On the Stability of a Galactic Disk in Modified Gravity

Roshan, Mahmood; Abbassi, Shahram

doi:10.1088/0004-637x/802/1/9

Cited by 28 publications

(39 citation statements)

References 48 publications

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“…As a final remark, we mention that the main result of this paper is somehow consistent with our recent results considering the local stability of the disks, Roshan & Abbassi (2015). In fact in Roshan & Abbassi (2015) we have found the generalized version of the Toomre criterion in MOG and shown that MOG increases the growth rate of the local perturbations.…”

Section: Modified Poisson Equations In Mogsupporting

confidence: 91%

“…In fact in Roshan & Abbassi (2015) we have found the generalized version of the Toomre criterion in MOG and shown that MOG increases the growth rate of the local perturbations. In other words, galactic disk are more unstable against local axi-symmetric perturbations in MOG than in Newtonian gravity.…”

Section: Modified Poisson Equations In Mogmentioning

confidence: 92%

“…In other words, regarding the practical role of the Maclaurin disk for better understanding of the global stability in Newtonian gravity, we have chosen it to compare the global stability of galactic disks in Newtonian gravity and MOG. It is necessary to mention that the local stability of spiral galaxies in MOG has been already investigated in Roshan & Abbassi (2015).…”

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confidence: 99%

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On the Gravitational Stability of the Maclaurin Disk

Roshan

Abbassi

Khosroshahi

2016

ApJ

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We study the global gravitational stability of a gaseous self-gravitating Maclaurin disk in the absence of a halo. Further, we replace Newtonian gravity with the specific Modified gravity theory known as MOG in the relevant literature. MOG is an alternative theory for addressing the dark matter problem without invoking exotic dark matter particles, and possesses two free parameters α and µ 0 in the weak field limit. We derive the equilibrium gravitational potential of the Maclaurin disk in MOG and develop a semi-analytic method for studying the response of the disk to linear non-axysymmetric perturbations. The eigenvalue spectrum of the normal modes of the disk is obtained and its physical meaning has been explored. We show that Maclaurin disks are less stable in MOG than in Newtonian gravity. In fact both parameters (α, µ 0 ) have destabilizing effects on the disk. Interestingly µ 0 excites only the bar mode m = 2 while α affects all the modes. More specifically, when α > 1, the bar mode is strongly unstable and unlike in Newtonian gravity can not be avoided, at least in the weak field limit, with increasing the pressure support of the disk.

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Section: Modified Poisson Equations In Mogsupporting

confidence: 91%

Section: Modified Poisson Equations In Mogmentioning

confidence: 92%

mentioning

confidence: 99%

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On the Gravitational Stability of the Maclaurin Disk

Roshan

Abbassi

Khosroshahi

2016

ApJ

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“…2 we show the evolution of ω eff and ω DE . -p 8,9 : Unstable unaccelerated era These critical points are on the lines p 1,2 . In the case of p 8,9 the effective equation of state parameter is − .…”

Section: Mog Without Cosmological Constant ( = 0)mentioning

confidence: 99%

The phase-space analysis of modified gravity (MOG)

Jamali

Roshan

2016

Eur. Phys. J. C

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We investigate the cosmological consequences of a scalar-vector-tensor theory of gravity known as modified gravity (MOG). In MOG, in addition to metric tensor, there are two scalar fields G(x) and μ(x), and one vector field φ α (x). Using the phase space analysis, we explore the cosmological consequences of a model of MOG and find some new interesting features which are absent in CDM model. More specifically we study the possibility that if the extra fields of this theory behave like dark energy to explain the cosmic speedup. More interestingly, with or without cosmological constant, a strongly phantom crossing occurs. Also we find that this theory in its original form ( = 0) possesses a true sequence of cosmological epochs. However, we show that, surprisingly, there are two radiation-dominated epochs, f 5 and f 6 , two matter-dominated phases, f 3 and f 4 , and two late time accelerated eras, f 12 and f 7 . Depending on the initial conditions the universe will realize only three of these six eras. However, the matter-dominated phases are dramatically different from the standard matter-dominated epoch. In these phases the cosmic scale factor grows as a(t) ∼ t 0.46 and t 0.52 , respectively, which are slower than the standard case, i.e. a(t) ∼ t 2/3 . Considering these results we discuss the cosmological viability of MOG.

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“…In fact, it has been observed that the rotation curves of galaxies do not fit the theoretically predicted curves, and this has motivated the development of theories like the MOND [17,18] and MOG [19,20]. So, we expect the deviation from the Newtonian potential to become effective at galactic scale.…”

Section: Introductionmentioning

confidence: 97%

Clustering of galaxies in brane world models

2016

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In this paper, we analyze the clustering of galaxies using a modified Newtonian potential. This modification of the Newtonian potential occurs due to the existence of extra dimensions in brane world models. We will analyze a system of galaxies interacting with each other through this modified Newtonian potential. The partition function for this system of galaxies will be calculated, and this partition function will be used to calculate the free energy of this system of galaxies. The entropy and the chemical potential for this system will also be calculated. We will derive explicit expression for the clustering parameter for this system. This parameter will determine the behavior of this system, and we will be able to express various thermodynamic quantities using this clustering parameter. Thus, we will be able to explicitly analyze the effect that modifying the Newtonian potential can have on the clustering of galaxies. We also analyze the effect of extra dimensions on the two-point functions between galaxies.

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On the Stability of a Galactic Disk in Modified Gravity

Cited by 28 publications

References 48 publications

On the Gravitational Stability of the Maclaurin Disk

On the Gravitational Stability of the Maclaurin Disk

The phase-space analysis of modified gravity (MOG)

Clustering of galaxies in brane world models

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