9,329 research outputs found
State morphism MV-algebras
We present a complete characterization of subdirectly irreducible MV-algebras
with internal states (SMV-algebras). This allows us to classify subdirectly
irreducible state morphism MV-algebras (SMMV-algebras) and describe single
generators of the variety of SMMV-algebras, and show that we have a continuum
of varieties of SMMV-algebras
Estimating the Explosion Time of Core-Collapse Supernovae from Their Optical Light Curves
Core-collapse supernovae are among the prime candidate sources of high energy
neutrinos. Accordingly, the IceCube collaboration has started a program to
search for such a signal. IceCube operates an online search for neutrino
bursts, forwarding the directions of candidate events to a network of optical
telescopes for immediate follow-up observations. If a supernova is identified
from the optical observations, in addition to a directional coincidence a
temporal photon-neutrino coincidence also needs to be established. To achieve
this, we present a method for estimating the supernova explosion time from its
light curve using a simple model. We test the model with supernova light curve
data from SN1987A, SN2006aj and SN2008D and show that the explosion times can
be determined with an accuracy of better than a few hours.Comment: Version accepted for publication by Astroparticle Physics; 13 pages,
5 figure
Physics of Quantum Relativity through a Linear Realization
The idea of quantum relativity as a generalized, or rather deformed, version
of Einstein (special) relativity has been taking shape in recent years.
Following the perspective of deformations, while staying within the framework
of Lie algebra, we implement explicitly a simple linear realization of the
relativity symmetry, and explore systematically the resulting physical
interpretations. Some suggestions we make may sound radical, but are arguably
natural within the context of our formulation. Our work may provide a new
perspective on the subject matter, complementary to the previous approach(es),
and may lead to a better understanding of the physics.Comment: 27 pages in Revtex, no figure; proof-edited version to appear in
Phys.Rev.
Modeling of the hydrogen Lyman lines in solar flares
The hydrogen Lyman lines (91.2 nm < λ < 121.6 nm) are significant contributors to the radiative losses of the solar chromosphere, and they are enhanced during flares. We have shown previously that the Lyman lines observed by the Extreme Ultraviolet Variability instrument onboard the Solar Dynamics Observatory exhibit Doppler motions equivalent to speeds on the order of 30 km s−1. However, contrary to expectations, both redshifts and blueshifts were present and no dominant flow direction was observed. To understand the formation of the Lyman lines, particularly their Doppler motions, we have used the radiative hydrodynamic code, RADYN, along with the radiative transfer code, RH, to simulate the evolution of the flaring chromosphere and the response of the Lyman lines during solar flares. We find that upflows in the simulated atmospheres lead to blueshifts in the line cores, which exhibit central reversals. We then model the effects of the instrument on the profiles, using the Extreme Ultraviolet Variability Experiment (EVE) instrument's properties. What may be interpreted as downflows (redshifted emission) in the lines, after they have been convolved with the instrumental line profile, may not necessarily correspond to actual downflows. Dynamic features in the atmosphere can introduce complex features in the line profiles that will not be detected by instruments with the spectral resolution of EVE, but which leave more of a signature at the resolution of the Spectral Investigation of the Coronal Environment instrument onboard the Solar Orbiter
The Implications of M Dwarf Flares on the Detection and Characterization of Exoplanets at Infrared Wavelengths
We present the results of an observational campaign which obtained high time
cadence, high precision, simultaneous optical and IR photometric observations
of three M dwarf flare stars for 47 hours. The campaign was designed to
characterize the behavior of energetic flare events, which routinely occur on M
dwarfs, at IR wavelengths to milli-magnitude precision, and quantify to what
extent such events might influence current and future efforts to detect and
characterize extrasolar planets surrounding these stars. We detected and
characterized four highly energetic optical flares having U-band total energies
of ~7.8x10^30 to ~1.3x10^32 ergs, and found no corresponding response in the J,
H, or Ks bandpasses at the precision of our data. For active dM3e stars, we
find that a ~1.3x10^32 erg U-band flare (delta Umax ~1.5 mag) will induce <8.3
(J), <8.5 (H), and <11.7 (Ks) milli-mags of a response. A flare of this energy
or greater should occur less than once per 18 hours. For active dM4.5e stars,
we find that a ~5.1x10^31 erg U-band flare (delta Umax ~1.6 mag) will induce
<7.8 (J), <8.8 (H), and <5.1 (Ks) milli-mags of a response. A flare of this
energy or greater should occur less than once per 10 hours. No evidence of
stellar variability not associated with discrete flare events was observed at
the level of ~3.9 milli-mags over 1 hour time-scales and at the level of ~5.6
milli-mags over 7.5 hour time-scales. We therefore demonstrate that most M
dwarf stellar activity and flares will not influence IR detection and
characterization studies of M dwarf exoplanets above the level of ~5-11
milli-mags, depending on the filter and spectral type. We speculate that the
most energetic megaflares on M dwarfs, which occur at rates of once per month,
are likely to be easily detected in IR observations with sensitivity of tens of
milli-mags.Comment: Accepted in Astronomical Journal, 17 pages, 6 figure
Austempering transformation kinetics of austempered ductile iron obtained by Mössbauer Spectroscopy
The composition of metallic matrix in ductile iron as-cast and after austempering at temperatures of 280, 330 and 380oC (ADI) was examined. The study presents the results of these examinations obtained by Mössbauer spectroscopy. The specimens were taken from cast rods of 60mm diameter. Using calculated values of the parameters of hyperfine interactions (isomeric shift IS, quadrupole splitting QS and hyperfine effective magnetic field H), isolated by deconvolution of the experimental spectrum, the constituents of the metallic matrix were
identified in terms of both quantity and quality. The measured values as well as the data compiled in literature indicate that component Z1 (the, so called, Zeeman spectrum sextet) is related with 57Fe atoms present in the structure of ferrite α1 (I stage of o→α1 + st transformation), component Z2 is typical of ferrite α2 (II stage of st→α2 + carbides transformation), while component Z3 has its origin in 57Fe atoms seated in the structure of carbides (Fe3C, Fe2C or Fe2,4C). On the other hand, by analysis of the parameters of hyperfine interactions describing the non-magnetic components (L and Q) it has been proved that they are typical of austenite
First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved
We report the first direct detection of a strong, 5 kG magnetic field on the
surface of an active brown dwarf. LSR J1835+3259 is an M8.5 dwarf exhibiting
transient radio and optical emission bursts modulated by fast rotation. We have
detected the surface magnetic field as circularly polarized signatures in the
819 nm sodium lines when an active emission region faced the Earth. Modeling
Stokes profiles of these lines reveals the effective temperature of 2800 K and
log gravity acceleration of 4.5. These parameters place LSR J1835+3259 on
evolutionary tracks as a young brown dwarf with the mass of 554 M and age of 224 Myr. Its magnetic field is at least 5.1 kG and covers
at least 11% of the visible hemisphere. The active region topology recovered
using line profile inversions comprises hot plasma loops with a vertical
stratification of optical and radio emission sources. These loops rotate with
the dwarf in and out of view causing periodic emission bursts. The magnetic
field is detected at the base of the loops. This is the first time that we can
quantitatively associate brown dwarf non-thermal bursts with a strong, 5 kG
surface magnetic field and solve the puzzle of their driving mechanism. This is
also the coolest known dwarf with such a strong surface magnetic field. The
young age of LSR J1835+3259 implies that it may still maintain a disk, which
may facilitate bursts via magnetospheric accretion, like in higher-mass T
Tau-type stars. Our results pave a path toward magnetic studies of brown dwarfs
and hot Jupiters.Comment: ApJ, in pres
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