323,046 research outputs found
Charging the conformal window
No full textWe investigate the properties of near-conformal dynamics in a sector of large charge when
approaching the lower boundary of the conformal window from the chirally broken phase. To elucidate our approach we use the time-honored example of the phenomenologically relevant SU (2) color theory featuring Nf Dirac fermions transforming in the fundamental representation of the gauge group. In the chirally broken phase we employ the effective pion Lagrangian featuring also a pseudodilaton to capture a possible smooth conformal-to-nonconformal phase transition. We charge the baryon symmetry of the Lagrangian and study its impact on the ground state and spectrum of the theory as well as the would-be
conformal dimensions of the lowest large-charge operator. We moreover study the effects of and dependence on the fermion mass term
Near-conformal dynamics at large charge
No full textWe investigate four-dimensional near-conformal dynamics by means of the large-charge limit. We first introduce and justify the formalism in which near-conformal invariance is insured by adding a dilaton and then determine the large-charge spectrum of the theory. The dilaton can also be viewed as the radial mode of the effective field theory. We calculate the two-point functions of charged operators. We discover that the mass of the dilaton, parametrizing the near-breaking of conformal invariance, induces a novel term that is logarithmic in the charge. One can therefore employ the large-charge limit to explore near-conformal dynamics and determine dilaton-related properties
RV-detected planets around M dwarfs: Challenges for core accretion models
No full textPlanet formation is sensitive to the conditions in protoplanetary disks, for
which scaling laws as a function of stellar mass are known. We aim to test
whether the observed population of planets around low-mass stars can be
explained by these trends, or if separate formation channels are needed.
We address this question by confronting a state-of-the-art planet population
synthesis model with a sample of planets around M dwarfs observed by the HARPS
and CARMENES radial velocity (RV) surveys. To account for detection biases, we
performed injection and retrieval experiments on the actual RV data to produce
synthetic observations of planets that we simulated following the core
accretion paradigm.
These simulations robustly yield the previously reported high occurrence of
rocky planets around M dwarfs and generally agree with their planetary mass
function. In contrast, our simulations cannot reproduce a population of giant
planets around stars less massive than 0.5 solar masses. This potentially
indicates an alternative formation channel for giant planets around the least
massive stars that cannot be explained with current core accretion theories. We
further find a stellar mass dependency in the detection rate of short-period
planets. A lack of close-in planets around the earlier-type stars () in our sample remains unexplained by our model and
indicates dissimilar planet migration barriers in disks of different spectral
subtypes.
Both discrepancies can be attributed to gaps in our understanding of planet
migration in nascent M dwarf systems. They underline the different conditions
around young stars of different spectral subtypes, and the importance of taking
these differences into account when studying planet formation.Comment: Accepted for publication in A&A. 19 pages, 9 figure
Combined sample of clusters from Hunt and Reffert 2023 and YLAs from Gagné et al. 2018
No full textSub-sample of 254 clusters (Hunt+Reffert 2023) and 18 YLAs (Gagné+2018) analyzed in Swiggum+2024.
Columns are described below:
(0-63): Quantities reported by Hunt+Reffert (2023) Table A.1
(65) data_source,: Indicates original catalog source
(65) family: Assigned cluster family
(66) age_myr: age of cluster (Myr)
(67) rv_combined: median cluster RV from gaia/apogee/galah (km/s)
(68) x_helio: Heliocentric x position (pc)
(69) y_helio: Heliocentric y position(pc)
(70) z_helio: Heliocentric z position(pc)
(71) U: Heliocentric U velocity (km/s)
(72) V: Heliocentric V velocity (km/s)
(73) W: Heliocentric W velocity (km/s)
(74) x_helio_err: error in x_helio (pc)
(75) y_helio_err: error in y_helio (pc)
(76) z_helio_err: error in z_helio (pc)
(77) U_err: error in U (km/s)
(78) V_err: error in V (km/s)
(79) W_err: error in W (km/s)
(80) n_rv_combined: number of RVs
(81) mass_16: 16th percentile cluster mass estimate (Msun)
(82) mass_50: 50th percentile cluster mass estimate (Msun)
(83) mass_84: 84th percentile cluster mass estimate (Msun)
(84) n_sne_16: 16th percentile number of SNe
(85) n_sne_50: 50th percentile number of SNe
(86) n_sne_84: 84th percentile number of SNe
(87) n_stars_greater_8M_16: 16th percentile number of stars greater than 8Msun
(88) n_stars_greater_8M_50: 50th percentile number of stars greater than 8Msun
(89) n_stars_greater_8M_84: 84th percentile number of stars greater than 8Msun
(90) weight_score: average weight score assigned to cluster
(91) name_both: names of clusters; separated by a / if two names are given</p
Cluster analysis of signals from spectral activity indicators to search for shared periods
No full textContext. A multitude of spectral activity indicators are routinely computed nowadays from the spectra generated as part of planet-hunting radial velocity surveys. Searching for shared periods among them can help to robustly identify astrophysical quantities of interest, such as the stellar rotation period. However, this identification can be complicated due to the fact that many different peaks occur in the periodograms. This is especially true in the presence of aliasing and spurious signals caused by environmental influences affecting the instrument. Aims. Our goal is to test a clustering algorithm to find signals with the same periodicity, (i.e. with the stellar rotation period) in the periodograms of a large number of activity indicators. On this basis, we have looked to evaluate the correlations between activity indicators and fundamental stellar parameters. Methods. We used generalised Lomb–Scargle periodograms to find periodic signals in 24 activity indicators, spanning the VIS and NIR channels of the CARMENES spectrograph. Common periods were subsequently determined by a machine learning algorithm for density-based spatial clustering of applications with noise ( DBSCAN ). Results. The clustering analysis of the signals apparent in the spectral activity indicators is a powerful tool for the detection of stellar rotation periods. It is straightforward to implement and can be easily automated, so that large data sets can be analysed. For a sample of 136 stars, we were able to recover the stellar rotation period in a total of 59 cases, including 3 with a previously unknown rotation period. In addition, we analysed spurious signals frequently occurring at the period of one year and its integer fractions, concluding that they are likely aliases of one underlying signal. Furthermore, we reproduced the results of several previous studies on the relationships between activity indicators and the stellar characteristics
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Three planets around HD 27894: A close-in pair with a 2:1 period ratio and an eccentric Jovian planet at 5.4 AU
No full textAims. Our new program with HARPS aims to detect mean motion resonant planetary systems around stars which were previously reported to have a single bona fide planet, often based only on sparse radial velocity data.
Methods. Archival and new HARPS radial velocities for the K2V star HD 27894 were combined and fitted with a three-planet self-consistent dynamical model. The best-fit orbit was tested for long-term stability.
Results. We find clear evidence that HD 27894 is hosting at least three massive planets. In addition to the already known Jovian planet with a period Pb≈ 18 days we discover a Saturn-mass planet with Pc≈ 36 days, likely in a 2:1 mean motion resonance with the first planet, and a cold massive planet (≈5.3 MJup) with a period Pd ≈ 5170 days on a moderately eccentric orbit (ed = 0.39).
Conclusions. HD 27894 is hosting a massive, eccentric giant planet orbiting around a tightly packed inner pair of massive planets likely involved in an asymmetric 2:1 mean motion resonance. HD 27894 may be an important milestone for probing planetary formation and evolution scenarios.published_or_final_versio
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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