ترغب بنشر مسار تعليمي؟ اضغط هنا

A Simple Theoretical Prediction of the Data Corresponding to Observationally Estimated Value of Cosmological Constant

152   0   0.0 ( 0 )
 نشر من قبل Miodrag Krmar
 تاريخ النشر 2007
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

In this work a satisfactory, simple theoretical prediction of the data corresponding to observationally (by fine tuning condition) estimated value of the cosmological constant is given. It is supposed (in conceptually analogy with holographic principle) that cosmological constant, like classical surface tension coefficient by a liquid drop, does not correspond to a volume (bulk) vacuum mass (energy) density distribution but that it corresponds to a surface vacuum mass (energy) density distribution. Then form of given surface mass distribution and fine tuning condition imply observed growing (for $sim$ 61 magnitude order) of the scale factor (from initial, corresponding to Planck length, to recent, at the beginning of the cosmic acceleration, corresponding to 10 Glyr length).

قيم البحث

اقرأ أيضاً

58 - Claudio Nassif 2007
We will look for an implementation of new symmetries in the space-time structure and their cosmological implications. This search will allow us to find a unified vision for electrodynamics and gravitation. We will attempt to develop a heuristic model of the electromagnetic nature of the electron, so that the influence of the gravitational field on the electrodynamics at very large distances leads to a reformulation of our comprehension of the space- time structure at quantum level through the elimination of the classical idea of rest. This will lead us to a modification of the relativistic theory by introducing the idea about a universal minimum limit of speed in the space- time. Such a limit, unattainable by the particles, represents a preferred frame associated with a universal background field (a vacuum energy), enabling a fundamental understanding of the quantum uncertainties. The structure of space-time becomes extended due to such a vacuum energy density, which leads to a negative pressure at the cosmological scales as an anti-gravity, playing the role of the cosmological constant. The tiny values of the vacuum energy density and the cosmological constant will be successfully obtained, being in agreement with current observational results.
59 - Vladan Pankovic 2010
In this work we suggest (in a formal analogy with Linde chaotic inflation scenario) simple dynamical model of the dark energy or cosmological constant. Concretely, we suggest a Lagrangian dependent of Universe scale factor and scalar field (with cons tant and positive total energy density as cosmological constant). Then, Euler-Lagrange equation for Universe scale factor is equivalent to the second Friedman equation for the flat empty space with cosmological constant (in this sense our model is full agreement with recent astronomical observations). Also there is Euler-Lagrange equation for scalar field that includes additional friction term and negative first partial derivative of unknown potential energy density (this equation is, in some way, similar to Klein-Gordon equation modified for cosmic expansion in Linde chaotic inflation scenario). Finally, total time derivative of the (constant) scalar field total energy density must be zero. It implies third dynamical equation which is equivalent to usual Euler-Lagrange equation with positive partial derivative of unknown potential energy density (this equation is formally exactly equivalent to corresponding equation in static Universe). Last two equations admit simple exact determination of scalar field and potential energy density, while cosmological constant stands a free parameter. Potential energy density represents a square function of scalar field with unique maximum (dynamically non-stable point). Any initial scalar field tends (co-exponentially) during time toward the same final scalar field, argument of the maximum of the potential energy density. It admits a possibility that final dynamically non-stable scalar field value turns out spontaneously in any other scalar field value when all begins again (like Sisyphus boulder motion).
74 - Hemza Azri , A. Bounames 2014
We derive a model of dark energy which evolves with time via the scale factor. The equation of state $omega=(1-2alpha)/(1+2alpha)$ is studied as a function of a parameter $alpha$ introduced in this model. In addition to the recent accelerated expansi on, the model predicts another decelerated phase. The age of the universe is found to be almost consistent with observation. In the limiting case, the cosmological constant model, we find that vacuum energy gravitates with a gravitational strength, different than Newtons constant. This enables degravitation of the vacuum energy which in turn produces the tiny observed curvature, rather than a 120 orders of magnitude larger value.
69 - S.-H. Henry Tye 2007
In an earlier paper, it is proposed that, due to resonance tunneling effect, tunneling from a large cosmological constant $Lambda$ site in the stringy comic landscape can be fast, while tunneling from a small $Lambda$ site may take exponentially long time. Borrowing the renormalization group analysis of the conductance in the Anderson localization transition, we treat the landscape as a multi-dimensional random potential and find that the vastness of the landscape leads to a sharp transition at a small critical value $Lambda_{c}$ from fast tunneling for $Lambda > Lambda_{c} $ to suppressed tunneling for $Lambda_{c} > Lambda >0$. Mobility in the landscape makes eternal inflation highly unlikely. As an illustration, we find that $Lambda_{c}$ can easily be exponentially small compared to the string/Planck scale. These properties may help us in finding a qualitative understanding why todays dark energy is so small.
We consider a model with two parallel (positive tension) 3-branes separated by a distance $L$ in 5-dimensional spacetime. If the interbrane space is anti-deSitter, or is not precisely anti-deSitter but contains no event horizons, the effective 4-dime nsional cosmological constant seen by observers on one of the branes (chosen to be the visible brane) becomes exponentially small as $L$ grows large.
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