What is Inflation: Definition and 413 Discussions

In economics, inflation (or less frequently, price inflation) is a general rise in the price level of an economy over a period of time.
When the general price level rises, each unit of currency buys fewer goods and services; consequently, inflation reflects a reduction in the purchasing power per unit of money – a loss of real value in the medium of exchange and unit of account within the economy. The opposite of inflation is deflation, a sustained decrease in the general price level of goods and services. The common measure of inflation is the inflation rate, the annualised percentage change in a general price index, usually the consumer price index, over time.Economists believe that very high rates of inflation and hyperinflation are harmful, and are caused by excessive growth of the money supply. Views on which factors determine low to moderate rates of inflation are more varied. Low or moderate inflation may be attributed to fluctuations in real demand for goods and services, or changes in available supplies such as during scarcities. However, the consensus view is that a long sustained period of inflation is caused by money supply growing faster than the rate of economic growth.Inflation affects economies in various positive and negative ways. The negative effects of inflation include an increase in the opportunity cost of holding money, uncertainty over future inflation which may discourage investment and savings, and if inflation were rapid enough, shortages of goods as consumers begin hoarding out of concern that prices will increase in the future. Positive effects include reducing unemployment due to nominal wage rigidity, allowing the central bank greater freedom in carrying out monetary policy, encouraging loans and investment instead of money hoarding, and avoiding the inefficiencies associated with deflation.
Today, most economists favour a low and steady rate of inflation. Low (as opposed to zero or negative) inflation reduces the severity of economic recessions by enabling the labor market to adjust more quickly in a downturn, and reduces the risk that a liquidity trap prevents monetary policy from stabilising the economy. The task of keeping the rate of inflation low and stable is usually given to monetary authorities. Generally, these monetary authorities are the central banks that control monetary policy through the setting of interest rates, through open market operations, and through the setting of banking reserve requirements.

View More On Wikipedia.org
Recent contents Top users
  1. Rafid Mahbub

    A Numerical solution of the Mukhanov-Sasaki equation

    Hi, I am trying to figure out how to solve the Mukhanov equation numerically in Mathematica, but have some problems dealing with it. In terms of the number of efolds, the Fourier modes satisfy the following ODE in terms of the Hubble slow roll parameters: $$...
  2. Safinaz

    I Weyl Transformation of Metric: Cosmological Inflation

    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...
  3. ForgeJB

    I How can there be fluctuations in the inflaton field value?

    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...
  4. T

    How is the horizon length related to the power law spectrum

    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...
  5. A

    A Current Status of Eternal Inflation

    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...
  6. Spinnor

    I ....Alternatives to Inflation in Primordial Power Spectrum

    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...
  7. W

    I Testing Inflation: A Definitive Test & Laymen Explanation

    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...
  8. D

    I Troubles understanding slow-roll conditions in Inflation

    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##...
  9. l0st

    I Gravitational Waves Cause Uniform Space Expansion: Exploring MNRAS Papers

    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...
  10. Ranku

    I False vacuum and matter density

    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?
  11. Ranku

    I Inflation and density perturbations

    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?
  12. BadgerBadger92

    B What Causes the Phenomenon of Cosmic Inflation?

    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?
  13. J

    I Have we measured the change in the red shift over time?

    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...
  14. A

    A Multiverse reduction in the new Hawking/Hertog model?

    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"...
  15. nomadreid

    I Inter-Bubble Connections in Inflationary Multiverse Models?

    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...
  16. R

    I Did cosmic inflation happen everywhere in the Universe?

    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...
  17. W

    I VSl as an alternative to cosmic inflation

    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...
  18. Ranku

    I Inflation & Ω: Dark Matter & Energy Impact

    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?
  19. T

    Modern Cosmology Dodelson Problem 6.12b (Inflation)

    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...
  20. T

    Modern Cosmology by Dodelson: Problem 6.12 a

    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...
  21. Arman777

    B The Universe without Cosmic Inflation?

    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?
  22. Posty McPostface

    Your thoughts about excess reserves?

    Chart: Source. So, inflation has been low, which has been troubling economists and the FED over the effectiveness of undertaken Quantitive Easing (QE). What's the cause of this, and are banks holding onto excess reserves the real issue here? What are your thoughts about all this liquidity in...
  23. W

    I What is the universe expanding into ? Eternal 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...
  24. S

    I How fast do you need to cycle to simulate bicycle tire inflation

    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...
  25. S

    I Is Inflation unlikely or likely?

    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...
  26. T

    I Inflation theory and General Relativity

    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...
  27. ISamson

    B Exploring the Universe's Inflation: What is the Higgs Boson?

    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.
  28. V

    I Inflation as a phase transition

    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...
  29. N

    I Inflation "cooled Universe from 10^27 to 10^22 kelvins" why?

    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...
  30. S

    B Angular momentum, degeneracy pressure, and cosmic inflation

    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?
  31. DoobleD

    I Why is inflation initial patch length ~ 1 Hubble length ?

    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...
  32. bapowell

    Insights A Poor Man's CMB Primer. Part 5: Quantum Seeds - Comments

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

    I Inflation: meaning of χ (chi) for time scales?

    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...
  34. DoobleD

    I Inflation lecture from Guth : why does d(ρ)/dt = 0 ?

    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...
  35. DoobleD

    I The particle horizon value is ignoring inflation?

    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...
  36. S

    I Experimental bound on the scalar spectral index

    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...
  37. S

    A Calculating the power spectra of scalar perturbation

    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...
  38. K

    I Interesting controversy about inflation models of the universe

    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...
  39. S

    A Hubble scale and energy density during inflation

    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?
  40. W

    Mathematica Cosmic inflation using mathematica

    In cosmic inflation, we have the equation of motion for the inflaton given by, $$\ddot\phi + 3H(1 + Q)\dot\phi + V_\phi = 0$$ the Friedman equation is given by $$H^2 = \frac{1}{3 M_p^2}(\frac{1}{2} \dot\phi^2 + V + \rho_r)$$ where ##M_p## is the reduced Planck mass. The differential equation...
  41. W

    I Plateau models of inflation after Planck

    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...
  42. F

    A End of Inflation: Definition, Meaning & Models

    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...
  43. S

    A Decay of false vacuum in new inflation

    In new inflation, the time scale for the decay of the false vacuum is controlled by ##- m^{2} = \frac{\partial^{2}V}{\partial\phi^{2}}\bigg|_{\phi=0}.## This is the negative mass-squared of the scalar field when it is at the top of the hill in the potential diagram. This is an adjustable...
  44. HARVEYU1E1

    B Are Black Holes linked to our Universe & Dark Energy/Matter?

    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...
  45. R

    Deflection of hose when internally pressurised

    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...
  46. L

    I Exploring Evidence and Data Pre-CMB in the Early Universe

    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...
  47. T

    B Cause of Inflation: Link to Dark Energy & Quintessence?

    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...
  48. haushofer

    I Inflation, horizon-problem and thermal equilibrium

    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...
  49. W

    I Exact expression for the tensor-to-scalar ratio

    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...
  50. K

    I Problems with the theory of inflation

    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...
Back
Top