5,528 research outputs found
Ternary q-Virasoro-Witt Hom-Nambu-Lie algebras
In this paper we construct ternary -Virasoro-Witt algebras which
-deform the ternary Virasoro-Witt algebras constructed by Curtright, Fairlie
and Zachos using enveloping algebra techniques. The ternary
Virasoro-Witt algebras constructed by Curtright, Fairlie and Zachos depend on a
parameter and are not Nambu-Lie algebras for all but finitely many values of
this parameter. For the parameter values for which the ternary Virasoro-Witt
algebras are Nambu-Lie, the corresponding ternary -Virasoro-Witt algebras
constructed in this article are also Hom-Nambu-Lie because they are obtained
from the ternary Nambu-Lie algebras using the composition method. For other
parameter values this composition method does not yield Hom-Nambu Lie algebra
structure for -Virasoro-Witt algebras. We show however, using a different
construction, that the ternary Virasoro-Witt algebras of Curtright, Fairlie and
Zachos, as well as the general ternary -Virasoro-Witt algebras we construct,
carry a structure of ternary Hom-Nambu-Lie algebra for all values of the
involved parameters
The F-GAMMA program: Multi-frequency study of Active Galactic Nuclei in the Fermi era. Program description and the first 2.5 years of monitoring
To fully exploit the scientific potential of the Fermi mission, we initiated
the F-GAMMA program. Between 2007 and 2015 it was the prime provider of
complementary multi-frequency monitoring in the radio regime. We quantify the
radio variability of gamma-ray blazars. We investigate its dependence on source
class and examine whether the radio variability is related to the gamma-ray
loudness. Finally, we assess the validity of a putative correlation between the
two bands. The F-GAMMA monitored monthly a sample of about 60 sources at up to
twelve radio frequencies between 2.64 and 228.39 GHz. We perform a time series
analysis on the first 2.5-year dataset to obtain variability parameters. A
maximum likelihood analysis is used to assess the significance of a correlation
between radio and gamma-ray fluxes. We present light curves and spectra
(coherent within ten days) obtained with the Effelsberg 100-m and IRAM 30-m
telescopes. All sources are variable across all frequency bands with amplitudes
increasing with frequency up to rest frame frequencies of around 60 - 80 GHz as
expected by shock-in-jet models. Compared to FSRQs, BL Lacs show systematically
lower variability amplitudes, brightness temperatures and Doppler factors at
lower frequencies, while the difference vanishes towards higher ones. The time
scales appear similar for the two classes. The distribution of spectral indices
appears flatter or more inverted at higher frequencies for BL Lacs. Evolving
synchrotron self-absorbed components can naturally account for the observed
spectral variability. We find that the Fermi-detected sources show larger
variability amplitudes as well as brightness temperatures and Doppler factors,
than non-detected ones. Flux densities at 86.2 and 142.3 GHz correlate with 1
GeV fluxes at a significance level better than 3sigma, implying that gamma rays
are produced very close to the mm-band emission region.Comment: Accepted for publication in section 4. Extragalactic astronomy of
Astronomy and Astrophysics (18 pages, 9 figures
Common Cerambycid Pheromone components as attractants for Longhorn Beetles (Cerambycidae) breeding in ephemeral oak substrates in Northern Europe
Longhorn beetles are ecologically important insects in forest ecosystems as decomposers of woody substrates, microhabitat engineers, and as components of forest food webs. These species can be greatly affected both positively and negatively by modern forestry management practices, and should be monitored accordingly.
Through headspace sampling, coupled gas chromatography-electroantennography, gas chromatography-mass spectrometry, and field bioassays, we identified two compounds, 2-methyl-1-butanol and 3-hydroxy-2-hexanone, that constitute aggregation-sex pheromone attractants of three cerambycid species which breed primarily in different types of fresh, recently dead oak wood in Northern Europe: Pyrrhidium sanguineum (L.), Phymatodes alni ssp. alni (L.), and Phymatodes testaceus (L.) (Cerambycinae: Callidiini). Analyses of headspace volatiles collected from live insects indicated that the male-produced aggregation-sex pheromone of P. sanguineum is a 1â15:100 blend of (R)-2-methyl-1-butanol and (R)-3-hydroxy-2-hexanone, whereas the corresponding ratios for P. alni were 70â110:100. In field bioassays, adult P. sanguineum and P. alni were significantly attracted to multiple blends with varying ratios of the two compounds. When tested individually, the compounds were minimally attractive. In contrast, adult P. testaceus exhibited nonspecific attraction to both of the individual compounds and to different blends, despite the hydroxyketone not being part of its pheromone, which consists of (R)-2-methyl-1-butanol alone.
Overall, our results suggest that a blend of 50:100 of racemic 2-methyl-1-butanol and 3-hydroxy-2-hexanone is appropriate for parallel, cost-efficient pheromone-based monitoring of all three species. In particular, these species could serve as useful indicators of how modern forestry practices affect a whole guild of saproxylic insects that require ephemeral deadwood substrates for successful breeding
Renormalizing a BRST-invariant composite operator of mass dimension 2 in Yang-Mills theory
We discuss the renormalization of a BRST and anti-BRST invariant composite
operator of mass dimension 2 in Yang-Mills theory with the general BRST and
anti-BRST invariant gauge fixing term of the Lorentz type. The interest of this
study stems from a recent claim that the non-vanishing vacuum condensate of the
composite operator in question can be an origin of mass gap and quark
confinement in any manifestly covariant gauge, as proposed by one of the
authors. First, we obtain the renormalization group flow of the Yang-Mills
theory. Next, we show the multiplicative renormalizability of the composite
operator and that the BRST and anti-BRST invariance of the bare composite
operator is preserved under the renormalization. Third, we perform the operator
product expansion of the gluon and ghost propagators and obtain the Wilson
coefficient corresponding to the vacuum condensate of mass dimension 2.
Finally, we discuss the connection of this work with the previous works and
argue the physical implications of the obtained results.Comment: 49 pages, 35 eps-files, A number of typographic errors are corrected.
A paragraph is added in the beginning of section 5.3. Two equations (7.1) and
(7.2) are added. A version to be published in Phys. Rev.
Suzaku observations of Markarian 335: evidence for a distributed reflector
We report on a 151 ks net exposure Suzaku observation of the Narrow Line
Seyfert 1 galaxy Mrk 335. The 0.5-40 keV spectrum contains a broad Fe line, a
strong soft excess below about 2 keV and a Compton hump around 20-30 keV. We
find that a model consisting of a power law and two reflectors provides the
best fit to the time-averaged spectrum. In this model, an ionized, heavily
blurred, inner reflector produces most of the soft excess, while an almost
neutral outer reflector (outside ~40 r_g) produces most of the Fe line
emission. The spectral variability of the observation is characterised by
spectral hardening at very low count rates. In terms of our power-law +
two-reflector model it seems like this hardening is mainly caused by pivoting
of the power law. The rms spectrum of the entire observation has the curved
shape commonly observed in AGN, although the shape is significantly flatter
when an interval which does not contain any deep dip in the lightcurve is
considered. We also examine a previous 133 ks XMM-Newton observation of Mrk
335. We find that the XMM-Newton spectrum can be fitted with a similar
two-reflector model as the Suzaku data and we confirm that the rms spectrum of
the observation is flat. The flat rms spectra, as well as the high-energy data
from the Suzaku PIN detector, disfavour an absorption origin for the soft
excess in Mrk 335.Comment: 13 pages, 13 figures. Accepted for publication in MNRA
Temperature dependence of binary and ternary recombination of H3+ ions with electron
We study binary and the recently discovered process of ternary He-assisted
recombination of H3+ ions with electrons in a low temperature afterglow plasma.
The experiments are carried out over a broad range of pressures and
temperatures of an afterglow plasma in a helium buffer gas. Binary and
He-assisted ternary recombination are observed and the corresponding
recombination rate coefficients are extracted for temperatures from 77 K to 330
K. We describe the observed ternary recombination as a two-step mechanism:
First, a rotationally-excited long-lived neutral molecule H3* is formed in
electron-H3+ collisions. Second, the H3* molecule collides with a helium atom
that leads to the formation of a very long-lived Rydberg state with high
orbital momentum. We present calculations of the lifetimes of H3* and of the
ternary recombination rate coefficients for para and ortho-H3+. The
calculations show a large difference between the ternary recombination rate
coefficients of ortho- and para-H3+ at temperatures below 300 K. The measured
binary and ternary rate coefficients are in reasonable agreement with the
calculated values.Comment: 15 page
Measuring energy dependent polarization in soft gamma-rays using Compton scattering in PoGOLite
Linear polarization in X- and gamma-rays is an important diagnostic of many
astrophysical sources, foremost giving information about their geometry,
magnetic fields, and radiation mechanisms. However, very few X-ray polarization
measurements have been made, and then only mono-energetic detections, whilst
several objects are assumed to have energy dependent polarization signatures.
In this paper we investigate whether detection of energy dependent polarization
from cosmic sources is possible using the Compton technique, in particular with
the proposed PoGOLite balloon-experiment, in the 25-100 keV range. We use
Geant4 simulations of a PoGOLite model and input photon spectra based on Cygnus
X-1 and accreting magnetic pulsars (100 mCrab). Effective observing times of 6
and 35 hours were simulated, corresponding to a standard and a long duration
flight respectively. Both smooth and sharp energy variations of the
polarization are investigated and compared to constant polarization signals
using chi-square statistics. We can reject constant polarization, with energy,
for the Cygnus X-1 spectrum (in the hard state), if the reflected component is
assumed to be completely polarized, whereas the distinction cannot be made for
weaker polarization. For the accreting pulsar, constant polarization can be
rejected in the case of polarization in a narrow energy band with at least 50%
polarization, and similarly for a negative step distribution from 30% to 0%
polarization.Comment: 11 pages, 12 figures; updated to match version accepted for
publication in Astroparticle Physics (only minor changes
Inflationary Reheating in Grand Unified Theories
Grand unified theories may display multiply interacting fields with strong
coupling dynamics. This poses two new problems: (1) What is the nature of
chaotic reheating after inflation, and (2) How is reheating sensitive to the
mass spectrum of these theories ? We answer these questions in two interesting
limiting cases and demonstrate an increased efficiency of reheating which
strongly enhances non-thermal topological defect formation, including monopoles
and domain walls. Nevertheless, the large fluctuations may resolve this
monopole problem via a modified Dvali-Liu-Vachaspati mechanism in which
non-thermal destabilsation of discrete symmetries occurs at reheating.Comment: 4 pages, 5 ps figures - 1 colour, Revtex. Further (colour & 3-D)
figures available from http://www.sissa.it/~bassett/reheating/ . Matched to
version to appear in Phys. Rev. let
Invariants of Lie algebras extended over commutative algebras without unit
We establish results about the second cohomology with coefficients in the
trivial module, symmetric invariant bilinear forms and derivations of a Lie
algebra extended over a commutative associative algebra without unit. These
results provide a simple unified approach to a number of questions treated
earlier in completely separated ways: periodization of semisimple Lie algebras
(Anna Larsson), derivation algebras, with prescribed semisimple part, of
nilpotent Lie algebras (Benoist), and presentations of affine Kac-Moody
algebras.Comment: v3: added a footnote on p.10 about a wrong derivation of the correct
statemen
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