4,931 research outputs found
Duality and ontology
A âdualityâ is a formal mapping between the spaces of solutions of two empirically equivalent theories. In recent times, dualities have been found to be pervasive in string theory and quantum field theory. NaĂŻvely interpreted, duality-related theories appear to make very different ontological claims about the worldâdiffering in e.g. space-time structure, fundamental ontology, and mereological structure. In light of this, duality-related theories raise questions familiar from discussions of underdetermination in the philosophy of science: in the presence of dual theories, what is one to say about the ontology of the world? In this paper, we undertake a comprehensive and non-technical survey of the landscape of possible ontological interpretations of duality-related theories. We provide a significantly enriched and clarified taxonomy of optionsâseveral of which are novel to the literature
Age distribution of exoplanet host stars: Chemical and Kinematics age proxies from GAIA DR3
The GAIA space mission is impacting astronomy in many significant ways by
providing a uniform, homogeneous and precise data set for over 1 billion stars
and other celestial objects in the Milky Way and beyond. Exoplanet science has
greatly benefited from the unprecedented accuracy of stellar parameters
obtained from GAIA. In this study, we combine photometric, astrometric, and
spectroscopic data from the most recent Gaia DR3 to examine the kinematic and
chemical age proxies for a large sample of 2611 exoplanets hosting stars whose
parameters have been determined uniformly. Using spectroscopic data from the
Radial Velocity Spectrometer (RVS) onboard GAIA, we show that stars hosting
massive planets are metal-rich and -poor in comparison to stars hosting
small planets. The kinematic analysis of the sample reveals that the stellar
systems with small planets and those with giant planets differ in key aspects
of galactic space velocity and orbital parameters, which are indicative of age.
We find that the galactic orbital parameters have a statistically significant
difference of 0.06 kpc for and 0.03 for eccentricity respectively.
Furthermore, we estimated the stellar ages of the sample using the MIST-MESA
isochrone models. The ages and its proxies for the planet-hosting stars
indicate that the hosts of giant planetary systems are younger compared to the
population of stars harboring small planets. These age trends are also
consistent with the chemical evolution of the galaxy and the formation of giant
planets from the core-accretion process.Comment: Accepted for Publication in The Astronomical Journa
Rational invariants of even ternary forms under the orthogonal group
In this article we determine a generating set of rational invariants of
minimal cardinality for the action of the orthogonal group on
the space of ternary forms of even degree . The
construction relies on two key ingredients: On one hand, the Slice Lemma allows
us to reduce the problem to dermining the invariants for the action on a
subspace of the finite subgroup of signed permutations. On the
other hand, our construction relies in a fundamental way on specific bases of
harmonic polynomials. These bases provide maps with prescribed
-equivariance properties. Our explicit construction of these
bases should be relevant well beyond the scope of this paper. The expression of
the -invariants can then be given in a compact form as the
composition of two equivariant maps. Instead of providing (cumbersome) explicit
expressions for the -invariants, we provide efficient algorithms
for their evaluation and rewriting. We also use the constructed
-invariants to determine the -orbit locus and
provide an algorithm for the inverse problem of finding an element in
with prescribed values for its invariants. These are
the computational issues relevant in brain imaging.Comment: v3 Changes: Reworked presentation of Neuroimaging application,
refinement of Definition 3.1. To appear in "Foundations of Computational
Mathematics
Analytic Metaphysics versus Naturalized Metaphysics: The Relevance of Applied Ontology
The relevance of analytic metaphysics has come under criticism: Ladyman & Ross, for instance, have suggested do discontinue the field. French & McKenzie have argued in defense of analytic metaphysics that it develops tools that could turn out to be useful for philosophy of physics. In this article, we show first that this heuristic defense of metaphysics can be extended to the scientific field of applied ontology, which uses constructs from analytic metaphysics. Second, we elaborate on a parallel by French & McKenzie between mathematics and metaphysics to show that the whole field of analytic metaphysics, being useful not only for philosophy but also for science, should continue to exist as a largely autonomous field
Renal MRI diffusion: experimental protocol
Renal diffusion-weighted imaging (DWI) can be used to obtain information on the microstructure of kidney tissue, and has the potential to provide MR-biomarkers for functional renal imaging. Here we describe in a step-by-step experimental protocol the MRI method for measuring renal diffusion coefficients in rodents using ADC or IVIM models. Both methods provide quantification of renal diffusion coefficients; however, IVIM, a more complex model, allows for the calculation of the pseudodiffusion and fraction introduced by tissue vascular and tubular components. DWI provides information of renal microstructure contributing to the understanding of the physiology and the underlying processes that precede the beginning of pathologies.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis
uGMRT observations of the hot-Saturn WASP 69b: Radio-Loud Exoplanet-Exomoon Survey II (RLEES II)
Exomoons have so far eluded ongoing searches. Several studies have exploited
transit and transit timing variations and high-resolution spectroscopy to
identify potential exomoon candidates. One method of detecting and confirming
these exomoons is to search for signals of planet-moon interactions. In this
work, we present the first radio observations of the exomoon candidate system
WASP 69b. Based on the detection of alkali metals in the transmission spectra
of WASP-69b, it was deduced that the system might be hosting an exomoon. WASP
69b is also one of the exoplanet systems that will be observed as part of JWST
cycle-1 GTO. This makes the system an excellent target to observe and follow
up. We observed the system for 32 hrs at 150 MHz and 218 MHz using the upgraded
Giant Metrewave Radio Telescope (uGMRT). Though we do not detect radio emission
from the systems, we place strong upper limits of 3.3 mJy at 150 MHz
and 0.9 mJy at 218 MHz. We then use these upper limits to estimate the maximum
mass loss from the exomoon candidate.Comment: Accepted in MNRAS, 8 pages, 4 Figure
Associations between mothersâ perceptions of the cost of fruit and vegetables and childrenâs diets : Will children pay the price?
Background/Objectives: Perceptions that fruit and vegetables are expensive are more common among the socio-economically disadvantaged groups and are linked to poor dietary outcomes. Such perceptions may be exacerbated in countries recently affected by natural disasters, where devastation of fruit and vegetable crops has resulted in increase in prices of fruit and vegetables. Examining the associations of perceptions of fruit and vegetable affordability and children\u27s diets can offer insights into how the high prices of fruit and vegetables might have an impact on the diets of children.Subjects/Methods: We analysed the data from 546 socio-economically disadvantaged mother–child pairs to assess the relationship between maternal perceptions of fruit and vegetable affordability and the diets of their children.Results: Fruit consumption was lower among children whose mothers felt the cost of fruit was too high. Maternal perceptions of fruit and vegetable affordability were not associated with any other aspect of child\u27s diet.Conclusions: Our results suggest a possible role for maternal perceptions of fruit affordability in children\u27s diet, though further research is warranted.<br /
Fundamental representations and algebraic properties of biquaternions or complexified quaternions
The fundamental properties of biquaternions (complexified quaternions) are
presented including several different representations, some of them new, and
definitions of fundamental operations such as the scalar and vector parts,
conjugates, semi-norms, polar forms, and inner and outer products. The notation
is consistent throughout, even between representations, providing a clear
account of the many ways in which the component parts of a biquaternion may be
manipulated algebraically
PVA-PSSA Membrane with Interpenetrating Networks and its Methanol Crossover Mitigating Effect in DMFCs
Identifying the population of T-Tauri stars in Taurus: UV-optical synergy
With the third data release of the Gaia mission DR3 with its precise
photometry and astrometry, it is now possible to study the behaviour of stars
at a scale never seen before. In this paper, we developed new criteria to
identify T-Tauri stars (TTS) candidates using UV and optical CMDs by combining
the GALEX and Gaia surveys. We found 19 TTS candidates and 5 of them are newly
identified TTS in the Taurus Molecular Cloud (TMC), not catalogued before as
TMC members. For some of the TTS candidates, we also obtained optical spectra
from several Indian telescopes. We also present the analysis of the distance
and proper motion of young stars in the Taurus using data from DR3. We
found that the stars in Taurus show a bimodal distribution with distance,
having peaks at pc and pc. The
reason for this bimodality, we think, is due to the fact that different clouds
in the TMC region are at different distances. We further show that the two
populations have similar ages and proper motion distribution. Using the
DR3 colour-magnitude diagram, we show that the age of Taurus is consistent with
1 Myr.Comment: 13 pages, 10 figure
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