17,354 research outputs found
The Einstein-Hilbert Lagrangian Density in a 2-dimensional Spacetime is an Exact Differential
Recently Kiriushcheva and Kuzmin claimed to have shown that the
Einstein-Hilbert Lagrangian cannot be written in any coordinate gauge as an
exact differential in a 2-dimensional spacetime. Since this is contrary to
other statements on the subject found in the literature, as e.g., by Deser and
Jackiw, Jackiw, Grumiller, Kummer and Vassilevich it is necessary to do decide
who has reason. This is done in this paper in a very simply way using the
Clifford bundle formalism. In this version we added Section 18 which discusses
a recent comment on our paper just posted by Kiriushcheva and Kuzmin.Comment: 11 pages, Misprints in some equations have been corrected; four new
references have been added, Section 18 adde
Bounds on topological Abelian string-vortex and string-cigar from information-entropic measure
In this work we obtain bounds on the topological Abelian string-vortex and on
the string-cigar, by using a new measure of configurational complexity, known
as configurational entropy. In this way, the information-theoretical measure of
six-dimensional braneworlds scenarios are capable to probe situations where the
parameters responsible for the brane thickness are arbitrary. The so-called
configurational entropy (CE) selects the best value of the parameter in the
model. This is accomplished by minimizing the CE, namely, by selecting the most
appropriate parameters in the model that correspond to the most organized
system, based upon the Shannon information theory. This information-theoretical
measure of complexity provides a complementary perspective to situations where
strictly energy-based arguments are inconclusive. We show that the higher the
energy the higher the CE, what shows an important correlation between the
energy of the a localized field configuration and its associated entropic
measure.Comment: 6 pages, 7 figures, final version to appear in Phys. Lett.
Lunar subsurface architecture enhanced by artificial biosphere concepts
The integration of artificial biosphere technology with subselene architecture can create a life-enhancing, productive habitat that is safe from solar radiation and extreme temperature fluctuations while maximizing resources brought from Earth and derived from lunar regolith. In the short term, the resulting biotectural (biosphere and architectural) designs will not only make the structures more habitable, productive, and manageable, but will ultimately provide the self-sufficiency factors necessary for the mature lunar settlement. From a long-term perspective, this biotecture approach to astronautics and extraterrestrial development (1) helps reduce mass lift requirements, (2) contributes to habitat self-sufficiency, and (3) actualizes at least one philosophy of solar system exploration, which is to exploit nonterrestrial resources in an effort to conserve our natural resources on this planet
Ab initio study of electron transport in dry poly(G)-poly(C) A-DNA strands
The bias-dependent transport properties of short poly(G)-poly(C) A-DNA
strands attached to Au electrodes are investigated with first principles
electronic transport methods. By using the non- equilibrium Green's function
approach combined with self-interaction corrected density functional theory, we
calculate the fully self-consistent coherent I-V curve of various double-strand
polymeric DNA fragments. We show that electronic wave-function localization,
induced either by the native electrical dipole and/or by the electrostatic
disorder originating from the first few water solvation layers, drastically
suppresses the magnitude of the elastic conductance of A-DNA oligonucleotides.
We then argue that electron transport through DNA is the result of
sequence-specific short-range tunneling across a few bases combined with
general diffusive/inelastic processes.Comment: 15 pages, 13 figures, 1 tabl
DNA-psoralen: single-molecule experiments and first principles calculations
The authors measure the persistence and contour lengths of DNA-psoralen
complexes, as a function of psoralen concentration, for intercalated and
crosslinked complexes. In both cases, the persistence length monotonically
increases until a certain critical concentration is reached, above which it
abruptly decreases and remains approximately constant. The contour length of
the complexes exhibits no such discontinuous behavior. By fitting the relative
increase of the contour length to the neighbor exclusion model, we obtain the
exclusion number and the intrinsic intercalating constant of the psoralen-DNA
interaction. Ab initio calculations are employed in order to provide an
atomistic picture of these experimental findings.Comment: 9 pages, 4 figures in re-print format 3 pages, 4 figures in the
published versio
OGSA/Globus Evaluation for Data Intensive Applications
We present an architecture of Globus Toolkit 3 based testbed intended for
evaluation of applicability of the Open Grid Service Architecture (OGSA) for
Data Intensive Applications.Comment: To be published in the proceedings of the XIX International Symposium
on Nuclear Electronics and Computing (NEC'2003), Bulgaria, Varna, 15-20
September, 200
Studies of CMB structure at Dec=40. II: Analysis and cosmological interpretation
We present a detailed analysis of the cosmic microwave background structure
in the Tenerife Dec=+40 degrees data. The effect of local atmospheric
contributions on the derived fluctuation amplitude is considered, resulting in
an improved separation of the intrinsic CMB signal from noise. Our analysis
demonstrates the existence of common structure in independent data scans at 15
and 33 GHz. For the case of fluctuations described by a Gaussian
auto-correlation function, a likelihood analysis of our combined results at 15
and 33 GHz implies an intrinsic rms fluctuation level of 48^{+21}_{-15} uK on a
coherence scale of 4 degrees; the equivalent analysis for a
Harrison-Zel'dovitch model gives a power spectrum normalisation of Q_{rms-ps} =
22^{+10}_{-6} uK. The fluctuation amplitude is seen to be consistent at the 68%
confidence level with that reported for the COBE two-year data for primordial
fluctuations described by a power law model with a spectral index in the range
1.0 \le n \le 1.6. This limit favours the large scale CMB anisotropy being
dominated by scalar fluctuations rather than tensor modes from a gravitational
wave background. The large scale Tenerife and COBE results are considered in
conjunction with observational results from medium scale experiments in order
to place improved limits on the fluctuation spectral index; we find n=1.10 +/-
0.10 assuming standard CDM with H_{0}=50 kms^{-1}Mpc^{-1}.Comment: 10 pages LaTeX, including 8 PostScript figures. Accepted for
publication in MNRA
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