Newton’s gravity reads: In extra dimensions, , , it reads For extra dimensions, if their size are much smaller than considered distances, , then by matching So, gravitational is weak in our … Continue reading

# Category Archives: General Relativity

Happy New Year 2018, dear followers! Today is a special blog post! My 200th post! After a really terrible 2017 from the viewpoint of family, health and productivity, I wish this one will be a great year for me and … Continue reading

If you believe in both, relativity AND quantum mechanics, something that I presume you do due to experimental support, you are driven to admit that the speed of light is the maximal velocity (at least, the maximal 1-speed, in single … Continue reading

The main challenge we are left to the 21st century and beyond is to unify every interaction into a single theory. Today, we have two main theories: The Standard Model, for particle physics. The cosmological Standard Model, or -CDM, as … Continue reading

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

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