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Topic: Flatness problem


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In the News (Sat 25 May 19)

  
 Fine-tuning - Wikipedia, the free encyclopedia
Explanations often invoked to resolve fine-tuning problems include natural mechanisms by which the values of the parameters may be constrained to their observed values, the anthropic principle, and intelligent design.
The necessity of fine-tuning leads to various problems that do not show that our theories are incorrect, in the sense of disagreeing with observations, but nevertheless indicate that a piece of the story is missing.
For example, the cosmological constant problem (why is the cosmological constant so small?); the hierarchy problem; the strong CP problem, and others.
en.wikipedia.org /wiki/Fine-tuning   (177 words)

  
 ~@Com~|~~BIG BANG THEORY UNDER FIRE~~   (Site not responding. Last check: 2007-10-18)
It has been suggested that this singularity problem can be solved by postulating a universe of zero net energy;(2) a universe wherein the positive kinetic energy, the potential energy, and the Einsteinian equivalent energy of the mass of the universe is equal and opposite to the negative energy of gravity.
One of the older problems of BBT, that of its postulated large-scale smoothness of the universe, appears to be the result of what was originally a simplifying assumption(5-8) that was made to aid in the solution of Einstein's equations of general relativity on which the BB is based.
As in the case of the previously mentioned problems, the enormous rate of expansion of the early BB universe as postulated by inflation theory, is said to provide a solution to the flatness problem.
nowscape.com /big-ban2.htm   (7813 words)

  
 The Astrophysics Spectator: Commentary, The Lure of Natural Design
The flatness problem refers to the rate at which the universe is expanding.
The horizon problem refers to the observation that the universe looks the same in all directions, despite the fact that under the Big Bang theory, the various parts of the universe that we see are causally disconnects.
Both the horizon problem and the flatness problem focus on characteristics that extend throughout the universe within the bounds set by the microwave background and primordial nuclear synthesis.
www.astrophysicsspectator.com /commentary/commentary20050119.html   (684 words)

  
 I'm worried- should I be? 645n and film flatness
Since, if the film isn't flat, then the film isn't all uniformly on the focal plane, and the parts that aren't on the focal plane will be less sharp than the parts that are.
I had been having problems with my 35mm lens on my Mamiya 645 Pro (sections of the frame with soft focus), so I put a test roll of 120 film in it, advanced to the second or third frame, and let it sit for two days.
And guess what, in the 645NII manual Pentax admit that film flatness can be a problem when using 16 frames per 120 roll, something that is equal to saying that issue may be a constant issue on the N as it is fixed at 16 frames per 120 roll film.
www.photo.net /bboard/q-and-a-fetch-msg?msg_id=00AKv2   (2052 words)

  
 Big Bang   (Site not responding. Last check: 2007-10-18)
The possible overall forms that space and time could take — closed, open, or flat — are described by three different cosmological models.
Postulating this burst of exponential growth helps remove two major problems in cosmology: the horizon problem and the flatness problem.
The flatness problem is to explain why space, on a cosmic scale, seems to be almost exactly flat, leaving the universe effectively teetering on a knife-edge between eternal expansion and eventual collapse.
www.daviddarling.info /encyclopedia/B/Big_Bang.html   (1239 words)

  
 The Flatness Problem   (Site not responding. Last check: 2007-10-18)
Since an Omega of one corresponds to a flat universe, this is known as "The Flatness Problem."
Although the estimated values of Omega hover around one, the range implies a lot of uncertainty about the average density of the universe.
Part of the problem lies in the fact that we can only see a mere 5-10% of the matter that's thought to comprise the cosmos.
archive.ncsa.uiuc.edu /Cyberia/Cosmos/FlatnessProblem.html   (471 words)

  
 Journal of Manufacturing Systems: A genetic algorithm based approach for robust evaluation of form tolerances
As per ANSI,1 flatness is defined by a pair of parallel planes that completely enclose the data set in addition to being as close to each other as possible.
The flatness values were estimated, and a direct correlation between the cylindricity and flatness values was established.
The tolerance zone evaluation problem for flatness and cylindricity is difficult both in its exact and deterministic form.
www.findarticles.com /p/articles/mi_qa3685/is_200001/ai_n8893902   (1464 words)

  
 Summary 1   (Site not responding. Last check: 2007-10-18)
Problems of the Standard Big Bang Model However, the missing mass is not the only problem which seems to plague the standard Big Bang model.
The problems with the Big Bang theory could be rooted in disparities between our two main frameworks for understanding, namely quantum mechanics and general relativity.
I have no problem seeing that such things as force laws and physical constants could be properties of our particular universe and had it followed a different path in its development that they could be different.
www-ssg.sr.unh.edu /preceptorial/Summaries_95/sum3.htm   (1915 words)

  
 [No title]
In the inflationary theory this problem goes away completely, because in contrast to the conventional theory it postulates a period of accelerated expansion while this repulsive gravity is taking place.
In the case of the universe as a whole, once we assume that the universe is homogeneous and isotropic, then this issue of flatness becomes directly related to the relationship between the mass density and the expansion rate of the universe.
The generic inflationary model drives the universe to be completely flat, which means that one of the predictions is that today the mass density of the universe should be at the critical value which makes the universe geometrically flat.
www.edge.org /3rd_culture/guth02/guth02_p3.html   (948 words)

  
 Inflation   (Site not responding. Last check: 2007-10-18)
His model was motivated by the monopole problem (the abundance of magnetic monopoles should be high in many GUT theories; however we do not observe any), which is explained as well by inflation.
If the shape of the potential is flat enough, one can expect easily an increase of 50 orders of magnitude in the scale parameter of the universe before the Higgs field is drifted away to the true vacuum value, and the SU(5) symmetry is broken.
However, it is at present not known how to explain the shape of the potential of the Higgs field associated with the symmetry breaking that is needed to obtain a long enough period of inflation and the right amount of entropy generation and reheating at the end of the inflationary period.
www.nikhef.nl /~henkjan/astro/node20.html   (986 words)

  
 Inflation for Beginners   (Site not responding. Last check: 2007-10-18)
The second puzzle is called the flatness problem This is the puzzle that the spacetime of the Universe is very nearly flat, which means that the Universe sits just on the dividing line between eternal expansion and eventual recollapse.
This process would smooth out spacetime to make the Universe flat, and would also resolve the horizon problem by taking regions of space that were once close enough to have got to know each other well and spreading them far apart, on opposite sides of the visible Universe today.
Indeed, the biggest problem now is that the vocabulary of cosmology doesn't quite seem adequate to the task of describing all this activity.
aether.lbl.gov /www/science/inflation-beginners.html   (4780 words)

  
 Inflation
The flatness problem relates to the density parameter of the Universe, Ω.
And therefore, the flatness problem is that some mechanism is needed to get a value for Ω to be exactly one (to balance the pencil).
The solution to both the flatness and horizon problems is due to a phase of the Universe called inflation.
zebu.uoregon.edu /~js/cosmo/lectures/lec21.html   (1191 words)

  
 Cosmological Models
This problem is one of the lines of thought which led to the inflationary hypothesis put forth by Alan Guth in the early 1980's.
The answer to the horizon problem from the inflationary point of view is that there was a period of incredibly rapid inflation very early in the big bang process which increased the size of the universe by 10
This "inflationary model" was a way of dealing with both the flatness problem and the horizon problem.
hyperphysics.phy-astr.gsu.edu /hbase/astro/cosmo.html   (943 words)

  
 Film Flatness Issues   (Site not responding. Last check: 2007-10-18)
Film flatness is surprisingly critical in determining the overall camera performance - especially lens resolution or sharpness (as measured by lpmm) and lens contrast.
Film flatness in medium format is different from 35mm film, since rollfilm doesn't have the cartridge lips of the 35mm film cassette to cause warping problems.
Film flatness is clearly a concern to some LF photographers, who purchase vacuum backs made by various manufacturers so as to minimize these errors and related problems.
medfmt.8k.com /mf/flat.html   (19591 words)

  
 Science: Physics: Cosmology Problems Big Bang - Open Site
One of the older problems of Big Bang Theory, that of its postulated large-scale smoothness of the universe, appears to be the result of what was originally a simplifying assumption (5-8) that was made to aid in the solution of Einstein's equations of general relativity on which the Big Bang is based.
As in the case of the previously mentioned problems, the enormous rate of expansion of the early Big Bang universe as postulated by inflation theory, is said to provide a solution to the flatness problem.
Adding to those problems, recent observations have shown that the abundance of helium is less than that indicated by standard Big Bang Theory, and that the ratios of beryllium and boron are inconsistent with that theory.
open-site.org /Science/Physics/Cosmology_Problems_Big_Bang   (4771 words)

  
 ASTR 135 Course Notes
These shortcomings are called the horizon problem, the flatness problem, and the monopole problem.
Another way to look at the problem is to realize that at early times, the three possible fates for the universe resemble each other very closely, and in fact they all resemble the critical case.
Another way to look at the flatness problem is to recall that, at early times, the universe will appear to be at or near the critical case.
astro.wsu.edu /allen/courses/astr135/Notes/cosmology.html   (2777 words)

  
 Flatness problem -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-18)
Flatness problem -- Facts, Info, and Encyclopedia article
The flatness problem is a (additional info and facts about cosmological) cosmological problem with the ((cosmology) the cosmic explosion that is hypothesized to have marked the origin of the universe) Big Bang theory, which is solved by hypothesising an (additional info and facts about inflationary universe) inflationary universe.
In an expanding universe, the (A solemn and dignified feeling) gravity field created by the matter within the universe will tend to slow down its expansion.
www.absoluteastronomy.com /encyclopedia/f/fl/flatness_problem.htm   (341 words)

  
 Book Review for The Inflationary Universe
Inflation is an attractive idea because it solves three important problems of non-inflationary cosmology: (1) the flatness problem, (2) the horizon problem, or the causality connectedness problem and (3) the GUT monopole problem.
For the mass density to be within a factor of ten of its critical value nowadays, it needed to be fine-tuned to near its critical value with a precision of one part per million-billion at one second after the Big Bang.
Having understood the relation between mass density and the ultimate fate of the cosmos, the flatness problem can be rephrased as follows.
www.jupiterscientific.org /review/tiu.html   (2712 words)

  
 altvw111
The flatness problem is raised by the remarkable lack of curvature, either positive or negative, of the present universe.
The currently accepted solution for these problems, the "inflation scenario", assumes that in the very early stages of the Big Bang, for reasons not well understood, the universe expanded at an exponentially increasing rate, with the radius growing much faster than the speed of light.
The colliding branes are initially flat (in the sense of space curvature,) and this flatness is retained by our universe after the collision.
mist.npl.washington.edu /AV/altvw111.html   (1967 words)

  
 May 11: symmetry breaking, inflation   (Site not responding. Last check: 2007-10-18)
The flatness problem relates to the density parameter of the Universe,
Inflation solves the flatness problem because of the exponential growth.
The horizon problem is also solved in that our present Universe was simply a small piece of a larger Big Bang universe that was in causal connection before the inflation era.
blueox.uoregon.edu /~karen/astro123/lectures/lec17.html   (1072 words)

  
 Chapter 15: The Inflationary Universe
(2) The universe is nearly flat today, but this implies that it must have had an Omega very nearly equal to one at early times.
Unless the universe is exactly flat, this seems to require fine tuning.
This model posits that what became our observable universe was small enough to be in causal contact at the big bang; it then grew at an exponential rate during the inflationary epoch.
astsun.astro.virginia.edu /~jh8h/Foundations/chapter15.html   (545 words)

  
 New Astronomy.   (Site not responding. Last check: 2007-10-18)
04.25.Dm Chernin, Cosmic vacuum and the 'flatness problem' in the concordant model, New Astronomy 8 (1) (2003) pp.
A.D. Chernin, Cosmic vacuum and the 'flatness problem' in the concordant model, New Astronomy 8 (1) (2003) pp.
04.70.Dy Chernin, Cosmic vacuum and the 'flatness problem' in the concordant model, New Astronomy 8 (1) (2003) pp.
www.elsevier.com /cdweb/journals/13841076/viewer.htt?viewtype=keywords   (588 words)

  
 Film Flatness/Buckling Problem: Update
Todd, I have no film flatness problem with my Hasselblad backs (3 A12's with "12" in the release button, the generation just before the current ones with darkslide holders)even if I leave film in them for a month (which rarely happens but it has happened).
The only problem I had with Hasselblad backs was light leaking in the baffles, which should be serviced and replaced every two years or so, under heavy pro use.
Todd, the 645e is not a problem, you're right, the buckle is in between frames.
www.photo.net /bboard/q-and-a-fetch-msg?msg_id=003lUa   (1761 words)

  
 Cosmology
If the curvature of the universe was just a few percent off from perfect flatness within a few seconds after the Big Bang, the universe would have either recollapsed before fusion ever began or the universe would expanded so much that it would seem to be devoid of matter.
The horizon problem is solved by inflation because regions that appear to be isolated from each other were in contact with each other before the inflation period.
Type I supernovae are very luminous and can be used as standard candles to measure very large distances because they form from the collapse of a stellar core of a particular mass (1.4 solar masses).
www.astronomynotes.com /cosmolgy/s12.htm   (1999 words)

  
 TS-Aligner Home Page
If you encounter problems with accuracy, especially if you notice that the cuts aren't straight, then switching to a standard kerf blade will likely be the answer.
Fixing a fence flatness problem will not only make your saw safer, but you will regain control of your rip cuts.
If you determine that this is a problem, the far end of the fence can be clamped down to the table surface.
www.ts-aligner.com /external.htm   (795 words)

  
 I.06. What is inflation?
These problems are known as the flatness-oldness problem and the horizon problem.
The flatness problem has to do with the fact that density of the Universe appears to be roughly 10% of the critical density (see previous question).
Just like a football field on the Earth's surface can appear flat, even though the Earth itself is certainly curved, the portion of the Universe we can see might appear flat, even though the Universe as a whole would not be.
www.faqs.org /faqs/astronomy/faq/part9/section-8.html   (697 words)

  
 Four Cosmological Problems
Actually, the magnetic monopole issue may not be a problem because the lack of observation of proton decay disfavors grand unified gauge theories and string theory provides a unification mechanism not requiring a unifying gauge group.
It is straightforward to see why inflation solves the magnetic monopole problem if these particles are generated before inflation.
The small-scale inhomogeneity problem is solved because the minute fluctuations that exist in the original causally connected volume are stretched out over a wide range of distance scales.
www.jupiterscientific.org /sciinfo/cosmology/fourproblems.html   (812 words)

  
 Before the Big Bang?
Our observed expanding Universe is very well described by flat space, with critical density supplied mainly by dark matter and a cosmological constant, that should expand forever.
If the deviations from flatness are observed to be very small today, then extrapolating back to when the Universe was much smaller, the deviations from flatness must have been immeasurably small.
The cosmic microwave background is the cooled remains of the radiation from the radiation-dominated phase of the Big Bang.
www.superstringtheory.com /cosmo/cosmo4a.html   (794 words)

  
 Making Parts Flat
reader of this column called and told me he had a flatness problem with certain types of parts that his company was manufacturing.
Another is stresses within the material that relax (and distort flatness) when the periphery is released from the parent material or even when holes are pierced within the confines of the part.
A spring-loaded stripper for piercing is mandatory for flatness.
archive.metalformingmagazine.com /1997/04/bydes497.htm   (568 words)

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