Recent content by Safinaz

The value of H equals ## 10^{3}## in natural units, According to : https://en.wikipedia.org/wiki/Natural_units, ## t \sim 10^{-21} sec = 10^{21} Hz ##, and since ## \text{GeV} \sim 10^{24} \text{Hz } ##, ## GeV \sim 10^{24} \times 10^{-21} = 10^3 ## in natural units. So is this conversion...

So that they become: ## g^{\sigma \rho} \nabla_\sigma \nabla_\rho R ~g_{\mu\nu} + R ~R_{\mu\nu} - \nabla_\mu \nabla_\nu R ##

I tried to solve by calculating: ## \omega = \frac{v}{x} = 3100/ (4.2 \times10^7) ##, Which makes the frequency so small: ## f = 2 \pi \times 3100/ (4.2 \times10^7) \sim 10^{-5} ~ s^{-1} ## And also the acceleration and velocity. So I think there is a mistake in my solution. Any help to...

The units in this equation are equal on the right and the left-hand side of the equation since in natural units, the length unit = GeV## ^{-1} ##. Now my question about this [paper][2], where it's a 5D Supergravity model and alternatively the above relation is given by : ## M^2_{p_l} \sim...

The original quantity is given in this paper: [reference][1], equations: (31-33-34), where ##a(\eta)= \frac{1}{H\eta}##, so I considered in (1) only the constants which share by dimensions to ##P##. Any help is appreciated! [1]: https://arxiv.org/pdf/hep-th/0703290

Where ##\delta \phi## is the first-order perturbation of a scalar field, ##\Phi## is the first-order perturbation of the space-time metric, and ##H## is the universe’s scale factor. It’s mentioned that this relation is given in reference: https://arxiv.org/pdf/1002.0600.pdf But I can't find...

Thanks so much for the answer : )

Hi, thanks for reply. What range does the index ##i## run over: ##\left( 1,2,3\right)## or ##\left( 0,1,2,3\right)## or something else? Ans.: ##\left( 0,1,2,3\right)## What explicitly are the variables ##w^i## that you are differentiating with respect to, i.e...

Does this equation mean that: ## x+y =z ##, and ## x = y##? I mean ## \delta_{ij} ## terms in the LHS of the eqaution equal those at the RHS ? with knowing that ## \partial_i \partial_j x ## term dose not vanish for ## \delta_{ij}=1 ## Any help is appreciated!

So there is no any way to simplify ## \partial_i \partial_j \phi ## ?

How can the following term: ## T_{ij} = \partial_i \partial_j \phi ## to be written in terms of Kronecker delta and the Laplacian operator ## \bigtriangleup = \nabla^2 ##? I mean is there a relation like: ## T_{ij} = \partial_i \partial_j \phi = ?? \delta_{ij} \bigtriangleup \phi.## But...

So can it written as: ## Eq = e^{ -ht} ( e^{t\sqrt{x}} + e^{-t\sqrt{x}} ) = 2 e^{ -ht} Cosh ( t \sqrt{x}) ##?

The eqution can be written as: ## Eq= e^{t( -h + \sqrt{ x} )} + e^{t( -h -\sqrt{ x} )} ## Can this be written in terms of Cosh x ?

I try to figure out the identity that leads to equation (27) in the menstioned paper. and writting ##F(k_1)## or ##F(k_2)## just to simplify. So that I'm asking about the correct identity of Dirac Delta

In a previous step in the paper, a transformation has been done from ##x## space to ##k## space by fourier-transforming