Recent content by skydivephil

Yes agreed a cyclic universe by definition repeats. Can we also agree that a cyclic universe is not the only model where the universe is infinitely old ? Can we also agree that there are many different types of cyclic universe so if you are going to critique one you need to specify which one it...

Which cyclic model are you talking about? Ekpyrotic? CCC? VSl? Baum Frampton? Higgs Bang? There are many cyclic models so one should not talk of cyclic model generically. Moreover one does not even need to assume a cyclic universe to assume an infinitely old universe. Many models of quantum...

It depends on how you define big bang. If you define big bang as an evolution from a hot dense state then an infinitely old universe could easily have a big bang. In many cosmological models there are is a period of contraction prior to a period of expansion. This sort of evolution still has a...

The universe is not necesarily static prior to infation, here is one possibility: http://arxiv.org/abs/1302.0254

A simulation in a computer is not the same as doing an experiment or collecting data from nature. You can't do that with the constants of nature.

Just one thing to add the LWC bounce does not replace inflation Just one thing to add, there are bounce models that replace inflation but I think most papers in LQC assume inflation happens after the bounce. An interesting result in LQC is the claim that the supposed fine tuning of inflation...

A lot of people quote 10^ 500 as the number of different ways of compactifying the extra dimension in string theory. But I recall somoene saying at a talk that its now much larger than that. What's the current estimate?

Thanks Marcus.

Nor sure if this has already been discussed. But recently Rovelli has suggested the mysterious Fast Radio Bursts might be from Planck Stars : https://www.gravity.physik.fau.de/events/tux3/rovelli.pdf Any thoughts? What are the other explanation and how can resolve this?

So in that case, it seems to me that if we see a red tilted primordial gravity wave spectrum with no large devaition from gausianity then we can start handing out Nobel prizes for inflation, but not before? Do you agree?

Thanks for that Bapowell. Is this something that alternatives to inflation such as Ekpyrosis, VSL, CCC, string gas cosmology etc can explain as well or is it unique to inflation?

Al lot of the answers to your questions depends on how you define terms like "universe" and "big bang". these terms can have varying definitions and so you can get different answers depending upon which definition you use. Question: Was the universe a tiny ball? Firstly let's look at the word...

I think there is some confusion between chaotic inflation and eternal inflation. Even some big name comsologists like George Ellis seem to make this mistake. Eternal inflation leads to a multiverse, chaotic inflation is eternal inflation, but eternal inflation is not necessarily chaotic...

The model you are referring to ( colliding branes) is the Ekpyrotic model of Turok and Steinhardt. You can read abut it here: http://en.wikipedia.org/wiki/Ekpyrotic_universe In cosmology when people talk about a multiverse they are normally talking about eternal inflation which is a very...

If you were standing on the Earth during the HAdean era, would the outgassing of volcanoes prevent you from seeing the stars? Would the atmosphere be transparent; what about moving into the Archean Era?