ترغب بنشر مسار تعليمي؟ اضغط هنا

The cosmological behavior of Bekensteins modified theory of gravity

60   0   0.0 ( 0 )
 نشر من قبل D. F. Mota
 تاريخ النشر 2006
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

We study the background cosmology governed by the Tensor-Vector-Scalar theory of gravity proposed by Bekenstein. We consider a broad family of potentials that lead to modified gravity and calculate the evolution of the field variables both numerically and analytically. We find a range of possible behaviors, from scaling to the late time domination of either the additional gravitational degrees of freedom or the background fluid.



قيم البحث

اقرأ أيضاً

45 - Ofer Lahav 2019
Jacob Bekensteins pioneering contributions to the foundations of Gravity cover a broad range of scales, from Black Holes to the entire Universe. He is well known as the father of Black Hole Thermodynamics and the inventor of the TeVeS modified gravit y theory. I reflect here on my interaction with him, from the time he supervised me for my MSc project at Ben-Gurion University in the early 1980s to his sabbatical visit at UCL in 2014, about a year before he passed away (sadly just a month before the first LIGO discovery of Gravitational Waves from a Binary Black Hole). His quote I feel more comfortable in the world if I understand why things are happening reflects the way he viewed the world as a Physicist as well as his personal belief. He also allegedly said Sometimes theories are smarter than their inventors.
A relativistic theory of modified gravity has been recently proposed by Bekenstein. The tensor field in Einsteins theory of gravity is replaced by a scalar, a vector, and a tensor field which interact in such a way to give Modified Newtonian Dynamics (MOND) in the weak-field non-relativistic limit. We study the evolution of the universe in such a theory, identifying its key properties and comparing it with the standard cosmology obtained in Einstein gravity. The evolution of the scalar field is akin to that of tracker quintessence fields. We expand the theory to linear order to find the evolution of perturbations on large scales. The impact on galaxy distributions and the cosmic microwave background is calculated in detail. We show that it may be possible to reproduce observations of the cosmic microwave background and galaxy distributions with Bekensteins theory of MOND.
57 - Qasem Exirifard 2019
We study the gravitomagnetism in the Scalar-Vector-Tensor theory or Moffats Modified theory of Gravity(MOG). We compute the gravitomagnetic field that a slow-moving mass distribution produces in its Newtonian regime. We report that the consistency be tween the MOG gravitomagnetic field and that predicted by the Einsteins gravitional theory and measured by Gravity Probe B, LAGEOS and LAGEOS 2, and with a number of GRACE and Laser Lunar ranging measurements requires $|alpha| < 0.0013$. We provide a discussion.
356 - M. Ibison 2007
We test the Yilmaz theory of gravitation by working out the corresponding Friedmann-type equations generated by assuming the Friedmann-Robertson-Walker cosmological metrics. In the case that space is flat the theory is consistent only with either a c ompletely empty universe or a negative energy vacuum that decays to produce a constant density of matter. In both cases the total energy remains zero at all times, and in the latter case the acceleration of the expansion is always negative. To obtain a more flexible and potentially more realistic cosmology, the equation of state relating the pressure and energy density of the matter creation process must be different from the vacuum, as for example is the case in the steady-state models of Gold, Bondi, Hoyle and others. The theory does not support the cosmological principle for curved space K =/= 0 cosmological metrics.
We propose a modified gravity theory that propagates only two local gravitational degrees of freedom and that does not have an Einstein frame. According to the classification in JCAP 01 (2019) 017 [arXiv:1810.01047 [gr-qc]], this is a type-II minimal ly modified gravity theory. The theory is characterized by the gravitational constant $G_{rm N}$ and a function $V(phi)$ of a non-dynamical auxiliary field $phi$ that plays the role of dark energy. Once one fixes a homogeneous and isotropic cosmological background, the form of $V(phi)$ is determined and the theory no longer possesses a free parameter or a free function, besides $G_{rm N}$. For $V(phi) = 0$ the theory reduces to general relativity (GR) with $G_N$ being the Newtons constant and $V=const.$ being the cosmological constant. For $V(phi) e 0$, it is shown that gravity behaves differently from GR but that GR with $G_{rm N}$ being the Newtons constant is recovered for weak gravity at distance and time scales sufficiently shorter than the scale associated with $V(phi)$. Therefore this theory provides the simplest framework of cosmology in which deviations from GR can be tested by observational data.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا