Summary of this volume: The 14th Asia-Pacific Physics Conference 2019 (APPC14) held in November 2019 is the 14th in the series of APPC organized by the Association of Asia-Pacific Physical Societies. For the first time, the APPC is organized together with the divisions of Plasma Physics (DPP), Astrophysics, Cosmology and Gravitation (DACG), and Nuclear Physics (DNP). These proceedings consist of more than 80 research papers encompassing the following topics, including: astrophysics, cosmology and gravitation, nuclear physics, plasma physics, condensed matter, particle physics, strongly correlated electron systems, optics and lasers, synchrotron radiation, complex systems, mathematical physics and computational physics, biological and medical physics, physics education, women in physics, and quantum information. It provides insight on research activities in the region.
Several questions arise from the existence of such a structure. First, is it significant enough on the surface-layer heat budget to allow the formation of large-scale SST warm anomalies? Then, what allows such a structure to appear and persist on a seasonal timescale? In order to maintain a BL, the water of the mixed layer has to remain at the same temperature as the underlying BL. Does the net surface heat flux need to be close to zero in the WP in order to maintain the weak vertical temperature gradient between the surface layer and the BL as suggested by Lukas and Lindstrm (1991)? This study tries to address these questions using OGCM simulations. This paper (Part I) investigates the role of salinity in the physics of the WP warm and fresh pool. The modeling framework and the surface forcings are presented. Of course the large-scale modeling technique has its limits and some of them might be reached in this study of the fine mixed layer processes of the WP where high frequency and small-scale processes might be important (e.g., Tomczack 1995; Chen and Rohstein 1991). Much care will thus be taken in this paper to test the sensitivity of the simulated processes to the forcing and the resolution. Robust results of this study include the trapping of atmospheric fluxes in the surface layer of the warm pool by haline stratification, the role of the penetrative solar heat flux in the heat budget of the upper layers of the WP, and the impact of the BL on entrainment fluxes, especially near the equator. An associated paper (Part II, this issue) goes more deeply into the details of the large-scale BL formation processes and interannual variability.
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This paper is organized as follows. Section 2 describes the modeling approach. The simulated circulation and its sensitivity to the forcing and to some model parameters are described in section 3. The sensitivity of the vertical mixing to the haline stratification gives some insights on the role of the salinity in the physics of the warm pool. In section 4, the upper-layer structure of the warm pool is examined. A BL structure is found in the model results and its impact on the upper-layer heat budget is analyzed. Section 5 summarizes the more important results of this study. The uncertainties and shadow areas that remain are then discussed in section 6.
The Publications of the Astronomical Society of the Pacific publishes original research in astronomy and astrophysics; innovations in instrumentation, data analysis, and software; tutorials, dissertation summaries, and conference summaries; and invited reviews on contemporary topics.
The James Webb Space Telescope (JWST) is a large, infrared space telescope that has recently started its science program which will enable breakthroughs in astrophysics and planetary science. Notably, JWST will provide the very first observations of the earliest luminous objects in the universe and start a new era of exoplanet atmospheric characterization. This transformative science is enabled by a 6.6 m telescope that is passively cooled with a 5 layer sunshield. The primary mirror is comprised of 18 controllable, low areal density hexagonal segments, that were aligned and phased relative to each other in orbit using innovative image-based wave front sensing and control algorithms. This revolutionary telescope took more than two decades to develop with a widely distributed team across engineering disciplines. We present an overview of the telescope requirements, architecture, development, superb on-orbit performance, and lessons learned. JWST successfully demonstrates a segmented aperture space telescope and establishes a path to building even larger space telescopes.
The Vera C. Rubin Legacy Survey of Space and Time (LSST) holds the potential to revolutionize time domain astrophysics, reaching completely unexplored areas of the Universe and mapping variability time scales from minutes to a decade. To prepare to maximize the potential of the Rubin LSST data for the exploration of the transient and variable Universe, one of the four pillars of Rubin LSST science, the Transient and Variable Stars Science Collaboration, one of the eight Rubin LSST Science Collaborations, has identified research areas of interest and requirements, and paths to enable them. While our roadmap is ever-evolving, this document represents a snapshot of our plans and preparatory work in the final years and months leading up to the survey's first light.
The calculation of the molecular column density from molecular spectral (rotational or ro-vibrational) transition measurements is one of the most basic quantities derived from molecular spectroscopy. Starting from first principles where we describe the basic physics behind the radiative and collisional excitation of molecules and the radiative transfer of their emission, we derive a general expression for the molecular column density. As the calculation of the molecular column density involves a knowledge of the molecular energy level degeneracies, rotational partition functions, dipole moment matrix elements, and line strengths, we include generalized derivations of these molecule-specific quantities. Given that approximations to the column density equation are often useful, we explore the optically thin, optically thick, and low-frequency limits to our derived general molecular column density relation. We also evaluate the limitations of the common assumption that the molecular excitation temperature is constant and address the distinction between beam-averaged and source-averaged column densities. As non-LTE approaches to the calculation of molecular spectral line column density have become quite common, we summarize non-LTE models that calculate molecular cloud volume densities, kinetic temperatures, and molecular column densities. We conclude our discussion of the molecular column density with worked examples for C18O, C17O, N2H+, NH3, and H2CO. Ancillary information on some subtleties involving line profile functions, conversion between integrated flux and brightness temperature, the calculation of the uncertainty associated with an integrated intensity measurement, the calculation of spectral line optical depth using hyperfine or isotopologue measurements, the calculation of the kinetic temperature from a symmetric molecule excitation temperature measurement, and relative hyperfine intensity calculations for NH3 are presented in appendices. The intent of this document is to provide a reference for researchers studying astrophysical molecular spectroscopic measurements.
Stars strongly impact their environment, and shape structures on all scales throughout the universe, in a process known as "feedback." Due to the complexity of both stellar evolution and the physics of larger astrophysical structures, there remain many unanswered questions about how feedback operates and what we can learn about stars by studying their imprint on the wider universe. In this white paper, we summarize discussions from the Lorentz Center meeting "Bringing Stellar Evolution and Feedback Together" in 2022 April and identify key areas where further dialog can bring about radical changes in how we view the relationship between stars and the universe they live in.
Modern cosmology is broadly based on the Cosmological principle, which assumes homogeneity and isotropy as its foundational pillars. Thus, there is not much debate about the metric (i.e., Friedmann-Lematre-Robertson-Walker; FLRW) one should use to describe the cosmic spacetime. But Einstein's equations do not unilaterally constrain the constituents in the cosmic fluid, which directly determine the expansion factor appearing in the metric coefficients. As its name suggests, CDM posits that the energy density is dominated by a blend of dark energy (typically a cosmological constant, ), cold dark matter (and a "contamination" of baryonic matter) and radiation. Many would assert that we have now reached the age of "precision" cosmology, in which measurements are made merely to refine the excessively large number of free parameters characterizing its empirical underpinnings. But this mantra glosses over a growing body of embarrassingly significant failings, not just "tension" as is sometimes described, as if to somehow imply that a resolution will eventually be found. In this paper, we take a candid look at some of the most glaring conflicts between the standard model, the observations, and several foundational principles in quantum mechanics, general relativity and particle physics. One cannot avoid the conclusion that the standard model needs a complete overhaul in order to survive. be457b7860
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