Inflation Definition and 399 Threads

From the equation of motion of inflation, $$\frac{d^2\phi}{dt^2} + 3H\frac{d\phi}{dt} + \frac{dV}{d\phi} = 0$$ Example: ##V= \frac{1}{2}m^2\phi^2## $$\frac{d^2\phi}{dt^2} + 3H\frac{d\phi}{dt} + m^2\phi = 0$$ If I want to make the DE dimensionless then I let ##~t = \frac{1}{H_o} \tilde t~## and...

Is it fair to think about the statement "the big bang happened everywhere at once." as meaning the singularity that spawned the "big bang" was very large by cosmic scales, even infinitely large? (I am aware that the word "singularity" refers to a place where the math breaks down and not a point...

From the second Friedmann equation, $$H^2 = \frac{1}{3M_p^2} \rho \quad (k=0, flat)$$ In warm inflation, radiation is present all the way therefore not requiring proper reheating process, so $$\rho = \rho_\phi + \rho_r \, ; \quad \rho_\phi = inflaton, \, \rho_r = radiation$$ But, $$\rho =...

The available experimental data prefers plateau models of cosmic inflation, and among them Starobinsky inflation (aka R^2 inflation) is preferred, even if maybe not significantly. Since Starobinsky inflation is pure gravity (the inflaton field here is an effective incarnation of a higher...

We know from observations that the universe is expanding and that the speed of recession of celestial objects increases the further we look back in space. However, looking further in space is also looking back in time, so does this mean that we are looking at the end of inflation ?

Is there any link between the energy released from the annihilation of matter-antimatter during baryogenesis and cosmic inflation or expansion/dark energy? This question came up when reading: https://www.nasa.gov/mission_pages/chandra/news/08-160.html

https://arxiv.org/pdf/astro-ph/0006077v2.pdf page 5. Tensor Perturbations "Tensor perturbations do not couple strongly to the thermal background and so gravitational waves are only generated by quantum fluctuations, as in standard supercooled inflation". Why? Tensor perturbations are created...

The critical geometry of a thermal big bang Niayesh Afshordi, Joao Magueijo (Submitted on 9 Mar 2016 (v1), last revised 8 Nov 2016 (this version, v2)) We explore the space of scalar-tensor theories containing two non-conformalmetrics, and find a discontinuity pointing to a "critical"...

How do quantum fluctuations become gravity wells? I thought the whole idea of the fluctuation was that it had to happen so quickly that the universe didn't notice. I see how a field could have a random, but non-zero value, but I don't see how that momentary variation in the field can stick...

Hi I hope this is the right place for this questions, I started to think about this several years ago but had has a hard time finding anyone that's been interested in discussing this. As far as I understand time travel is not ruled out by modern physics at least if you limit yourself to go into...

One of the benefits of inflation often mentioned in beginner treatments is that it solves the horizon problem by taking a volume which was in thermal equilibrium and expanding it so much that it is now larger than the observable universe thus explaining how the CMB temperature is so uniform...

Is the possibility of unification of gravitation with the other three fundamental forces compatible with the idea of an 'eternally existing self-replicating inflationary universe' as proposed by Linde? In other words, for unification of the four fundamental forces, is it necessary for the...

multiple_authors submitted a new PF Insights post Where Did the Big Bang Happen? Continue reading the Original PF Insights Post.

Hello! I watched a video on the Youtube channel Kurzgesagt titled How far can we go? Limits of humanity The video attempts to explain why we may be limited to our local galaxy group even with science fiction technologies. During a part of the video (starting at 2:26), they try to explain how...

Its said that if there are different pocket universes made by inflation then this solves the alleged fine tuning of dark energy. My question is this: can the idea of different values for the vacuum energy density in these different pockets be derived from quantum field theory or does it need...

According to this paper, eternal inflation would be falsified by positive curvature: http://arxiv.org/pdf/1203.6876v2.pdf However the proposer of eternal inflation, Alex Vilenkin, has suggested spontaneous creation of the universe from"nothing". Apparently this doesn't violate the conservation...

I'm reading introductions about inflation and one thing they assume is that presently ##\ddot{a}<0## where ##a## is the parameter in our FRW metric. We know that this is observationally false, since in fact ##\ddot{a}>0##. But why do they assume this? My guess is that in the big-bang model...

The expansion of the inflationary universe is said to be roughly exponential. Why is it called "roughly" exponential?

Are virtual particles of the false vacuum during inflation indistinguishable from virtual particles of the true vacuum of the present universe?

Hi This question may have already been answered elsewhere. If so please accept my apologies in advance. I am confused! The textbok(s) I am reading describe a whole bunch of different causes for there being temperature fluctuations in the CBM, so I am confused about which one(s) of these...

nikkkom submitted a new PF Insights post A Brief on the Expansion of the Universe Continue reading the Original PF Insights Post.

Hi everyone: I have a few questions relating to inflation and money, which my roommate and I were talking about over dinner and into breakfast this morning. First, is there any way to track inflation each year? As in, how do you know how much inflation of the dollar took place for a year or...

My simple description of gravitational waves is that they are due to the relativistic principle of locality, i.e. the fact that the action of gravity is not instantaneous, something that you can’t see from the tidal effects in Newtonian physics. Is it correct? I've also found a comment...

I have read that the total energy of the universe is zero and that the big bang might have emerged from a quantum fluctuation. Also that there is a chance (extremely low) of another big bang occurring in the quantum vacuum energy fluctuations. As far as I understand the vacuum energy / dark...

Hi. I have no significant pure physics or math education or work experience (retired corporate analyst) but I was wondering what experts here might think about the relations between energy, dark energy and information. My understanding is that dark energy is the expansion of space, with space...

First and foremost, I apologize if this question is posted in the wrong section. I wasn't sure where to place it and figured it was at least tangentially related to math (and that the mods/admin would re-route my thread topic to a new location if appropriate :-p). On to my question...

I have observed that certain materials can drive fluids into themselves and push their own molecules apart, thus inflating itself. When, I try to reason, I'm not quite successful. Even if there is surface tension or under atm pressure, extension of intermol. distance is departure from...

Inflationary Theory postulates that the inflaton field and its associated particle were responsible for a huge space expansion in the very early universe. Now we observe again positive expansion, albeit at a very moderate rate, which we attribute to "dark energy" / "cosmological constant". Could...

Since the very rapid expansion of the Universe, ie Inflation, caused curvature to be smoothed out, the assumption must be that curvature existed between the time of the Big Bang and the start of Inflation. If that is correct, is this borne out by the Planck or any other theory?

The general logic of Inflation is that some field popped into existence just long enough to flatten out the universe, then disappeared again. Before the field, the universe had tiny fluctuations in the plasma. Inflation blew these up from the size of an atom to the size of a grapefruit (If I...

I have a question regarding the exact formulation of the mechanism of Inflation. In thehttp://www.damtp.cam.ac.uk/user/db275/Cosmology/Lectures.pdf he uses ##\frac{d}{dt} \frac{1}{aH} < 0## as an definition of inflation. I see that it yields ## \ddot a > 0##, but my confusion lies in the...

so last night I get on a sleep number bed and the remote reads 35 (unitless - I am assuming this number is related to pressure.) I click it down once to 30 and it deflates nearly completely. I get off the mattress, the reading drops to 5 or 10 and the mattress begins to inflate to 30. So this...

Currently, the favoured explanations for the accelerating expansion of the universe are the cosmological constant, and various scalar fields, most notably quintessence. All of these are mechanisms dependent on mathematical field properties. My question is: do any alternative hypotheses exist...

I have been puzzled about the possible interaction mechanisms among the various particles during inflation that would have performed the mixing of mass-energy (ME) required for the uniformity of the CBR. Here is my understanding about what must happen to acheve the necessary mixing of ME during...

Before I ask my questions I need some context. Here are two quotes about electroweak unification: from (1) https://en.wikipedia.org/wiki/Electroweak_interaction , and (2) from https://en.wikipedia.org/wiki/Fundamental_interaction . (1) Mathematically, the unification is accomplished under an...

What do we know or speculate as to the size of the visible and entire universe between the Planck time and the beginning of explosive inflation?

Do we know if the instantaneous/observed acceleration due to the vacuum is directly proportional to distance or possibly? (ignore any gravitational effects) A~D ? A~D^2 ? A~D^(1/2) ? A~D^(-2) A~D^(Other) ? OR A= constant (edited as I forgot this one) If not, is there a best guess/fit or...

One aspect of the Horizon Problem is that the observed equal CBR temperature from opposite directions of the sky is a mystery. If we choose two points, say A and B, at opposite ends of a arbitrary diameter of the observable universe, at the present time the distance between A and B would be D...

Hello everyone! I have found a pretty interesting problem on the internet about cosmology. I'm new into cosmology and I don't know exactly how to solve it... That's why I need a little help. I wrote under the problem text how I would do it.Measurement of the cosmic microwave background...

Assuming that the expectation that all matter and energy are quantized is correct, I'm making a further assumption that "random" means something like, "hypothetically predictable, but only by means at least possibly impractical on any permanent or general basis whatsoever, such as enumeration...

1. Inflation--I've been doing a little study into cosmic inflation, and a question that many people (including myself) seem to have a hard time wrapping their head around is why was there a need for inflation rather than just assuming that the universe just started off flat, homogeneous, and...

Hey there, i have a question regarding basic inflation and structure formation via linear first order perturbation theory in cosmology. I read through different material (Baumann lecture notes, wikipedia articles, Mukhanov, ...), but at this point i am just confused and find it hard to get an...

A very fundamental doubt. Was inflation expansion of just space or the universe with whatever the state of matter it had?

In the inflationary Big Bang model, our universe is one of the many pocket universes in the multiverse. How can we detect the existence of the other pocket universes? I presumed that all the pocket universes exist in the same physical space. So in principle, they can exert influence on one...

I'm trying to understand more about how our present universe is supposed to be the result of a false vacuum falling to the present vacuum energy. I've been told (correct this if it's wrong), the universe initially underwent a kind of hyperinflation, expanding exponentially due to a much higher...

I am reading some of "Planck 2013 results. XXII. Constraints on inflation." The paper is full of values for various inflationary parameters under various models, with their confidence intervals. For instance, in Table 5 on page 13, the authors report that — for a model including both running of...

I am a high school student and I was searching the inflation theory.When I searched I found that inflation starts a certain time (10-35) how physicists know that 10-35 is the "true" or"right" time ?

According to inflation theory, there first was a scalar quantum field in a false-vacuum (the inflaton). The whole inflationary expansion only got started when the inflaton decayed to its true vacuum. But then people say that the dark energy that causes the universe to expand today, could be...

I read the following passage from a book that does not look correct to me. I understood that the geometry of the universe as far as we can tell is flat to within the error bars of our measurements and that is therefefore either infinite or at least much much larger than our observable patch...

Why have the density perturbations of all lengths a relation to the constant radius c/H? I suppose this is the origin for scale invariance and gaussianity.