9,015 research outputs found
Determination of the X-ray reflection emissivity profile of 1H 0707-495
When considering the X-ray spectrum resulting from the reflection off the
surface of accretion discs of AGN, it is necessary to account for the variation
in reflected flux over the disc, i.e. the emissivity profile. This will depend
on factors including the location and geometry of the X-ray source and the disc
characteristics. We directly obtain the emissivity profile of the disc from the
observed spectrum by considering the reflection component as the sum of
contributions from successive radii in the disc and fitting to find the
relative weightings of these components in a relativistically-broadened
emission line. This method has successfully recovered known emissivity profiles
from synthetic spectra and is applied to XMM-Newton spectra of the Narrow Line
Seyfert 1 galaxy 1H 0707-495. The data imply a twice-broken power law form of
the emissivity law with a steep profile in the inner regions of the disc (index
7.8) and then a flat region between 5.6rg and 34.8rg before tending to a
constant index of 3.3 over the outer regions of the disc. The form of the
observed emissivity profile is consistent with theoretical predictions, thus
reinforcing the reflection interpretation.Comment: 9 pages, 10 figures. Accepted for publication in MNRA
The Hopf algebra structure of the Z-graded quantum supergroup GL
In this work, we give some features of the Z-graded quantum supergroup
On Spinors Transformations
We begin showing that for even dimensional vector spaces all
automorphisms of their Clifford algebras are inner. So all orthogonal
transformations of are restrictions to of inner automorphisms of the
algebra. Thus under orthogonal transformations and - space and time
reversal - all algebra elements, including vectors and spinors ,
transform as and for some
algebra element . We show that while under combined spinor remain in its spinor space, under or separately
goes to a 'different' spinor space and may have opposite chirality.
We conclude with a preliminary characterization of inner automorphisms with
respect to their property to change, or not, spinor spaces.Comment: Minor changes to propositions 1 and
The trends and dependencies between air and water temperatures in lakes in northern Poland in 1961?2000
International audienceOver 40 years, from 1961?2000, daily mean values of surface lake water temperatures at 0.4 m depth in six lakes in northern Poland were recorded with nearby mean daily air temperatures at 2 m. Air temperatures increased on average from 0.020 to 0.025°C year?1 while lake-water temperatures varied more but increased by 0.005 to 0.028°C year-1. For shorter periods (for instance, for 10 days) the pattern of trend directions and values was more complex, depending on the morphometric and trophic conditions of the lakes. It has been concluded that changes in lake water temperatures during climate warming may be documented by studies of lakes located relatively closely together (up to 300 kilometres). Keywords: physical limnology, climate changes, lake water, temperatur
Non-linear sigma-models in noncommutative geometry: fields with values in finite spaces
We study sigma-models on noncommutative spaces, notably on noncommutative
tori. We construct instanton solutions carrying a nontrivial topological charge
q and satisfying a Belavin-Polyakov bound. The moduli space of these instantons
is conjectured to consists of an ordinary torus endowed with a complex
structure times a projective space .Comment: Latex, 10 page
Electro-optical properties of an orthoconic liquid crystal mixture (W-182) and its molecular dynamics
We observed that the perfect dark state problem could be solved by using orthoconic antiferroelectric liquid crystal (OAFLC) instead of normal AFLC by comparing the properties of isocontrast and dispersion chromaticity of W-182 OAFLC and normal AFLC CS-4001. We electro-optically observed that several subphases such as SmCγ*, SmC*β, SmC*α and antiferroelectric SmI*A phases exist in W-182 OAFLC. We dielectrically observed in 4 μm thin cell that during heating, several new phases appeared. In the high temperature antiferroelectric region, a higher order than SmC* phase could be detected dielectrically, in the temperature range of 91–98 °C, behaving similar to SmCγ* and also, another phase below SmC* region could be dielectrically detected in the temperature range of 103–1100 °C, behaving similar to SmCα*, and an antiferroelectric, similar to SmIA* phase, was observed in the lower temperature region of the antiferroelectric phase; those are definitely arising due to surface force and interfacial charges interactions. We observed both PH and PL relaxation modes in both cells, although they differed in their strength and relaxation frequency. We studied extensively our observations of PH and PL modes in the antiferroelectric region, a Goldstone mode in the ferroelectric region and a soft mode in the ferroelectric region and SmA* phases
Magnetic Stress at the Marginally Stable Orbit: Altered Disk Structure, Radiation, and Black Hole Spin Evolution
Magnetic connections to the plunging region can exert stresses on the inner
edge of an accretion disk around a black hole. We recompute the relativistic
corrections to the thin-disk dynamics equations when these stresses take the
form of a time-steady torque on the inner edge of the disk. The additional
dissipation associated with these stresses is concentrated relatively close
outside the marginally stable orbit, scaling as r to the -7/2 at large radius.
As a result of these additional stresses: spin-up of the central black hole is
retarded; the maximum spin-equilibrium accretion efficiency is 36%, and occurs
at a/M=0.94; the disk spectrum is extended toward higher frequencies; line
profiles (such as Fe K-alpha) are broadened if the line emissivity scales with
local flux; limb-brightening, especially at the higher frequencies, is
enhanced; and the returning radiation fraction is substantially increased, up
to 58%. This last effect creates possible explanations for both synchronized
continuum fluctuations in AGN, and polarization rises shortward of the Lyman
edge in quasars. We show that no matter what additional stresses occur, when
a/M < 0.36, the second law of black hole dynamics sets an absolute upper bound
on the accretion efficiency.Comment: 11 pages, 15 figures, accepted for publication in the Astrophysical
Journa
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