Abrikosov, Gorkov, Dzyaloshinski, Methods of quantum field theory in statistical physics Fetter, Walecka, Quantum theory of many-particle systems T. Schaefer, Quark Matter, hep-ph/0304281. J. Kogut, M. Stephanov, The Phases of QCD, Cambridge University Press (2004). K. Rajagopal, F. Wilczek, The Condensed Matter Physics of QCD, hep-ph/0011333. J. Lattimer and M. Prakash, The Physics of Neutron Stars, astro-ph/0405262. D. Kaplan, Five lectures on effective field theory, nucl-th/0510023.
The orbital solutions for astrometric (unresolved) binary stars provided in the Gaia mission Data Release 3 reveal an obvious deficit of face-on orbits with line-of-sight inclinations close to 0 or $π$. This is shown to be an intrinsic mathematical feature of the orbit estimation technique involving the intermediate Thiele-Innes parameters, which are transformed to the Campbell geometric parameters. A direct condition equation defining the inclination angle via the Thiele-Innes values independently of the other orbital elements is used to investigate the origin of this near-degeneracy for face-on orbits. The emerging bias and correlation of inclination and semimajor axis are illustrated using Monte Carlo simulations for two specific template configurations representing face-on and edge-on orbits. The results have significant impact on the interpretation and follow-up confirmation of Gaia-detected binary systems, including candidate exoplanets and brown dwarf companions.
The existence of a deficit of brown dwarfs (BDs) in close orbit around main-sequence stars is one of the most intriguing questions in stellar physics. This so-called BD desert may result from the transition between two different dominant formation processes occurring for different mass regimes. While the BD mass derived from radial-velocity measurements helps confirm the nature of the analyzed objects, the BD radius obtained from transits is important to better constrain the BD age, as BDs are believed to contract with age. Such objects with well-constrained parameters, although in small number, are of prime interest for deeper investigations of BD structure and chemical composition. The present document aims at presenting the first results of a search for BD transits among a sample of approximately 3300 host star candidates observed by the Transiting Exoplanet Survey Satellite during Cycle 6.
Jagodish C. Sarker, Tannith-Jade Cole, Xiang Xu
et al.
Diaryldithiocarbamate complexes, [Fe(S2CNAr2)3], have been prepared and their structure, reactivity, and thermal degradation to afford iron sulfide nanomaterials have been investigated. The addition of three equivalents of LiS2CNAr2 to FeCl2·4H2O in water-air affords dark red [Fe(S2CNAr2)3] in high yields. All show magnetic measurements consistent with a predominantly high-spin electronic arrangement at room temperature. The molecular structure of [Fe{S2C(N-p-MeOC6H4)2}3] reveals the expected distorted octahedral geometry, but Fe-S distances are more consistent with a low-spin electronic configuration, likely a result of the low temperature (120 K) of the data collection. The thermal stability of [Fe{S2C(N-p-MeC6H4)2}3] has been investigated. TGA shows that it begins to decompose at a significantly lower temperature (ca. 160 °C) than previously observed for [Fe(S2CNEt2)3], and this is further lowered (to ca. 100 °C) in oleylamine. The decomposition of [Fe{S2C(N-p-MeC6H4)2}3] in oleylamine, via either a heat-up or hot injection process, affords nanoparticles of Fe3S4 (greigite), while in contrast, dry heating at 450 °C affords FeS (troilite) as large agglomerates.
This paper explores the potential of contextualized word embeddings (CWEs) as a new tool in the history, philosophy, and sociology of science (HPSS) for studying contextual and evolving meanings of scientific concepts. Using the term"Planck"as a test case, I evaluate five BERT-based models with varying degrees of domain-specific pretraining, including my custom model Astro-HEP-BERT, trained on the Astro-HEP Corpus, a dataset containing 21.84 million paragraphs from 600,000 articles in astrophysics and high-energy physics. For this analysis, I compiled two labeled datasets: (1) the Astro-HEP-Planck Corpus, consisting of 2,900 labeled occurrences of"Planck"sampled from 1,500 paragraphs in the Astro-HEP Corpus, and (2) a physics-related Wikipedia dataset comprising 1,186 labeled occurrences of"Planck"across 885 paragraphs. Results demonstrate that the domain-adapted models outperform the general-purpose ones in disambiguating the target term, predicting its known meanings, and generating high-quality sense clusters, as measured by a novel purity indicator I developed. Additionally, this approach reveals semantic shifts in the target term over three decades in the unlabeled Astro-HEP Corpus, highlighting the emergence of the Planck space mission as a dominant sense. The study underscores the importance of domain-specific pretraining for analyzing scientific language and demonstrates the cost-effectiveness of adapting pretrained models for HPSS research. By offering a scalable and transferable method for modeling the meanings of scientific concepts, CWEs open up new avenues for investigating the socio-historical dynamics of scientific discourses.
As machine learning algorithms become increasingly accessible, a growing number of organizations and researchers are using these technologies to automate the process of exoplanet detection. These mainly utilize Convolutional Neural Networks (CNNs) to detect periodic dips in lightcurve data. While having approximately 5% lower accuracy than CNNs, the results of this study show that One-Class Support Vector Machines (SVMs) can be fitted to data up to 84 times faster than simple CNNs and make predictions over 3 times faster on the same datasets using the same hardware. In addition, One-Class SVMs can be run smoothly on unspecialized hardware, removing the need for Graphics Processing Unit (GPU) usage. In cases where time and processing power are valuable resources, One-Class SVMs are able to minimize time spent on transit detection tasks while maximizing performance and efficiency.
William H. Skinner, Nicola Robinson, Gareth R. Hardisty
et al.
SERS microsensors (SERS-MS) are polymer microparticles coated in gold nanoparticles and functionalised with mercaptobenzoic acid. SERS-MS were incorporated into human airway organoids to measured pH optically.
Após o desenvolvimento do Modelo Padrão da Cosmologia, o Modelo do Big Bang, ao que tudo indicava, havia-se construído uma teoria satisfatória capaz de descrever a evolução do Universo a partir de um estado quente e denso inicial. No entanto, algumas questões em aberto levaram à proposta do modelo da Inflação Cosmológica, o qual descreve uma expansão acelerada no Universo antigo que teria durado uma fração de segundo, e após a qual o Universo teria seguido sua expansão conforme previsto pelo Modelo do \textit{Big Bang}. Embora hoje existam alternativas à Inflação que são capazes de resolver as mesmas questões, a Inflação foi a primeira teoria com a qual foi possível se fazer previsões consistentes sobre a estrutura do Universo em larga escala, como a distribuição de galáxias, aglomerados etc., ao fornecer uma descrição para a origem das mesmas. Neste artigo será apresentado o Modelo Inflacionário, desde uma perspectiva histórica e também matemática. Serão abordadas as críticas e desafios que acercam este modelo atualmente e também as perspectivas futuras no que se refere a testes do modelo inflacionário com os novos experimentos.
Apresentamos neste artigo um panorama da nucleossíntese cosmológica, estelar e catastrófica que leva a povoar a Tabela Periódica do elementos criada por D. Mendeleev há mais de um século.
In a recent paper (Chabrier et al. 2019), we have derived a new equation of state (EOS) for dense hydrogen/helium mixtures which covers the temperature-density domain from solar-type stars to brown dwarfs and gaseous planets. This EOS is based on the so-called additive volume law and thus does not take into account the interactions between the hydrogen and helium species. In the present paper, we go beyond these calculations by taking into account H/He interactions, derived from quantum molecular dynamics simulations. These interactions, which eventually lead to H/He phase separation, become important at low temperature and high density, in the domain of brown dwarfs and giant planets. The tables of this new EOS are made publicly available.
Geoffrey W. Marcy, Nathaniel K. Tellis, Edward H. Wishnow
A search was conducted for laser signals, both sub-second pulses and continuous emission, from the regions of the sky opposite Proxima and Alpha Centauri. These regions are located at the foci of the gravitational lensing caused by the Sun, ideal for amplifying transmissions between our Solar System and those two nearest stellar neighbors. During six months in 2020 and 2021, 88000 exposures for Proxima Cen and 47000 exposures for Alpha Cen were obtained. No evidence was detected of light pulses or continuous laser emission in the wavelength range of 380 to 950 nm. We would have detected a laser having a power of just 100 Watts.
Um quarto do conteúdo energético do Universo está na forma de matéria escura. A natureza dessa matéria ainda é um enigma, mas há poucas dúvidas de que sua solução requer uma extensão do modelo padrão da física de partículas, com a inclusão de novas partículas elementares e talvez novas interações. Após rever algumas evidências cosmológicas indicando a existência dessa componente escura do cosmos, mostramos como as ferramentas teóricas já disponíveis podem ser utilizadas para explicar sua origem no Universo primordial, e discutimos brevemente alguns dos cenários de candidatos mais promissores a essa forma de matéria. Uma importante conclusão é que o estudo desse setor escuro pode lançar nova luz sobre alguns dos enigmas relacionados ao comportamento da matéria bariônica usual.
KIC 5773205 is the least luminous eclipsing M dwarf found in the Villanova catalog of eclipsing binaries detected by the {\it Kepler} mission. We processed and analyzed the three available quarters of mission data for this star and discovered a persistent periodic variation of the light curve with a period, which is in exact 4:5 commensurability to the orbital period. Three routes of interpretation are considered: 1) non-radial pulsations excited by the tidal interaction at a specific eigenfrequency; 2) a high-order spin-orbit resonance caused by the tides; 3) an ellipsoidal deformation caused by an outer orbiting companion in a mean motion resonance. All three explanations meet considerable difficulties, but the available facts seem to favor the tidally driven pulsation scenario. The star may represent a new type of heartbeat binary with tidally excited pulsations that are close to the orbital motion in frequency.
We use a simplified model to study wave reflection and transmission at interface of convective region and stably stratified region (e.g. radiative zone in star or stratification layer in gaseous planet). Inertial wave in convective region and gravito-inertial wave in stably stratified region are considered. We begin with polar area and then extend to any latitude. Six cases are discussed (see Table 1), and in Case 2 both waves co-exist in both regions. Four configurations are further discussed for Case 2. The angles and energy ratios of wave reflection and transmission are calculated. It is found that wave propagation and transmission depend on the ratio of buoyancy frequency to rotational frequency. In a rapidly rotating star or planet wave propagates across interface and most of energy of incident wave is transmitted to the other region, but in a slowly rotating star or planet wave transmission is inhibited.
We present a fix to the overdamping problem found by Laibe & Price (2012) when simulating strongly coupled dust-gas mixtures using two different sets of particles using smoothed particle hydrodynamics. Our solution is to compute the drag at the barycentre between gas and dust particle pairs when computing the drag force by reconstructing the velocity field, similar to the procedure in Godunov-type solvers. This fixes the overdamping problem at negligible computational cost, but with additional memory required to store velocity derivatives. We employ slope limiters to avoid spurious oscillations at shocks, finding the van Leer Monotonized Central limiter most effective.
Diego Lorenzo-Oliveira, Jorge Meléndez, Geisa Ponte
et al.
We present a detailed analysis of the possible future Sun's rotational evolution scenario based on the 8 Gyr-old solar twin HIP 102152. Using HARPS high-cadence observations (and TESS light curves), we analyzed the modulation of a variety of activity proxies (Ca II, HI Balmer, and Na I lines), finding a strong rotational signal of 35.7 $\pm$ 1.4 days ($\log B_{\rm factor}\sim70$, in the case of Ca II K line). This value matches with the theoretical expectations regarding the smooth rotational evolution of the Sun towards the end of the main-sequence, validating the use of gyrochronology after solar age.
Chloe Beddingfield, Cheng Li, Sushil Atreya
et al.
Ice giants are the only unexplored class of planet in our Solar System. Much that we currently know about these systems challenges our understanding of how planets, rings, satellites, and magnetospheres form and evolve. We assert that an ice giant Flagship mission with an atmospheric probe should be a priority for the decade 2023-2032.