692 research outputs found
Lessons of spin and torsion: Reply to ``Consistent coupling to Dirac fields in teleparallelism"
In reply to the criticism made by Mielke in the pereceding Comment [Phys.
Rev. D69 (2004) 128501] on our recent paper, we once again explicitly
demonstrate the inconsistency of the coupling of a Dirac field to gravitation
in the teleparallel equivalent of general relativity. Moreover, we stress that
the mentioned inconsistency is generic for {\it all} sources with spin and is
by no means restricted to the Dirac field. In this sense the
-covariant generalization of the spinor fields in the teleparallel
gravity theory is irrelevant to the inconsistency problem.Comment: Revtex, 4 pages, no figure
On closed rotating worlds
A new solution for the stationary closed world with rigid rotation is
obtained for the spinning fluid source. It is found that the spin and vorticity
are locally balanced. This model qualitatively shows that the local rotation of
the cosmological matter can be indeed related to the global cosmic vorticity,
provided the total angular momentum of the closed world is vanishing.Comment: 10 pages, Revtex, to appear in Phys. Rev. D6
Comparative experimental study of local mixing of active and passive scalars in turbulent thermal convection
We investigate experimentally the statistical properties of active and
passive scalar fields in turbulent Rayleigh-B\'{e}nard convection in water, at
. Both the local concentration of fluorescence dye and the local
temperature are measured near the sidewall of a rectangular cell. It is found
that, although they are advected by the same turbulent flow, the two scalars
distribute differently. This difference is twofold, i.e. both the quantities
themselves and their small-scale increments have different distributions. Our
results show that there is a certain buoyant scale based on time domain, i.e.
the Bolgiano time scale , above which buoyancy effects are significant.
Above , temperature is active and is found to be more intermittent than
concentration, which is passive. This suggests that the active scalar possesses
a higher level of intermittency in turbulent thermal convection. It is further
found that the mixing of both scalar fields are isotropic for scales larger
than even though buoyancy acts on the fluid in the vertical direction.
Below , temperature is passive and is found to be more anisotropic than
concentration. But this higher degree of anisotropy is attributed to the higher
diffusivity of temperature over that of concentration. From the simultaneous
measurements of temperature and concentration, it is shown that two scalars
have similar autocorrelation functions and there is a strong and positive
correlation between them.Comment: 13 pages and 12 figure
Metric-affine gauge theory of gravity II. Exact solutions
In continuing our series on metric-affine gravity (see Gronwald IJMP D6
(1997) 263 for Part I), we review the exact solutions in this theory.Comment: Revtex file, 25 pages, final version to appear in IJMP
Reply to the comment by D. Kreimer and E. Mielke
We respond to the comment by Kreimer et. al. about the torsional contribution
to the chiral anomaly in curved spacetimes. We discuss their claims and refute
its main conclusion.Comment: 9 pages, revte
Resource+Potential+of+Volunteers+With+Professional+Knowledge+for+the+Development+of+Regional+Socially+Oriented+Non-Profit+Organizations+in+Russia
Resource Potential of Volunteers With Professional Knowledge for the Development of Regional Socially Oriented Non-Profit Organizations in Russia
Received 16 May 2023. Accepted 26 July 2023. Published online 6 October 2023.This article discusses the work models that have arisen in the nonprofit sector of Russian regions, including those that involve volunteers with specialized professional knowledge and skills. The socio-economic situation is currently leading to a general lack of resources, especially in the socially oriented non-profit organizations of the regions. One of the channels for additional capacity attraction for SO NPOs is the appeal for free assistance to professional volunteers in certain areas. In this regard, it is important to find ways to attract and work with such professionals, since simple financial motivation is excluded from the process of functioning. Accordingly, this article focuses on the issue of finding effective models to organize the activities of volunteers with professional skills in regional SO NPOs. Materials obtained in a series of 29 semi-structured interviews with the managers of regional SO NPOs show that the main models of work with volunteers have been developed in Russia. As a result of attracting volunteers on a gratuitous basis, organizations manage to cover the demand for rare specialists, quickly solve the arising problems that go beyond the specialization of SO NPOs, and gain access to innovative technologies for their activities.The article was prepared within the framework of the Basic Research Program at HSE University
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