This post contains some exercises and challenges for you. In fact, crazy me, I used some of them for my classroom usage (just a fun way to survive is to design and propose maniac ultrageek problems to your students, … Continue reading

# Category Archives: General Relativity

Hi, folks! Before the upcoming series of thematic blog posts (they are on their way, eager readers), I found a very interesting paper to discuss. The paper is this http://arxiv.org/abs/1408.1820 and the pdf file can be found here http://arxiv.org/pdf/1408.1820v1.pdf . The author of the … Continue reading

The second post in this thread is completely speculative. 1) Suppose that Dark Energy is some kind of “fluid” made of some long wavelength “particles” or “exotic stuff”. 2) How different are those “Dark Energy particles” from the particles we … Continue reading

In my final post of this basic Cosmology thread, I am going to discuss scalar perturbations and to review some of the recent results about cosmological parameters by WMAP and PLANCK. One of the predictions of the Standard Cosmological … Continue reading

The topic today: problems in the Standard Cosmological Model (LCDM), inflation and scalar fields! STANDARD COSMOLOGICAL MODEL: ISSUES Despite the success of the Standard Cosmological model (or LCDM), today it is widely accepted that it is not complete, even if … Continue reading

Recombination When the Universe cooled up to , the neutrinos decoupled from the primordial plasma (soup). Protons, electrons and photons remained tighly coupled by 2 main types of scattering processes: 1) Compton scattering: 2) Coulomb scattering: Then, there were little … Continue reading

Today, a new post in this fascinating Cosmology thread… The Big Bang Nucleosynthesis in a nutshell When the Universe was young, about , the following events happen 1st. Some particles remained in thermodynamical equilibrium with the primordial plasma (photons, positrons … Continue reading

The current Universe has evolved since its early phase of thermal equilibrium until the present state. The departure from thermal equilibrium in the early Universe made a fossil record we can observe at current time! There are some easy rules … Continue reading

Evolution of the Universe: the scale factor The Universe expands, and its expansion rate is given by the Hubble parameter (not constant in general!) Remark (I): The Hubble “parameter” is “constant” at the present value (or a given time/cosmological age), … Continue reading

The next thread is devoted to Cosmology. I will intend to be clear and simple about equations and principles of current Cosmology with a General Relativity background. First of all…I will review the basic concepts of natural units I am … Continue reading