Secular Expansion Research Articles

Energy dissipation in synchronous binary asteroids

Synchronous binary asteroids can experience libration about their tidally-locked equilibrium, which will result in energy dissipation. This is an important topic to the Asteroid Impact and Deflection Assessment, where excitation caused by the DART kinetic impact in the Didymos binary asteroid system may be reduced through dissipation before Hera arrives to survey the effects of the impact. We develop a numeric model for energy dissipation in binary asteroids to explore how different system configurations affect the rate of energy dissipation. We find tumbling within the synchronous state eliminates a systematic trend in libration damping on short timescales (several years), but not over long times (hundreds of years) depending on the material conditions. Furthermore, damping of libration, eccentricity, and fluctuations in the semimajor axis are primarily dependent on the stiffness of the secondary, whereas the semimajor axis secular expansion rate is dictated by the stiffness of the primary, as expected. Systems experiencing stable planar libration in the secondary can see a noticeable reduction in libration amplitude after only a few years depending on the stiffness of the secondary, and thus dissipation should be considered during Hera’s survey of Didymos. For a very dissipative secondary undergoing stable libration, Hera may be able to calculate the rate of libration damping in Dimorphos and therefore constrain its tidal parameters.

Monetary solidarity in Europe: can divisive institutions become ‘moral opportunities’?

How does the inherent norm of integration, notably to share risks among its members in good faith, become a self-sustaining practice? I address this question generally and for a critical case of a divisive institution, i.e. the evolution of sovereign bailout funding in the Euro Area since 2010. Community building between states is a potential outcome of solidaristic practices, reinforced by positive feedback processes. Inspired by Deborah Stone’s [Stone, D. A. (1999). Beyond moral hazard: Insurance as moral opportunity. Connecticut Insurance Law Journal, 6(1), 12–46] work on insurance, I demonstrate that there are social mechanisms at play that favour the secular expansion of risk sharing between states.

Baryon-driven decontraction in Milky Way-mass haloes

ABSTRACT We select a sample of Milky Way (MW) mass haloes from a high-resolution version of the EAGLE simulation to study their inner dark matter (DM) content and how baryons alter it. As in previous studies, we find that all haloes are more massive at the centre compared to their dark matter-only (DMO) counterparts at the present day as a result of the dissipational collapse of baryons during the assembly of the galaxy. However, we identify two processes that can reduce the central halo mass during the evolution of the galaxy. First, gas blowouts induced by active galactic nuclei feedback can lead to a substantial decrease of the central DM mass. Secondly, the formation of a stellar bar and its interaction with the DM can induce a secular expansion of the halo; the rate at which DM is evacuated from the central region by this process is related to the average bar strength, and the time-scale on which it acts determines how much the halo has decontracted. Although the inner regions of the haloes we have investigated are still more massive than their DMO counterparts at z = 0, they are significantly less massive than in the past and less massive than expected from the classic adiabatic contraction model. Since the MW has both a central supermassive black hole and a bar, the extent to which its halo has contracted is uncertain. This may affect estimates of the mass of the MW halo and of the expected signals in direct and indirect DM detection experiments.

Mapping the Galactic disc with the LAMOST and Gaia red clump sample: II. 3D asymmetrical kinematics of mono-age populations in the disc between 6–14 kpc

ABSTRACT We perform analysis of the 3D kinematics of Milky Way disc stars in mono-age populations. We focus on stars between Galactocentric distances of R = 6 and 14 kpc, selected from the combined LAMOST Data Release 4 (DR4) red clump giant stars and Gaia DR2 proper motion catalogue. We confirm the 3D asymmetrical motions of recent works and provide time tagging of the Galactic outer disc asymmetrical motions near the anticentre direction out to Galactocentric distances of 14 kpc. Radial Galactocentric motions reach values up to 10 km s−1, depending on the age of the population, and present a north–south asymmetry in the region corresponding to density and velocity substructures that were sensitive to the perturbations in the early 6 Gyr. After that time, the disc stars in this asymmetrical structure have become kinematically hotter, and are thus not sensitive to perturbations, and we find the structure is a relatively younger population. With quantitative analysis, we find stars both above and below the plane at R ≳ 9 kpc that exhibit bending mode motions of which the sensitive duration is around 8 Gyr. We speculate that the in-plane asymmetries might not be mainly caused by a fast rotating bar, intrinsically elliptical outer disc, secular expansion of the disc, or streams. Spiral arm dynamics, out-of-equilibrium models, minor mergers or others are important contributors. Vertical motions might be dominated by bending and breathing modes induced by complicated inner or external perturbers. It is likely that many of these mechanisms are coupled together.

Cosmic Snow Clouds: Self-gravitating Gas Spheres Manifesting Hydrogen Condensation

Abstract We present hydrostatic equilibrium models of spherical, self-gravitating clouds of helium and molecular hydrogen, focusing on the cold, high-density regime where solid- or liquid-hydrogen can form. The resulting structures have masses from 0.1 M ⊙ down to several ×10−8 M ⊙, and span a broad range of radii: 10−4 ≲ R(au) ≲ 107. Our models are fully convective, but all have a two-zone character with the majority of the mass in a small, condensate-free core, surrounded by a colder envelope where phase equilibrium obtains. Convection in the envelope is unusual in that it is driven by a mean-molecular-weight inversion, rather than by an entropy gradient. In fact, the entropy gradient is itself inverted, leading to the surprising result that envelope convection transports heat inward. In turn, that permits the outer layers to maintain steady-state temperatures below the cosmic microwave background. Among our hydrostatic equilibria we identify thermal equilibria appropriate to the Galaxy, in which radiative cooling from H2 is balanced by cosmic-ray heating. These equilibria are all thermally unstable, albeit with very long thermal timescales in some cases. The specific luminosities of all our models are very low, and they therefore describe a type of baryonic dark matter. Consequently such clouds are thermally fragile: when placed in a harsh radiation field, they will be unable to cool effectively and disruption will ensue as heat input drives a secular expansion. Disrupting clouds should leave trails of gas and H2 dust in their wake, which might make them easier to detect. Our models may be relevant to the cometary globules in the Helix Nebula and the G2 cloud orbiting Sgr A*.

Measuring the Expansion and Age of the Nova Shell IPHASX J210204.7+471015

The parallax expansion and kinematics of a nova shell can be used to assess its age and distance, and to investigate the interaction of the ejecta with the circumstellar medium. These are key to understand the expansion and dispersal of the nova ejecta in the Galaxy. Multi-epoch images and high-dispersion spectroscopic observations of the recently discovered classical nova shell IPHASXJ210204.7+471015 around a nova-like system have been used to derive a present day expansion rate of 0.100 arcsec/yr and an expansion velocity of 285 km/s. These data are combined to obtain a distance of 600 pc to the nova. The secular expansion of the nova shell place the event sometime between 1850 and 1890, yet it seems to have been missed at that time. Despite its young age, 130-170 yrs, we found indications that the ejecta has already experienced a noticeable deceleration, indicating the interaction of this young nova shell with the surrounding medium.

Evidence for Highly Complex Redox Conditions and Strong Water‐Column Stratification in an Early Cambrian Continental‐Margin Sea

AbstractAlthough oxic surface, ferruginous deep, and euxinic intermediate waters have been documented, the redox heterogeneity of early Cambrian oceans remains largely unclear, precluding our understanding of the relationship between marine redox evolution and early animal diversification. In this study, we analyzed iron species, redox‐sensitive trace elements, and S‐N‐C isotopes of deepwater black shales in the Silikou section in the continental‐margin Nanhua Basin (South China), which represent extensive clastic input mainly from the Cathaysia Block during the early Cambrian (~541–509 Ma). Integrated data reveal a continuous shift in bottom‐water redox conditions at Silikou from euxinic in the lowermost black‐shale interval (BS1, 0–37.4 m) to oxic in the uppermost black‐shale interval (BS4, 296–372.9 m) accompanying a progressive movement of the O2/H2S redoxcline into the sediment. In between, most importantly, the BS2 interval (91–154 m) accumulated under manganous‐ferruginous conditions (i.e., Fe‐Mn reduction zone) characterized by an active Fe‐Mn particulate shuttle, and the BS3 interval (204–260 m) under nitrogenous conditions (i.e., nitrate reduction zone) characterized by strong denitrification processes, suggesting highly complex redox conditions in early Cambrian oceans. The observed sequence of redox conditions supports a strong lateral and depth‐related redox stratification in the early Cambrian ocean, including (from surface to deep and from nearshore to offshore) oxic, nitrate reduction, Fe‐Mn reduction, and euxinic zones, which were sequentially recorded at Silikou likely due to secular expansion of the oxic surface layer and/or long‐term relative sea level fall. Our study highlights the need for continued paleo‐redox studies to explore the redox heterogeneity of early Cambrian oceans.

The Great Escape: The Multinational Trade Deficit in Historical Perspective

:During the Bretton Woods era, the debate surrounding U.S. export sales versus U.S. multinational production focused primarily on the maintenance of pegged exchange rates and labor’s concern over the export of jobs. The collapse of Bretton Woods gave at least the hope that a decline in the dollar would expand exports and limit imports. Yet, the forty-year secular decline in the dollar has been one with a secular expansion of U.S. trade deficits. The older concerns of U.S. multinational sales competing with U.S. exports retain a current relevance. They help explain the unending nature of U.S. trade deficits.

RADIAL MOTIONS IN DISK STARS: ELLIPTICITY OR SECULAR FLOWS?

ABSTRACT Average stellar orbits of the Galactic disk may have some small intrinsic ellipticity which breaks the exact axisymmetry and there may also be some migration of stars inwards or outwards. Both phenomena can be detected through kinematic analyses. We use the red clump stars selected spectroscopically from the APO Galactic Evolution Experiment, with known distances and radial velocities, to measure the radial component of the Galactocentric velocities within 5 kpc < R < 16 kpc, , and within 20° from the Sun–Galactic center line. The average Galactocentric radial velocity is V R = (1.48 ± 0.35)[R(kpc) − (8.8 ± 2.7)] km s−1 outwards in the explored range, with a higher contribution from stars below the Galactic plane. Two possible explanations can be given for this result: (i) the mean orbit of the disk stars is intrinsically elliptical with a Galactocentric radial gradient of eccentricity around 0.01 kpc−1; or (ii) there is a net secular expansion of the disk, in which stars within R ≈ 9–11 kpc are migrating to the region R ≳ 11 kpc at the rate of ∼2 M ⊙ yr−1, and stars with R ≲ 9 kpc are falling toward the center of the Galaxy. This migration ratio would be unattainable for a long time and should decelerate, otherwise the Galaxy would fade away in around 1 Gyr. At present, both hypotheses are speculative and one would need data on the Galactocentric radial velocities for other azimuths different to the center or anticenter in order to confirm one of the scenarios.

Initial conditions of formation of starburst clusters: constraints from stellar dynamics

AbstractHow starburst clusters form out of molecular clouds is still an open question. In this article, I highlight some of the key constraints in this regard, that one can get from the dynamical evolutionary properties of dense stellar systems. I particularly focus on secular expansion of massive star clusters and hierarchical merging of sub-clusters, and discuss their implicationsvis-á-visthe observed properties of young massive clusters. The analysis suggests that residual gas expulsion is necessary for shaping these clusters as we see them today, irrespective of their monolithic or hierarchical mode of formation.

Two-Body Orbit Expansion Due to Time-Dependent Relative Acceleration Rate of the Cosmological Scale Factor

By phenomenologically assuming a slow temporal variation of the percent acceleration rate S̈S -1 of the cosmic scale factor S(t), it is shown that the orbit of a local binary undergoes a secular expansion. To first order in the power expansion of S̈S -1 around the present epoch t0, a non-vanishing shift per orbit (Δr) of the two-body relative distance r occurs for eccentric trajectories. A general relativistic expression, which turns out to be cubic in the Hubble parameter H0 at the present epoch, is explicitly calculated for it in the case of matter-dominated epochs with Dark Energy. For a highly eccentric Oort comet orbit with period Pb ≈ 31 Myr, the general relativistic distance shift per orbit turns out to be of the order of (Δr) ≈ 70 km. For the Large Magellanic Cloud, assumed on a bound elliptic orbit around the Milky Way, the shift per orbit is of the order of (Δr) ≈ 2–4 pc. Our result has a general validity since it holds in any cosmological model admitting the Hubble law and a slowly varying S̈S-1(t). More generally, it is valid for an arbitrary Hooke-like extra-acceleration whose “elastic” parameter κ is slowly time-dependent, irrespectively of the physical mechanism which may lead to it. The coefficient κ1 of the first-order term of the power expansion of κ(t) can be preliminarily constrained in a model-independent way down to a κ1 ≲ 2 x 10-13 year-3 level from latest Solar System’s planetary observations. The radial velocities of the double lined spectroscopic binary ALPHA Cen AB yield κ1 ≲ 10-8 year-3.

On the Expanding Earth and Shrinking Moon

Exactly 101 years ago, German scientist Alfred Lothar Wegener, sailed against the prevailing wisdom of his day when he posited that not only have the Earth’s continental plates receded from each other over the course of the Earth’s history, but that they are currently in a state of motion relative to one another. To explain this, Wegener set forth the hypothesis that the Earth must be expanding as a whole. Wegener’s inability to provide an adequate explanation of the forces and energy source responsible for continental drift and the prevailing belief that the Earth was a rigid solid body resulted in the acrimonious dismissal of his theories. Today, that the continents are generally receding from each other is no longer a point of debate but a sacrosanct pillar of modern geology and geophysics. What is debatable is the energy source driving this phenomenon. Herein, we hold that continental drift is a result of the Earth undergoing a secular radial expansion. An expanding Earth hypothesis is currently an idea that is not accepted on a general consensus level. Be thatas it may, we show herein that the law of conservation of angular momentum and energy entail that the Earth must not only expand as a consequence of the secular recession of the Earth-Moon system from the Sun, but invariably, that the Moon must contract as well. As a result, the much sort for energy source driving plate tectonics can (hypothetically) be identified with the energy transfers occurring between the orbital and rotational kinetic energy of the Earth. If our calculations are to be believed—as we do; then, the Earth must be expanding radially at a paltry rate of about +1.50 mm/yr while the Moon is contracting radially at a relatively high rate of about -410 mm/yr.

Bagehot was a Shadow Banker: Shadow Banking, Central Banking, and the Future of Global Finance

At the heart of both the modern shadow banking system and the 19th century banking system described by Walter Bagehot is the wholesale money market, with the central bank providing a liquidity backstop. We characterize shadow banking as “money market funding of capital market lending” and construct a model of such a system with dealers making markets and setting prices for funding and risk. Using this model, we describe the secular expansion of the market-based credit system and its rapid collapse during the global financial crisis. The model also clarifies the economic functions of the market-based credit system, the role of the central bank in such a system, and the global character of US dollar funding markets.

Expansion of subarctic water masses in the North Atlantic and Pacific oceans and implications for mid‐Pleistocene ice sheet growth

Past surface ocean circulation changes associated with the mid‐Pleistocene transition, 0.9–0.6 Ma, were reconstructed in the northern North Atlantic (ODP 983) and the northwest Pacific (ODP 882), using proxies for subarctic/subpolar water mass distributions (%C37:4alkenone) and sea surface temperature (U37K). Both sites experienced a secular expansion of subarctic waters from ∼1.15 Ma, spanning both glacial and interglacial intervals. After 0.9 Ma, low %C37:4at Site 983 records a northward retreat of subarctic waters during interglacials in the Atlantic, while continued high glacial %C37:4indicate extensive subarctic waters during glacial maxima associated with the development of the larger late Pleistocene ice sheets. In contrast, a secular decline in %C37:4occurred at Site 882 from 0.9 to 0.5 Ma, marking a more gradual retreat of subarctic conditions in the Pacific. It is proposed that the expansion of subarctic waters between 1.15 and 0.9 Ma exerted negative feedbacks to the moisture supply to the ice sheet source regions and may account for the apparent delayed ice sheet response to atmosphere‐ocean circulation changes associated with the mid‐Pleistocene transition that began as early as 1.2 Ma.

Origins of Common‐Law Restrictions on Water Transfers: Groundwater Law in Nineteenth‐Century California

Abstract Despite the fact that court‐mandated restrictions on voluntary transfers of water are common throughout the western United States, we currently lack a good economic understanding of the historical origins of many of those restrictions. In nineteenth‐century California, groundwater law evolved from an initial regime of virtually no legal restrictions on transfers to one of significant restrictions after the turn of the century. This doctrinal shift was given partial impetus by increasing scientific understanding of groundwater flows, which was reflected in increasingly sophisticated court rulings. However, it was a dramatic deterioration in groundwater conditions in southern California around the turn of the century that triggered a significant change in the court treatment of groundwater transfers. This deterioration resulted from drought conditions and a secular expansion in irrigated agriculture during the 1890s and major technological improvements that made large‐scale groundwater pumping incr...

Small Town in Mass Society Revisited1

Abstract The case study of a small New York town that dramatized the thesis that the secular expansion of macro forces—urbanization, industrialization, bureaucratization—has permanently reduced the autonomy of all small communities is an example of a special type of discovery/persuasion strategy in the social sciences: the “opposition case study.” In contrast to the more rigorous “competitive test” or the atheoretical “negative case,” opposition case studies confront the dominant perspective with a qualitative illustration of a new theory in the context of a zero‐sum game. When they are successful, opposition cases meet four criteria: the dominant view is immediately rendered obsolete; the origin of the new idea supports its plausibility; the new perspective is shown to be testable; and the new perspective quickly generates new lines of research. Small Town in Mass Society meets the first criterion, and may have been heuristic, but its probable origin in populist ideology undermines its testability.

Reflexive Adaptation of Business to Regulation and Regulation to Business

Regulatory change is driven by competitive struggle. Regulatees struggle with each other for customers and with regulators to lessen the burden of the rules being enforced. Regulators compete for regulatees and for the confidence of customers and the general public.Competition among regulators is imperfect. Along with better rules, new entrants must offer reputational capital, financial strength, and recognized enforcement powers. These entry requirements have supported a secular expansion of government suppliers relative to private suppliers. Principal‐agent conflicts inherent in representative democracy establish incentives for this expanding sector to produce regulatory services of poor quality. Finding ways to make top government regulators economically accountable for acts of misregulation is a critical problem.

The ‘eclipse’ of folk medicine in western society

Abstract Folk medicine is generally treated as a residue from pre‐scientific times. This article discusses contemporary folk medical practices and locates them firmly in postmodern economy and society. The central theme is that recent transformations in the economy have been paralleled by changes in cultural practices. This is manifest in the increased general awareness of ‘green’ issues and the rejection of ‘modernism’ in all its forms including the industrialised therapies of biomedicine which are seen to exacerbate rather than resolve public health problems. It is argued that popular dissatisfaction with biomedicine has increased and that the cultural gap between biomedical practitioners and their patients has become much more visible in recent times. This has contributed greatly to the secular expansion of folk therapies throughout western society. Finally, the article notes the gaps in current research into alternative medical practices and practitioners.

Exploding neutron stars near the minimum mass

view Abstract Citations (40) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Exploding Neutron Stars near the Minimum Mass Colpi, Monica ; Shapiro, Stuart L. ; Teukolsky, Saul A. Abstract The dynamical instability of a neutron star just below the minimum mass along the mass versus density equilibrium curve is explored. For the case in which the the interior of the compact star is modeled as an ideal gas of neutrons, electrons, and protons, the star is shown to undergo secular expansion on time scales of greater than 500,000 years. For the case of the more realistic Harrison et al. (1965) nuclear model, neutron decay occurs in nuclei on a time scale that can approach the dynamical time. Publication: The Astrophysical Journal Pub Date: April 1989 DOI: 10.1086/167299 Bibcode: 1989ApJ...339..318C Keywords: Magnetohydrodynamic Stability; Neutron Stars; Nuclear Astrophysics; Stellar Mass; Supernovae; Binary Stars; Gravitational Collapse; Neutrinos; Radioactive Decay; Stellar Models; Astrophysics; DENSE MATTER; STARS: INTERIORS; STARS: NEUTRON full text sources ADS |

Variable Trends in Economic Time Series

The two most striking historical features of aggregate output are its sustained long run growth and its recurrent fluctuations around this growth path. Over horizons of a few years, these shorter cyclical swings can be pronounced; for example, the 1953, 1957, and 1974 recessions are evident as substantial temporary declines in aggregate activity. These cyclical fluctuations are, however, dwarfed in magnitude by the secular expansion of output. But just as there are cyclical swings in output, so too are there variations in the growth trend: growth in GNP in the 1960s was much stronger than it was in the 1950s. Thus, changes in long-run patterns of growth are an important feature of postwar aggregate economic activity. In this article, we discuss the implications of changing trends in macroeconomic data from two perspectives. The first perspective is that of a macroeconomist reassessing the conventional dichotomy between growth and stabilization policies. As an empirical matter, does this dichotomy make sense for the postwar United States? What is the relative “importance” of changes in the trend and cyclical swings in explaining the quarterly movements in economic aggregates? We next adopt the perspective of an econometrician interpreting empirical evidence based on data that contain variable trends. The presence of variable trends in time series data can lead one to draw mistaken inferences using conventional econometric techniques. How can these techniques -- or our interpretation of them -- be modified to avoid these mistakes?