44,247 research outputs found
Modeling Variable Emission Lines in AGNs: Method and Application to NGC 5548
We present a new scheme for modeling the broad line region in active galactic
nuclei (AGNs). It involves photoionization calculations of a large number of
clouds, in several pre-determined geometries, and a comparison of the
calculated line intensities with observed emission line light curves. Fitting
several observed light curves simultaneously provides strong constraints on
model parameters such as the run of density and column density across the
nucleus, the shape of the ionizing continuum, and the radial distribution of
the emission line clouds. When applying the model to the Seyfert 1 galaxy NGC
5548, we were able to reconstruct the light curves of four ultraviolet
emission-lines, in time and in absolute flux. This has not been achieved by any
previous work. We argue that the Balmer lines light curves, and possibly also
the MgII2798 light curve, cannot be tested in this scheme because of the
limitations of present-day photoionization codes. Our fit procedure can be used
to rule out models where the particle density scales as r^{-2}, where r is the
distance from the central source. The best models are those where the density
scales as r^{-1} or r^{-1.5}. We can place a lower limit on the column density
at a distance of 1 ld, of N_{col}(r=1) >~ 10^{23} cm^{-2} and limit the
particle density to be in the range of 10^{12.5}>N(r=1)>10^{11} cm^{-3}. We
have also tested the idea that the spectral energy distribution (SED) of the
ionizing continuum is changing with continuum luminosity. None of the
variable-shape SED tried resulted in real improvement over a constant SED case
although models with harder continuum during phases of higher luminosity seem
to fit better the observed spectrum. Reddening and/or different composition
seem to play a minor role, at least to the extent tested in this work.Comment: 12 pages, including 9 embedded EPS figures, accepted for publication
in Ap
On the problem of inflation in nonlinear multidimensional cosmological models
We consider a multidimensional cosmological model with nonlinear quadratic
and quartic actions. As a matter source, we include a monopole form
field, D-dimensional bare cosmological constant and tensions of branes located
in fixed points. In the spirit of the Universal Extra Dimensions models, the
Standard Model fields are not localized on branes but can move in the bulk. We
define conditions which ensure the stable compactification of the internal
space in zero minimum of the effective potentials. Such effective potentials
may have rather complicated form with a number of local minima, maxima and
saddle points. Then, we investigate inflation in these models. It is shown that
and models can have up to 10 and 22 e-foldings, respectively. These
values are not sufficient to solve the homogeneity and isotropy problem but big
enough to explain the recent CMB data. Additionally, model can provide
conditions for eternal topological inflation. However, the main drawback of the
given inflationary models consists in a value of spectral index which is
less than observable now . For example, in the case of
model we find .Comment: 18 pages, RevTex4, References are correcte
Majorana Fermions in Strongly Interacting Helical Liquids
Majorana fermions were proposed to occur at edges and interfaces of gapped
one-dimensional systems where phases with different topological character meet
due to an interplay of spin-orbit coupling, proximity-induced superconductivity
and external magnetic fields. Here we investigate the effect of strong particle
interactions, and show that the helical liquid offers a mechanism that protects
the very existence of Majorana edge states: whereas moderate interactions close
the proximity gap which supports the edge states, in helical liquids the gap
re-opens due to two-particle processes. However, gapless fermionic excitations
occur at spatial proximity to the Majorana states at interfaces and may
jeopardize their long term Majorana coherence.Comment: 7 pages, 4 figure
Bodily undoing: somatics as practices of critique
This co-authored volume of The Journal for Dance and Somatic Practices (JDSP) focuses on construction and articulating the field of Somatics as critical practices. Glenna Batson (2017) argues towards the need for a new critique to fully address Somatics in the face of neoliberal globalization and an increasing planetary poly-crisis. How do we locate our embodied practices beyond commodification as critical and empowering practices? How do we question relevance, access, inclusion, and modes of knowledge production within our work? How do we articulate a critical stance toward elitism, Euro-centrism and under-theorisation historically associated with the field? Somatic practices can be understood as reflective processes of undoing existing patterns so that new ones can emerge. How can this transformative undoing be extended beyond the body of the individual to the body politic or the social body? How might we construct Somatics and affiliated transdisciplinary arts practices as practices of critique that might contribute to an alternative social imaginary or way of world-making? Can somatic processes and performance practices foster a capacity for self-reflection and criticality as feature of the ‘democratic citizen’ as ‘a member of the body politic’ (Morin 1999) within growing totalitarian socio-cultural contexts
Massive binaries in the vicinity of Sgr A*
A long-term spectroscopic and photometric survey of the most luminous and
massive stars in the vicinity of the super-massive black hole Sgr A* revealed
two new binaries; a long-period Ofpe/WN9 binary, GCIRS 16NE, with a modest
eccentricity of 0.3 and a period of 224 days and an eclipsing Wolf-Rayet binary
with a period of 2.3 days. Together with the already identified binary GCIRS
16SW, there are now three confirmed OB/WR binaries in the inner 0.2\,pc of the
Galactic Center. Using radial velocity change upper limits, we were able to
constrain the spectroscopic binary fraction in the Galactic Center to at a confidence level of 95%, a massive binary
fraction similar to that observed in dense clusters. The fraction of eclipsing
binaries with photometric amplitudes is , which is consistent with local OB star clusters ().
Overall the Galactic Center binary fraction seems to be close to the binary
fraction in comparable young clusters.Comment: 5 figures, submitted to Ap
Variability of Objectively Measured Sedentary Behavior
The primary purpose of this study was to evaluate variability of sedentary behavior (SB) throughout a 7-d measurement period and to determine if G7 d of SB measurement would be comparable with the typical 7-d measurement period. Methods: Retrospective data from Ball State University_s Clinical Exercise Physiology Laboratory on 293 participants (99 men, 55 T 14 yr, body mass index = 29 T 5 kgImj2; 194 women, 51 T 12 yr, body mass index = 27 T 7 kgImj2) with seven consecutive days of data collected with ActiGraph accelerometers were analyzed (ActiGraph, Fort Walton Beach, FL). Time spent in SB (either G100 counts per minute or G150 counts per minute) and breaks in SB were compared between days and by sex using a two-way repeated-measures ANOVA. Stepwise regression was performed to determine if G7 d of SB measurement were comparable with the 7-d method, using an adjusted R2 of Q0.9 as a criterion for equivalence. Results: There were no differences in daily time spent in SB between the 7 d for all participants. However, there was a significant interaction between sex and days, with women spending less time in SB on both Saturdays and Sundays than men when using the 100 counts per minute cut-point. Stepwise regression showed using any 4 d would be comparable with a 7-d measurement (R2 9 0.90). Conclusions: When assessed over a 7-d measurement period, SB appears to be very stable from day to day, although there may be some small differences in time spent in SB and breaks in SB between men and women, particularly on weekend days. The stepwise regression analysis suggests that a measurement period as short as 4 d could provide comparable data (91% of variance) with a 1-wk assessment. Shorter assessment periods would reduce both researcher and subject burden in data collection
A General Optimization Technique for High Quality Community Detection in Complex Networks
Recent years have witnessed the development of a large body of algorithms for
community detection in complex networks. Most of them are based upon the
optimization of objective functions, among which modularity is the most common,
though a number of alternatives have been suggested in the scientific
literature. We present here an effective general search strategy for the
optimization of various objective functions for community detection purposes.
When applied to modularity, on both real-world and synthetic networks, our
search strategy substantially outperforms the best existing algorithms in terms
of final scores of the objective function; for description length, its
performance is on par with the original Infomap algorithm. The execution time
of our algorithm is on par with non-greedy alternatives present in literature,
and networks of up to 10,000 nodes can be analyzed in time spans ranging from
minutes to a few hours on average workstations, making our approach readily
applicable to tasks which require the quality of partitioning to be as high as
possible, and are not limited by strict time constraints. Finally, based on the
most effective of the available optimization techniques, we compare the
performance of modularity and code length as objective functions, in terms of
the quality of the partitions one can achieve by optimizing them. To this end,
we evaluated the ability of each objective function to reconstruct the
underlying structure of a large set of synthetic and real-world networks.Comment: MAIN text: 14 pages, 4 figures, 1 table Supplementary information: 19
pages, 8 figures, 5 table
Quark Mass Matrices with Four and Five Texture Zeroes, and the CKM Matrix, in terms of Mass Eigenvalues
Using the triangular matrix techniques of Kuo et al and Chiu et al for the
four and five texture zero cases, with vanishing (11) elements for U and D
matrices, it is shown, from the general eigenvalue equations and hierarchy
conditions, that the quark mass matrices, and the CKM matrix can be expressed
(except for the phases) entirely in terms of quark masses. The matrix
structures are then quite simple and transparent. We confirm their results for
the five texture zero case but find, upon closer examination of all the CKM
elements which our results provide, that six of their nine patterns for the
four texture zero case are not compatible with experiments. In total, only one
five-texture zero and three four-texture zero patterns are allowed.Comment: 15 pages, 3 table
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