Early universe Definition and 112 Threads

When temperature of the universe falls below nucleon mass ##T<<1## GeV, the number densities of nucleons (proton and neutron) which are in kinetic equilibrium can be obtained as ##n_i=g_i (\frac{m_i T}{2\pi})^{3/2} e^{\frac{\mu_i-m_i}{T}}##. Since baryon number should be conserved, then I...

Background: Neutrinos decouple at around 10^10 K (or 1 MeV). This is normally shown as the interaction rate (between neutrinos and electrons) over the Hubble constant: Gamma/H = (T/10^10 K)^3 My problem: I have a function which is dependent on the neutrino-electron interaction. But it does...

Penrose wrote in the Road to Reality that gravitational clumping increases the entropy of the universe. The early universe was very low in entropy because it was very smooth, with very little clumping. So, is it accurate to say that the early universe was high in entropy except for the...

I'm having some trouble understand this correctly, so I was hoping someone could enlighten me a bit :) Okay, so in the early Universe most of the hydrogen and helium was formed, and then kept in equilibrium, and ionized via photons. So we have a plasma of baryonic matter, including dark matter...

I'm currently reading about the Boltzmann equation, used for the early Universe. The equation I end up with, after some simplifications is the following: \begin{equation} a^{-3}\frac{d}{dt}\left(n_1a^3\right) = n_1^{(0)}n_2^{(0)}\langle\sigma v\rangle\left[\frac{n_3 n_4}{n_3^{(0)}n_4^{(0)}} -...

Homework Statement I've been told to calculate the energy density in the early Universe. It states that it is completely dominated by neutrinos (3 species), photons, electrons, and positrons. Homework EquationsThe Attempt at a Solution Now, I've found an equation to calculate the energy...

Apparently the early universe was opaque because the atoms were ionized. I'm wondering, why do electrons scatter photons but atoms don't? I'm presuming it's the electrons that do the scattering.

As i understand it, at some point in the early unvierse, the Higgs field was off, then it swtiched on. Is this correct? I can't find when this is supposed to have happened, does anyone know?

Hope this isn't too simplistic, but; Type 1a supernovae tell us gravity is constant for as far as we can observe Type 1a also provide evidence that the rate of cosmic expansion is accelerating Wouldn't the early universe have at some point been below the density required by the...

This has probably been covered here before, and it's a pretty basic question but one I've often wondered at. I read somewhere recently (and have heard it said) that we can now 'see' very distant galaxies. I forget the exact numbers but things like we are seeing galaxies that are maybe 80% as...

Hi there, I've done some searching around on the forums and in the library, but I haven't found what I was looking for - some information of symmetry violation in the early universe. I know some small pieces of information but I'm currently trying to consolidate that so that I have an actual...

Hi there, I've done some searching around on the forums and in the library, but I haven't found what I was looking for - some information of symmetry violation in the early universe. I know some small pieces of information but I'm currently trying to consolidate that so that I have an actual...

I have been trying to get my head around this topic for a while. As I go through the description of scalar fields, the inflation and the potential inflaton, (in description as in ned.ipac.caltech.edu), I constantly miss a concept. There must be a fundamental difference between the type of...

We define time by the rate at which physical processes (i.e. clocks) tick. With atoms for example we can define time by their energy transition rates such as in atomic clocks. But, what before atoms existed? Current cosmology theories make statements such as that '0.5 seconds after the Big...

Homework Statement At very high temperatures (as in the very early universe), the proton ad neutron can be thought of as two different states of the same particle, called the "nucleon". (The reactions that convert a proton to a neutron or vice versa require the absorption of an electron or a...

When the universe was young, and everything was closer together, did the extra gravity cause time to run slower than it does now?

Hi again not sure if to post here or in the beyond SM section, but because it is to do with early universe/inflation i posted here. I have been reading that gravitinos can be produced during reheating after inflation (particular in fermionic preheating). Does anyone know why fermionic...

I really think this paper http://arxiv.org/abs/1212.1087 which Chronos mentioned in another thread deserves its own thread. Has anyone had a chance to look at it? what do you think? This has been a lot of noise about this issue raised by people like Roger Penrose and Sean Caroll . They have...

Homework Statement Calculate the number g* of effective relativistic degrees of freedom as the universe cools through the temperature ranges (i) T > 103 GeV, (ii) 1 MeV < T < 100 MeV, and (iii) T < 0:1 MeV. Homework Equations for the equation that is required to be used look the...

Hi folks, I asked a form of this question in another forum and didn't get a satisfying answer. As I understand it, there is a time in the early universe (t < 10–12 s) when particles have not acquired mass. According to special relativity, massless particles travel at c. Also according to...

One of the aims of the Large Hadron Collider is that it may be able to re-create conditions in the early universe and therefore produce the quark-gluon plasma that appeared microseconds after the universe's birth. However a fundamental difference between the universe now (in which the...

So, if our observable universe was less than a centimeter across, why didn't it collapse into a super black hole? The gravitational field of all that matter... inflation seems weird when you think that it could become into a big black hole (and it didn't; right?)

Hello Folks, I have an interesting question (I think)... how far back in the history of universe would you have to go before any form of life existed? Thanks. CJ

I watched a few of the videos on line at the PI http://pirsa.org/C11008 Some thoughts: it seems to me Penrose did show some new material on observational evidence of CCC, in particular he argued that families of 3 or 4 concentric circles were observed more frequently than a Gausian analysis...

First, I am a rank novice in cosmology, very rank. However, I do see something that puzzles me. I put some numbers in an Excel spread sheet and I calculate that the early universe was far from homogeneous. I did a few limited searchs and did not find a discussion. Here is what I have...

I'm pretty ignorant about astrophysics, but this made it into the newspaper today, and it seemed interesting. http://arxiv.org/abs/1106.3079 "Black hole growth in the early Universe is self-regulated and largely hidden from view," Treister et al. "The formation of the first massive...

Hi. First of all I apologize because I already posted this topic in the "Homework & Coursework Questions > Advanced Physics" but since it exquisitely concerns astrophysics and it is not getting many answers, I believe it's better to post it here. If a moderator wants to merge the two...

Hi. I am studying the evolution of the universe. In particular, I am reading the history of the universe happening just under a temperature of 100 MeV. At this time, it is said that neutrons and protons are present along with some other particles: electrons, positrons, photons, neutrinos...

Hello people! I’m an engineer, and i’ve received math training, but i assume not to the level necessary to understand the deepest laws of the nature. Since I’ve reading about the Large Hadron Collider, I’ve been more and more interested in the cosmology. I’m interested in the VERY VERY EARLY...

Soft Article: http://www.sciencedaily.com/releases/2011/04/110420152059.htm Journal Article: http://prl.aps.org/abstract/PRL/v106/i10/e101101

For a long time I was thinking that even SM has lack of deep philosophic insight, it is self-consistent and, within its own framework, can answer all questions, making all paradoxes non-issues. As a reminder, in SM macroscopic events are atomic, while all other stuff (fields, real particles...

Homework Statement The present number density of electrons in the Universe is the same as that of protons, about 0.2m−3. Consider a time, long before the formation of atoms and CMB, when the scale factor was one millionth of its present value. What was the number density of electrons then...

Sometimes we need to calculate the evolution of the scalar field \phi with the equation of motion \frac{\partial^2 \phi}{\partial t^2}+3H\frac{\partial \phi}{\partial t}+m_\phi^2 \phi = 0. And we can get the field \phi=Ae^{im_\phi t} where A is the amplitude of the scalar field (damped by...

What gave rise to cosmic inflation of the early Universe?

Presently we can effectively understand the Universe down to the Plank Time - 10-43 seconds. That's pretty small, but obviously within that time interval a large number of interactions between particles occurred. Before that time we need a better theory of quantum gravity to unify the four...

Say we are in the early Universe where energies are large compared with any rest mass in the standard model. At this time how will the energy in the electron field compare with the energy in the photon field? Thanks for any help!

Hello!:wink: May I ask for a little assistance in filling in the gaps of my understanding? :S I understand that the current large scale structure of the Universe is thought to be the result of early fluctuations in density which have been stretched out in the expansion of the Universe. I...

Would it not be possible for many black holes to form in the beginning stages of the universe since the universe was very dense? Can that be the cause of the so called "Dark Energy" or "Dark Matter"?

I can't imagine an object more compact than a black hole for a certain radius and personally don't think it makes sense. Yet for earlier stages of the Universe, without a variable c , it gets far more compact than a black hole. Shouldn't major parts of the early universe simply collapse into...

Hey all, I was reading some stuff on-line, when I saw a post by someone that said: Hydrogen, a colourless, odourless gas, which left long enough will turn into people. Someone replied: Negative. An abundance of primordial helium is also required otherwise fusion in stars proceed too quickly...

In case anyone wants to comment, I thought I'd start a thread on it. http://arxiv.org/abs/0908.3683 Early Universe models from Noncommutative Geometry Matilde Marcolli (Caltech), Elena Pierpaoli (USC) 49 pages, 26 figures (Submitted on 25 Aug 2009) "We investigate cosmological predictions on...

Planck craft launched May 14 is now in position and is operating. ESA says it began taking scientific data yesterday June 14. Going around the sun, about 1 million miles or 1.5 million km farther out than the Earth is. http://www.rssd.esa.int/index.php?project=PLANCK&page=dev_news...

Is it possible that particle physics is over complicating theories about why all the matter in the early universe didn't annihilate, even though equal amounts of matter and antimatter existed? Is it possible that inflation happened quickly enough that antimatter and matter were blown clear of...

Homework Statement At very high temperatures (as in the early universe), the proton and the neutron can be thought of as two different states of the same particle, called the “nucleon”. (The reactions that convert a proton to a neutron or vice versa require the absorption of an electron or a...

Could anyone suggest a book/lecture notes on the early universe, especially the thermodynamics of it i.e. Big-Bang Nucleosynthesis etc.. I have a book -Early Universe by Kolb and Turner, but I dint really find it readable. Its not exactly reader friendly. But I would be really glad if someone...

http://www.esf.org/research-areas/physical-and-engineering-sciences/news/ext-news-singleview/article/europeans-unite-to-tap-early-universe-for-secrets-of-fundamental-physics-442.html this release reports on the European Science Foundation exploratory meeting held 27-29 March on ASTROPHYSICAL...

They say the universe is 14 or so billion years old. We can observe the early formation of the universe at this time, but how then did we get to this position here on Earth before the light of the early universe arrived. We traveled faster than the light traveling 14 billion light years?

This meeting is taking place at Cambridge University in a couple of weeks time to commemerate a meeting that took place 25 years ago, on this very topic (and partly, I think, to publicise its new "Centre for Theoretical Cosmology" that is opening soon). The list of speakers is quite...

If the Hubble parameter is always decreasing for very early stages of Big Expansion of manifold (i.e. Big Bang), then what was it decreasing from?

Does anyone know where I can learn more about the relation between the reaction rate ( \Gamma ) of the primordial elements and the Hubble parameter ( H ) at the early universe? Principaly at the transition from the radiation dominated era to the the matter dominated era?