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.

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  1. T

    B White Hole as an explanation for the big bang and inflation

    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...
  2. Ranku

    I Chaotic Inflation: Does it Involve Phase Transition?

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

    A Understanding the Relationship Between Inflation and Quantum Fluctuations

    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?
  4. Buzz Bloom

    I Inflation and Gaussian CBR pertubations

    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...
  5. S

    I Rescaling the equation of motion of inflation

    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...
  6. CaptDude

    I Question about "the big bang happened everywhere at once"

    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...
  7. S

    I Different forms of energy density in inflation

    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 =...
  8. Urs Schreiber

    A Starobinsky Inflation and Supergravity

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  9. P

    I Inflation and expansion of the universe

    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 ?
  10. S

    B Matter-antimatter annihilation and 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
  11. S

    A Gravitational waves in warm inflation

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  12. K

    I Magueijo paper -- Faster than c light vs inflation

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  13. Doctor Strange

    A How do quantum fluctuations become gravity wells?

    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...
  14. wolram

    B Lectures on Inflation: Learn Math Skills

    This is far to mathy for me but i thought i would flag it as useful to somehttp://arxiv.org/pdf/1609.00716.pdf
  15. AlgoJerViA

    Time loops, black hole and time dilation.

    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...
  16. GeorgeDishman

    I Reheating and the horizon problem - chicken and egg?

    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...
  17. Ranku

    I Can Unification of Forces Coexist with an Eternally Inflating Universe?

    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...
  18. Multiple_Authors

    Insights Where Did the Big Bang Happen? - Comments

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  19. PrincePhoenix

    B Is the formation of galaxy groups explained correctly here?

    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...
  20. W

    I Vacuum energy density after inflation

    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...
  21. W

    I Does positive curvature disprove eternal inflation?

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  22. K

    I Two numerical questions about inflation and the flatness problem

    Good day to you all I just started studying cosmology recently using several book and especially using TASI Lectures on Inflation(https://arxiv.org/abs/0907.5424) On page 25 the fine tuning problem of the flatness is introduced with conditions as |Ω(BBN)-1|≤ ο(10-16) |Ω(GUT)-1|≤ ο(10-55)...
  23. davidbenari

    I Inflation assumes ##\ddot{a}<0## after inflation?

    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...
  24. Ranku

    I Exponential expansion of inflation

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

    I Virtual Particles: Inflation vs Present Universe

    Are virtual particles of the false vacuum during inflation indistinguishable from virtual particles of the true vacuum of the present universe?
  26. resurgance2001

    I Cosmic Microwave Background Radiation Anisotropies

    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...
  27. N

    Insights A Brief on the Expansion of the Universe - Comments

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

    Question about Inflation & Money

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  29. G

    Gravitational Waves vs Tidal Effects: Exploring Nature & Inflation

    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...
  30. w0_0dy

    The big bang was a fluctuation of what?

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  31. G

    Relationship between energy, information and dark energy

    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...
  32. B

    I Don't Understand Why Printing Money = Inflation

    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...
  33. V

    Material Inflation: Analysis of Intermolecular Forces

    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...
  34. G

    Might Dark Energy have anything to do with Inflation?

    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...
  35. Pianorak

    Inflation and Curvature: Examining the Relationship Since the Big Bang

    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?
  36. Dr. Strange

    Why do Quantum Fluctuations need Inflation?

    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...
  37. J

    Inflation, comoving Hubble radius and particle horizon

    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...
  38. Shahrokh

    Exploring Bosonic Decays After Inflation

    Inflation , as proposed, leaves the universe cold and empty. The compensating theory of reheating or preheating then needed to operate after inflationary era. Such theories prefer three legs bosonic decays φ→χχ, which doesn't have any analogy with standard model processes as much as I know. How...
  39. E

    Air mattress pressure question regarding partial inflation

    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...
  40. R

    Alternative hypotheses regarding dark energy?

    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...
  41. Buzz Bloom

    Random Walk Question re Inflation

    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...
  42. Buzz Bloom

    Questions re electroweak de-unification during inflation

    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...
  43. C

    Size of Universe: Planck Time to Inflation

    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?
  44. 6

    Is vacuum acceleration directly proportional to distance?

    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...
  45. Buzz Bloom

    What is math showing inflation solves horizon problem?

    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...
  46. R

    Cosmology: Estimating CMBR Horizon Distances & Inflation Size

    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...
  47. slatts

    Do geodesics of measure zero allow past-eternal inflation?

    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...
  48. DiracPool

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    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...
  49. J

    Inflation & Pertubative 1st order Cosmology: A timeline?

    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...
  50. CassiopeiaA

    Does Inflation Refer to the Expansion of Space or the Entire Universe?

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