Cosmology Definition and 951 Threads

First MOND was the first to predict the cosmic background radiation, as repeated in this recent article (2011) http://prl.aps.org/abstract/PRL/v106/i12/e121303 in its page 121303-3: Whereas the LCDM-1999 prediction was falsified (A1:2 = 1.8). Only after the WMAP data was known (A1:2 = 2.34 ±...

Hello, Has anyone read any good or interesting Cosmology books lately? Thanks

Hi, I am currently reading Liddles Introduction to Modern Cosmology (2nd Ed) and having trouble with problem 8.4, about the age of the universe with a cosmological constant. The question asks to derive the formula for the age by first writing the Fridemann equation in such a model as...

As someone trained in IT, having spent 15+ years as a network consultant, it sometimes surprises me that people expect you to be an expert in other areas of IT. I know networks and subnets, protocols, infrastructure, network security, data packets, switching, wireless and related things - that...

I am currently in first year physics at university. I have looked at lots of courses that my university offers (u of Manitoba), and at many others, and I can't find any many undergrad courses, just astrophysics courses. None of the other universities that I have checked have degrees in physics...

Is there a current list of the major problems or conflicts with the standard cosmology models?

My ongoing study of https://www.physicsforums.com/showthread.php?t=483871" that this has something to do with the fact that the shear viscosity to entropy ratio of a strongly coupled N=4 super-Yang-Mills plasma is 1/4π. Sheppeard has her own program of deriving field theory from categorical...

Once I read a famous quote from a science book, but I do remember the name of the book, neither the name of the speaker. The general idea of the famous quote is that, "All the knowledge we have are in principle some parts of cosmology." It implies that since all the phenomena we see are parts...

Hi all, I am new here. Can you please give me a list of good conferences for publishing cosmology related papers?

which journal specifically i have to hope a little time for a response of acept or reject? and , where the time of to hope is big?

Gravity, information, and cosmology (was "Thoughts about the universe") There was a thread here a few minutes ago, posted by a new user, called "Thoughts about the universe". It contained reflections about gravity, information, and the universe, that were probably inspired by the holographic...

Should I study cosmology? Am I too old?? Hello eveyone, Im 24 years old. I wasted a lot of time before. I've just finished the 1st of university. Then I left. I regreted what I've done before. Cuz I looked for wrong things all the time. Since last year, i started reading lots books about...

i want to study cosmology,and i am going to apply this year. i am not qualified for the top 20 universities' Ph.D program, and i think i should apply some universities ranking from 30 to 100, i mean , ranking of physics, but still strong enough in theory cosmology. however, i have no idea...

Just curious as to what you think about this recent paper from Max Tegmark: How unitary cosmology generalizes thermodynamics and solves the inflationary entropy problem Abstract: "We analyze cosmology assuming unitary quantum mechanics, using a tripartite partition into system, observer...

Since the second law of thermodynamics builds upon the first, if the first law doesn't apply to cosmology like it keeps being repeated around here, it would seem to follow that that the second law doesn't apply either. Could this be clarified by someone tat actually knows about cosmology...

Sorry if this has already been discussed, i couldn't find any thing.arXiv:1108.0893 (cross-list from gr-qc) [pdf, ps, other] Loop Quantum Cosmology: A Status Report Abhay Ashtekar, Parampreet Singh Comments: 136 pages, 15 figures Subjects: General Relativity and Quantum Cosmology...

arXiv:1108.0079 [pdf, ps, other] Gravitational wave generation in loop quantum cosmology Paulo M. Sá, Alfredo B. Henriques Comments: 7 pages, 8 figures, revtex4 Subjects: General Relativity and Quantum Cosmology (gr-qc) We calculate the full spectrum, as observed...

Let us consider the cosmological metric: {ds}^{2}{=}{dt}^{2}{-}{[}{a}{(}{t}{)}{]}^{2}{[}\frac{{dr}^{2}}{{1}{-}{k}{r}^{2}}{+}{r}^{2}{(}{d}{\theta}^{2}{+}{sin}^{2}{(}{\theta}{)}{d}{\phi}^{2}{]} -------------- (1) For closed models k is positive We shall consider here a closed one: We write...

In <Cosmology> written by Weinberg, in page 109, it says that \epsilon=\alpha_{B}T^4+\frac{3}{2}n_{B}Nk_{B}T p=\frac{1}{3}\alpha_{B}T^4+n_{B}Nk_{B}T \alpha_{B}T^4is the average energy density of black-body radition, then what does \frac{3}{2}n_{B}Nk_{B}Tmeans? the energy density of...

Homework Statement Calculate the comobile distance of a galaxy with z=7.3, H_{0}=72 km/s/Mpc, universe with \Omega_{0}=\Omega_{0,m}=1 Calculate the scale factor when the galaxy emitted the light we receive today. Homework Equations Friedmann equation (\frac{\dot{a}}{a})^{2}=(H_{0})^{2}[...

This article : http://www.sciencedaily.com/releases/2011/06/110630111540.htm claims to rule out "some" string and loop models but doesn't really elaborate, I couldn't find that claim in the original article: http://arxiv.org/abs/1106.1068 anyone care to discuss?

How are time and distance measured in cosmology? Relativity says that time isn't absolute. For example, the rate at which a clock runs depends on its state of motion. Because of this, it's not trivial to define what is meant by phrases like "the age of the universe," or "three minutes after the...

Hello, My name is Eric, I will be starting college soon but it seems when it is time to decide on my future occupation I am at a loss. Due to the fact that I grew up in a Very sheltered town being surrounded by people who didn't really think college was something needed. I...

For the most part I've been using the Hubble constant of: H0 = 72 km/s/Mpc but I've started seeing it expressed as: H0 = 100 h100 km/s/Mpc. what is h100 and why is it coming up in this?? I've also seen the critical density for the shape of the universe (flat/open/closed ect) as: Rhoc = 1.879...

Homework Statement Estimate the pressure of the CMB photons today. [You will need to choose a reasonable value for the present value of the temperature of the CMB. The radiation constant is α = 7.56 × 10−15erg cm−3K−4 Assume that a new population of stars is discovered, and their age is...

Hi, I am a physics grad student, hoping to do theoretical cosmology. I've recently been thinking a lot about practical things like career tracks, postdoc jobs, etc. So I thought I'd ask a couple questions here to see what others think: 1) I hear that the job scene for fundamental theory...

Hi all, Is there a timeline somewhere which shows a history of theories, breakthroughs, discoveries, especially with regard to cosmology. And is there a summary of the types of work being done in this area currently? It's probably a big question, but I'm keen to understand how some of the...

In question 4 of this paper, I am trying to find the sign of \Lambda Since we have the vacuum einstein eqns G_{\mu \nu}=-\Lambda g_{\mu \nu} we can just contract to get R-\frac{4}{2} R=-4\Lambda \Rightarrow \Lambda=\frac{R}{4} So \Lambda will have the same sign as R Now given the...

Hello. I have been working through some questions and answers to do with cosmology. One of them asks you to consider a model where: \Omega_{MO}=3 \Omega_{\Lambda O}=0.01 \Omega_{RO}=0 and asks you to show mathematically that the model re-collapses. Following through the math, I get three...

I'm looking through the solution to a problem and am stuck with some of the maths. The solution can be found here: http://www.damtp.cam.ac.uk/user/r.ribeiro/supervisions_files/Cosmo1sol_M2010.pdf The pages are numbered in the bottom right corner. I am on p12. We have an expression 1+z...

Not sure if this is OT for the cosmology forum.. pls move if so. I'm wondering about examples of where cosmology science has helped in a practical way. Not being facetious.. genuinely curious (and I think knowledge for knowledge sake is almost always a good thing). Cosmology has helped...

Hi, I am 15 years old boy. I've just appeared from 10th grade exams. I am interested in cosmos. I like Stephen Hawking's shows too much, and other shows which are related wih cosmos. I want to become cosmologist or astronomoer. I've much curosity about cosmos. I am interested in...

Hello everybody, I'am a new membre. I'am working on an introduction to cosmology, but I haven't yet the necessary documents:confused:, and hence I"ll be very thankful if you help me:smile:. I want a undergraduate and graduate (not very complex) books but not old if you can. thanks

Is there any cosmology book out there that is up to date, more substantial than Linder, but less so than Weinberg? I own Linder and have read it, and it's fine, but it only goes so far. I have a pretty firm grasp of GR, but if I bought Weinberg I think the chances I'd wade through it are slim...

Hey I didnt know where to put this so the masters projects we can do for next year came out .. but I am not really interested in any of them However we can propose projects So i was thinking if anyone could lead me in the right direction Im want something in either COSMOLOGY or...

Hey I didnt know where to put this so the masters projects we can do for next year came out .. but I am not really interested in any of them However we can propose projects So i was thinking if anyone could lead me in the right direction Im want something in either COSMOLOGY or THEORETICAL...

For a random field, f, the two point correlator is defined as \xi(x,y)=\langle f(x) f(y) \rangle = \int \mathcal{D}f \text{Pr}[f] f(x) f(y) where \text{Pr}[f] is the probability of realising some field configuration. Statistical homogeneity means that \text{Pr}[f(x)]=Pr[f(x-a)]...

Hi, I have basic understanding of calculus and geometry.Can you please suggest some book on cosmology and space time with some mathematical component to it.

constraining dark matter and dark energy with sunyaev-zeldovich effect. need help on this topic

If had empty cosmology? What would happen if we had no matter or radiation or dark energyand only had curvature? How would this effect luminosity distance? From the friedman equations I get that H2=-k/R2. Is this right?

http://pirsa.org/11040063/ Big Perimeter audience, appreciative interest, long question period after. He undercuts his critics (who said the concentric circles could have appeared by chance) by criticising their methods and makes at least one valid point. I would say that the critics still...

A ways back, I seem to remember reading on the Planck Mission page that it's observations of the CMB could help foster support for M-theory cosmology and weaken support for Inflation, or vice-versa. I thought it had something to do with detection of Non-Gaussianity in the CMB. I could not...

What advances is theoretical or observational cosmology in the last decade have for you been the most impressive? This is open to all, but especially to the pros!

I am doing question A1/16 part (i) at the top of page 13 here: http://www.maths.cam.ac.uk/undergrad/pastpapers/2001/Part_2/list_II.pdf I am stuck on the last part where we're given the equation of state P=\sigma\rho c^2 and we have to find a(t) and SHOW a(0)=0. I will work through to where...

I think this conversion is so valuable, I decide to share it with you all. We come up with two models, one is playing cards. one is lottery. they both work. "To deal with such paradoxes we shall adopt an approach that we call model-dependent realism...

http://arxiv.org/abs/1103.2475 Probability of Inflation in Loop Quantum Cosmology Abhay Ashtekar, David Sloan 34 pages, 3 figures (Submitted on 12 Mar 2011) "Inflationary models of the early universe provide a natural mechanism for the formation of large scale structure. This success brings...

This raises an interesting physics question. What physics reason could there be for the shift of researcher interest in quantum cosmology which this Inspire search illustrates? Here is the Inspire top ten quantum cosmo list for 1996-1998...

Hello! I am a physicist. Although I think I understand quite well the laws of Newtonian physics and general relativity that explain the observable universe, I am a complete dummy in what concerns doing measurements in the universe. For instance, I have no idea how to measure the distance to a...

How is the large investment spent on say... space missions or large telescopes justified when the country is in a recession? Can you guys think of any examples of large investments into cosmology that were fruitful/failed?

Now I’ve been trying to read up on this Shockwave cosmology model and wanted to see if I have the correct view since most of the math is over my head. Now from what I understand in this model is that there is a white hole singularity that explodes and instantly disappears and it produces a...