1,168 research outputs found
Fuga 1 / del Sigl. J. P. Kellner
No full textFUGA 1 / DEL SIGL. J. P. KELLNER
Fuga 1 / del Sigl. J. P. Kellner (1)
Fuga I. (1)
Fuga II. (3)
Fuga III. (5)
Fuga No. 4 (7)
Fuga No. 5 (9)
Preludium et Fuga ex G Dur pro Organe et Pedale obliga (11
Lorentz Violation and Ultrahigh-Energy Photons.
No full textThe propagation of photons, electrons and positrons at ultra-high energies
above eV can be changed considerably if the dispersion relations
of these particles are modified by terms suppressed by powers of the Planck scale.
We recently pointed out that the current non-observation of photons in the
ultra-high energy cosmic ray flux at such energies can put strong constraints
on such modified dispersion relations. In the present work we generalize these
constraints to all three Lorentz invariance breaking parameters that can occur
in the dispersion relations for photons, electrons and positrons at first and second
order suppression with the Planck scale. We also show how the excluded regions in these three-dimensional
parameter ranges would be extended if ultra-high energy photons are detected in the future
Volcanic stratospheric sulfur injections during the Holocene (past 11 500 years) from a bipolar ice-core array, HolVol version 1.1
No full textBased on a set of continuous sulfate and sulfur records from four ice cores, one from Greenland and three from Antarctica, the HolVol v.1.0 database (Sigl et al., 2021, PANGAEA) included estimates of the magnitudes and approximate source latitudes of major volcanic stratospheric sulfur injection (VSSI) events for the Holocene (from 9500 BCE or 11 500 years BP to 1900 CE). In total, we reconstructed 850 volcanic eruptions with injections more than 1 teragram of sulfur (Tg S). These eruptions injected 7410 Tg S into the stratosphere. With the entire reconstructions based on the same four ice cores this reconstruction is best suited to study the frequency and spatial distribution of volcanic activity and resulting VSSI over long time periods and to study drivers and feedbacks between volcanism and climate through time (Sigl et al., 2022).
Here we update the database to HolVol v.1.1 as follows: First, we replace the HolVol reconstruction younger than 500 BCE with a similar reconstruction (eVolv2k; Toohey & Sigl 2017) which is based on a larger network of ice cores with on average higher depth resolution and for which important eruption source parameters (i.e. SSI, latitude, eruption season) have been constrained through dedicated geochemical (e.g. cryptotephra, sulfur isotopes, trace element) analyses (eVolv2k_version4, Sigl & Toohey, PANGAEA, doi:10.1594/PANGAEA.971968). For consistency across the different datasets, we updated the default latitudes for unidentified volcanic eruptions suspected in the Northern Hemisphere extra-tropics from 45°N to 48°N, for those suspected in the Southern Hemisphere extra-tropics from 45°S to 37°S and for those suspected in the tropics from 0° to 5°N (with the latter values being the default latitudes for HolVol, calculated from the mean distribution of large volcanic eruptions in geologic eruption catalogues).
Second, we updated strengths of VSSI, the timing and location of specific caldera-forming (VEI≥6) volcanic eruptions that we identified through geochemical fingerprinting (e.g. cryptotephra analysis; sulfur isotope analysis) and geochronological tools during the Mid-to-late Holocene using additional ice cores and new analyses (e.g. Aniakchak II, Crater Lake). The new HolVol v.1.1 database includes 1365 VSSI events between 9500 BCE to 2000 CE which injected in total 7370 TgS or 0.65 TgS per year on average. Dating uncertainties are +/- 1 to +/-3 years over the past 2,500 years, +/-5 years between 2000 BCE and 500 BCE, and less than +/-10 years before 2000 BCE
Lorentz Violation in the Photon Sector and Ultra-High Energy Cosmic Rays
No full textLorentz symmetry breaking at very high energies may lead
to photon dispersion relations of the form
with new terms suppressed by a power of the Planck mass . We show
that first and second order terms of size
and ,
respectively, would lead to a photon component in cosmic rays above
eV that should already have been detected.
This suggests that LI breaking suppressed up to second order
in the Planck scale are unlikely to be phenomenologically viable
for photon
Ultrahigh-Energy Photons as Probes of Lorentz Symmetry Violations in Stringy Space-Time Foam Models
No full textThe time delays between gamma-rays of different energies from extragalactic sources have often been used to probe quantum gravity models in which Lorentz symmetry is violated. It has been claimed that these time delays can be explained by or at least put the strongest available constraints on quantum gravity scenarios that cannot be cast within an effective field theory framework, such as the space-time foam, D-brane model. Here we show that this model would predict too many photons in the ultra-high energy cosmic ray flux to be consistent with observations. The resulting constraints on the space-time foam model are much stronger than limits from time delays and allow for Lorentz violations effects way too small for explaining the observed time delays
Dynamical evolution of axion condensates under stimulated decays into photons
No full textDark matter axion condensates may experience stimulated decays into photon pairs. This effect has been often interpreted as a parametric resonance of photons from the axion-photon coupling, leading to an exponential growth of the photon occupation number in a narrow instability band. Most of the previous literature does not consider the possible evolution of the axion field due to the photon growth. We revisit this effect presenting a mean field solution of the axion-photon kinetic equations, in terms of number of photons and pair correlations. We study the limit of no axion depletion, recovering the known instability. Moreover, we extend the results including a possible depletion of the axion field. In this case we find that the axion condensate exhibits the behavior of an inverted pendulum. We discuss the relevance of these effects for two different cases: a homogeneous axion field at recombination and a localized axion clump and discuss constraints that could result from the induced photon background
Possible cosmogenic neutrino constraints on Planck-scale Lorentz violation
No full textWe study, within an effective field theory framework, O (E-2/M-Pl(2)) Planck-scale suppressed Lorentz invariance violation (LV) effects in the neutrino sector, whose size we parameterize by a dimensionless parameter eta(nu). We find deviations from predictions of Lorentz invariant physics in the cosmogenic neutrino spectrum. For positive O (1) coefficients no neutrino will survive above 10(19) eV. The existence of this cutoff generates a bump in the neutrino spectrum at energies of 10(17) eV. Although at present no constraint can be cast, as current experiments do not have enough sensitivity to detect ultra-high-energy neutrinos, we show that experiments in construction or being planned have the potential to cast limits as strong as eta(nu) less than or similar to 10(-4) on the neutrino LV parameter, depending on how LV is distributed among neutrino mass states. Constraints on eta(nu) < 0 can in principle be obtained with this strategy, but they require a more detailed modeling of how LV affects the neutrino sector
ICF-based comparison of disease-specific instruments measuring physical functional ability for ankylosing spondylitis
No full textObjectives: To link validated and widely used instruments measuring physical functional ability in ankylosing spondylitis to the International Classification of Functioning, Disability, and Health (ICF) and to compare their contents, based on the results of the linking process. Methods: The Bath Ankylosing Spondylitis Functional Index (BASFI), the Dougados Functional Index (DFI), the Health Assessment Questionnaire modified for the spondylarthropathies (HAQ-S), and the Revised Leeds Disability Questionnaire (RLDQ) were linked to the ICF separately by two trained health professionals according to 10 linkage rules. Results: All concepts contained in the items of the selected instruments could be successfully linked to the ICF except for “illness” included in the HAQ-S. Altogether 55 different ICF categories were linked. Seven belonged to “body functions”, 43 to “activities and participation”, and five to “environmental factors”. The component “body structure” was not contained in any of the four instruments. Only two ICF categories were common to all selected questionnaires, but there was a high level of concordance on the concepts represented in them. However, especially in terms of “activities and participation”, the emphasised aspects differed. Conclusions: The ICF provides an excellent common framework for the comparison of disease specific instruments for ankylosing spondylitis. For a future revision of the ICF, a specification of major limitations in patients with ankylosing spondylitis is suggested
Effect of interface mechanical properties on pull-out in a SiC fiber reinforced - LAS glass-ceramic matrix
No full text- …
