Slowly rotating fluid spheres in the Einstein–Yukawa theory

1983 ◽  
Vol 61 (9) ◽  
pp. 1324-1327
Author(s):  
K. D. Krori ◽  
A. R. Sheikh
Keyword(s):  
Analytic Solutions ◽  
The Other ◽  
Slow Rotation ◽  
Rotating Fluid ◽  
Physical Conditions ◽  
Fluid Spheres ◽  
Interior Solutions ◽  
Yukawa Theory

We introduce slow rotation to a solution given by Krori et al. which represents fluid spheres in the Einstein–Yukawa theory, and present two new analytic solutions which are nonsingular and satisfy physical conditions throughout the spheres. One of the interior solutions represents uniformly rotating spheres and the other represents differentially rotating spheres. We also match the interior and exterior solutions on the boundary.

Exact interior solutions in Einstein–Cartan–Yukawa theory

1988 ◽  
Vol 66 (2) ◽  
pp. 126-131
Author(s):  
K. D. Krori ◽  
P. Borgohain ◽  
Kanika Das ◽  
Arunima Sarma
Keyword(s):  
Massive Star ◽  
The Other ◽  
Simple Method ◽  
Physical Conditions ◽  
Interior Solutions ◽  
Yukawa Theory

A simple method of obtaining singularity-free interior solutions in Einstein–Cartan–Yukawa theory is presented here. The validity of the solution is shown by considering two types of configurations, one Schwarzschild-like and the other Tolman-IV-like. We recover the Schwarzschild and Tolman-IV solutions as soon as the Cartan and Yukawa effects are switched off. In both cases the necessary physical conditions are satisfied. The possible role of torsion in halting the collapse of a massive star is also studied.

Fluid spheres in Einstein–Yukawa theory

1983 ◽  
Vol 61 (2) ◽  
pp. 239-243 ◽  
Author(s):  
K. D. Krori ◽  
R. Bhattacharjee ◽  
Sumita Chaudhury ◽  
Madhumita Barua
Keyword(s):  
Neutron Stars ◽  
Complete Solution ◽  
Positive Pressure ◽  
Order Of Approximation ◽  
Physical Conditions ◽  
Fluid Spheres ◽  
Yukawa Theory

We present here a complete solution (to a certain order of approximation) of fluid spheres in the Einstein–Yukawa theory. It is nonsingular and satisfies physical conditions (positive pressure and density). The solution has some relevance to neutron stars.

Interior solutions for rotating fluid spheres

1985 ◽  
Vol 32 (8) ◽  
pp. 1857-1862 ◽  
Author(s):  
Patrick G. Whitman
Keyword(s):  
Rotating Fluid ◽  
Fluid Spheres ◽  
Interior Solutions

scholarly journals Warm gas in protostellar outflows

2019 ◽  
Vol 629 ◽  
pp. A77
Author(s):  
A. I. Gómez-Ruiz ◽  
A. Gusdorf ◽  
S. Leurini ◽  
K. M. Menten ◽  
S. Takahashi ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
High Velocity ◽  
The Other ◽  
Mass Star ◽  
Intermediate Mass ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Low Mass ◽  
Kinematic Properties

Context. OMC-2/3 is one of the nearest embedded cluster-forming regions that includes intermediate-mass protostars at early stages of evolution. A previous CO (3–2) mapping survey towards this region revealed outflow activity related to sources at different evolutionary phases. Aims. The present work presents a study of the warm gas in the high-velocity emission from several outflows found in CO (3–2) emission by previous observations, determines their physical conditions, and makes a comparison with previous results in low-mass star-forming regions. Methods. We used the CHAMP+ heterodyne array on the APEX telescope to map the CO (6–5) and CO (7–6) emission in the OMC-2 FIR 6 and OMC-3 MMS 1-6 regions, and to observe 13CO (6–5) at selected positions. We analyzed these data together with previous CO (3–2) observations. In addition, we mapped the SiO (5–4) emission in OMC-2 FIR 6. Results. The CO (6–5) emission was detected in most of the outflow lobes in the mapped regions, while the CO (7–6) was found mostly in the OMC-3 outflows. In the OMC-3 MMS 5 outflow, a previously undetected extremely high-velocity gas was found in CO (6–5). This extremely high-velocity emission arises from the regions close to the central object MMS 5. Radiative transfer models revealed that the high-velocity gas from MMS 5 outflow consists of gas with nH2 = 104–105 cm−3 and T > 200 K, similar to what is observed in young Class 0 low-mass protostars. For the other outflows, values of nH2 > 104 cm−3 were found. Conclusions. The physical conditions and kinematic properties of the young intermediate-mass outflows presented here are similar to those found in outflows from Class 0 low-mass objects. Due to their excitation requirements, mid − J CO lines are good tracers of extremely high-velocity gas in young outflows likely related to jets.

scholarly journals On the convection of ionospheric density features

2019 ◽  
Vol 37 (2) ◽  
pp. 201-214
Author(s):  
John D. de Boer ◽  
Jean-Marc A. Noël ◽  
Jean-Pierre St.-Maurice
Keyword(s):  
Collision Frequency ◽  
Analytic Solutions ◽  
The Other ◽  
Density Difference ◽  
Density Gradients ◽  
Scale Invariant ◽  
The Real ◽  
Altitude Dependence ◽  
Density Enhancement ◽  
Auroral Arcs

Abstract. We investigate whether the boundaries of an ionospheric region of different density than its surroundings will drift relative to the background E×B drift and, if so, how the drift depends on the degree of density enhancement and the altitude. We find analytic solutions for discrete circular features in a 2-D magnetised plasma. The relative drift is proportional to the density difference, which suggests that where density gradients occur they should tend to steepen on one side of a patch while they are weakened on the other. This may have relevance to the morphology of polar ionospheric patches and auroral arcs, since the result is scale-invariant. There is also an altitude dependence which enters through the ion-neutral collision frequency. We discuss how the 2-D analytic result can be applied to the real ionosphere.

scholarly journals General Discussion of Accretion Disks

1999 ◽  
Vol 194 ◽  
pp. 321-322
Author(s):  
Vahagn G. Gurzadyan
Keyword(s):  
Magnetic Field ◽  
Accretion Disks ◽  
Galactic Nuclei ◽  
The Other ◽  
Seminal Paper ◽  
Physical Conditions ◽  
Electron Positron ◽  
Free Parameters ◽  
The Stability ◽  
Electron Positron Pair

Even 25 years after the Shakura-Sunyaev seminal paper on the α-disk, we cannot claim that we have a reliable theory of accretion disks in galactic nuclei. Why? Because the problem is extremely complicated, it is essentially nonlinear and contains a number of parameters (i.e. is many-dimensional). The key point is whether it is possible to determine the magneto-hydrodynamical viscosity self-consistently, i.e. as a function of parameters of the disk - the temperature, matter and radiation densities, magnetic field, radius, etc., both in the radiation dominated and matter dominated regions. Another class of fundamental problems concerns the stability of the disk; Krolik mentioned only one instability - in the radiation dominated region, but there are many other types of instabilities which are quite sensitive to the physical conditions in the disk, for example, to the anisotropy of the ion pressure in the outer regions and possible electron-positron pair production near the inner edge of the disk. The other problems include those of the radiative transfer within the disk in various conditions, Comptonization of the outgoing radiation, radiation reflections by the desk, etc. Therefore it is not suprising that one can ‘explain' almost whatever he wants - spectra, variability, jets, wind, etc., by proper fit of the ‘free’ (which are never free) parameters and ignoring the instabilities and so on.

scholarly journals The impact of spectra quality on nebular abundances

2020 ◽  
Vol 495 (1) ◽  
pp. 1016-1034 ◽  
Author(s):  
Mónica Rodríguez
Keyword(s):  
Planetary Nebulae ◽  
The Other ◽  
Statistical Equilibrium ◽  
Emission Lines ◽  
Reference Spectrum ◽  
Equilibrium Equations ◽  
Chemical Abundances ◽  
Physical Conditions ◽  
Observational Errors ◽  
The Impact

ABSTRACT I explore the effects of observational errors on nebular chemical abundances using a sample of 179 optical spectra of 42 planetary nebulae (PNe) observed by different authors. The spectra are analysed in a homogeneous way to derive physical conditions and ionic and total abundances. The effects of recombination on the [O ii] and [N ii] emission lines are estimated by including the effective recombination coefficients in the statistical equilibrium equations that are solved for O+ and N+. The results are shown to be significantly different than those derived using previous approaches. The O+ abundances derived with the blue and red lines of [O ii] differ by up to a factor of 6, indicating that the relative intensities of lines widely separated in wavelength can be highly uncertain. In fact, the He ii lines in the range 4000–6800 Å imply that most of the spectra are bluer than expected. Scores are assigned to the spectra using different criteria and the spectrum with the highest score for each PN is taken as the reference spectrum. The differences between the abundances derived with the reference spectrum and those derived with the other spectra available for each object are used to estimate the 1σ observational uncertainties in the final abundances: 0.11 dex for O/H and Ar/H, 0.14 dex for N/H, Ne/H, and Cl/H, and 0.16 dex for S/H.

Petrology of Mg-Mn amphibole-bearing assemblages in manganese silicate rocks of the Sausar Group, India

1988 ◽  
Vol 52 (364) ◽  
pp. 105-111 ◽  
Author(s):  
Somnath Dasgupta ◽  
P. K. Bhattacharya ◽  
G. Chattopadhyay ◽  
H. Banerjee ◽  
N. Majumdar ◽  
...  
Keyword(s):  
Present Situation ◽  
Amphibolite Facies ◽  
The Other ◽  
Bivalent Cation ◽  
Manganese Silicate ◽  
Physical Conditions ◽  
Total Absence ◽  
Other Hand ◽  
Silicate Rocks

AbstractMg-Mn amphibole (tirodite), with or without pyroxmangite in the total absence of pyroxenes and high-calcic pyroxenoids, occurs in the Mn silicate rocks of the Sausar Group, India. The rocks were metamorphosed to amphibolite facies condition (T ∼ 650°C, P ∼ 6 kbar). Tirodite-pyroxmangite pairs developed in both carbonate-free and rhodochrosite-bearing assemblages. Also tirodite coexists with either kutnahorite or manganoan calcite in the absence of pyroxmangite. Mineral reactions inferred from modal abundances and compositions of the phases indicate stabilization of the amphibole alone from a bivalent cation-bearing residual unbuffered XCO2 system with XMn < 0.3. On the other hand, tirodite-pyroxmangite pairs appeared in unbuffered low to intermediate XCO2 assemblages with XMn > 0.35. Pyroxenes and high-calcic pyroxenoids did not appear in the present situation, though they occur elsewhere in rocks with broadly similar contents of immobile components. Closely associated assemblages of diverse mineralogy suggest that the XMn and XCO2, rather than the physical conditions of metamorphism, are the decisive factors in promoting the observed phase assemblages.

scholarly journals STATIC CYLINDRICALLY SYMMETRIC INTERIOR SOLUTIONS IN f(R) GRAVITY

2012 ◽  
Vol 27 (25) ◽  
pp. 1250138 ◽  
Author(s):  
M. SHARIF ◽  
SADIA ARIF
Keyword(s):  
Energy Density ◽  
Exact Solutions ◽  
Perfect Fluid ◽  
Functional Form ◽  
Ricci Scalar ◽  
The Other ◽  
New Exact Solutions ◽  
Cylindrically Symmetric ◽  
Theory Of Gravity ◽  
Interior Solutions

We investigate some exact static cylindrically symmetric solutions for a perfect fluid in the metric f(R) theory of gravity. For this purpose, three different families of solutions are explored. We evaluate energy density, pressure, Ricci scalar and functional form of f(R). It is interesting to mention here that two new exact solutions are found from the last approach, one is in particular form and the other is in the general form. The general form gives a complete description of a cylindrical star in f(R) gravity.

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