Rapidly rotating relativistic stars

1992 ◽  
Vol 340 (1658) ◽  
pp. 391-422 ◽  
Keyword(s):  
Neutron Stars ◽  
Numerical Models ◽  
Normal Modes ◽  
Rotating Stars ◽  
Relativistic Stars ◽  
Small Oscillations ◽  
Perfect Fluids ◽  
Upper Limits ◽  
Viscosity Limit

Within the last decade, significant progress has been made in modelling rotating stars in general relativity and in relating observable properties to the equation of state of matter at high density. A formalism describing rotating perfect fluids is presented and numerical models of neutron stars are briefly discussed, with emphasis on upper limits on mass and rotation. The equations governing small oscillations are reviewed, and a variational principle appropriate both to eulerian and lagrangian perturbations is obtained. This extends to relativity an eulerian principle used to find non-axisymmetric stability points for perfect fluids. A related eulerian approach has been recently used to obtain normal modes of rotating newtonian stars. The review concludes with an outline of this work and of the two types of instability that can restrict the range of neutron stars. In particular, current work shows that several kinds of effective viscosity limit the possible role of a non-axisymmetric instability driven by gravitational waves.

On the non-radial oscillations of slowly rotating stars induced by the Lense-Thirring effect

1991 ◽  
Vol 433 (1888) ◽  
pp. 423-440 ◽  
Keyword(s):  
Neutron Stars ◽  
Characteristic Frequency ◽  
Selection Rule ◽  
Inertial Frame ◽  
Normal Modes ◽  
Decisive Factor ◽  
Rotating Stars ◽  
Opposite Parity ◽  
Axial Mode ◽  
Polar Mode

In a star that is rotating so slowly that the distortion of its figure may be ignored, the axial modes of non-radial oscillation exhibiting resonance can be excited by the polar modes of perturbation by the coupling derived from the dragging of the inertial frame by the rotation of the star (i. e. by the Lense-Thirring effect). The coupling of these two modes of opposite parity is subject to the standard selection rule, ∆ l = ±1. Also, the excitation of ( l + 1)-axial mode by the l -polar mode is favoured relative to the excitation of the ( l - 1)-axial mode, in conformity with the ‘propensity’ rule. As an illustrative example, the excitation of the sextupole axial modes of oscillation by the quadrupole polar perturbations is considered in some detail; and it is shown that both the real and the imaginary parts of the characteristic frequency of the quasi­-normal modes decrease dramatically with the amplitude of the coupling. The relatively very long damping times of these rotationally induced oscillations may be a decisive factor in their eventual detection in neutron stars following the glitches.

A RELATIVISTIC EFFECTIVE MODEL WITH PARAMETERIZED COUPLINGS FOR NEUTRON STARS: THE ROLE OF ANTIKAON CONDENSATES

2011 ◽  
Vol 20 (supp02) ◽  
pp. 133-139
Author(s):  
ALEXANDRE MESQUITA ◽  
MOISÉS RAZEIRA ◽  
DIMITER HADJIMICHEF ◽  
CÉSAR A. Z. VASCONCELLOS ◽  
ROSANA O. GOMES ◽  
...  
Keyword(s):  
Neutron Stars ◽  
Coupling Constants ◽  
Effective Model ◽  
Extended Model ◽  
Many Body ◽  
Parametric Dependence ◽  
Interaction Terms ◽  
Coupling Terms ◽  
Effective Models

We study the effects of antikaon condensates in neutron stars in the framework of a relativistic effective model with derivative couplings which includes genuine many-body forces simulated by nonlinear interaction terms involving scalar-isoscalar (σ, σ*), vector-isoscalar (ω, ɸ), vector-isovector (ϱ), scalar-isovector (δ) mesons. The effective model presented in this work has a philosophy quite similar to the original version of the model with parameterized couplings. But unlike that, in which the parametrization is directly inserted in the coupling constants of the Glendenning model, we present here a method for the derivation of the parametric dependence of the coupling terms, in a way that allows in one side to consistently justify this parametrization and in the other to extend in a coherent way the range of possibilities of parameterizations in effective models with derivative couplings. The extended model is then applied to the description of the mass of neutron stars.

scholarly journals The Role of Lower Crustal Rheology in Lithospheric Delamination During Orogeny

2021 ◽  
Vol 9 ◽  
Author(s):  
Lin Chen
Keyword(s):  
Lower Crust ◽  
Numerical Models ◽  
The Tibetan Plateau ◽  
Mantle Lithosphere ◽  
Laboratory Studies ◽  
Surface Uplift ◽  
Continental Lower Crust ◽  
Lower Crustal ◽  
Flow Laws

The continental lower crust is an important composition- and strength-jump layer in the lithosphere. Laboratory studies show its strength varies greatly due to a wide variety of composition. How the lower crust rheology influences the collisional orogeny remains poorly understood. Here I investigate the role of the lower crust rheology in the evolution of an orogen subject to horizontal shortening using 2D numerical models. A range of lower crustal flow laws from laboratory studies are tested to examine their effects on the styles of the accommodation of convergence. Three distinct styles are observed: 1) downwelling and subsequent delamination of orogen lithosphere mantle as a coherent slab; 2) localized thickening of orogen lithosphere; and 3) underthrusting of peripheral strong lithospheres below the orogen. Delamination occurs only if the orogen lower crust rheology is represented by the weak end-member of flow laws. The delamination is followed by partial melting of the lower crust and punctuated surface uplift confined to the orogen central region. For a moderately or extremely strong orogen lower crust, topography highs only develop on both sides of the orogen. In the Tibetan plateau, the crust has been doubly thickened but the underlying mantle lithosphere is highly heterogeneous. I suggest that the subvertical high-velocity mantle structures, as observed in southern and western Tibet, may exemplify localized delamination of the mantle lithosphere due to rheological weakening of the Tibetan lower crust.

scholarly journals The role of Edge-Driven Convection in the generation of volcanism I: a 2D systematic study

2020 ◽  
Author(s):  
Antonio Manjón-Cabeza Córdoba ◽  
Maxim Ballmer
Keyword(s):  
Numerical Models ◽  
High Volume ◽  
Oceanic Lithosphere ◽  
Companion Paper ◽  
Small Scale ◽  
Continental Lithosphere ◽  
Transient Phenomenon ◽  
Mantle Viscosity ◽  
Wide Range

Abstract. The origin of intraplate volcanism is not explained by the plate tectonic theory, and several models have been put forward for explanation. One of these models involves Edge-Driven Convection (EDC), in which cold and thick continental lithosphere is juxtaposed to warm and thin oceanic lithosphere to trigger convective instability. To test whether EDC can produce long-lived high-volume magmatism, we run numerical models of EDC for a wide range of mantle properties and edge (i.e., the oceanic-continental transition) geometries. We find that the most important parameters that govern EDC are the rheological paramaters mantle viscosity η0 and activation energy Ea. However, even the maximum melting volumes found in our models are insufficient to account for island-building volcanism on old seafloor, such as at the Canary Islands and Cape Verde. Also, beneath old seafloor, localized EDC-related melting commonly transitions into widespread melting due to small-scale sublithospheric convection, inconsistent with the distribution of volcanism at these volcanic chains. In turn, EDC is a good candidate to sustain the formation of small seamounts on young seafloor, as it is a highly transient phenomenon that occurs in all our models soon after initiation. In a companion paper, we investigate the implications of interaction of EDC with mantle-plume activity.

scholarly journals The role of edge-driven convection in the generation of volcanism – Part 1: A 2D systematic study

Solid Earth ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 613-632
Author(s):  
Antonio Manjón-Cabeza Córdoba ◽  
Maxim D. Ballmer
Keyword(s):  
Numerical Models ◽  
High Volume ◽  
Oceanic Lithosphere ◽  
Companion Paper ◽  
Rheological Parameters ◽  
Small Scale ◽  
Transient Phenomenon ◽  
Mantle Viscosity ◽  
Wide Range

Abstract. The origin of intraplate volcanism is not explained by plate tectonic theory, and several models have been put forward for explanation. One of these models involves edge-driven convection (EDC), in which cold and thick continental lithosphere is juxtaposed with warm and thin oceanic lithosphere to trigger convective instability. To test whether EDC can produce long-lived high-volume magmatism, we run numerical models of EDC for a wide range of mantle properties and edge (i.e., the oceanic–continental transition) geometries. We find that the most important parameters that govern EDC are the rheological parameters mantle viscosity η0 and activation energy Ea. However, even the maximum melting volumes predicted by our most extreme cases are insufficient to account for island-building volcanism on old seafloor, such as at the Canary Islands and Cabo Verde. Also, beneath old seafloor, localized EDC-related melting commonly transitions into widespread melting due to small-scale sublithospheric convection, inconsistent with the distribution of volcanism at these volcano chains. In turn, EDC is a good candidate to sustain the formation of small seamounts on young seafloor, as it is a highly transient phenomenon that occurs in all our models soon after initiation. In a companion paper, we investigate the implications of interaction of EDC with mantle plume activity (Manjón-Cabeza Córdoba and Ballmer, 2021).

scholarly journals Tidal deformations of neutron stars: The role of stratification and elasticity

2011 ◽  
Vol 84 (10) ◽  
Author(s):  
A. J. Penner ◽  
N. Andersson ◽  
L. Samuelsson ◽  
I. Hawke ◽  
D. I. Jones
Keyword(s):  
Neutron Stars ◽  
Tidal Deformations

Alkaline phosphatase activity in the plasma of children and adolescents.

1977 ◽  
Vol 23 (3) ◽  
pp. 469-472 ◽  
Author(s):  
G A Fleisher ◽  
E S Eickelberg ◽  
L R Elveback
Keyword(s):  
Alkaline Phosphatase ◽  
Public Schools ◽  
Phosphatase Activity ◽  
Alkaline Phosphatase Activity ◽  
Serum Alkaline Phosphatase ◽  
Intraclass Correlation ◽  
Serum Alkaline Phosphatase Activity ◽  
Upper Limits ◽  
Prepubertal Girls

Abstract We determined plasma (serum alkaline phosphatase activity in 854 healthy students of the Rochester, Minnesota, public schools. Prepubertal girls had somewhat greater upper limits than did boys, and there was a low trend of increasing activity in both sexes. At the beginning of adolescence increasing activities were observed, which peaked at ages 11 to 12 years in girls and at ages 13 to 14 in boys. Adult values were not reached until six to eight years later. In 180 pairs of siblings, a significant intraclass correlation was noted. A possible role of alkaline phosphatase in the regulation of protein synthesis is suggested.

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