Cosmology Definition and 915 Threads

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...

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 THEORETICAL...

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?

I'm currently a high school freshman in NYC and was wondering what classes I should focus on in school and what programs are available in astrophysics, cosmology, and or relating to it for someone my age? Thanks so much.

Hi folks, I'm a 3rd year student doing a BSc in Mathematics and Physics (in Scotland) and I was wondering if anyone could share with me their experiences of the MSc particles, strings and cosmology at Durham (previously MSc elementary particle theory) or any of the other similar courses at...

Hi, http://www.msnbc.msn.com/id/3077693/ns/technology_and_science-space/ http://thefutureofthings.com/news/5497/dark-matter-filament-detected-near-the-milky-way.html What are these filaments in space? Are they made of pure plasma or is dark matter involved too? How could dark...

Spinfoam cosmology is a fast-growing field, since it represents the application of the full LQG theory to the BB and expanding universe. In the early years loop cosmology addressed a restricted model with just a small number of degrees of freedom. Going from oldfashioned LQC loop cosmology to...

According to SR relativity of simultaneity, the temporal order of events depends on the frame of reference from which the observer watches the events and different observers with a spacelike separation between them or at relativistic speeds won't agree in the order of events. Now , in...

Homework Statement The redshift of a galaxy is measured at the present epoch t0 and again at the infnitesimal future epoch t0 + δt0. Show that the rate of change of z with t0 is given by \frac{dz}{dt_{o}}=(1+z)H_{o}-H(z) Homework Equations Hint - Start From: \frac{\delta z}{\delta...

I would like to ask what topics one should study before studying cosmology. I have begun self-learning physics since last summer, and my goal is to build a foundation solid enough to learn cosmology in great depth. I seem to be just touching on different topics: relativity, the uncertainty...

Could anyone suggest good universities in the UK for studying cosmology at a PhD level? Thank you!

Hi, I graduate university this summer with a physics degree, (4 year masters, specialising in astrophysics and particle physics), and I'm very keen to do a PhD in cosmology. Does anyone know which departments are the best to work in, for this field? I'd love a project on QSOs as a probe of...

I've asked a similar question earlier already, but I want to be more specific now. I'm contemplating doing a PhD in cosmology (mainly numerical analysis of galaxy observations). It's a good group with a good international standing. I'm just a bit worried about the time after my PhD. How...

I have some general, fundermental questions about Cosmology and the future of Cosmology: 1. Is there a resource or management initative of some kind, which is keeping track of all the theories, sub theories, completely different theories and competing theories related to cosmology? If so is...

I am trying to learn gauge issues in cosmology from Weinberg's "Cosmology". However, I am completely stumped at how he gets 5.3.4 from 5.3.3. I was doing great until that point and now I'm going crazy. Any help would be highly appreciated!

We had a discussion of Penrose's conformal cyclic cosmology last month: https://www.physicsforums.com/showthread.php?t=427567 His popular-level book Cycles of Time was published first in the UK, but is now available in the US. I got a copy and have read it, so I can report on a few of the...

Hello Its 2010 now and I am not really up to date with careers. Is it still an extremely risky to go into astrophysics and/or cosmology? Can you guys tell me how things are going for scientists of all branches if you know? Thanks

http://arxiv.org/abs/1010.1258 Big Bounce in Dipole Cosmology Marco Valerio Battisti, Antonino Marciano 5 pages (Submitted on 6 Oct 2010) "We derive the cosmological Big Bounce scenario from the dipole approximation of Loop Quantum Gravity. We show that a non-singular evolution takes place for...

In Superstring Cosmology and Superstring Gas Cosmology they try to address the question as to how compactification occurs. Is it believed that possibly cosmic strings wrapped themselves around 7 dimensions and collapsed due to their tension? This isn't a personal theory just a curiosity as to...

Will the results from the PLanck satellite shed any light on Loop Quantum Cosmology or any other form of matter bounce?

Hi all, it's my first post here, and I'm glad to have found it. I'm a software engineer by trade, but I've always been immensely fascinated by cosmology, and I think it's my true passion (when I went to school, I was concerned that pursuing cosmology would not pay the bills, so the pragmatist in...

Cycles of time--Penrose says his cyclic cosmology obeys thermodynamics. Roger Penrose has devised a cyclic cosmology which he sees as not violating the second law of thermodynamics. There are several online videos of him lecturing about it. I'll get some links. I'm curious to know if others...

What are the top undergrad universities for a major in Cosmology minus Ivy?

Hello, I've been thinking recently about the truths and realities that are found in the Universe and I just wanted to share a bit of what I have been thinking about. I'm 16 years old right now and I have a drive to understand the way nature displays itself to conscious beings. I'd like to...

Loop Quantum Cosmology could be interesting to discuss because 1) it has been radically transformed since 2007 (with what Ashtekar calls "improved dynamics") 2) it has begun a phase of rapid growth (new crop of researchers , publication rate more than doubled since 2006) 3) it now includes...

Is there a consesnsus as to whether the big bang represent an ultimate beginning ? it seems to me that the answer to that question is no. The reason for this is that we need a quantum theoy of gravity to describe the moment of the big bang and all current attempts at this eg LQG, Hoyava...

So basically I am about to embark on my Msc in the pure maths department. Now I wish to conduct research on the subject of arithmetic quantum chaos and its applications in number theory and in gravity and cosmology. In my university I found someone who is an expert in its applications to...

Can Conformal Weyl Gravity be considered a viable cosmological theory?

Hi All, I am a computer science engineering graduate , currently working in software company. I am very much interested in cosmology since my childhood. I tried putting off my urge to choose cosmology as my career for a very long time. But I can't do that anymore. So can anyone suggest me...

I am just going into my fourth year of a 4 year MSci course and have got my results from my third year. It's not as good as I had hoped and my average is a 2.1. I know that Cosmology is very difficult to get into and PhD's are over subscribed. I was also hoping to work at one of the...