Cosmology Definition and 951 Threads

I need integrate "over heavy momenta" the following equation \sigma v>= <\sigma v>= \frac{1}{n^{(0)}_1n^{(0}}_2 \int \frac{d^3p_1}{(2Pi)^3 2 E_1} \int \frac{d^3p_2}{(2Pi)^3 2 E_2} \int \frac{d^3p_3 }{(2Pi)^3 2 E_3} \int \frac{d^3p_4}{(2Pi)^3 2 E_4} e^{-(E_1+E_2)/T} \\ \cdot (2 Pi)^4 \delta^3...

By quantitative cosmology I mean with real times, distances, expansion rates, horizons, CMB stationary observers etc , derived from the standard model fitted to data. I don't mean ideas about conditions shortly before or after the start of expansion, although that is very interesting too. The...

This is quite an entertaining 15 minute video that provides a high level discussion for a general public audience. [A physics teacher and childhood friend uses the video in her advanced placement HS physics classes in New York. Her students are one group of US kids that I know get a good...

New release of Jorrie's tabular calculator. http://www.einsteins-theory-of-relativity-4engineers.com/LightCone1.0/LightCone.html this is clearly the best on-line cosmology calculator for the general user on the web. Hands down. Lightcone rules. that's all there is to say. Check it out...

Hello folks My name is Mike. I am into Cosmology ever since I was a kid. Throughout the years I strayed away from Cosmology unfortunately but I am very very fond of Cosmology...and thus...call me an amateur Cosmologist :D Anyway... These days couple of questions puzzle me in the...

Homework Statement The assignment is to find the energy loss constant for the theory of tired light. If redshift isn't caused by the expansion of the universe but from a loss of energy, how much of a photons energy is lost per unit distance(MegaParseC) for some set Hubble constant. Homework...

I am an aspiring physicist. My main interests are Particle Physics, Cosmology and Black hole physics. I am going to join a college this year for the same. I applied to two colleges and got selected. University of Lancaster and University of Birmingham. I have applied for the course - Physics...

This paper; 'What have we learned from observational cosmology ?', http://arxiv.org/abs/1304.4446, provides a good overview on the evidence supporting the LCDM model and why it is currently favored by mainstream scientists. It also offers considerable discussion on the motivation for Dark Matter...

Conspiratorial cosmology - the case against the Universe Sounds pretty serious to me... Garth

I've been looking for a few websites good for Cosmology and Physics, maybe you guys can help? I'm in 8thgrade, but I can comprehend a lot, just try to stay away from websites that have excessive technical math please. All posts are appreciated.

Hey there! I recently bought said book and would highly recommend it for any Astronomy and Cosmology undergrads. However, one little niggling thing about it (something that grinds my gears in general with textbooks) is that it features end of chapter questions yet no set of answers for the...

Homework Statement i i am trying to derive \dot{\rho_{R}}+4H\rho_{R}-\Gamma_{\phi}\rho_{\phi}=0 as in Kolb an turner (Boltzmann describing reheating). Is the correct approach to, use the 1st law dU=dQ-pdV, but what would dQ be?

Can anyone explain: why COBE measured IR and microwave as opposed to visible light, when surely we are measuring photons that have decoupled? why Planck is measuring light polarisation?

http://www.perimeterinstitute.ca/seminar/rethinking-cosmology In five days Paul Steinhardt (Princeton) will give a colloquium talk at Perimeter. He has a 90 minute timeslot. Steinhardt has been a proponent of "brane-clash" cosmology. Sometimes called Cyclic or Ekpyrotic. Two spatial...

Is the key difference between coasting and static cosmology models the presence of a linear acceleration, or are there other major differences? Regards, Noel.

I was reading Weinberg's book Cosmology. When I went to chapter 2, under the subsection 2.1 "Expectations and discovery of the microwave background" I could not understand one statement. ---Quote--- The work done by pressure in an expanding fluid uses heat energy drawn from the fluid. The...

In Mukhanov's Physical Foundations of Cosmology p348, he writes "Decoherence is a necessary condition for the emergence of classical inhomogeneities and can easily be justified for amplified cosmological perturbations. However, decoherence is not sufficient to explain the breaking of...

Author: William Lewis Burke Title: Spacetime, Geometry, Cosmology Amazon Link: https://www.amazon.com/dp/0935702016/?tag=pfamazon01-20 Prerequisities: Level:

"APS Physics" view of pre-inflation cosmology article The APS has an online periodical that publishes "Viewpoints" on current research, for instance http://physics.aps.org/articles/v5/142 is an interpretive explanatory viewpoint, written for non-specialists, on the article by Agullo Ashtekar...

I have a few questions so I hope it is okay if I ask them all here in this thread. They are all related somewhat. According to brane cosmology, our 4-D universe is embedded inside a higher dimensional space, a hyperspace if you will, called the bulk. The reason we cannot perceive or interact...

Homework Statement Decide the density parameter from the following data: z=0.04, m= 17.38 and σ=0.19 Homework Equations Definition of the density parameter: Where p0 is the current density and pc is the critical density. The Attempt at a Solution I feel like I don't...

Homework Statement Show that by using the Friedmann-equation you can determine the scale factor for a Universe in it's early stages (starting with the Big Bang) to: Homework Equations The equation for the scale factor: Where r(t) is the distance from us to a given galaxy to the time t...

In brane cosmology how can there be no such thing as inflation. I was watching a lecture with Neil Turok and he said he made a bet with Hawking that says that the new Planck satellite will give us information that could prove against inflation. So, my question being, instead of inflation in the...

Hi there, the full question is as follows: Suppose omega_m = 0.2. If we observe cosmic acceleration at z=0, what is the possible range of values of q_0? What is the minimum value of lambda? What is omega_total? so I'm having trouble with the relationship between q_{0}, \Omega_{m,0}, \lambda...

The recent report from the South Pole Telescope seemed to several of us to be exceptionally interesting making one think we might have a thread that just lists recent papers, as they come out, which seem as if they might be important to cosmology. Here are a few. http://arxiv.org/abs/1210.7231 A...

There's an interesting conference taking place this month at the NORDITA institute for theoretical physics in Stockholm. It brings together, from a number of different areas, researchers working on various models of what was happening around the start of expansion--replacing the "singularity"...

A friend of mine was reading Penrose's new book on CCC; I do not want to discuss this story here but a rather interesting detail which could be relevant w/o the whole CCC stuff. SR and GR rely on (global and local) Lorentz invariance. From these symmetries one can derive invariant mass M² and...

Starting with the Robertson-Walker metric \large ds^2 = -dt^2 + a^2(t) [ \frac{dr^2}{1-kr^2} + r^2(d\theta^2+\sin^2\theta d\phi^2] Consider a light ray emitted at the Big Bang traveling radially outwards from our position. Therefore we have: ds = 0 d\theta = d\phi = 0 Substituting...

When talking cosmology what exactly is a manifold, is there any observational evidence that we live in one ?

I’m a layman new to the Cosmology Forum and just finished reading through the very helpful, “Effort to get us all on the same page (balloon analogy anyone?)” by Marcus et. al. followed by “Look 88 billion years…”. [If you’re in a hurry see the nice summary by Mark M at cosmo.pdf.] Along the...

Homework Statement "Consider a perfectly homogeneous and isotropic universe filled with dust of uniform density ρ(t). Let universe expand, dust is carried radially outward from origin. Conservation of total energy E. E = K(t) + U(t) K(t) = (1/2)*mv^2(t) and U(t) = -GMm/r(t) where M =...

Hi. I'm an undergraduate student interested in cosmology. Initially, it was astrophysics, and I know it's a large field and I'm generalizing, but I felt a lot of the work was statistical analysis and letting the computer crunch images and letting it do things for you. I know a lot of...

In a serious thread, a newbie brought up Carmelian cosmology and clearly thinks it's meaningful but in the brief look I gave it, it looks like nonsense, which is why I put this post in Skepticism & Debunking. Any thoughts? Thanks EDIT: Never mind. I spent a few more minutes looking at it...

Hey guys, I am currently in year 12 and have been asked to develop a thesis on cosmology for an Extended research task (ERT) and I am bewildered. Nothing is coming to mind at the moment and I am struggling. I have no idea what to do mine on. the teacher gave us a list of topics that we might...

There have been a few threads of late on the multiverse concept in cosmology, and whether it can be viewed as a viable, albeit currently underconstrained cosmological theory that is leading us to demonstrably correct discoveries about our universe, or if it is essentially a fairly arbitrary...

hi i am looking at uni courses and i a a bit confused between the differences between; astrophysics, astronomy, cosmology and space science in terms of what is covered in each . Can anyone help please. Ryan

Hello, I am a 12 years old in 6th grade. It's been my dream (since I was five) to become a cosmologist. Sadly at school we do not learn about cosmology, because of "religious" reasons. I would greatly appreciate it if anyone would know where there is a beginners area for cosmology.

Homework Statement Find the change in temperature due to conservation of entropy, which happens during reheating when pions ( \pi^{\pm},\ \pi^0 ) get out of thermodynamic equilibrium beneath 140 MeV. Homework EquationsThe Attempt at a Solution I tried to compare this to the exiting of...

Hello everyone, I am a student in particle physics and cosmology in some Belgian university. I'll finish my master degree in June of this year. I am searching for PhD studentships in Europa or US, but it is very difficult to get a place somewhere. I applied to some universities, I'm still...

I am working on an introduction to cosmology, I have began by the Newtoniant one (the Hubble law, the Friedmann, fluid and acceleration equations), and some of the aspects of the relativitic one. I want to relate the tow parts by mentioning the shortcomings of the first, and then mentioning the...

I should start a new thread for my questions rather than hijack others... Posted this on another thread but it didn't get any response, so bear with me if you've seen it. Has anybody looked into Cantor's works on infinity and seen how they relate to the question of an infinite universe...

Besides having the best academic record and publications, what else can one do to improve his chances to be accepted to this prestige club? Just a dream... :-(

What is the difference between Astronomy, Astrophyics and Cosmology?

I'm a Physics Senior in the United States. I would like to participate in an Undergraduate Research Program in the UK this summer. I've applied to several here in the US, but I'd enjoy a pretense to both further my studies of novel space-time geometries using non-FRW models and visit some some...

Hello. What are some good books for learning cosmology? I know GR (At the level of Schutz) And /some/ QFT. So...How much particle physics/QFT are required for a book like Weinberg or Dodelson? Should I do my QCD and Electroweak theory and particle physics before doing cosmology?

What do I need to know before I can study Cosmology. I think I'm going to read this text: https://www.amazon.com/dp/0198526822/?tag=pfamazon01-20 Cosmology by Steven Weinberg. I'm going to read this College Physics text first by Serway...

Hi, I have one question about the expansion of the universe. Say, that there is a part which is that far away that we can't see it any more more because the speed of light is succeded. Wouldn't this mean that those part of the universe has no more influence on us at all? In ohther words...

I was wondering whether I should brush up on ode's/pde's or just go through the math appendix of Griffiths to prepare myself. How much ode's/pde's is needed for Griffiths and Ryden? Thanks

Hello, I am a first year undergraduate student at University of Toronto planning to pursue cosmology as a field of study in the future. There are currently two specialist programs being offered that relate to my interests (unfortunately, I was unable to find a direct link to the programs, so...

In equation below 〖H₁〗^2/〖H₀〗^2 =Ω₀(cri) (R₀⁴)/(R₁⁴(1+z(eq))) Why is the term “(1+z(eq))” negligible in denominator according to the term “ R₁⁴ ” ? Weinburg did it in his book named "Cosmology".