642,861 research outputs found
Star-formation rate in compact star-forming galaxies
We use the data for the Hbeta emission-line, far-ultraviolet (FUV) and
mid-infrared 22 micron continuum luminosities to estimate star formation rates
averaged over the galaxy lifetime for a sample of about 14000 bursting
compact star-forming galaxies (CSFGs) selected from the Data Release 12 (DR12)
of the Sloan Digital Sky Survey (SDSS). The average coefficient linking
and the star formation rate SFR_0 derived from the Hbeta luminosity at zero
starburst age is found to be 0.04. We compare s with some commonly used
SFRs which are derived adopting a continuous star formation during a period of
~100 Myr, and find that the latter ones are 2-3 times higher. It is shown that
the relations between SFRs derived using a geometric mean of two star-formation
indicators in the UV and IR ranges and reduced to zero starburst age have
considerably lower dispersion compared to those with single star-formation
indicators. We suggest that our relations for determination are more
appropriate for CSFGs because they take into account a proper temporal
evolution of their luminosities. On the other hand, we show that commonly used
SFR relations can be applied for approximate estimation within a factor of ~2
of the averaged over the lifetime of the bursting compact galaxy.Comment: 11 pages, 7 figures, accepted for publication in Astrophysics and
Space Scienc
Basic Features of Global Circulation in the Mesopause Lower Thermosphere Region
D1 and D2 techniques have been used and are being used for observations at stations located in the high, middle, and low latitudes of both hemispheres. The systematical and wind velocity measurements with these techniques make it possible to specify and to refine earlier mesopause-lower thermosphere circulation models. With this in view, an effort was made to obtain global long term average height-latitude sections of the wind field at 70 to 110 km using the analysis of long period D1 and D2 observations. Data from 26 meteor radar and 6 ionospheric stations were taken for analysis
Lagrangian constraints and renormalization of 4D gravity
It has been proposed in \cite{Park:2014tia} that 4D Einstein gravity becomes
effectively reduced to 3D after solving the Lagrangian analogues of the
Hamiltonian and momentum constraints of the Hamiltonian quantization. The
analysis in \cite{Park:2014tia} was carried out at the classical/operator
level. We review the proposal and make a transition to the path integral
account. We then set the stage for explicitly carrying out the two-loop
renormalization procedure of the resulting 3D action. We also address a
potentially subtle issue in the gravity context concerning whether
renormalizability does not depend on the background around which the original
action is expanded.Comment: 40 pages, 5 figures, minor corrections, version to appear in JHE
Hypersurface foliation approach to renormalization of ADM formulation of gravity
We carry out ADM splitting in the Lagrangian formulation and establish a
procedure in which (almost) all of the unphysical components of the metric are
removed by using the 4D diffeomorphism and the measure-zero 3D symmetry. The
procedure introduces a constraint that corresponds to the Hamiltonian
constraint of the Hamiltonian formulation, and its solution implies that the 4D
dynamics admits an effective description through 3D hypersurface physics. As
far as we can see, our procedure implies potential renormalizability of {the
ADM formulation of} 4D Einstein gravity for which a complete gauge-fixing in
the ADM formulation and hypersurface foliation of geometry are the key
elements. If true, this implies that the alleged unrenormalizability of 4D
Einstein gravity may be due to the presence of the unphysical fields. The
procedure can straightforwardly be applied to quantization around a flat
background; the Schwarzschild case seems more subtle. We discuss a potential
limitation of the procedure when applying it to explicit time-dependent
backgrounds.Comment: 29 pages, 3 figures, expanded for clarity, refs added, the version to
appear in EPJ
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