publisher). Changes to Sections 5.2,
6.1 and 7.4. Section 7.4 responds to Russell et al. 2013 (MNRAS, 431, 405)
who find no evidence for a correlation between the power of ballistic jets
and black hole spi
Search for Heavy Neutral and Charged Leptons in e+ e- Annihilation at LEP
A search for exotic unstable neutral and charged heavy leptons as well as for
stable charged heavy leptons is performed with the L3 detector at LEP.
Sequential, vector and mirror natures of heavy leptons are considered. No
evidence for their existence is found and lower limits on their masses are set
Production of singlet P-wave and states
No spin-singlet quarkonium state has yet been observed. In this
paper we discuss the production of the singlet P-wave and
states and . We consider two possibilities. In the first the
states are produced via the electromagnetic cascades \ups(3S) \to
\eta_b(2S) + \gamma \to h_b + \gamma \gamma \to \eta_b +\gamma\gamma\gamma
and . A more promising process consists of single pion
transition to the state followed by the radiative transition to the
state: \ups(3S)\to h_b + \pi^0 \to \eta_b + \pi^0 +\gamma and . For a million \ups(3S) or
's produced we expect these processes to produce several hundred events.Comment: 13 pages, LaTeX, 1 figure, to be published Phys. Rev. D. Some
equation numbers and one table number correcte
Metal complex of the Bronze Age from an Alakul burial ground (typology and manufacturing techniques)
The article deals with metal artifacts from an Alakul burial ground, which is considered to be one of the largest and brightest monuments of the Alakul culture in the Trans-Urals. There is a description of morphological and typological characteristics of the metal complex which determined the main types of objects, a circle of cultural analogies, and also artifacts which aren't found among materials of other monuments. The main raw materials for production of artifacts were tin bronze (71,6 %). Concentration of tin in jewelry markers of the Alakul culture (cross-shaped pendants) could reach 25â30 %. The obtained data reflect the extent of expansion of use of tin alloy with simultaneous reduction of number of products made of pure copper by the Alakul populations, in comparison with the previous Petrovka culture. This process was promoted by the established relations with sources of metal raw materials and, in particular, of tin alloy arriving in the form of small rectangular bars with concentration of tin of 2â5 %, possibly from centers of production of metal in Central Kazakhstan and the Altai.
The metallographic analysis revealed 8 technological schemes applied to produce an inventory complex and jewelry with a prevalence of high-temperature modes. The fact that masters of the Alakul burial ground chose from such big variety of technological schemes calls attention, because they adopted traditional methods of Petrovka metal working. However, the increase in share of forge technologies of molding in combination with forging hot metal processing at temperatures of full red heat, increase in application of preliminary homogenization annealing, which is necessary when working with high tin bronze, were, undoubtedly, a progressive phenomenon. The received data characterize the studied metal complex as traditional for the entire Alakul culture of the Tobol river basin, on the one hand, and as original and unique, on the other hand
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