Cosmology Definition and 951 Threads

Homework Statement I am just looking through some old notes I have from for cosmology, and there's something cropped up that i can't seem to figure out: Say I have two (or more) values for H_o each with errors such as: H_{o_1}=70^{+a+b}_{-c-d} and H_{o_2}=69^{+e+f}_{-g-h} How would I go...

Would general relativity (axiom: spacetime is continuous) still work if we changed the axiom to: spacetime is discrete (but each individual chunk of it is so incredibly small* relative to a quark or gluon that it makes no difference)? *e.g. 3D's of Planck length, 1D of Planck time

Hi, I don't know where to begin, please forgive me for asking this if it's been answered before. I'm confused, I don't know what to study, can you help me out? I'm fascinated by the Universe, my only regret in life is that I don't live in space far away from humans. I've always liked...

Is there a preferred axis in cosmology, if there is what is the origin? arXiv:1604.05484 [pdf, other] Preferred axis in cosmology Wen Zhao, Larissa Santos Comments: 21 pages, 9 figures, 8 tables, invited review Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity...

Another way to ask is if I can go to my PhD in Cosmology through Astrophysics. Many people will thought that obviously yes, but notice Cosmology isn't a branch of Astrophysics, but of Theoretical Physics. Now you'll think this is a completely nonsense, so that Astrophysics is very similar to...

Homework Statement 1) Calculate the angular diameter distance to the last scattering surface in the following cosmological models: i) Open universe, ΩΛ= 0.65, Ωm = 0.30 ii) Closed universe, ΩΛ = 0.75, Ωm = 0.30 ii) Flat universe, ΩΛ = 0.75, Ωm = 0.25 Describe how the CMB power spectrum...

A good year ago, quantum corrections have been proposed to the very early Universe. It was concluded that these quantum corrections contain a precise estimation for the cosmological constant and the so-called radiation term. The authors even have interpreted the latter as evading the big-bang...

In which branch of physics we can put Quantum Gravity and Cosmology ? -astrophysics ? -relativity ? -quantum mechanics ? -classical mechanics? Or other ?

In the spring 2016 issue of the Johns Hopkins Magazine, there is a non-technical article (in graphic novel format) about a new instrument, dubbed CLASS, which is intended to detect "pinwheel patterns" caused by gravitational waves originating in the inflation era acting on the CBR. If these...

AFAIK super symmetry as yet has no experimental evidence in cosmology, will it become part of cosmology in some useful application?

https://www.sciencedaily.com/releases/2012/01/120111135928.htm When will SUSY detection be, 10yrs 30yrs what will SUSY tell us about cosmology. A better understanding of the universe will be the outgrowth of the discovery of the Higgs boson, according to a team of University of Oklahoma...

Expanding universe or contracting matter? this may look very weird question, but what if instead of that the universe is expanding, all matter is contracting as a function of its (proper) time? Δs' = Δs_0 /F(t) The contraction of matter would effect on the length unit what we use. I am...

My daughter's high school physics class is using Giancoli (6th ed.) as their text. I'd previously looked at the treatment of SR, and it seemed OK, although old-fashioned. But this morning I started flipping through ch. 33, "Astrophysics and Cosmology," and I was pretty shocked. It reads like a...

What parts of cosmology can be tested positively in the lab, and what parts can be tested for via electromagnetic radiation .

I am a 49 years old electrical engineer who lectures Optical Communications at the University of Seville. I learned QED because I wanted to understand the ground principles of my area of expertise. I was amazed and thrilled by the beauty of QFT, so I decided to keep on studying. Fearly recently...

1.- Electroweak interaction broke its symmetry about 1ps after the Big Bang and two different types of interactions appeared: weak interactions and electrodynamics. 2.- The LHC at Geneva is routinely conducting experiments above the energy threshold of electroweak unification. Could these...

which of the two is better supported by observational evidence and is more researched?

An article stating Cosmology is in crisis because of our tendency to interpret data to fit our beliefs. Are we guilty of this? http://singularityhub.com/2016/01/09/cosmology-is-in-crisis-but-not-for-the-reason-you-may-think/

after having an integrated m.sc and p.hd from any institute of India qualified through JEST exam ,what i have to do to have an entrance in Princeton university for post doctorate in Cosmology?

Hello, all! My name is Marina and I currently live in Honolulu, HI. I'm an ocean engineering major, but my primary interests are in astronomy and astrophysics! I'm hoping to meet a lot of people here that can help me deepen my understanding of those subjects, and maybe even find some people...

Hi guys, I am an italian student in the first year of Msc in physics. I'd like to make a good Physics Phd in USA/Canada in one of the top 30 cosmology schools(I know some good place in Europe, such as ETH, Scuola Normale di Pisa,...). I'd like to make theoretical cosmology. For now I'm...

Why do scientists think that dark matter annihilates just like antimatter? How is it that dark matter during annihilation can produce light when it cannot emit or absorb light itself?

P.Bull, Y. Akrami, et al. "Beyond ΛCDM: Problems, solutions, and the road ahead" 77 pages + 517 references arXiv:1512.05356 Written not without humour: e.g. pg. 67: "As Tom Shanks once said, there are only two things wrong with ΛCDM: Λ and CDM." " ΛCDM is like Hotel California: it is very...

Dear all, I am trying to understand the physics behind the "number density" formula given by Weinberg. Is there anyone who can explain these parameters to me: 1- "Initial fluctuation strength": \begin{equation} \rho_1= \lim_{t \to 0}\frac{\Delta \rho_M^3}{\bar{\rho}^2_M}\end{equation} However...

Hello All, I've just recently read David Deutsch and Michael Lockwood article about Time Travel of 1994 in Scientific American.They stated,that although among the physicists Everett's theory remains controversial,it has no alternatives in Quantum Cosmology and Quantum Computing.Is it really...

Hi, I am currently in the first of two years of the leaving cert course (A levels), and I am considering a degree with a view to having a career in Astrophysics or Cosmology. I study along with the compulsory subjects of Irish English and Maths Physics Chemistry Spanish and History. I do...

Hi! I'm a first year MPhil student starting my project on black hole growth and dark matter annihilation. I have been struggling with some fundamental things such as getting connected. I would like to be able to discuss my work with people but I am not really sure where to start.

Well I was just wondering that what exactly difference between Cosmology and Astronomy...?

Good day :smile: For quite some time now, I've been thinking about what I should make my Internal Assessment for the IB course in physics on. The main objective of the IA is to find and prove a mathematical relationship between an independent and dependent variable. A very, very, simple example...

I have been looking at several articles recently about the Rh = ct cosmology, but none of them have explained the meaning of the equation. They just assume than anyone looking at such an article will already know what it means. I guess that (1) h is the Hubble "constant", and (2) c is the...

http://physics.princeton.edu/~steinh/lambda16.pdf In this research article the authors suggest a cyclic universe, specifically one involving collisions of higher dimensional branes (an idea taken out of string theory), could indirectly explain why the observed cosmological constant is so small...

Homework Statement Question: Homework Equations [/B] Dp=R(t)Dc where R(t) is the scale factor, Dc is the comoving distance The Attempt at a Solution [/B] I must have tried solving this starting 10 different ways now, starting with the fact that distance=integral over velocity dt...

Hello Everyone, Back when Einstein was formulating General Relativity his equations just could not predict a static universe. I have read that they actually predicted an expanding Universe. Later Friedmann derived an equation from GR that would explain how an Expanding Universe would evolve...

Dear all, Can anyone give me a time scale/ redshift range as an estimate for the formation of magnetic fields in the universe?

Homework Statement The aim is to find a solution for the scale factor in a Robertson Walker Metric with a scalar field and a Lagrange multiplier. Homework Equations I have this action S=-\frac{1}{2}\int...

Homework Statement Numerically integrate and report the particle horizon distance today for the currently fa- vored model \Omega_M=1-\Omega_{DE}=0.25,\omega=-1. Assume the scaled Hubble constant to be h = 0.72, and report the particle horizon in billions of lyr (Gyr). Homework EquationsThe...

Homework Statement Assume the cosmological model with H0=72,Omega_M=1-Omega_lamda=0.3,(so dark energy with w = − 1) and a flat universe.) a) Find the redshift z at which the universe starts accelerating (that is, when it transitions from decelerating to accelerating). b) How long ago did this...

Currently, the favoured explanations for the accelerating expansion of the universe are the cosmological constant, and various scalar fields, most notably quintessence. All of these are mechanisms dependent on mathematical field properties. My question is: do any alternative hypotheses exist...

Homework Statement Plot luminosity distance and redshift z Homework Equations $$d_L(z)=(1+z)r(z)$$ where d_L(z) is luminosity distance and r(z) is the comoving distance. and we have $$r(z)= \frac{H_0^{-1}}{\sqrt\Omega_K}*sinn[\sqrt{\Omega_K}\int_0^z\frac{dz'}{\sqrt{\Omega_M(1+z')^3}}]$$ where...

Homework Statement Consider a universe described by the Friedmann-Robertson-Walker metric which describes an open, closed, or at universe, depending on the value of k: $$ds^2=a^2(t)[\frac{dr^2}{1-kr^2}+r^2(d\theta^2+sin^2\theta d\phi^2)]$$ This problem will involve only the geometry of space at...

As above. In a radiation dominated how do I show this equation? http://i.imgur.com/nMwxvD5.png (It's easier for me to post the image to imgur than use latex. I know g is the relativistic degrees of freedom. I think that the scale factor a(t) is proportional to 1/t and that a(T) is proportional...

What Is the difference between Cosmology and Astronomy..?

For this we need a thought experiment: imagine you're on a gedanken planet manning a gedanken laser cannon, and it's pointing straight up. The light doesn't curve round, or slow down as it ascends, or fall down. It goes straight up. Now let's keep you safe in a bubble of artistic licence, and...

What are the essentials to starting on this topic from the very beginning? What are topics I should have covered before starting? Suggestions please? Thank you.

http://phys.org/news/2015-07-cosmology-standard.html The most popular candidate for the elusive particles that give the Universe extra mass is Cold Dark Matter (CDM). CDM particles are thought to move slowly compared to the speed of light and interact very weakly with electromagnetic radiation...

I have been looking for literature on this question but can not find any, will a (bounce) retain all the information of the previous galaxy ?

Assuming a neutron star is a uniformly dense sphere of radius 10km and mass =1.4 mass of sun, derive the period of radial oscillations.First use hydrostatic equilibrium to calculate p, then the velocity of sound is $$v= \sqrt{ \gamma p / \rho}$$, so the period of pulsation is time it takes from...

I'm looking for some appropriate 1st year, or possibly 2nd year, level grad texts on galaxies and cosmology. The grad course at my university requires Cosmological Physics by Peacock and Galaxy Formation by Longair. I've noticed many old cosmology course websites require Weinberg or Dodelson or...

This paper states that gravity gravitates, to me that is mind boggling, i can not even understand how these additive effects may alter cosmology. arXiv:1509.06682 Let us start by recalling how interaction energies work in relativistic gravity. It is well known that gravity gravitates in...

The Big Bang process (with or without inflation) followed known rules which had to exist prior to time zero (start of big bang). For example, some of the obvious rules of the game included: mathematics, conservation laws (symmetry), thermodynamic laws (energy conserved, entropy increases)...