The Λ Cold Dark Matter model (ΛCDM) represents the current standard model in cosmology. Within this, there is a tension between the value of the Hubble constant, H0, inferred from local distance indicators and the angular scale of fluctuations in the Cosmic Microwave Background (CMB). In terms of Bayseian evidence, we investigate whether the tension is significant enough to warrant new physics in the form of modifying or adding energy components to the standard cosmological model. We find that late time dark energy explanations are not favoured by data whereas a pre-CMB decoupling extra dark energy component has a positive, although not substantial, Bayesian evidence. A constant equation of state of the additional early energy density is constrained to 0.086+0.04−0.03. Although this value deviates significantly from 1/3, valid for dark radiation, the latter is favoured based on the Bayesian evidence. If the tension persists, future estimates of H0 at the 1% level will be able to decisively determine which of the proposed explanations is favoured.
The PTOLEMY project aims to develop a scalable design for a Cosmic Neutrino Background (CNB) detector, the first of its kind and the only one conceived that can look directly at the image of the Universe encoded in neutrino background produced in the first second after the Big Bang. The scope of the work for the next three years is to complete the conceptual design of this detector and to validate with direct measurements that the non-neutrino backgrounds are below the expected cosmological signal. In this paper we discuss in details the theoretical aspects of the experiment and its physics goals. In particular, we mainly address three issues. First we discuss the sensitivity of PTOLEMY to the standard neutrino mass scale. We then study the perspectives of the experiment to detect the CNB via neutrino capture on tritium as a function of the neutrino mass scale and the energy resolution of the apparatus. Finally, we consider an extra sterile neutrino with mass in the eV range, coupled to the active states via oscillations, which has been advocated in view of neutrino oscillation anomalies. This extra state would contribute to the tritium decay spectrum, and its properties, mass and mixing angle, could be studied by analyzing the features in the beta decay electron spectrum.
V. P. Shcherbakov, F. Lhuillier, S. K. Gribov
et al.
Abstract Volcanic rocks, preserving paleorecords of Earth's magnetic field, are essential to constrain the working of the geodynamo, provided their primary signal was not biased. Using a thermomagnetometer, we simulate a situation where a sample's primary record, carried by a thermoremanence (TRM, acquired by cooling in air from 600°C to room temperature), is partly overprinted by a chemical remanence (CRM, acquired by 200 hr of isothermal exposure at 400°C). This situation leads to two directional and intensity components (in the form of linear segments) in the Zijderveld and Arai‐Nagata diagrams. In the case of unstable titanomagnetite grains prior to CRM acquisition, we show that both components can be strongly biased by up to ∼50° for paleodirections and ∼50% for paleointensities. In such a worst‐case scenario, the secondary CRM strongly overprints the primary TRM, rendering the common interpretation of Zijderveld and Arai‐Nagata diagrams in terms of characteristic components invalid.
This study addresses the problem of finding the optimal correspondence for a given synthetic aperture radar (SAR) image patch from a large collection of optical reference patches, which is crucial for various applications, including remote sensing, place recognition, and aircraft navigation. However, achieving one-to-one SAR-Optical patch correspondence is challenging due to the distinct modal discrepancy and the poor discriminability of the target instances. To address these challenges, we propose a cross-modal patch correspondence scheme that consists of two modules: A retrieval-based coarse search module and a correspondence refinement module. Specifically, to explicitly represent the modal discrepancy, we first introduce a cross-modal adversarial learning strategy in the coarse search module and learn the modal-invariant feature embedding for retrieval. Furthermore, to improve the instance discriminability of retrieved candidates, we propose a graph representation in the refinement module to integrate the visual and spatial information, which is finally fed to an attention graph network to estimate the optimal correspondence. To evaluate the effectiveness of the proposed scheme, we also propose three new SAR-Optical patch correspondence datasets. Comprehensive experiments show that our approach significantly outperforms the competitors on all three datasets.
Abstract The evolution of tropical sea surface temperatures (SSTs) in response to greenhouse warming is of great societal and scientific interest. Most state‐of‐the‐art climate models predict a mean “El Niño‐like” warming pattern by century‐end, characterized by greater warming over the Pacific cold tongue compared to the western warm pool. However, it is unclear which proposed mechanism dominates in this response. Here, we present partially coupled abrupt CO2 doubling experiments in which surface wind stress and shortwave heating are overridden to values from a control simulation. Contrary to previous studies, we find that experiments with overriding of surface wind stress exhibit only 58% of the full reduction in east‐west SST contrast. When both surface wind stress and shortwave flux are overridden, only 34% of the full reduction remains, controlled by spatially‐varying evaporative cooling. These results underscore the importance of Bjerknes and shortwave feedbacks in the tropical Pacific SST response to global warming.
The physical motivations, present status, main results in study of cosmic rays and in the field of gamma-ray astronomy as well future plans of the TAIGA-1 (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) project are presented. The TAIGA observatory addresses ground-based gamma-ray astronomy and astroparticle physics at energies from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV. The pilot TAIGA-1 complex is located in the Tunka valley, ~50 km west from the southern tip of the lake Baikal.
More convolutional neural network (CNN) methods are widely utilized for ship detection in synthetic aperture radar (SAR) images. Nevertheless, there are still some problems that need to be addressed. First, detection methods may misclassify islands and onshore objects as ships. Second, due to the large scale and low resolution, a majority of ships are regarded as small targets and difficult to detect. Third, due to the different sizes of ships, the hyperparameters of anchor-based methods are difficult to set. Thus, we propose an anchor-free method called improved fully convolutional one-stage object detector (Improved-FCOS) to solve these problems. First, a multilevel feature attention mechanism is proposed to extract effective features and collect global context information. Second, we propose a feature refinement and reuse module with two stages to refine small ship features. Third, a head improvement module is designed to optimize the methods for classification and localization of ship targets. Finally, a modified varifocal loss is adopted to better train the classification branch. We conduct ablation experiments on LS-SSDD-v1.0 and verify the detection performance of the proposed modules. Additionally, we compare the Improved-FCOS with other state-of-the-art methods by experiments on three datasets, including the SAR-Ship-Dataset, HRSID, and LS-SSDD-v1.0. Detection results show that Improved-FCOS obtains the best detection performance on all datasets and indicate that the Improved-FCOS is more accurate and robust.
Esta contribución es una breve reseña del libro “Sistemas Fluviales: Organización, Evolución e Importancia Económica”, que fuera publicado por la Asociación Geológica Argentina gracias al trabajo del Dr. José Matildo Paredes. El libro está estructurado en diez capítulos que tratan una amplia variedad de conceptos de los sistemas fluviales, principalmente de índole sedimentológica y estratigráfica, a diferentes escalas de análisis. En esta reseña se realiza una descripción sucinta y crítica de los temas abordados en cada capítulo, enfatizando aquellos tópicos más relevantes para la comprensión de la dinámica de estos ambientes particularmente complejos.
It has been shown a specific Horndeski theory of gravity arises from a consistent Kaluza-Klein reduction of the gravi-dilaton sector of the low-energy effective heterotic string action with a first α' correction. Here we provide a first investigation of the cosmological solutions to the lower dimensional theory by constructing exact solutions to the field equations in various frames. At tree level, in string frame, we find the duality symmetry of the parent theory is unaltered by dimensional reduction, leading to standard bouncing and pre-Big Bang scenario solutions. For α'≠0, we uncover exact models exhibiting cosmic acceleration, where we find interesting physics concerning the number of noncompact dimensions. Certain stability requirements demand the inclusion of a dilaton potential.
The most exciting future observation in cosmology will feature a monitoring of the cosmic expansion in real time, unlike anything that has ever been attempted before. This campaign will uncover crucial physical properties of the various constituents in the universe, and perhaps answer a simpler question concerning whether or not the cosmic expansion is even accelerating. An unambiguous yes/no response to this query will significantly impact cosmology, of course, but also the standard model of particle physics. Here, we discuss—in a straightforward way—how to understand the so-called ‘redshift drift’ sought by this campaign, and why its measurement will help us refine the standard-model parameters if the answer is ‘yes.’ A ‘no’ answer, on the other hand, could be more revolutionary, in the sense that it might provide a resolution of several long-standing problems and inconsistencies in our current cosmological models. An outcome of zero redshift drift, for example, would obviate the need for a cosmological constant and render inflation completely redundant.
The epoch of Cosmic Dawn, when the first stars and galaxies were born, is widely considered as the final frontier of observational cosmology today. Mapping the period between Cosmic Dawn and the present-day provides access to more than 90% of the baryonic (normal) matter in the universe, and unlocks several thousand times more Fourier modes of information than available in today’s cosmological surveys. We review the progress in modeling baryonic gas observations as tracers of the cosmological large-scale structure from Cosmic Dawn to the present day. We illustrate how the description of dark matter haloes can be extended to describe baryonic gas abundances and clustering. This innovative approach allows us to fully utilize our current knowledge of astrophysics to constrain cosmological parameters from future observations. Combined with the information content of multi-messenger probes, this will also elucidate the properties of the first supermassive black holes at Cosmic Dawn. We present a host of fascinating implications for constraining physics beyond the [Formula: see text]CDM model, including tests of the theories of inflation and the cosmological principle, the effects of nonstandard dark matter, and possible deviations from Einstein’s general relativity on the largest scales.
Se estudió la geomorfología submarina y se efectuaron mediciones de corrientes de marea en el canal San Blas para determinar la dinámica sedimentaria actual. Se relevó un sector del fondo del canal con el sistema batimétrico GeoSwath para describir exhaustivamente la morfología de un campo de dunas. Su asimetría permite inferir un transporte residual del material del fondo hacia el interior de la Bahía Anegada sobre el veril NE del canal. Se realizó un estudio de la dinámica de las corrientes de marea, determinándose sus velocidades y direcciones durante un ciclo completo de marea en toda la columna de agua y a lo largo de un perfil transversal a la costa mediante un ADCP. A pesar que el ambiente corresponde a un régimen micromareal (rango de marea alrededor de 2 m), en el canal San Blas existen fuertes corrientes de marea que desde el sector medio transportan todo el material inconsolidado del fondo, formando un delta de reflujo en la boca externa del canal y un delta de flujo en la Bahía Anegada. Se reconocieron diferentes geoformas costeras que permiten inferir un transporte litoral hacia el exterior del canal sobre la costa sur del mismo. Basándose en sus características morfodinámicas, es posible definir el canal San Blas como una entrada de marea que conecta el mar abierto con la Bahía Anegada.
In the quest for unification of the Standard Model with gravity, classical scale invariance can be utilized to dynamically generate the Planck mass MPl. However, the relation of Planck scale physics to the scale of electroweak symmetry breaking μH requires further explanation. In this paper, we propose a model that uses the spontaneous breaking of scale invariance in the scalar sector as a unified origin for dynamical generation of both scales. Using the Gildener-Weinberg approximation, only one scalar acquires a vacuum expectation value of υS ∼ (1016−17) GeV, thus radiatively generating MP1≈βS1/2υS\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {M}_{\mathrm{P}1}\approx {\beta}_S^{1/2}{\upsilon}_S $$\end{document} and μH via the neutrino option with right handed neutrino masses mN = yMυS ∼ 107 GeV. Consequently, active SM neutrinos are given a mass with the inclusion of a type-I seesaw mechanism. Furthermore, we adopt an unbroken Z2 symmetry and a Z2-odd set of right-handed Majorana neutrinos χ that do not take part in the neutrino option and are able to produce the correct dark matter relic abundance (dominantly) via inflaton decay. The model also describes cosmic inflation and the inflationary CMB observables are predicted to interpolate between those of R2 and linear chaotic inflationary model and are thus well within the strongest experimental constraints.
Cosmic censorship is known to fail in some well-controlled phenomena, calling into question the predictive power of General Relativity and opening up the possibility of observing Planck-scale physics. We propose that the cosmic censorship conjecture can be amended so that its spirit prevails. Naked singularities that, classically, have zero mass are allowed. Physically, these are Planck-sized “black holes”, which evaporate in a few Planck times. General Relativity fails only for a tiny interval in time, to then quickly regain control in a Miltonian evolution that returns us to the predictive paradise of Einstein’s equations. If this refinement of the conjecture is correct, then, even though Nature does allow to expose breakdowns in the smooth fabric of spacetime, it limits them to a mostly harmless minimum.