Inflation Definition and 399 Threads

Hello, I’m new to the cosmological inflation so in this paper: https://arxiv.org/abs/1809.09975 Has some one an idea how to make the Weyl transformation of the metric ## g_{\mu\nu}## Equation (3) , and how to get the potential (4) from the action (3) by this transformation as explained after...

http://www.counterbalance.org/cq-turok/etern-body.html https://ned.ipac.caltech.edu/level5/Kolb/Kolb3_1.html) http://www.astronomy.ohio-state.edu/~dhw/A873/notes7.pdf) According to QFT, if you make repeated measurements of some property of the field then you will in general measure a...

Homework Statement For a power spectrum density fluctuations ##P(k) \propto k^n##, I need to find the scaling (with respect to ##a##) of the horizon wavenumber ##\frac{2\pi}{\chi_H}## in a matter dominated universe in terms of ##n##. ##\chi_H(a)## is the evolving particle horizon, in a flat...

In 1979 Alan Guth came up with the theory of cosmic inflation. A mechanism by which a proposed field named the inflaton would give rise to a period of massive expansion brought on by quantum fluctuations eventually bringing about the uniform distribution of matter in the universe that we see...

Unique Fingerprints of Alternatives to Inflation in the Primordial Power Spectrum "Massive fields in the primordial universe function as standard clocks and imprint clock signals in the density perturbations that directly records the scale factor of the primordial universe as a function of...

A new paper has recently popped up claiming it is possible to make a more definitive test of inflation versus certain alternatives like the matter bounce or ekpyrotic universe. https://arxiv.org/pdf/1809.02603.pdf I was wondering what people thought of it. Any good laymen explanation of what is...

I've been reading up on inflation, and have arrived at the so-called slow roll conditions $$\epsilon =-\frac{\dot{H}}{H^{2}}\ll 1\; ,\qquad\eta =-\frac{\ddot{\phi}}{H\dot{\phi}}\ll 1$$ I have to admit, I'm having trouble understanding a couple of points. First, how does ##\epsilon\ll 1##...

I am looking at a couple of very interesting papers, published in MNRAS, that deduce, that the accelerated expansion of the Universe we observe can be attributed to gravitational waves, produced by a very distant merger of two or more universe-mass-scale black holes. The last one is on the...

The false vacuum of the inflationary universe is described as a 'peculiar state of matter'. We know that matter density in the big bang universe dilutes as ρM ∝ a-3. Is it possible to assign a dilution rate to the 'peculiar state of matter' of the false vacuum as well?

Is it possible to estimate the rate of false vacuum decay in the inflationary universe by looking at the density perturbations in the big bang universe?

Not long after the Big Bang, space expanded faster than light for a brief amount of time, slowed down, then sped up again. Is there an answer to this question?

Have experiments been done to measure the red shifts of distant objects over time? If inflation is correct, the the speed at which an object is receding relative to us is based on how far away that object is located. Therefore, the most distant objects would also have the highest acceleration...

Hawking and Hertog's new paper "A Smooth Exit from Eternal Inflation?" does away with the infinite multiverse of Hawking's previous theory and proposes a cosmology that predicts "a simpler and finite universe". But I can't figure out the extent of this reduction to a "simpler and finite"...

I know this is getting into the highly speculative, but given the mathematics that has been done on versions of these concepts that are not known to be inconsistent: In the inflation concept which leads to a multiverse of the "bubble universes" type, in which the laws governing the space-time...

General Relativity equations tells us that the earliest time of the universe which our physics can tell us had infinite space and infinite density (i.e. matter). Then space started expanding, thus increasing the distance of any 2 points of that infinite dense matter, thus making it less dense...

It has been proposed that a varying speed of light can resolve certain cosmological problems thought to be solved by cosmic inflation. An example is this paper here by Albrecht and Magueijo: https://arxiv.org/pdf/astro-ph/9811018.pdf and this paper by Moffat https://arxiv.org/abs/gr-qc/9211020 I...

Inflation leads to Ω=1. But we also have Ωmatter+Ωdark matter+Ωdark energy = 1. So if there were no dark energy and dark matter present in the universe, would Ω have eventually deviated away from 1?

Homework Statement Show that ##4\pi G(\dot \phi)^2=\epsilon a^2 H^2## Homework Equations Over dots mean derivative with respect to ##\eta##. $$\frac{1}{a}\frac{d}{d\eta}=\frac{d}{dt}$$ $$H=\frac{\dot a}{a^2}$$ $$\epsilon=\frac{-\dot H}{aH^2}$$ $$(\frac{\dot...

Homework Statement The general goal of the problem is to derive some useful identities involving the slow-roll parameters during inflation. For part a show that: $$\frac {d} {d\eta} (\frac {1} {aH})= \epsilon - 1$$ Homework Equations $$\epsilon \equiv \frac {d} {dt} (\frac {1} {H})= \frac...

I don't know this question makes sense or not but; Respect to the two possible size universe models (finite and infinite) how would be the evolution of the universe without the cosmic inflation?

Normally when one is asked what is the universe expanding into, the answer is its not expanding into anything. Space itself can expand. However In the context of eternal inflation, our universe is a bubble in a sea of inflating space. And hence assuming eternal inflation is right, does the...

My question comes from a moment when I was riding my bike. I had a flat tire. My question then was how fast do i need to cycle so that i don't ride on my rim's anymore. I tride calculating this with the force that i put on the tire (15kg+70kg= mass of the bike and I)*g= 833,85 N that devided by...

Sabine Hossenfelder and others think it’s unlikely because the latest Planck Satellites didn’t support some observations such as: http://backreaction.blogspot.com/2017/10/is-inflationary-universe-scientific.html...

Does General Relativity predicts that in the early universe vacuum energy was converted into matter? How does it relates to the Inflation Theory by Allan Guth? I'm asking this because I remember reading in a book on GR that there are ways of calculating the total amount of energy in the...

Hello, I have read somewhere that the Higgs Boson particle (or field) is responsible for the inflation of the universe. Does anybody have more information? Thanks.

Hello, I have heard that one of most acceptable theory (or hypothesis) describing the inflation phase of universe is that energy to this stage is drawn from phase transition when strong interaction is separated from "preinteraction" (when all interactions were undistinguishable) Do you agree...

I've seen numerous descriptions of inflationary phase a-la "The universe was supercooled from about 10^27 down to 10^22 kelvins". However, I do not understand what is the basis for such estimation. We do not even know with any certainty how long the inflationary phase lasted. For one, "eternal...

Considering the angular momentum of a collapsing star preventing it from resulting in a black hole by degeneracy pressure, are there ekpyrotic universe models that include angular momentum and degeneracy pressure as key factors of cosmic inflation?

I'm asking many questions on inflation, I hope this is the last one... If inflation is correct, our observable Universe would have been a tiny homogeneous patch before inflation started (if it started at all). The length of that initial patch is estimated to be of the order of 1 Hubble length...

bapowell submitted a new PF Insights post A Poor Man's CMB Primer. Part 5: Quantum Seeds Continue reading the Original PF Insights Post.

This is another question related to an undergrad video lecture on inflation by Guth. In the course, he derives the inflationary expansion rate : a(t) ~ eχt, with χ = sqrt(8πGρf/3), and ρf being the mass density of the false vacuum energy. Later in the lecture, around 51:35, Guth gives sample...

I watched a video lecture from Alan Guth on inflation (undergrad level), and there is something in it I don't understand. He first presents the inflation scalar field, Φ, which has an energy density associated with it, V(Φ). V(Φ) is stuck at a local minimum, at Φ = 0 (what is called a "false...

In a paper from 2003, it has been shown that the particle horizon is about 14300 Mpc, or 46.6 billion light years (and it has been recalculated in 2016 with more accurate parameters values at around 14200 Mpc = 46.3 billion ly). From what I understand, the calculation proposed in 2003 takes the...

Based on the paper by Visinelli (https://arxiv.org/abs/1605.06449), He stated in page 6 that the scalar spectral index as given by the Planck 2013 data (https://arxiv.org/abs/1303.5076) is, ##n_s = 0.9655 \pm 0.0062~~## (##68\%## C.L.) but when I looked into the Planck 2013 paper, I did not...

I'd like to numerically calculate the power spectra of the scalar perturbation at the Hubble crossing in warm inflation, my problem is that I don't know how to do it. As I know, the Hubble crossing happens at the onset of warm inflation where the different modes become larger than the Hubble...

I'm opening this thread for discussion on the latest debate over inflationary cosmology as outlined over at scientific american the original article on inflation was Scientific American published an article by Ijjas, Steinhardt and Loeb https://www.cfa.harvard.edu/~loeb/sciam3.pdf then a...

Is the energy density ##\rho## in the early universe and the Hubble scale ##H## during inflation related by the formula $$H^{4} = \frac{9}{64\pi^{2}} \frac{\rho^{2}}{M_{P}^{4}}?$$ Here, ##M_{P}## is the Planck mass. Can you suggest any resources where this is explained?

Reading some of the critics and defenders of inflation in various papers, one thing I note they have in common is that both seem to agree the plateau models of inflation are favoured by Planck. According to one of the critics of inflation "The plateau-like potentials selected by Planck2013 are...

From cosmology, the end of inflation is usually defined as when the Hubble slow roll parameter is equal to one, ##\epsilon_{H} = -\frac{\dot H}{H^2} = -\frac{d\ln H}{dN} = 1## Is this really the definition of the end of inflation? Or is it for the standard cold inflation only? How about the...

After a quick and not fruitful Google Search I leave this question in better minds than my own. Q- Has there been any discussion linking the start of our Universe with a black hole? <Reason behind Question> I feel as if certain phenomenon seems quite similar to one another. A) star dies...

Hi, I have carried out an experiment on 2 hoses. Hose A, a typical garden hose of 15mm OD 10mm ID and hose B a polyester woven lay flat fire type hose of 52mm OD 49mm ID. When inflated to 4 bar pressure hose A didn't straighten and was only seen to bulge in the circumferential direction...

I have been looking online and in other resources for some answers to no avail. Thought I would sign up on astrophysics forums to find the answer.What is the evidence and data for the period before the cosmic microwave background (CMB) in the early universe? In other words, is the idea of energy...

Is the cause of inflation unknown? Is it possible that it might have in part at least been caused by radiation pressure as a result of matter annihilating anti-matter at extremely high densities? Does the theory of quintessence mainly try to say that inflation and dark energy are linked in some...

Dear all, for the topic https://www.physicsforums.com/threads/problems-with-the-theory-of-inflation.905230/ I came across the following paper: https://arxiv.org/abs/1505.01456. In this paper the following arguments are given why the horizon problem is a fake problem. It raised by me the...

Based on the vast cosmology texts, I have seen that the expression for the tensor-to-scalar ratio ##r## in cold inflation is, ##r=16\epsilon_H = -16\frac{\dot H}{H^2}\qquad## where, ##~~~\epsilon_H = -\frac{\dot H}{H^2}## ##H## is the Hubble parameter, and ##\epsilon_H## is the Hubble slow...

what is the current consensus on inflation, as recent article in SciAM https://www.cfa.harvard.edu/~loeb/sciam3.pdf the 3 authors are highly respected physicists in the field they conclusion inflation is internally inconsistent and inconsistent with best measurements from PLANCK CMB...

Was the concept of a White Hole ever intended to as a POSSIBLE explanation for the Big Bang, inflation and dark energy expansion of the Universe? Or is it considered crack pottery by the cosmology community? I presume the observable Universe would need to be as small as say a single atom in...

Does chaotic inflation involve phase transition, and if not, when does the phase transition of the breakdown of GUT symmetry occur?

I was reading something and I came along this: "Is inflation self-sustaining through inflation of quantum-mechanical fluctuations?" How can inflation be self sustained through quantum fluctuations, is it possible?

I have been exploring the paper: Statistical Tests for the Gaussian Nature of Primordial Fluctuations Through CBR Experiments http://lss.fnal.gov/archive/1993/pub/Pub-93-294-A.pdf . Here is a quote. Cosmic inflation [1], on one hand, provides a natural way to generate Gaussian initial...